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Weed Management Strategies for Organic Tomato, Pepper, and Eggplant in the Southern United States

mer, 2012/09/12 - 15:59

eOrganic author:

Dr. Mark Schonbeck, Virginia Association for Biological Farming


In organic production, tomato, pepper, and eggplant are normally started indoors and transplanted to the field to give them a head start on the weeds. Crops kept free of weeds for the first 4–8 weeks (tomato) or 8–10 weeks (eggplant, pepper) after transplanting can usually outcompete later-emerging weeds. However, late-season weeds can interfere with harvest, promote disease, and propagate themselves.

The most serious weeds of solanaceous (nightshade family) vegetables in the southern United States include yellow and purple nutsedges, morning glories, pigweeds, solanaceous weeds that host tomato or pepper diseases, and several winter annual weeds that harbor tomato spotted wilt virus and an insect pest (thrips) that transmits the virus from weed to crop. Fields heavily infested with these weeds should not be planted in tomato, pepper, or eggplant, and should be rotated to weed-smothering cover crops or perennial sod until weed populations decline to tolerable levels.

Important weed-preventive measures include: crop rotations that alternate warm- and cool-season vegetables, cover cropping, providing sufficient but not excessive nutrients from slow-release organic sources, and stale seedbed (planting delayed after seedbed preparation to allow removal of the inital flush of weeds) to draw down the weed seed bank.

Most organic farmers use one of two strategies to control weeds in solanaceous vegetables:

  • Black plastic mulch laid just before transplanting; alley weeds managed by cultivation, mowing, or organic mulch.
  • Cultivation to remove early-season flushes of weeds, followed by hay, straw, or other organic mulch.

Variations on these strategies include opaque white or light-reflecting (aluminized) plastic mulch for later plantings when soil warming is not desired; spreading organic mulch over plastic films several weeks after planting to prevent excessive soil heating; and in situ organic mulch from mowed or roll-crimped cover crops.

This article outlines organic weed management strategies and techniques for tomato and related vegetable crops, based on an understanding of:

  • General principles of ecological weed management.
  • Crop growth habits, life cycles, cultural practices, and organic production systems.
  • Inherent vulnerabilities and strengths of tomato, pepper, and eggplant in relation to weeds.

Tomato, pepper, and eggplant require good early-season weed control for successful production. Once established, these warm-season solanaceous vegetables become less vulnerable to competition from newly-emerging weeds, and tall tomato varieties can hinder weed growth by shading. late-season weeds must be managed to maintain adequate air circulation around crop foliage, and to prevent weed propagation during the long harvest season.

Crop Life Cycle and Growth Habit, Impacts of Weeds, and Minimum Weed-Free Period

Tomato, pepper, and eggplant are frost-tender summer annual crops in the solanaceous (nightshade) plant family. They require warm temperatures and an adequate supply of nutrients throughout the season to support good growth and yields. Newly-emerged seedlings are highly vulnerable to weed competition, and are usually started indoors in a weed-free potting mix. Once established, these crops become more tolerant of weed pressure. In tomato, the minimum weed-free period (to prevent yield losses to weed competition) has been estimated as the first 4–8 weeks after transplanting (Monks, 1993; Riggs et al., 1991; Teasdale and Colacicco, 1985; Weaver and Tan, 1983). Minimum weed-free periods for pepper and eggplant may be a little longer (8–10 weeks), owing to their slower development and shorter stature.

Because harvests continue until plants are killed by fall frost or disease, mature solanaceous crops remain in the field for a long period, during which additional weed management may be needed. Weeds that emerge after the crop's minimum weed-free period and are allowed to grow can interfere with harvest, promote disease by harboring pathogens or curtailing air circulation, or set seed.

When solanaceous vegetables reach a height of 12 inches or so, they tolerate some hilling up during cultivation, which buries and kills small within-row weeds. Hilling can benefit tomato by stimulating adventitious rooting from the stem, and diverting excess moisture away from the base of the plants (Diver et al., 2007). However, hilling can promote development of southern stem blight (Sclerotium rolfsii), and should be avoided where this pathogen is present (Louws, 2009).

Sweet and hot peppers, eggplant, and compact determinate varieties of tomato (varieties that grow to a fixed mature size and ripen all their fruit in a short period) form upright, bushy plants two to three feet tall. Indeterminate and semi-determinate tomato varieties form longer vines (five feet or more), and are normally staked or trellised.

Tomato prefers moderately warm conditions, giving best growth and production at daily mean air temperatures of 70–75 °F (Peet, 1996, Swaider et. al, 1992) and soil temperatures of 68–86 °F (Tindall et al., 1990). On good soil without hardpan (compact layer that restricts root growth), tomato forms a deep (five feet) root system, which can make established plants less susceptible to weed competition for soil moisture. The heavy foliage of a vigorous tomato crop can shade out weeds; however managing the crop to promote canopy closure can aggravate disease problems, leading to defoliation and yield losses.

Peppers require similar growing conditions to tomatoes, and prefer slightly warmer temperatures, especially the pungent varieties (Peet, 1996, Swaider et al., 1992). Unlike tomato, pepper has a shallow root system, which makes it more vulnerable to weed competition for soil moisture, and to detrimental root pruning from cultivation. Pepper is less prone to foliar diseases than tomato, and can be managed for canopy closure within the bed when disease pressure is light.

Eggplants prefer higher temperatures (daily means about 80 °F, nights not cooler than 65 °F) and a longer growing season than other solanaceous vegetables (Swaider et al., 1992). Like pepper, it can be managed to close canopy within the bed for suppression of late-emerging weeds. The crop develops a moderately deep root system (four feet), and can tolerate shallow cultivation for weed control.

Cultural Practices and Weed Management

Tomato, pepper, and eggplant are normally started in the greenhouse in a weed-free potting mix, and transplanted to the field at an age of 5–7 weeks (tomato) or 8–10 weeks (pepper, eggplant). Although some large scale conventional growers direct-seed solanaceous crops and apply selective herbicides, nearly all organic farmers minimize early-season weed competition by transplanting vigorous starts (Fig. 1). Tomato is set out after the last spring frost date; pepper and eggplant are often planted a few weeks later, when the soil is thoroughly warm.

Some farmers do succession plantings, with early crops set out in high tunnels before the last spring frost date, and field plantings continuing into late June or early July. Later plantings set out after the late spring flush of weed emergence allow the farmer to reduce weed pressure by preparing a stale seedbed or growing a weed-suppressive spring cover crop. When using the stale seedbed technique (also known as false seedbed), the farmer delays crop planting for several weeks after initial seedbed preparation to allow one or more flushes of weed seedlings to emerge. These are removed by shallow cultivation or flame weeding, and the crop is planted immediately after the final cultivation or flaming.

Vigorous tomato and pepper starts
Figure 1. (a) Vigorous tomato starts at 6 weeks after seeding, ready for transplanting. (b) Pepper starts 8 weeks after seeding. Photo credits: Mark Schonbeck, Virginia Association for Biological Farming.

Tomato, pepper, and eggplant require a moderate amount of available N, about 70–130 lb/ac from planting through early fruit set, and ample phosphorus (P) and potassium (K) to support good root growth and fruit quality, respectively (Swaider et al., 1992). Good organic soil management and attention to maintaining optimum growing conditions can enhance the crop's competitiveness toward weeds. Planting when temperatures are below optimum can prolong the minimum weed-free period. Providing too much available N early in the season can give weeds a competitive advantage over the crop, and excessive N later in the season may result in plants with dense foliage and few fruit.

Tomato is usually planted in single rows spaced 5–6 feet apart, either in raised beds or on the flat, with individual plants set 12–48 inches apart, depending on cultivar and production system. Some organic growers use wider row spacing (8–10 feet) to enhance air circulation, sometimes planting a low-growing vegetable or cover crop in the intervening spaces. Plants are normally supported (staked, trellised, or caged), and pruned (suckered) regularly to promote rapid drying of foliage for disease control, and to enhance fruit yield, quality, and ripening. Trellising and stake-and-weave systems that train the crop to a single line allow close cultivation or mulching under the plants, while cages limit weed control options near plant bases. Short varieties and processing tomatoes are sometimes grown without support (ground culture); however, the sprawling plants are difficult to keep weeded unless a plastic mulch is used.

Pepper and eggplant are often planted in staggered double rows, with plants spaced 18–24 inches apart in the row, and double rows on 5–7 foot centers. With this planting pattern, the crop often closes canopy within the bed, thereby suppressing the growth of late-emerging weeds. Pepper is sometimes staked to prevent the shallow-rooted plants from falling over during heavy fruit set.

Solanaceous crops respond very well to mulching. Many commercial organic producers routinely use synthetic mulch—most often black polyethylene film (black plastic)—for tomato, pepper, and eggplant (Fig. 2). Black plastic effectively controls most weeds and warms the soil, thereby promoting crop earliness and sometimes total yield. Drip irrigation is usually laid under the mulch to deliver water and liquid organic fertilizer to the crop. Some growers prefer black woven landscape fabric, which can be reused for seven or more years. Weeds emerging through planting holes are removed manually, and alley weeds are managed by hoeing, cultivation, mowing, organic mulch, or cover cropping.

NOTE: When plastic or other synthetic mulches are used for organic production, they must be removed from the field at the end of the growing or harvest season.

Tomatoes in black plastic
Figure 2. (a) Vegetable growers setting tomato starts into black plastic mulch. (b) Tomato at flowering in black plastic, with hay mulch in alleys. Photo credits: (a) Becky Crouse, Marketing Manager, Potomac Vegetable Farms, Purcellville, VA; (b) Mark Schonbeck, Virginia Association for Biological Farming.

Because tomato yield and quality can suffer from excessive soil heating, some growers spread straw or hay over black plastic mulch when summer heat arrives, or use a light-colored plastic for later plantings. In hot climates, a light-reflecting film mulch may be appropriate for main-season or late plantings of pepper and eggplant as well (Fig. 3).

Light-reflecting film mulch
Figure 3. This light-reflecting film mulch (opaque polyethylene with an aluminized surface), results in lower soil temperatures than black plastic, and repels aphids and some other pests from the pepper crop. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

If plastic mulch is not used, farmers either hoe or cultivate the crop as needed through the minimum weed-free period, or cultivate once or twice, then spread an organic mulch, such as straw or hay, to delay weed emergence until the crop is fully established (Fig. 4). Because organic mulch conserves moisture and moderates soil temperature, it can enhance tomato yields if applied after the soil has warmed sufficiently (Schonbeck and Evanylo, 1998).

Straw mulch for tomatoes, peppers, and eggplant.
Figure 4. (a) Tomato in hay mulch passed through its minimum weed-free period before weeds began to break through the mulch. (b) Straw mulch, applied after cultivation and when soil temperatures were near optimal for eggplant and pepper, has given excellent weed control. Crops were planted in double rows, and the eggplant has closed canopy, thus shading out late-emerging weeds. Photo credits: Mark Schonbeck, Virginia Association for Biological Farming.

Tall tomato varieties grown on trellises or tall stakes can cast sufficient shade to hinder between-row weed growth. However, in moist conditions, the tomato crop may lose its foliage to diseases toward the end of the harvest period, which allows weed growth to resume.

Most Serious Weeds in Solanaceous Crops in the Southern Region

Some of the most widespread and troublesome weeds in solanaceous crops in the Southern region include yellow nutsedge (Cyperus esculentus), purple nutsedge (C. rotundus), morning glories (Ipomoea spp.), and pigweeds (Amaranthus spp.) (Fig. 5) (Webster, 2006). Bermuda grass (Cynodon dactylon), johnsongrass (Sorghum halapense), crabgrasses (Digitaria spp.), foxtails (Setaria spp.), and galinsoga (Galinsoga spp.) have also been cited as major weeds of tomato family in some southern states.

Troublesome weeds for solanaceous crops
Figure 5. Some troublesome weeds for solanaceous crops: (a) Yellow nutsedge and two species of morning glory emerging in alley between tomato rows. (b) Purple nutsedge competing severely against pepper. (c) late-season morning glories climbing mature tomato plants, with pigweeds growing in alleys (foreground). Photo credits: Mark Schonbeck, Virginia Association for Biological Farming.

Morning glories are especially troublesome because they can emerge through six inches of straw mulch, readily grow toward and emerge through planting holes in plastic mulches, and climb crop plants. The fast-growing, entangling vines interfere with harvest and can smother the crop.

The sharp-pointed shoots of emerging nutsedges and Bermuda grass can penetrate black plastic film or landscape fabric. The weeds then compete with the crop, and complicate end-of-season mulch removal.

Pigweeds compete aggressively against solanaceous crops, owing to their tall stature and rapid growth during hot weather. Later-emerging pigweed can cause problems, even when the crop is large enough to shade out most grassy weeds and nutsedges.

Horsenettle (Solanum carolinense) (Fig. 6a), black nightshade (Solanum nigrum) and other solanaceous weeds are alternate hosts for diseases such as early blight (Alternaria solani), septoria leaf spot (Septoria lycopersici), and late blight (Phytophthora infestans) of tomato, and phytophthora blight (P. capsici) of pepper. Many weed species, including winter annuals like common chickweed (Stellaria media) (Fig. 6b), mouse ear chickweed (Cerastium vulgatum), cutleaf evening primrose (Oenothera laciniata), and cudweeds (Gnaphalium spp.) can harbor tomato spotted wilt virus (TSWV) and thrips (Thysanoptera), an insect pest that acts as a vector (carrier) and transmits the virus from weed to crop (Louws, 2009; Martinez, 2008). TSWV is most serious in areas with mild winters that do not kill off thrips populations.

Horsenettle and common chickweed
Figure 6. Two weeds that pose a disease and pest hazard to solanaceous crops. (a) Horsenettle hosts early blight and septoria leaf spot of tomato, phytophthora blight of pepper, and false potato beetle, which can severely damage eggplant. (b) Common chickweed can harbor the tomato spotted wilt virus (TSWV) and its thrips vector over the winter, thereby propagating the disease from one season to the next. Photo credits: Mark Schonbeck, Virginia Association for Biological Farming.

Preventive Weed Management in Solanaceous Crops

Preventive weed management begins with planning and field preparation. If possible, avoid planting tomato, pepper, and eggplant in fields with high populations of nutsedge, Bermuda grass, or other aggressive weeds. Use stale seedbed prior to planting to reduce seed populations of pigweed, morning glory, and other summer annual weeds. Weeds known to carry a disease or pest of solanaceous crops that is prevalent in the area should be well controlled before rotating the field to tomato or other crops in this plant family.

A good crop rotation that includes weed-smothering cover crops can reduce weed problems in tomato, pepper, and eggplant (Diver et al., 2007). Alternate warm- and cool-season vegetables in successive years, and grow competitive summer cover crops like buckwheat, cowpea, and sorghum–sudangrass during the season prior to tomato family production. Rotate heavily weed-infested fields into a perennial grass–clover sod for 1–3 years to reduce the weed seed bank.

Optimize soil temperature for crop establishment. For early plantings, use black plastic or fabric mulches, low or high tunnels (Fig. 7), or other strategies to raise soil temperature, so that crop development is not delayed by cold soil. Be sure the soil is thoroughly warm, (~70 °F) before transplanting eggplant or hot pepper. Delay application of straw or other soil-cooling mulches near plants until the soil has reached optimal temperatures. For late-season tomato plantings during hot weather, use a white or reflective film mulch (for best weed control, use an opaque white-on-black film, or coat black plastic with a nontoxic whitewash), or apply straw soon after planting to limit solar heating of the soil.

Companion-cropped high tunnel tomatoes
Figure 7. Tomato planted in March in a high tunnel will begin producing fruit by June at Dayspring Farm in the Tidewater region of Virginia. The companion crops of lettuce and bok choi have limited early-season weed growth, and will soon be harvested. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Use slow-release organic nutrient sources to meet crop nutritional needs. Avoid more soluble, faster-releasing fertilizers, which could stimulate early-season growth of pigweeds, black nightshade, and other N-responsive weeds. On good, biologically active soil, tomato N needs can be fully met with legume cover crops and compost, and yield better with these N sources than with soluble fertilizers (Diver et al., 2007).

Use in-row drip irrigation to deliver water and liquid organic fertilizers (if needed) preferentially to the crop (Fig. 8). Subsurface drip irrigation (lines buried several inches deep in the crop row) provides moisture to crop roots while leaving the soil surface dry and thereby deterring weed seed germination.

In-row drop irrigation of tomatoes
Figure 8. In-row drip irrigation can give the crop the edge over weeds, especially in a dry season. A mulch application would further enhance the crop's advantage. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Transplant the crop immediately after preparing the bed, especially if plastic mulch is not laid before planting. Even a couple days' delay can give the weeds a significant head start. For tomato, choose row spacing, plant spacing, and method of support that optimizes air circulation for disease control, and facilitates cultivation or mulching. For pepper and eggplant, where disease pressure is light, plant a staggered double row at a plant spacing that promotes canopy closure within the bed or grow zone without unduly crowding the plants.

Cultivation and Other Weed Control Tactics

If plastic film or fabric mulch is not used, cultivate or hoe around the plants when the first flush of weeds is less than one inch tall. Cultivate shallowly to avoid root pruning, especially in pepper. If crop plants are large enough and the southern stem blight pathogen is not present in the soil, adjust cultivation implements to throw soil into the crop rows to bury small within-row weeds, rather than trying to sever or uproot them.

Without mulch, as many as three cultivations may be needed before the end of the minimum weed-free period. Many organic growers hoe or cultivate once or twice to remove early weeds, then apply 3–4 inches of straw, hay, or other organic mulch. This approach conserves soil moisture, adds organic matter, prevents soil splash during rains, and can provide excellent weed control in fields that are not heavily infested with aggressive perennial weeds or morning glories.

For tomato, pepper, and eggplant transplanted into plastic film or fabric mulch, some manual labor is usually needed to remove weeds that emerge through planting holes. Usually, one manual weeding is sufficient, after which the growing crop shades out emerging weeds. Control alley weeds by cultivation, hoeing, mowing, or spreading straw or other organic mulch in alleys and overlapping edges of the plastic.

Once the crop has passed through its minimum weed-free period, manage later-season weeds so that they do not hinder air circulation and promote foliar diseases (Fig. 9), interfere with harvest, or propagate themselves. Pull or cut morning glories and other vining weeds before they begin to climb the crop. Remove large "escapes" before they set seed. Hoe, cultivate or mow closely any nutsedge or other invasive perennials to disrupt formation of new rhizomes and tubers.

Late-season weeds in tomatoes
Figure 9. These weeds emerged late enough not to compete directly with the established tomato crop; however, they reduced air circulation and promoted the development of fungal diseases, which have defoliated the lower parts of these plants. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Additional Weed Management Strategies

Winter cover crops, such as cereal rye–hairy vetch or barley–crimson clover, can be roll-crimped or flail-mowed for no-till planting of summer vegetables. The rye–vetch mulch appears especially promising for tomato production. In a study in Beltsville, MD, tomato planted in mow-killed hairy vetch yielded about 20% more than tomato in black plastic (Abdul-Baki and Teasdale, 1993, 1997). Mowed rye mulch can suppress weeds for 4–8 weeks without adversely affecting tomato yield (Smeda and Weller, 1996) and vetch residues have been shown to enhance disease resistance, prolong active photosynthesis and delay leaf senescence in tomato by modifying tomato gene expression (Kumar et al., 2004). No-till planting into mechanically killed cover crop is recommended for main-season and late tomato plantings, but not early plantings, as the cover crop mulch may delay soil warming, crop establishment, and fruit ripening.

Winter cover crops can be strip-tilled several weeks before tomato or pepper planting to promote soil warming in the crop grow-zone. Cover crops growing in alleys can be maintained by mowing to keep alley weeds down (Fig. 10); in some cases, the mowings can provide clean mulch for the vegetable. Season-long living mulches of white clover, subterranean clover, or ryegrass, managed by mowing or partial tillage, have also been used successfully for alley weed control in tomato (Diver et al., 2007). However, clovers host nematode pests that affect tomato, such as root-knot nematode; thus, clovers should not be grown with or immediately before solanaceous vegetables in fields in which these nematode pests are present.

Strip-tilled rye before transplanting tomatoes
Figure 10. A winter rye cover crop was strip-tilled prior to transplanting tomato at Seven Springs Farm in Check, VA (Appalachian region). The cover crop, maintained by mowing, has suppressed alley weeds. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Finally, cover crops can be planted in alleys between beds several weeks after vegetable planting (relay intercropping) to suppress weeds, protect soil, and add organic matter. Examples include buckwheat, cowpea, millet, or white clover, mowed if needed to maintain air circulation around the crop.

References Cited
  • Abdul-Baki, A. A., and J. R. Teasdale. 1993. A no-tillage tomato production system using hairy vetch and subterranean clover mulches. HortScience 28: 106–108.
  • Abdul-Baki, A. A., and J. Teasdale. 1997. Sustainable production of fresh market tomatoes and other summer vegetables with organic mulches. Farmers' Bulletin No. 2279. USDA–Agriculture Research Service, Washington, D.C. (Available online at: http://www.ars.usda.gov/is/np/SustainableTomatoes2007/SustainableTomatoes2007Intro.htm) (verified 10 Sept 2012).
  • Diver, S., G. Kuepper, and H. Born. 2007. Organic tomato production [Online]. Available at: https://attra.ncat.org/attra-pub/summaries/summary.php?pub=33 (verified 10 Sept 2012).
  • Kumar, V., D. J. Mills, J. D. Anderson, and A. K. Mattoo. 2004. An alternative agriculture system is defined by a distinct expression profile of select gene transcripts and proteins. Proceedings of the National Academy of Sciences 101: 10535–10540. (Available online at: http://dx.doi.org/10.1073/pnas.0403496101) (verified 10 Sept 2012).
  • Louws, F. 2009. Managing vegetable diseases. Presentation at the 24th annual Sustainable Agriculture Conference of the Carolina Farm Stewardship Association, Black Mountain, NC, Dec 5, 2009.
  • Martinez, N. 2008. Tospoviruses in Solanaceae and other crops in the coastal plain of Georgia: Epidemiology, weed hosts. University of Georgia. (Available online at: http://www.caes.uga.edu/topics/diseases/tswv/vegcrops/tospoviruses/epidemiologywh.html) (verified 10 Sept 2012).
  • Monks, D. 1993. Veg-I-News. Cooperative Extension Service, North Carolina State University. Vol. 12, No. 4.
  • Peet, M. 1996. Sustainable practices for vegetable production in the South. Focus Publishing, R. Pullins Company, Newburyport, MA.
  • Riggs, D.I.M., R. R. Bellinder, and R. W. Wallace. 1991. The effect of one, two and three month weed-free periods on yield of late season tomatoes. HortScience 26: 152. (Available online at: http://hortsci.ashspublications.org/content/26/6/768.4.abstract) (verified 10 Sept 2012).
  • Schonbeck, M. W., and G. E. Evalylo. 1998. Effects of mulches on soil properties and tomato production. I. Soil temperature, soil moisture, and marketable yield. Journal of Sustainable Agriculture 13: 55–81. (Available online at: http://dx.doi.org/10.1300/J064v13n01_06) (verified 10 Sept 2012).
  • Smeda, R. J., and S. C. Weller. 1996. Potential of rye (Secale cereale) for weed management in transplant tomatoes (Lycopersicon esculentum). Weed Science 44: 596–602. (Available online at: http://www.jstor.org/stable/4045642) (verified 10 Sept 2012).
  • Swaider, J. M, G. W. Ware, and J. P. McCollum. 1992. Producing vegetable crops, 4th ed. Interstate Publishers, Inc, Danville, IL.
  • Teasdale, J. R., and D. Colaccicco. 1985. Weed control systems for fresh market tomato production on small farms. Journal of the American Society of Horticultural Science 110: 533–537.
  • Tindall, J. A., H. A. Mills, and D. E. Radcliffe. 1990. The effect of root zone temperature on nutrient uptake of tomato. Journal of Plant Nutrition 13: 939–956. (Available online at: http://dx.doi.org/10.1080/01904169009364127) (verified 10 Sept 2012).
  • Weaver, S. E., and C. S. Tan. 1983. Critical period of weed interference in transplanted tomatoes (Lycopersicon esculentum): Growth analysis. Weed Science 31: 476–481. (Available online at: http://www.jstor.org/stable/4043595) (verified 10 Sept 2012).
  • Webster, T. M. 2006. Weed survey – southern states. Vegetable, fruit and nut crops subsection. Proceedings of the Southern Weed Science Society 59: 260–277. (Available online at: http://www.swss.ws/NewWebDesign/Publications/Weed%20Survey%20Archives/Southern%20Weed%20Survey%202006%20Vegetables%20and%20Fruits.pdf) (verified 10 Sept 2012).


This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

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This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

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September 2012 eOrganic Newsletter

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In this Issue
  • What's New at eOrganic
  • New Video: What is Organic?
  • New Farmer's Guide to Organic Contracts
  • New Organic Literacy Initiative by the NOP
  • NOP News: Last Call for Certification Cost Share
  • NCAT Webinar on Organic Conservation Practice Standards
  • CCOF Upcoming Webinars and Events
What's New at eOrganic

Organic Mulching Materials for Weed Management, by Mark Schonbeck, Virginia Association for Biological Farming. Available at http://www.extension.org/pages/65025

Synthetic Mulching Materials for Weed Management, by Mark Schonbeck, Virginia Association for Biological Farming. Availble at http://www.extension.org/pages/65191

Video: Healthy Cow Check-Up—How to Perform a Physical Exam. Dr. Hubert Karreman, Penn Dutch Cow Care. Available at http://www.extension.org/pages/64752

Organic News and Announcements New Video: What is Organic?

A new video filmed for the St. Paul, farmer's market features eOrganic certification group leader Jim Riddle, who addresses the question "What is Organic" from his Minnesota farm.  Watch the video at http://www.youtube.com/watch?v=BQskVbWGT2c

New Farmer's Guide to Organic Contracts Available Online

The goal of FLAG's new Farmers' Guide to Organic Contracts is to help organic farmers make informed decisions when evaluating, negotiating, and managing contract agreements with buyers of organic farm products. This farmer-friendly guide includes: 1) a basic overview of contract laws important to farmers; 2) a Quick Organic Contract checklist and practical toolkit farmers can use to review contract offers; 3) highlighted sections showing how NOP regulations interact with organic contracts; 4) explanations and examples of over 100 types of organic contract provisions; and 5) detailed information about solving the types of contract disputes that commonly arise in the organic market. The guide is available for free download at http://www.flaginc.org.

New Organic Literacy Initiative by the NOP

On September 4, the U.S. Department of Agriculture released a series of resources as part of its new Organic Literacy Initiative, an effort to help connect current and prospective organic farmers, ranchers, and processors with relevant USDA resources. Find all the publications at the new Organic Literacy Home Page. The purpose of the Organic Literacy Initiative is to provide USDA staff as well as organic producers and handlers with detailed and consistent information about organic agriculture and the programs and services USDA offers to support it. One of the goals of the initiative is to help USDA staff around the U.S. be better equipped to help farmers, ranchers, and processors understand organic certification and access relevant USDA services.

The materials available include:

An Organic 101 training about what the organic label means and how certification works;
A brochure that contains information about organic standards and certification and a brief description of USDA resources;
An Organic Resource Guide that outlines how each USDA agency supports organic agriculture and provides relevant USDA contact information; and
A USDA blog that highlights organic topics.

NOP News: Last call for Organic Certification Cost Share

Funds are still available for the 2012 Organic Certification Cost Share Program—as much as $750 per certified operation—to certified organic farmers and businesses to help cover the cost of organic certification. Newly certified applicants must have an organic certificate dated between October 1, 2011 and September 30, 2012 to apply during the 2012 funding cycle. If you are renewing your certification, you can submit your application as soon as you pay your certification fees. Contact your state’s department of agriculture for an application. You can find names and phone numbers at http://www.ams.usda.gov/NOPCostShareProgramParticipants, and some states have forms online for you to download. Your state’s deadline may be as early as September 30th, so don’t wait—apply today!

NCAT Webinar on Conservation Practice Standards on September 27, 2012

NCAT is hosting a webinar on September 27, 2012 at 1-2 PM Eastern Time on the Links between Biodiversity Requirements of Organic Systems and NRCS Practice Standards.  The webinar is funded by an NRCS Conservation Innovation Grant. Register at https://www2.gotomeeting.com/register/359336938.

Biodiversity conservation is part of the definition of organic farming, and the NOP requires that farmers and ranchers maintain or improve their soil, water, wetlands, woodlands, and wildlife. In addition, seven other NOP regulations relate to biodiversity and natural resource conservation. NRCS Conservation Practice Standards that help operators meet these NOP requirements will be discussed, including those protecting resources, providing conservation buffers, and supporting wildlife habitat. Also presented will be examples of practices used by organic farmers to maintain or enhance natural resources on their operations. Presenters: Jo Ann Baumgartner, Wild Farm Alliance, Jim Riddle, University of Minnesota, and Tom Broz, Live Earth Farms.

CCOF Upcoming Webinars and Events

California Certified Organic Farmers is hosting several marketing webinars this fall: Marketing 101 on September 26, and Sales Basics on October 3rd—as well as an in-person, all-day Organic Wholesale Market Tour on October 16 in San Francisco! Register early since space is limited. Find out more information on their Education and Events page at http://ccof.org/programs.php

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This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 8211

eOrganic Updates

lun, 2012/09/10 - 17:44

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic T1123

Can I Use This Input on My Organic Farm?

mar, 2012/09/04 - 13:43
imageUsing an input that is not approved can cost you your organic certification. Learn how to determine if a synthetic or natural material can be used in organic production.

eOrganic authors:

Nick Andrews, Oregon State University

Brian Baker, Organic Materials Research Institute

Jim Riddle, University of Minnesota

Assessing Inputs

The National Organic Program (NOP) final rule (United States Department of Agriculture [USDA], 2000) emphasizes the use of preventive and cultural methods such as crop rotation, cover cropping, sanitation measures, and nutritious feed rations to build soil fertility, prevent pest problems, and maintain livestock health. In fact, the NOP requires that management practices to prevent pests, weeds and diseases, including soil-building crop rotations; sanitation measures to remove disease vectors, weed seeds, and pest habitat; selection of site-suitable and resistant plant and livestock species and varieties; release of pest predators and parasites; development of habitat for pest predators; lures, traps and repellants; mulching, mowing, grazing, mechanical, flame, and/or hand weeding; and cultural practices to prevent weed, pest and disease problems must be implemented, and found to be insufficient, prior to the use of any input.

Many organic farmers save money and produce high-quality crops with little or no off-farm inputs, but most producers rely on at least some purchased inputs. Purchasing inputs brings up the question: Is this product allowed? Given that most agricultural inputs are not produced with NOP standards in mind, those of us trying to meet the standards have to ensure that we use only approved products.

With full implementation of the National Organic Program regulations on October 21, 2002, it’s the National Organic Program (NOP) that allows or prohibits a material, via the National List of Allowed and Prohibited Substances (National List). This is a generic materials list. The NOP does not publish a brand name materials list. Brand name lists evaluate a formulated product’s compliance to the requirements of the National List, but do not carry any regulatory weight. Of course, you are free to use brand name lists for guidance (as most organic certifiers do), but certification agencies are responsible for evaluating materials to be used by producers and handlers for compliance with the National List requirements. As a producer, this means that you must submit a list of all inputs you use or intend to use as part of your Organic System Plan, and your certification agency will determine if the substances are allowed for organic production.

Making Sense of the National List

The portion of the NOP concerned with the National List begins at section 205.105 (see “NOP on materials” below). Simply put, it says we cannot use products with synthetic ingredients for orgsanic crop or livestock production, unless they are specifically allowed and appear on the National List (see definition in “NOP on materials”). Some nonsynthetic (natural) substances are also prohibited (see sections 205.602 and 205.604). In other words, synthetic materials cannot be used unless they are specifically approved, and natural materials can be used unless they are specifically prohibited. The National List specifies the allowed synthetic substances and prohibited nonsynthetic substances (see section 205.601), along with specific restrictions, or annotations, regarding the source or use of the substance. The National List doesn’t include numerous natural, nonsynthetic substances, such as gypsum, limestone, or rock phosphate, which are allowed by definition.

Reading Labels

Next stop is the product label. If the ingredients are nonsynthetic and not included as prohibited in section 205.602, they are allowed. If there are synthetic ingredients, check to see if they are specifically allowed. Be sure to check section 205.601 for crop and 205.603 for livestock annotations. These annotations are where I’ve seen some challenges for growers. The annotations often regulate or place certain restrictions on the manufacturing processes or the use of a material. For example, Lidocaine is allowed as a local anesthetic, but its use requires a withdrawal period of 90 days for livestock intended for slaughter and seven days for dairy animals. Compliance with restrictions must be documented when an annotated material is used.

Reading the label may not be enough to determine if a product complies with National List annotations. Labels frequently do not provide all the information about the manufacturing process. For example, liquid fish products are allowed as plant or soil amendments (see §205.601.j.7). They “can be pH adjusted with sulfuric, citric or phosphoric acid. The amount of acid used shall not exceed the minimum needed to lower the pH to 3.5.” Ingredient lists on liquid fish do not address this issue. Before purchasing or using a liquid fish product, a grower should contact the manufacturer or confirm that the product is listed on a brand name list of NOP compliant products.

Non-active or inert ingredients in pesticide formulations are classified according to the level of toxicological concern. EPA has changed how it lists inert ingredients, and the NOP has taken over the maintenance of the list of substances used as inert ingredients that EPA determined to be of minimal concern prior to 2004. To be NOP compliant, all synthetic inert ingredients in pesticides must be classified as minimum risk, appear specifically on the National List, or be used in passive pheromone dispensers. Inert ingredients do not appear on labels, so verifying compliance with this annotation requires the cooperation of the pesticide registrant.

If you contact manufacturers, try to get answers in writing or at least record what you learn. If you are unsure of the information that you need, contact your certifier for guidance and they should be able to help you ask the right questions. When considering a new product, be sure to plan ahead. In trickier cases, a simple “yes” or “no” answer may not be possible over the phone.

As the saying goes, “The devil is in the details.” It’s these tricky cases that cause the headaches. It’s tempting to just refer to a brand name materials list and use those products. But remember, just because a product is not on a particular brand name materials list does not necessarily mean that it is prohibited by the NOP. Also remember that only the NOP carries regulatory weight; all other lists are based on evaluations of compliance to the rule. 

Brand Name Material Lists

The NOP established a policy that each Accredited Certifying Agent (ACA, certifier) is responsible for conducting its own reviews of inputs for agricultural production, such as formulated pesticides and soil amendments. The NOP also allows certifying agents to recognize reviews conducted by other certifying agents and competent third-party reviewers as described in a letter to organic certifiers on verification of materials (Robinson and Bradley, 2008), and later confirmed by a Policy Memo in the NOP Policy Handbook. All ACAs are required to verify, along with their clients, that all materials used or planned for use by certified organic operations comply with the NOP. To paraphrase, ACAs have three options available to determine whether branded or formulated products comply:

  1. ACAs can contact the manufacturer to obtain disclosure of the contents of the product and verify that they all comply;
  2. ACAs may consult with another ACA that has reviewed the information and accept their determination that the material is NOP compliant; or
  3. ACAs may consult with a reputable third party source, such as the Environmental Protection Agency (EPA) or the Organic Materials Review Institute (OMRI), that reviews materials for compliance with the NOP regulation.

ACAs must document their determinations and verify that the inputs are used according to the regulation. ACAs must either have the capacity and expertise to review products, or contract with organizations accredited do so. Many ACAs contract with OMRI, a non-profit initially established by certifiers specifically for that purpose. The Washington State Department of Agriculture (WSDA) also reviews products according to the NOP and publishes a list of brand name products that other ACAs use. These lists are not comprehensive, so there may be other brand name products that can be used. However, in order to be sure that a product complies, the manufacturer must fully disclose all ingredients and manufacturing processes to an ACA or a third party contracted by the ACA. All ingredients must comply with the standards described above.

One Step at a Time

Before using a new product, check for recent OMRI or WSDA approval of the product. If it isn’t listed, follow these steps:

  1. Evaluate each label ingredient for compliance with the NOP and any annotations on the National List. The OMRI Generic Materials List may also be helpful.
  2. Contact the manufacturer if necessary.
  3. Document compliance with all NOP crop and livestock annotations.

Since this process can take some time, be sure to plan ahead when developing or updating your Organic System Plan (OSP). Keep records of all communications with input manufacturers, certifiers, and input review services. Keep labels, receipts, shipping invoices, and input application records. The documentation required to demonstrate compliance with the NOP can seem daunting and sometimes takes time away from working the land. However, this careful verification gives organic consumers confidence in the organic standard they have grown to trust.

NOP Citations on Materials

§ 205.105 Allowed and prohibited substances, methods, and ingredients in organic production and handling.
To be sold or labeled as “100 percent organic,” “organic,” or “made with organic (specified ingredients or food group(s)),” the product must be produced and handled without the use of:
(a) Synthetic substances and ingredients, except as provided in § 205.601 or § 205.603;
(b) Nonsynthetic substances prohibited in § 205.602 or § 205.604;
(c) Nonagricultural substances used in or on processed products, except as otherwise provided in § 205.605;
(d) Nonorganic agricultural substances used in or on processed products, except as otherwise provided in § 205.606;
(e) Excluded methods, except for vaccines, provided that the vaccines are approved in accordance with § 205.600(a);
(f) Ionizing radiation, as described in Food and Drug Administration regulation, 21 CFR 179.26; and
(g) Sewage sludge.

§ 205.206 Crop pest, weed, and disease management practice standard
(e) When the practices provided for in paragraphs (a) through (d) of this section are insufficient to prevent or control crop pests, weeds, and diseases, a biological or botantical substance or a substance included on the National List of synthetic substances allowed for use in organic crop production may be applied to prevent, suppress, or control pests, weeds, or diseases; Provided, That, the conditions for using the substance are documented in the organic system plan.

§ 205.602 Synthetic substances allowed for use in organic crop production.
In accordance with restrictions specified in this section, the following synthetic substances may be used in organic crop production: Provided, That, use of such substances do not contribute to contamination of crops, soil, or water. Substances allowed by this section, except disinfectants and sanitizers in paragraph (a) and those substances in paragraphs (c), (j), (k), and (l) of this section, may only be used when the provisions set forth in §205.206(a) through (d) prove insufficient to prevent or control the target pest.

  § 205.602 Nonsynthetic substances prohibited for use in organic crop production.
The following nonsynthetic substances may not be used in organic crop production:
(a) Ash from manure burning
(b) Arsenic
(c) Lead salts
(d) Sodium fluoaluminate (mined)
(e) Strychnine
(f) Tobacco dust (nicotine sulfate)
(g) Potassium chloride—unless derived from a mined source and applied in a manner that minimizes chloride accumulation in the soil.
(h) Sodium nitrate—unless use is restricted to no more than 20 percent of the crop’s total nitrogen requirement.
(i-z) [Reserved]

§ 205.604 Nonsynthetic substances prohibited for use in organic livestock production.
The following nonsynthetic substances may not be used in organic livestock production:
(a) Strychnine
(b)-(z) [Reserved]

NOP definition of "synthetic" -  "A substance that is formulated or manufactured by a chemical process that chemically changes a substance extracted from naturally occurring plant, animal or mineral sources, except that such term shall not apply to substances created by naturally occurring biological processes."

References and Citations Additional Resources


This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 2473

Organic Vegetable Production Systems, Soil and Fertility Management in Organic Farming Systems

mar, 2012/09/04 - 12:24

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic T879,867

Soil and Fertility Management in Organic Farming Systems

mar, 2012/09/04 - 12:24

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic T867

Soil Nematodes in Organic Farming Systems

mar, 2012/09/04 - 12:21

eOrganic authors:

Carmen Ugarte, University of Illinois

Ed Zaborski, University of Illinois


Nematodes are microscopic, wormlike organisms (Fig. 1) that live in water films and water-filled pore spaces in the soil. Typically, they are most abundant in the upper soil layers where organic matter, plant roots, and other resources are most abundant. Nematode abundance in soils—managed and unmanaged—ranges from 1–10 million individuals/m2 (Peterson and Luxton, 1982; Lavelle and Spain, 2001).

Figure 1. A typical free-living, bacterial-feeding nematode.
Figure 1. A typical free-living, bacterial-feeding nematode, less than 1mm (0.04in) in length. Figure credit: Ed Zaborski, University of Illinois.

Most research on soil nematodes has focused on the plant-parasitic nematodes that attack the roots of cultivated crops. Less attention has been given to nematodes that are not plant-feeders and play beneficial roles in the soil environment. This article describes the important roles played by nematodes in soil ecosystems, as well as their potential to be used as indicators of soil condition in organic farming systems.

Nematode Feeding Habits

Nematodes can be classified into functional groups based on their feeding habits, which can often be deduced from the structure of their mouthparts (Fig. 2). In agricultural soils, the most common groups of nematodes are the bacterial-feeders, fungal-feeders, plant parasites, predators, and omnivores. Predatory nematodes feed on protozoa and other soil nematodes. Omnivores feed on different foods depending on environmental conditions and food availability; for example, omnivorous nematodes can be predators, but in the absence of their primary food source, they can feed on fungi or bacteria.

Figure 2. Nematode feeding types; mouthpart structures.
Figure 2. Nematodes can be classified into different feeding groups based on the structure of their mouthparts. (a) bacterial feeder, (b) fungal feeder, (c) plant feeder, (d) predator, (e) omnivore. Figure credit: Ed Zaborski, University of Illinois.

Importance of Nematodes in Agricultural Systems

Nematodes contribute to a variety of functions within the soil system. In agricultural systems, nematodes can enhance nutrient mineralization and act as biological control agents.

Nematodes and Soil Fertility

Soil nematodes, especially bacterial- and fungal-feeding nematodes, can contribute to maintaining adequate levels of plant-available N in farming systems relying on organic sources of fertility (Ferris et al., 1998). The process of converting nutrients from organic to inorganic form is termed mineralization; mineralization is a critical soil process because plants take up nutrients from the soil primarily in inorganic forms. Nematodes contribute directly to nutrient mineralization through their feeding interactions. For example, bacterial-feeding nematodes consume N in the form of proteins and other N-containing compounds in bacterial tissues and release excess N in the form of ammonium, which is readily available for plant use. Indirectly, nematodes enhance decomposition and nutrient cycling by grazing and rejuvenating old, inactive bacterial and fungal colonies, and by spreading bacteria and fungi to newly available organic residues. In the absence of grazers, such as nematodes and protozoa, nutrients can remain immobilized and unavailable for plant uptake in bacterial and fungal biomass.

Bacterial-feeding nematodes are the most abundant nematode group in agricultural soils. Their abundance closely follows that of bacterial populations, which tend to increase when soil disturbances, such as tillage, increase the availability of readily-decomposable organic matter. Nitrogen mineralization in the soil occurs at a higher rate when bacterial-feeding nematodes are present than when they are absent. The contribution of bacterial-feeding nematodes to soil N supply depends, in part, on the quality and quantity of soil organic matter fueling the system. Net N mineralization from decomposing organic residues takes place when the carbon:nitrogen (C:N) ratio of organic residue is below 20 (that is, 20 parts C to 1 part N). When the C:N ratio is greater than 30, the rate of mineralization decreases because microbes compete for N to meet their nutritional requirements. In this situation, N is immobilized in the microbial biomass. Incorporation of manure, compost, and cover crops with intermediate C:N ratios (ranging from 10 to 18) may stimulate bacterial growth and the abundance of bacterial-feeding nematodes, and increase soil N availability to plants.

Fungal-feeding nematodes are relatively more abundant in less-disturbed (e.g. notill systems) and perennial systems, where conditions for fungal growth are promoted, than in disturbed systems. Like bacterial feeding nematodes, fungal-feeding nematodes contribute to the process of nutrient mineralization by releasing N and other plant nutrients from consumed fungal tissue. However, in agricultural systems, bacterial-feeding nematodes typically release more inorganic N than fungal-feeding nematodes.

Nematodes as Natural Enemies and Biological Control Agents

Predatory nematodes are of interest because of their role in regulating the populations of other organisms. They generally feed on smaller organisms like protozoa and other nematodes. Thus they can help moderate population growth of bacterial- and fungal-feeding nematodes and protozoa, and help regulate populations of plant-parasitic nematodes.

Insect-parasitic nematodes are species of bacterial-feeding nematodes that live in close association with specific species of bacteria; together, they can infect and kill a range of insect hosts. The infective juvenile stage of insect-parasitic nematodes seeks out insect hosts to continue its development into adults. Once a host is found, the nematodes penetrate the insect body and release their bacterial associates into the insect’s body cavity. These bacteria multiply and overwhelm the immune response of the host insect, ultimately killing the host. The nematodes feed on these bacteria, mature, and reproduce until all the resources within the insect host are consumed; then, infective juvenile nematodes escape the insect host's body and disperse in the soil to seek new hosts. Insect-parasitic nematodes are available commercially for use in inundative releases to manage the populations of a variety of insect pests.

Plant-Parasitic Nematodes

Most plant-parasitic nematodes feed on the roots of plants. Some species attach to the outside surface of plant roots (Fig. 3), piercing the root tissue to suck up the cellular content; other species pierce and penetrate the roots of plants, living and reproducing entirely within the root itself. A relatively small number of important plant-parasitic nematode species are known to cause substantial economic damage in cropping systems around the world. The determination of tolerance limits or economic thresholds for plant-parasitic nematodes varies with many factors like species, plant tolerance, and soil type. Because plant parasitic nematodes show varying degrees of host specificity, carefully designed crop rotations are usually a powerful tool for reducing nematode-associated yield losses.

Figure 3. Symptoms of white potato cyst nematode, Globodera pallida.
Figure 3. White potato cyst nematode, Globodera pallida (Stone) Behrens, on plant roots. Cyst nematode females attach to root systems with their mouthparts to feed, and then their bodies swell into egg-filled cysts that can be visible to the naked eye. Figure credit: Bonsak Hammeraas, Bioforsk—Norwegian Institute for Agricultural and Environmental Research, Bugwood.org.

Soil Nematode Communities

The proportions of the different feeding groups in the soil nematode community vary between systems and seasons, and they are influenced by a variety of factors, including crop and soil management practices (Freckman and Ettema, 1993) and the presence and abundance of natural enemies. Management practices like tillage, crop rotation, and the use of organic amendments influence the physical and biological characteristics of the soil that influence the abundance of nematodes. Fungal-feeding, predatory, and omnivorous nematodes are very sensitive to soil disturbances (Ferris et al., 2001), and agricultural systems with fewer physical and chemical disturbances, such as pastures, hay fields, and orchards, tend to support larger populations of these nematodes than more frequently disturbed systems like vegetable- and row-crop fields. On the other hand, tillage and incorporation of organic residues increase the proportion of some bacterial-feeding nematodes (Griffiths et al., 1994; Ferris et al., 2001; Nahar et al., 2006), often offsetting declines in the numbers of other feeding groups and increasing the total abundance of nematodes (Neher, 1999). The wide variety of natural enemies that feed on or infect nematodes—predatory nematodes, predatory microarthropods, and nematode-trapping fungi, for example—may have a considerable impact on nematodes in agricultural systems (Stirling, 1991).

Implications for Farming System Management

Agricultural management may increase the abundance of soil nematodes, primarily through the increase in the abundance of bacterial-feeding nematodes associated with tillage and the incorporation of organic residues (Neher, 1999). Soil conditions in agricultural production systems can be improved by enhancing nutrient availability and providing habitat for beneficial soil organisms. Maintenance of large populations of bacterial-feeding nematodes with practices that promote N mineralization throughout the growing season may enhance crop productivity, but a surplus of mineral N is not desirable from the environmental point of view because of an increased risk of nitrate leaching. In an ideal production system, N supply would be synchronized with plant demand. On the other hand, cultural practices like tillage or cultivation may reduce the complexity of the soil food web. Thus, a decrease in the frequency and intensity of tillage may promote the conservation of predatory nematodes and contribute to improved farming system performance.

  • Ferris, H., T. Bongers, and R. G. M. de Goede. 2001. A framework for soil food web diagnostics: Extension of the nematode faunal analysis concept. Applied Soil Ecology 18: 13–29.
  • Ferris, H., R.C. Venette, H.R. van der Meulen, and S.S. Lau. 1998. Nitrogen mineralization by bacterial-feeding nematodes: Verification and measurement. Plant and Soil 203: 159–171.
  • Freckman, D.W., and C.H. Ettema. 1993. Assessing nematode communities in agroecosystems of varying human intervention. Agriculture, Ecosystems & Environment 45: 239–261.
  • Griffiths, B.S., K. Ritz, and R.E. Wheatley. 1994. Nematodes as indicators of enhanced microbiological activity in a Scottish organic farming system. Soil Use and Management. 10: 20–24.
  • Lavelle, P., and A.V. Spain. 2001. Soil ecology. Kluwer Academic Publishers, Boston, MA.
  • Nahar, M.S., P.S. Grewal, S.A. Miller, D. Stinner, B.R. Stinner, M.D. Kleinhenz, A. Wszelaki, and D. Doohan. 2006. Differential effects of raw and composted manure on nematode community, and its indicative value for soil microbial, physical and chemical properties. Applied Soil Ecology 34: 140–151.
  • Neher, D.A. 1999. Soil community composition and ecosystem processes: Comparing agricultural systems with natural ecosystems. Agroforestry Systems 45: 159–185.
  • Peterson, H., and M. Luxton. 1982. A comparative analysis of soil fauna populations and their role in decomposition processes. Oikos 39: 287–388.
  • Stirling, G.R. 1991. Biological control of plant parasitic nematodes. CAB International, Wallingford, U.K.
Further Reading
  • Ferris, H. 1998. The role of nematodes in soil fertility [Online]. NEMAPLEX: the Nematode–plant expert information system. A virtual encyclopedia on soil and plant nematodes. University of California. Available at: http://plpnemweb.ucdavis.edu/Nemaplex/Ecology/fertil.htm (verified 4 April 2011).
  • Guerena, M. 2006. Nematodes: Alternative controls [Online]. ATTRA publication #IP287. Available at: http://attra.ncat.org/attra-pub/nematode.html (verified 4 April 2011).
  • Ugarte, C., M. Wander, and E. Zaborski. 2006. So you want to manage soil food webs? Focus on nematodes [Online]. New Agricultural Network, Vol. 3 No. 8. Available at: iwww.ipm.msu.edu/new-ag/issues06/7-26.htm (verified 4 April 2011).


This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 4495

Certification of Organic Farming Systems

ven, 2012/08/31 - 12:54

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic T869

Organic Seed Growers Conference 2012: Selected Live Broadcasts

jeu, 2012/08/30 - 17:35

eOrganic and the Organic Seed Alliance brings you selected live broadcasts from the Organic Seed Growers Conference in Port Townsend, WA. This conference brings together hundreds of farmers, seed production and distribution companies, researchers, plant breeders, pathologists, and university extension in two days of informative presentations, panel discussions, and networking events.

Visit the Organic Seed Alliance's website to learn more about the Organic Seed Grower's Conference »

Find other upcoming and recorded eOrganic webinars »

Recordings and Slides


Introduction to On-Farm Plant Breeding Workshop.

An increasing number of farmers are starting to breed new varieties and reselect older varieties for their farms. This presentation will introduce you to the steps needed to create new crop varieties on your farm with little or no hand-pollination or specialized tools. Presenter: John Navazio, Organic Seed Alliance and Washington State University


Organic Wheat Breeding Workshop

With the explosion of local organic grains, mills and bakeries, organic farmers are looking for wheat varieties that thrive in their systems. This workshop will take you through the process of creating your own wheat variety and describe some of the current organic what breeding projects. Presenters: Stephen Jones, Washington State University; Richard Little, University of Nebraska-Lincoln; Dean Spaner, University of Alberta

  • Winter Wheat Breeding Basics. Richard Little - Video | Handout
  • Organic Wheat Breeding and Agronomy Research. Dean Spaner - Video | Handout


Breeding Peas, Sweet Corn, Broccoli, Winter Squash and Carrots as part of NOVIC

NOVIC is a national project to breed new vegetable varieties for organic agriculture. You will learn from the panelists about the techniques they are using to breed new organically adapted varieties of peas, sweet corn, broccoli, squash, and carrots. Presenters: Jim Myers, Oregon State University; Michael Mazourek, Cornell University; William Tracy, University of Wisconsin-Madison; John Navazio, Organic Seed Alliance and Washington State University; Laurie McKenzie, Oregon State University; Adrienne Shelton, University of Wisconsin.


Organic Corn Breeding Workshop

King corn is grown on more acres than any other crop. What is being done to breed corn for organic systems, and how can you take part? This workshop will describe the process of breeding corn for organic agriculture and some of the current organic corn breeding projects. Presenters: Frank Kutka, NPSAS Farm Breeding Club; William Tracy, University of Wisconsin-Madison.

  • Corn Reproduction: Inbreds and Hybrids. William Tracy
  • Sweet Corn: Organic Breeding Considerations. William Tracy
  • Breeding High Quality Corn for Sustainable and Organic Farmers. Walter Goldstein


Breeding for Nutrition Workshop

This broadcast was repeated as an eOrganic webinar on March 23, 2012. Please find the handout for the webinar here.

Organic eaters want nutritious food, but some modern breeding programs may be increasing yields at the cost of nutrition. Learn about breeding programs working with classical breeding methods (non-gmo) to breed nutritionally superior crops.

  • Prospects and Challenges for Plant Breeders. Philipp Simon - Video | Handout
  • Breeding Tomatoes for Increased Flavonoids. Jim Myers - Video | Handout
  • Breeding Corn for Nutritional Value. Walter Goldstein - Video | Handout
  • Full version with all 3 presentations and discussion - Video | Handout


Breeding for Positive Microbial Interactions Workshop

We know that many beneficial soil microorganisms provide plants with access to nutrients, improve water uptake and even have the potential to suppress certain soil borne diseases. The ability to breed plants to optimize their interaction with the soil microbiology holds great potential to enhance organic farming systems. Hear about the latest studies in this important and expanding field of science.

  • Wheat Varietal Selection and Annual Versus Perennial Growth Habit Impact Soil Microbes and Apple Replant Disease Suppression. Lori Hoagland -Video | Handout
  • Linking Hairy Vetch Germplasm Diversity to Traits Facilitating Improved Nitrogen Fixation. Jude Maul -Video | Handout
  • Breeding Corn for Positive Soil Microbial Interactions. Walter Goldstein -Video | Handout

organic seed growers conference 2012

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 7461

Webinars by eOrganic

mar, 2012/08/21 - 20:01
imageLive and archived webinars on organic farming and research.

Learn the latest in organic farming practices and research by attending or watching an eOrganic Webinar. Sign up for upcoming Webinars to watch slides, listen to the presenter, and type in questions during the live event. To receive notices about upcoming Webinars, and when we post the archived sessions, sign up for the eOrganic newsletter.

Learne how to earn CCA credits for eOrganic webinar recordings


Archived Webinars Link Presenters Date CCA
Credits Sourcing Organic Seed Just Got Easier: An Introduction to Organic Seed Finder Watch Chet Boruff, AOSCA, Kristina Hubbard, Organic Seed Alliance August 21, 2012   Your Organic Dairy Herd Health Toolbox Watch Dr. Hubert Karreman, Penn Dutch Cow Care July 16, 2012   International Organic Fruit Symposium Recordings coming soon
various June 19 and 21, 2012   Breeding and Genetics: Considerations for Organic Dairy Farms Watch
Brad Heins, University of Minnesota June 19, 2012   Organic Weed Management on Livestock Pastures Watch
Sid Bosworth, University of Vermont 5/15/12   Live Broadcast from Fly Management on Your Organic Dairy Workshop Watch Roger Moon, University of Minnesota; J Keith Waldron, Cornell; Wes Watson, North Carolina State University 4/19/12   NRCS EQIP Technical and Financial Support for Conservation on Organic Farms Webinar Watch Sarah Brown, Oregon Tilth 3/29/12   Organic Seed Breeding for Nutrition Watch
Philipp Simon, Walter Goldstein, Jim Myers, Micaela Colley 3/23/12   Cover Crops for Disease Suppression Watch
Alex Stone, Oregon State University 3/20/12   Fire Blight Control in Organic Pome Fruit Systems Under the Proposed Non-antibiotic Standard Watch
Ken Johnson, Oregon State University, Rachel Elkins, UC Cooperative Extension 3/13/12   The Role of Cover Crops in Organic Transition Strategies Watch Brian McSpadden Gardener, The Ohio State University 3/6/12   Optimizing the Benefits of Hairy Vetch in Organic Production Watch John Teasdale, USDA-ARS Sustainable Agricultural Systems Lab, Beltsville, MD 2/28/12   Stink Bug Management with Trap Crops Watch
Russell Mizell, University of Florida 2/21/12   Veggie Compass: Whole Farm Profit Management
Watch Erin Silva and Rebecca Claypool, University of Wisconsin-Madison 2/14/12   Cultivation and Seedbank Management for Improved Weed Control Watch Eric Gallandt, University of Maine 2/7/12   Participatory On-farm Research: Beyond the Randomized Complete Block Design Watch Sieglinde Snapp, Michigan State University 1/31/12   The OrganicA Project: Current Research on Organic Production of Ginger Gold, Honeycrisp, Zestar!, Macoun, and Liberty Apples Watch Lorraine Berkett, University of Vermont 1/24/12   The Organic Seed Grower's Conference, Port Townsend Washington: Selected Live Broadcasts Watch various 1/20/12 and 1/21/12   Ecological Farm Design for Pest Management In Organic Vegetable Production: Successes and Challenges on Two Farms Watch Helen Atthowe, Doug O'Brien 1/18/12   Carolina Organic Commodities and Livestock Conference: Selected Live Broadcasts Watch various 1/12/12 and 1/13/12   Why Eat Organic: Live Broadcast from the Illinois Specialty Crops, Agritourism and Organic Conference Watch Jim Riddle, University of Minnesota 1/12/12   Reduced Tillage in Organic Vegetable Production: Successes, Challenges, and New Directions Watch Helen Atthowe, Biodesign Farm, Consultant 12/13/11   Microbial Food Safety Issues of Organic Foods Watch Francisco Diez-Gonzalez, University of Minnesota 12/6/11   Starting Up Small-Scale Organic Hops Production Watch Rob Sirrine, Michigan State University, Brian Tennis, Michigan Hop Alliance 11/15/11   Dryland Organic Agriculture Symposium from the Washington Tilth Conference 2011 Watch Various speakers, morning and afternoon sessions. 11/11/11   Tracking Your Produce--For Your Business and Health Watch Collen Collier Bess, Michigan Dept of Agriculture 11/8/11   Healthy Soils for a Healthy Organic Dairy Farm -- Broadcast from 2011 NOFA-NY Organic Dairy Conference Watch Heather Darby, University of Vermont, Cindy Daley, University of California, Chico 11/4/11   Root Media and Fertility Management for Organic Transplants Watch John Biernbaum, Michigan State University 11/1/11   Plan for Marketing Your Organic Products Watch Susan Smalley, Michigan State University 10/25/11   How to Breed for Organic Production Systems Watch Jim Myers, Oregon State University 10/18/11   Flooding and Organic Certification Watch Jim Riddle, University of Minnesota 10/13/11   Stockpiling Forages to Extend the Grazing Season on Your Organic Dairy Watch
Laura Paine, Wisconsin Department of Agriculture, Trade and Consumer Protection 7/28/11   Fly Management in the Organic Dairy Pasture Watch Donald Rutz, Keith Waldron, New York State IPM Program 7/6/11   Using Small Grains as Forages on Your Organic Dairy Watch Heather Darby, University of Vermont Extension 4/14/11   Third Party Audits for Small and Medium Sized Meat Processors Watch Jim Riddle, Joe McCommons, and the Quality Control Manager of Lorentz Meats 4/5/11   A Novel Strategy for Soil-borne Disease Management: Anaerobic Soil Disinfestation (ASD) Watch Joji Muramoto, Carol Shennan, David Butler, Maren Mochizuki, Erin Rosskopf 3/30/11 Earn credit Integrated Pest Management in Organic Field Crops Watch Eileen Cullen. Robin Mittenthal, University of Wisconsin, Christine Mason, Standard Process Farm 3/29/11 Earn credit The Evolution, Status, and Future of Organic No-Till in the Northeast US Watch Bill Curran, Penn State, Steven Mirsky, USDA, Bill Mason, Mason's Heritage Farms 3/22/11   USDA ERS 2011 Organic Farming Systems Conference Webinars Watch various 3/16/11   Local Dirt: Beyond Marketing. Find Buyers, Sell Online, Source & Buy Product…Yourself Watch Heather Hilleren, Kassie Rizzo, Local Dirt 3/15/11   GMO Contamination: What's an Organic Farmer to Do? Watch Jim Riddle, University of Minnesota 3/9/11   North Carolina's Statewide Initiative for Building a Local Food Economy Watch Nancy Creamer, Teisha Wymore, North Carolina State University 3/1/11   Grafting for Disease Management in Organic Tomato Production Watch Frank Louws North Carolina State University Cary Rivard, Kansas State University 2/22/11   Shades of Green Dairy Farm Calculator Watch Charles Benbrook, The Organic Center 2/1/11   Greenhouse Gas Emissions Associated with Dairy Farming Systems Watch Tom Richard, Gustavo Camargo, Penn State 1/25/11   Assessing Nitrogen Contribution and Rhizobia Diversity Associated with Winter Legume Cover Crops in Organic Systems Watch Julie Grossman, North Carolina State University 12/14/10   Using Winter Killed Cover Crops to Facilitate Organic No-till Planting of Early Spring Vegetables Watch Mike Snow, Farm Manager, Accokeek Ecosystem Farm; Charlie White, Penn State 12/7/10   Using Cover Crops to Suppress Weeds in Northeast US Farming systems Watch William Curran, Matthew Ryan, Penn State 12/2/10   Transitioning Organic Dairy Cows off and on Pasture Watch Rick Kersbergen, University of Maine 11/23/10   Greenhouse Gases and Agriculture: Where does Organic Farming fit? Watch David Granatstein, Lynne Carpenter-Boggs, Washington State University, Dave Huggins 11/15/10   Impact of Grain Farming Methods on Climate Change Watch Michel Cavigelli, USDA, Beltsville MD 11/12/10   Setting up a Grazing System on Your Organic Dairy Farm Watch Sarah Flack, Sarah Flack Consulting, Cindy Daley, California State University, Chico 10/1/10   Maximizing Dry Matter Intake on Your Organic Dairy Farm Watch Karen Hoffman, USDA-NRCS 9/16/10   How to Calculate Pasture Dry Matter Intake on Your Organic Dairy Farm Watch Sarah Flack, Sarah Flack Consulting 8/20/10   Late Blight Control in Your Organic Garden Watch Meg McGrath, Cornell 7/21/10   Late Blight Control on Organic Farms Watch Meg McGrath, Cornell, Sally Miller, Ohio State 7/1/10   Increasing Plant and Soil Biodiversity on Organic Farmscapes Watch Louise Jackson, University of California-Davis 5/4/10   Cover Crop Selection Watch Jude Maul, USDA ARS 4/27/10   The Economics of Organic Dairy Farming in New England Watch Bob Parsons, University of Vermont 4/13/10   Estimating Plant-Available Nitrogen Contribution from Cover Crops Watch Nick Andrews, Dan Sullivan, Oregon State 4/13/10   Planning for Flexibility in Effective Crop Rotations Watch Chuck Mohler, Cornell 4/6/10   Using NRCS Conservation Practices and Programs to Transition to Organic Watch David Lamm, USDA NRCS 3/30/10   Planning Your Organic Farm for Profit Watch Richard Wiswall, Cate Farm 3/22/10   A Look at the Newly Released Organic Pasture Rule Watch Kerry Smith, USDA, AMS, National Organic Program 3/17/10   Organic Blueberry Production Watch Bernadine Strik, Handell Larco, Oregon State University, David Bryla, USDA 3/9/10   High Tunnel Production and Low Cost Tunnel Construction Watch Tim Coolong, University of Kentucky 3/2/10   Getting EQIPed: USDA Conservation Programs for Organic and Transistioning Farmers Watch Jim Riddle, University of Minnesota 2/23/10   Organic Certification of Research Sites and Facilities Watch Jim Riddle, University of Minnesota 2/9/10   Grafting Tomatoes for Organic Open Field and High Tunnel Production Watch David Francis, Ohio State 2/2/10   Undercover Nutrient Investigation: The Effects of Mulch on Nutrients for Blueberry Watch Dan Sullivan, Ryan Costello, Luis Valenzuela, Oregon State 1/26/10   ABCs of Organic Certification Watch Jim Riddle, University of Minnesota 1/19/10   Organic Farming Financial Benchmarks Watch Dale Nordquist, University of Minnesota 1/12/10  


This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 4942

Sourcing Organic Seed Just Got Easier: An Introduction to Organic Seed Finder

mar, 2012/08/21 - 20:00

Find all eOrganic upcoming and archived webinars »

About the Presenters

Chet Boruff is the Chief Executive Officer of the Association of Official Seed Certifying Agencies (AOSCA). AOSCA provides seed certification and related services to the global seed industry, and it will manage the Organic Seed Finder.

Kristina Hubbard is the director of advocacy and communications for Organic Seed Alliance. She is facilitating the Organic Seed Finder project.

About eOrganic

eOrganic contains articles, videos, and webinars for farmers, ranchers, agricultural professionals, certifiers, researchers and educators seeking reliable information on organic agriculture, published research results, farmer experiences, and certification. The content is collaboratively authored and reviewed by our community of University researchers and Extension personnel, agricultural professionals, farmers, and certifiers with experience and expertise in organic agriculture.

Find all upcoming and archived eOrganic webinars at http://www.extension.org/pages/25242

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 8063

Organic Mulching Materials for Weed Management

mer, 2012/08/15 - 13:18

eOrganic author:

Dr. Mark Schonbeck, Virginia Association for Biological Farming


Organic mulches can suppress annual weeds and offer other important benefits, such as organic matter, nutrients, moisture conservation, soil protection, and moderation of soil temperature. Drawbacks include costs and labor of application, limited efficacy on perennial weeds, delayed soil warming, and the potential to carry weed seeds and harbor pests.

Hay, straw, and fresh-cut forage or cover crops are among the most versatile and widely-used organic mulches. They can suppress weed germination and emergence when applied at reasonable rates, are fairly easy to apply, reduce evaporative losses of soil moisture while allowing rainfall to reach the soil, and provide other benefits. Caution is needed to avoid bringing in weed seeds or herbicide residues with hay from off-farm sources. Tree leaves, chipped brush, and other forest-based mulches are often beneficial to small fruit and other perennial crops, but may not be an economical option for weed control at a multi-acre scale. This article explores in greater depth the properties, uses, advantages, and disadvantages of a variety of organic mulch materials.


Organic mulch materials include grain straw, fresh or old hay, fresh-cut forage or cover crops, chipped brush, wood shavings, tree leaves, cotton gin waste, rice or buckwheat hulls, and other crop residues. Hay and straw are among the most widely used organic mulches in organic horticulture. Cover crops can be grown to maturity (flowering), mechanically killed, and left on the soil surface to provide an in-situ organic mulch for no-till planting. Leaf mold (decomposed tree leaves), compost, and aged manure have also been used as organic mulches, although their crumbly texture may not provide as effective a barrier to weed seedlings as other materials.

Organic mulches suppress weeds in several ways. First, they block seed germination stimuli by intercepting light, reducing soil temperature, and greatly dampening day–night temperature fluctuations. As a result, fewer weed seeds germinate under the mulch than in uncovered soil. Second, the mulch physically hinders emergence of those weeds that do germinate. If the mulch is thick enough to prevent light from reaching the trapped seedlings, they eventually die. Third, some mulch materials, such as grain straw and fresh-cut forages like sorghum-sudangrass, release natural substances that inhibit weed seedling growth for several weeks after application, a process known as allelopathy. Finally, organic mulch can enhance crop growth and competitiveness against weeds by conserving soil moisture and moderating soil temperature.

Straw and other organic mulches effectively block emergence of most weeds germinating from seed, although grasses and large-seeded broadleaf weeds may require a greater thickness of material than small-seeded broadleaf weeds, which have more delicate seedlings. Perennial weeds arising from rootstocks, rhizomes, tubers, or other vegetative propagules can penetrate most organic mulches.

Weeds that have already emerged at the time of mulch application should be cultivated or hoed out before spreading mulch; simply laying the organic materials over established weeds is less effective. Once the weeds break through the mulch, they will enjoy the same mulching benefits as the crop, and will grow vigorously.

Usually, some weeds will eventually emerge through an organic mulch. Fast-growing, canopy-forming crop like sweet potato, squash, or snap bean often shade-out these late emerging weeds. In slower-growing, less competitive vegetables like onion and carrot, manual weeding or application of additional mulch may be required to maintain satisfactory weed control.


Hay is often used to mulch horticultural crops in regions such as southern Appalachia, where the predominant farming systems include hay production, and old hay is more affordable than straw and other materials. Hay has some drawbacks and must be chosen and used with care. However, it is fairly easy to apply in small scale plantings, and is usually beneficial to soil quality and crop production (Fig. 1). A hay mulch of about 3–4 inch thickness can:

  • Reduce emergence of weed seedlings, especially small–seeded broadleaf annuals.
  • Provide habitat for beneficial organisms, including ground beetles and other weed seed consumers.
  • Allow air and rain to reach the soil.
  • Moderate soil temperature during hot weather.
  • Conserve soil moisture.
  • Prevent soil crusting and erosion.
  • Keep pumpkins, melons, and other fruiting crops out of direct contact with soil, and therefore cleaner.
  • Add significant amounts of organic matter and slow-release nutrients, especially potassium (K).

mulched garlic and tomatos
Figure 1. (a) Garlic mulched with hay immediately after planting in October; photographed in April. (b) Tomato mulched with hay after the crop became established, several weeks before the photo was taken. The mulch delayed weed emergence and provided favorable conditions for crop growth. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Hay also has some significant drawbacks, in that it:

  • Does not suppress most perennial weeds.
  • May contain weed seeds (Fig. 2) or herbicide residues (see Sidebar).
  • Can harbor slugs, squash bugs, voles, and other pests.
  • Can keep the soil too cool or wet, slowing crop growth or maturation.
  • Can accentuate frost damage by keeping the soil's radiant heat from reaching crop foliage.
  • Can build up excessive soil K levels when used year after year.

Figure 2. This hay was cut too late in its development, and carried mature seeds. As a result, forage grasses (fine–textured seedlings) are growing in this cucumber bed. Additional weeds have emerged from the soil's weed seed bank because the mulch application was not sufficiently heavy to cover the soil surface completely. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Sidebar: Hay Mulch—Check Your Source!

Hay from off-farm sources is a notorious source for new and serious weed species on a farm. Even in fields with good weed management, hay that has been cut too late in its development will carry seeds of the forage species themselves, which can be a nuisance if they come up in a vegetable crop. In addition to weed seed, the grower must be alert to the possibility of herbicide residues.

Some grass hay is produced with the use of weed control products that contain highly persistent active ingredients, including clopyralid, aminopyralid, picloram, and aminocyclopyrachlor, all of which are highly toxic to broadleaf plants. Hay from fields treated with any of these materials can cause severe damage to tomato family, cucurbit family, and other vegetable crops around which the hay is applied as mulch (Plaksin and Bynum, 2007). Symptoms include curling and twisting of leaves and petioles (leaf stalks), and stunted growth, which can lead to crop failure or plant death. Subsequent vegetable or broadleaf cover crop plantings may continue to show symptoms for a year or more after initial contamination, and the field may lose eligibility for organic certification until herbicide residues have disappeared.

These herbicides are not degraded by composting. If horses or cattle graze or eat hay from treated fields, and their manure is hot-composted, cured for a year, and applied to vegetable beds, the vegetables can still suffer damage.

It always pays to check with the farmer who grew the hay regarding weed management practices, herbicide use, and time of cutting relative to forage seed set, before bringing hay onto the farm for use as mulch on horticultural crops.

Not all hay is alike. Grass hay is lower in nitrogen (N) and phosphorus (P), higher in K, and more persistent and weed-suppressive than legume hay. Because of its high cargon-to-nitrogen (C:N) ratio, grass hay has sometimes been reported to tie up soil N. However, this is most likely to occur when the hay is incorporated into the soil, not when it is applied to the surface as a mulch. A grass–legume mix (such as timothy–alfalfa, fescue–red clover, or rye–hairy vetch) yields a more balanced mulch that provides slow release nutrients to soil life and crops, and persists long enough to provide several weeks of weed suppression.

Fresh hay is more pleasant to spread but more likely to contain large numbers of viable weed seeds than old, spoiled hay. Second or third cuttings of hay are especially likely to have weed seeds (Mohler and DiTommaso, unpublished). Leaving hay bales or rolls in the rain for a year or so reduces weed seed viability, but moldy hay can be nasty and hazardous to handle, and does not provide as clean or long-lasting a mulch. A better solution is to grow and harvest mulch hay on farm, taking care to cut the mulch crop before viable seeds are formed. Mulch hay can be derived from perennial forages or annual cover crops (rye, sorghum-sudangrass, etc.). Note that repeated hay harvests from a given field can deplete soil nutrients, notably P, K, and calcium (Ca). Crop rotations that alternate annual or perennial mulch crops with vegetables that receive the mulch can promote better nutrient balance by minimizing the nutrient depletion of hay harvest while avoiding the potential K excesses from repeated mulch application.

Applying hay manually is most feasible at a small scale, for example, a half acre of a high value crop. A few farmers have used bale choppers to mechanize application of hay or straw in small rectangular bales. Large rolls (round bales) are commonly unrolled between rows of widely spaced crops like tomato, a job which usually requires a tractor to place the ~1,000 lb roll at the beginning of the crop row, and two people to unroll it.

A number of farmers have streamlined on-farm harvest and application of mulch by using a flail chopper and forage wagon for harvest, and then pitchforking the fresh-cut forage off the wagon as it is pulled slowly along crop rows (Kittredge, 2008–09a). Other producers, including David Stern of Rose Valley Farm in upstate New York, grow alternate rows of vegetable and cover crop (e.g., potato and sorghum-sudangrass), and periodically mow the cover crop, blowing the clippings into the vegetable row as mulch (Schonbeck, 2007). This approach saves the labor and costs of curing, baling, and storing hay. However, fresh grass or legume "green chop" has been reported to promote certain soil-borne pathogens for a short period after application (Mohler and DiTommaso, unpublished); thus, fresh-cut forage mulches should be tested on a small area for each crop before field-wide application.

Some tips for optimal use of hay mulch for weed control:

  • Grow and use on-farm hay if practical.
  • Check sources of off-farm hay for weed seeds and herbicide residues before purchasing.
  • Apply mulch when crops are well established, and soil temperature and moisture are optimum for the crops being grown (exception: fall planted garlic is mulched immediately after planting).
  • Hoe or cultivate at the beginning of a warm sunny day, wait 12–36 hours to let uprooted weeds die, then spread mulch (applies to all organic mulches).
  • Use enough hay to suppress most weed seedlings, about 3–4 inches or 5–10 tons per acre.
  • Monitor soil nutrient levels, especially K.
  • Rotate mulched vegetables with non-mulched crops or hay production.

Straw, defined here as the stalks and other residues left after harvest of a mature grain, is similar to hay in texture, potential for soil protection and moisture conservation, weed suppression, and application methods. Straw differs from hay in that it:

  • Has higher carbon to nitrogen (C:N ratio).
  • Provides a cleaner, more persistent mulch that is slower to decompose, and more effective in keeping the fruit of pumpkin and other vine crops clean.
  • May carry seeds of the grain crop itself, but is less likely to carry other weed seeds.
  • Has somewhat lower K levels and slower K release.
  • Is lighter colored and more reflective, hence it may cool soil more than hay.

Because straw is so much less likely to introduce serious new weed problems than hay, organic horticultural farmers located in or near grain-producing regions where straw is available and affordable often prefer straw over hay. The high C:N ratio of straw precludes much release of N from mulch to the current year's crop, but usually does not lead to tie-up of soil N, as long as the mulch lies on top of the soil and is not tilled in.

The dramatic soil cooling under straw can delay crop growth (Fig. 3); however it can be beneficial for cool weather crops like potato, in which tuber growth is inhibited by soil temperatures above 70°F (Fig. 4a); and for other crops during hot summer weather (Fig. 4b). For example, tomato shows optimal nutrient uptake and production at root zone temperatures of 70–85°F, and becomes stressed at higher temperatures (Abdul-Baki and Teasdale, 1994, Tindall et al., 1990, Tindall et al., 1991); thus, it often performs better in organic than in plastic mulches during the heat of summer. Bright, reflective straw can intensify heating of crop foliage under a row cover, resulting in crop damage (Kittredge, 2008–09a), and may also increase damage from frosts.

Figure 3. The light colored grain straw was applied too early in the season. The mulch has suppressed weeds, but also seriously delayed soil warming and tomato growth (compare to plastic mulched tomato in upper left). Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

mulched potatoes and eggplant
Figure 4. (a) Potato tuber yields are often enhanced by the cooler soil conditions under a straw mulch. (b) The straw was applied after the soil had warmed to optimal temperatures for eggplant, and is now helping the crop thrive during intense summer heat. A few weeds have emerged at this point, but are unlikely to affect yield in the vigorous, established eggplant crop.
Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Rye, wheat, and other grain crops cut for mulch at an earlier stage of maturity (e.g., head emergence or pollen shed) are richer in nutrients and less likely to immobilize soil N than straw left by grain harvest. Rye, triticale, and other winter grains cut at the milk stage (before the seeds become viable) yields excellent straw for mulch, and minimize the risk of volunteer cereal grains becoming a weed (Fig. 5). Cereal grain cover crops rolled down at the milk stage are particularly popular for no-till pumpkin production, as they help keep the fruit clean, reduce soilborne diseases, and promote even color development (Ron Morse, Virginia Tech, pers. comm.).

Figure 5. Self-seeding of cereal grain occasionally causes a weed problem in straw mulch. In order to avoid this problem, some farmers grow their own grain straw for mulch, and harvest the mulch crop before seeds become viable. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Tree Leaves

Hardwood leaves that fall naturally in autumn are sometimes used as mulch in vegetable production (Fig. 6a). They are rich in calcium (Ca) and micronutrients, contain small to moderate amounts of N, P, and K, and decompose gradually to form leaf mold, a humus-like material that is valued by horticulturists. Millions of suburban residents rake up autumn leaves for disposal, and a growing number of farmers and other entrepreneurs accept leaves for mulch or for making compost. Leaves are often used for berries and some other perennials that tolerate or prefer some acidity. Pine needles (pine straw) are lower in nutrients, more persistent, and more acidic than hardwood leaves, and can be especially useful for blueberries, which require a low pH (Fig. 6b). Tree leaves are much less likely than hay to carry the seeds of agricultural weeds; however, they have been observed to carry tree seeds (especially maple or ash), which germinate into vigorous seedlings that readily emerge through the mulch.

mulched onions and blueberries
Figure 6. (a) Onion mulched with tree leaves gathered the preceding autumn at Potomac Vegetable Farms in Vienna, VA, near Washington, DC. (b) New blueberry planting in Floyd, VA mulched with pine needles (foreground) and grain straw (background). Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Some disadvantages of tree leaves as a mulch include:

  • A tendency to mat down when wet, creating soggy or airless soil conditions.
  • A tendency to blow away in the wind when dry, or to blow onto and smother young crop seedlings.
  • Labor intensive application, not feasible at a larger scale.
  • Presence of trash (cans, glass, plastic, etc.) in municipal leaves or yard waste.

The soil benefits of tree leaves can also be realized by including them in compost piles, or making leaf mold (leaves aged for 1–2 years until crumbly), which is an excellent soil amendment or potting mix ingredient.

Chipped Brush, Wood Shavings, Bark

These forest product mulches are most often used on perennial crops such as berries (Fig. 7) and ornamental perennials, many of which like a somewhat acidic soil rich in mycorrhizae and other beneficial fungi supported by these materials. They tend to be coarser and higher density than hay or straw, require higher tonnage per acre to suppress weeds, and may not be economical for most larger-scale applications. Other characteristics include:

  • High C:N ratio.
  • Relatively long lived.
  • Allelopathic properties when fresh, especially walnut and some conifers (softwoods).
  • Provide calcium (Ca), micronutrients, and small amounts of N, P, and K.
  • Formation of stable humus when fully decomposed.

Figure 7. A perennial variety of strawberry in a garden in Floyd, VA thrives and yields well in a mulch of chipped brush, aged about one year before application. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

Wood based or bark mulches should be aged for at least a year outdoors before application near crop rows, to minimize possible allelopathic suppression of crop growth. However, fresh chipped brush can be useful for suppressing weeds in paths or alleys between beds. One grower in New Jersey has had excellent results with 1–2 year old hardwood chips as mulch, and 8–11 year aged hardwood chips as a soil amendment for blueberry (Kittredge, 2008-09b).

Wood chip and bark mulches should not be piled against the bases of trees or shrubs, as this can promote the development of fungal diseases. Limit mulch depth to 1–2 inches adjacent to and within 6–12 inches from the base, then increase the depth further away.


Sawdust is chemically similar to other wood products, but because it is so finely divided, it has the following disadvantages as a mulching material:

  • Tends to mat down and keep soil wet and airless.
  • Can tie up soil N as small particles or soluble carbohydrates leach into the soil.
  • Can be quite allelopathic against crops for a short time.
  • May be penetrated by some weeds, and may provide a good germination medium for wind-borne weed seeds.
  • May be washed away by heavy rain on sloping fields (Fig. 8).

mulching blueberries
Figure 8.(a) An intense rainstorm has washed a fine sawdust mulch away from newly planted blueberries. (b) The same storm damaged soil structure in un-mulched beds (right and background), whereas chipped brush held firm, protecting both soil and crop (left foreground). Several years after these photos were taken, the blueberry bushes mulched with sawdust remained visibly smaller than those in other mulches, as a result of N immobilization by the fine sawdust. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.


A few growers use compost as mulch, although the quantities required for effective weed suppression may not be economically feasible. In a study in Virginia, 1½–2 inches of leaf mold compost (50–90 tons per acre) did not suppress weeds quite as well as 4 inches (~8 tons per acre) of hay (Fig. 9) (Schonbeck, 1998). Compost is much more effective and economical to use as an ingredient in potting mixes (at 10–50% of total volume), or as a soil amendment at 1–10 tons/ac to inoculate the soil with beneficial organisms, provide slow-release nutrients, and improve soil structure. Higher application rates, such as those used in the study, commonly leads to excessive levels of P, K, and some micronutrients in the soil. The surplus P and K can favor the growth of weeds over crops in subsequent years.

mulching with compost
Figure 9. Mulching with compost (a) A municipal compost, based primarily on tree leaves, was applied at 50 tons per acre in this trial. (b) By midsummer, considerably more weeds emerged through the compost than through a 4–inch (~8 tons per acre) hay mulch. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.


Manure is not recommended as a mulch for weed control. Many weed seeds pass through livestock digestive tracts unharmed, and the readily available nutrients in the manure stimulate weed growth. Lambsquarters (Chenopodium album) and spiny amaranth (Amaranthus spinosus) are just two of many nutrient-responsive weeds that are frequently spread in manure. Furthermore, uncomposted manure cannot be applied to USDA certified organic vegetable crops within 90–120 days of harvest, and applying sufficient manure to suppress weed seedling emergence from the soil is likely to create gross excesses of soil P and K.

Other Organic Residues

Crop residues—especially materials like cotton gin waste, rice hulls, peanut hulls, and buckwheat hulls—may be available in quantity in certain locales. Their ability to suppress weeds may vary, depending on texture and possibly chemical properties. Care should be taken to avoid crop residues that carry crop pathogens, weed seeds, or herbicide residues. Buckwheat hulls have been reported to attract cats using the mulched bed as a litter box, and thus may not be a good choice in neighborhoods with high cat populations.

Living Mulch

For many years, some growers have experimented with living mulches—perennial or annual cover crops growing between crop rows—in an effort to build soil quality while suppressing weeds. Experience has shown that living mulches allowed to grow in close proximity to crops often compete with the crop for moisture or nutrients, resulting in lower yields. However, in wide-spaced plantings, such as berries, alleys can be maintained in a perennial living mulch, while the area near crop rows are kept free of competing vegetation and mulched with straw, wood chip,or other organic materials (Fig. 10). Living mulches can also be planted in 2–3 foot wide strips between permanent vegetable beds to create firm, mud-free paths for tractor and foot traffic; define where workers and u-pickers should walk, and provide habitat for beneficial insects. Clippings from periodic mowing of the living mulch can be used to supplement organic mulch in crop beds.

Figure 10. A perennial living grass–clover mulch, maintained by regular mowing, maintains soil quality and suppresses weeds in alleys, while a 4-ft-wide zone for each row of blueberries is kept free of competing vegetation and mulched with straw and clippings from the alleys, to allow the new planting to become established. The grass-covered alleys also provide a better surface for foot traffic and minimize soil damage in u-pick berry fields. Photo credit: Mark Schonbeck, Virginia Association for Biological Farming.

References Cited
  • Abdul-Baki, A. A., and J. R. Teasdale. 1994. Sustainable production of fresh market tomatoes with organic mulches. USDA Farmers' Bulletin FB-2279.
  • Kittredge, J. 2008-09a. Mulching at Pleasant Valley Farm. The Natural Farmer 2(79): 32–39 (Winter 2008–09). (Available online at: http://www.nofa.org/tnf/Winter2008.pdf) (verified 12 Jan 2012).
  • Kittredge, J. 2008-09b. 24 acres of mulch. The Natural Farmer 2(79): 13–18 (Winter 2008–09). (Available online at: http://www.nofa.org/tnf/Winter2008.pdf) (verified 12 Jan 2012).
  • Mohler, C. L., and A. DiTommaso. Unpublished. Manage weeds on your farm: a guide to ecological strategies; version 5.1 (Cornell University, Dec. 4, 2008).
  • Plaksin, E., and R. Bynum. 2007. Contaminated hay ruins crops. Growing for Market 16: 1, 4–7. (Available online at: http://www.growingformarket.com/articles/20071220_28) (verified 12 Jan 2012).
  • Schonbeck, M. W. 1998. Weed suppression and labor costs associated with organic, plastic, and paper mulches in small-scale vegetable production. Journal of Sustainable Agriculture. 13: 13–33. (Available online at: http://dx.doi.org/10.1300/J064v13n02_04) (verified 12 Jan 2012).
  • Schonbeck, M. W. 2007. Beating the weeds with low-cost cover crops, intercropping, and steel. The Virginia Biological Farmer 30: 7–8.
  • Tindall, J. A., R. B. Beverly, and D. E. Radcliffe. 1991. Mulch effects on soil properties and tomato growth using micro-irrigation. Agronomy Journal 83: 1028–1034. (Available online at: https://www.crops.org/publications/aj/abstracts/83/6/AJ0830061028) (verified 12 Jan 2012).
  • Tindall, J. A., H. A. Mills, and D. E. Radcliffe. 1990. The effect of root zone temperature on nutrient uptake of tomato. Journal of Plant Nutrition 13: 939–956. (Available online at: http://dx.doi.org/10.1080/01904169009364127) (verified 12 Jan 2012).


This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 4871

Making and Using Compost for Organic Farming

mer, 2012/08/15 - 12:53

eOrganic authors:

Emily Marriott, University of Illinois at Urbana-Champaign

Ed Zaborski, University of Illinois at Urbana-Champaign


Composting transforms raw organic residues into humus-like material through the activity of soil microorganisms. Mature compost stores well and is biologically stable, free of unpleasant odors, and easier to handle and less bulky than raw organic wastes. In agronomic and horticultural operations, compost can be used as a soil amendment, seed starter, mulch, container mix ingredient, or natural fertilizer, depending on its characteristics. Composting can also reduce or eliminate weed seeds and plant pathogens in organic residues.

Compost provides many benefits as a soil amendment and a source of organic matter by improving soil biological, chemical, and physical characteristics:

  • Increases microbial activity
  • Enhances plant disease suppression
  • Increases soil fertility
  • Increases cation exchange capacity
  • Improves soil structure in clayey soils
  • Improves water retention in sandy soils
  • Reduces bioavailability of heavy metals
Overview of the Composting Process

Microorganisms drive the composting process, so creating an optimal environment for microbial activity is crucial for successful and efficient composting. Assembling an appropriate mix of organic residues or feedstocks and maintaining adequate moisture and oxygen levels are all necessary.

As soon as feedstocks are compiled, the composting process begins. As microorganisms begin to decompose the organic materials, the compost pile heats up and the active phase of composting begins. During this phase of rapid decomposition, temperatures in the pile increase to 130–150°F and may remain elevated for several weeks. Maintaining adequate aeration during this phase of intense microbial activity is especially important because aerobic decomposition is most efficient and produces finished compost in the shortest amount of time. As readily available organic matter is consumed and decomposition slows, temperatures in the compost pile decrease to around 100°F and the curing phase begins. At this stage, the compost can be stockpiled.

Common methods of on-farm composting include static piles, windrows (elongated piles), and in-vessel (enclosed) composting. Static piles are compost piles that are not turned. To meet National Organic Program requirements, static pile systems must be aerated to sustain microbial activity and adequate temperatures. To that end, perforated pipe is installed at the base of the pile and in some cases fans or blowers are used to force air through the pile.

Static compost piles with passive aeration tubes
Figure 1. Static compost piles with passive aeration tubes. Photo credit: Robert Rynk, Compost Education and Resources for Western Agriculture project, Washington State University.

Windrows, or enlongated piles of compost feedstocks, are turned or mixed regularly to aerate the pile and to reestablish pore space.

Profiles of compost windrows at a dairy in eastern Washington
Figure 2. Profiles of compost windrows at a dairy in eastern Washington. Photo credit: David Granatstein, Compost Education and Resources for Western Agriculture project, Washington State University.

 this farm-scale rotating drum is used at a Texas site
Figure 3. An example of in-vessel composting. This farm-scale rotating drum is used at a Texas site. Photo credit: Robert Rynk, Compost Education and Resources for Western Agriculture project, Washington State University.

How to Compost

Several comprehensive resources providing detailed explanations of the composting process and specific information on how to make compost are available; examples include The Art and Science of Composting (Cooperband, 2002a), Composting on Organic Farms (Baldwin and Greenfield, 2009), and On-Farm Composting Handbook (Rynk, 1992).

Large-scale composting is regulated in most states. Check with your state government to ensure compliance with composting regulations.

Compost and the National Organic Program

The use of composted plant and animal materials to maintain or improve soil organic matter is supported by the National Organic Program (NOP) final rule (United States Department of Agriculture [USDA], 2000):

The producer must manage plant and animal materials to maintain or improve soil organic matter content in a manner that does not contribute to contamination of crops, soil, or water by plant nutrients, pathogenic organisms, heavy metals, or residues of prohibited substances.

~ 7 CFR 205.203(c)

The composition, production, and use of compost in organic production systems is regulated by the NOP final rule; the NOP provided clarification of these regulations in guidance on the allowance of green waste in organic production systems (NOP, 2010a) and in draft guidance on compost and vermicompost in organic crop production (NOP, 2010b). In addition, the NOP provided guidance on uncomposted, processed animal manures in organic crop production (NOP, 2010c).


According to NOP's guidance on the allowance of green waste in organic production systems (NOP, 2010a) and draft guidance on compost and vermicompost in organic crop production (NOP, 2010b), approved feedstocks for compost include:

  • Plant and animal materials, such as, crop residues, animal manure, food waste, yard waste
  • Nonsynthetic substances not prohibited by 7 CFR 205.602
  • Synthetic substances specifically allowed for use as a compost feedstock per 7 CFR 205.601 [only "newspapers or other recycled paper, without glossy or colored inks"]
  • Synthetics approved for use as plant or soil amendments

NOP regulation states that compost that is produced with prohibited feedstocks (urea, recycled wallboard, or sewage sludge, for example) is prohibited, and it does not permit the use of compost that contains synthetic substances that are not on the National List of synthetic substances allowed for use in organic crop production (see Can I Use this Input on My Organic Farm?). However, recognizing that background levels of pesticides are present in the environment (referred to as unavoidable residual environmental contamination—UREC—in the regulations) and may be present in organic production systems, NOP regulation does not mandate zero tolerance for synthetic pesticide residues in inputs, such as compost. According to NOP guidance,

Green waste and green waste compost that is produced from approved feedstocks, such as, non-organic crop residues or lawn clippings may contain pesticide residues. Provided that the green waste and green waste compost (i) is not subject to any direct application or use of prohibited substances (i.e. synthetic pesticides) during the composting process, and (ii) that any residual pesticide levels do not contribute to the contamination of crops, soil or water, the compost is acceptable for use in organic production.

~ NOP, 2010a

What constitutes "contamination of crops, soil or water"? The NOP final rule states (USDA, 2000, 7 CFR 205.671) "When residue testing detects prohibited substances at levels that are greater than 5 percent of the Environmental Protection Agency's tolerance for the specific residue detected or unavoidable residual environmental contamination, the agricultural product must not be sold, labeled, or represented as organically produced." NOP is thus far silent on what constitutes contamination of soil or water.

Compost feedstocks may contain synthetic pesticide contaminants that are not degraded in the composting process, and can contribute to crop, soil, or water contamination. This was the case for the herbicide clopyralid, which was used on turfgrass as well as in agriculture. It passes through animals in the urine, and therefore if they eat forage with clopyralid residues, the herbicide ends up in the bedding and potentially in the compost. Similarly, clopyralid can contaminate compost made from clippings from treated lawns. The uses of this herbicide have been restricted to avoid this problem, but it is advisable to ask the compost vendor or the provider of raw feedstock materials about such potential contaminants. For more information, see the Washington State University Puyallup Research Center publications on clopyralid in compost.

The source of all compost feedstock materials should be known to ensure that they are allowed for use in organic production. Knowing the feeding practices used for manure sources and having the manure tested can also provide information about possible antibiotic and heavy metal contamination. The use of compost containing these contaminants is not permitted in organic crop production; however, the organic rule does not require that manures come from organic livestock farms to be used in organic compost production.

The use of broiler litter as a feedstock for compost production poses some additional concerns. Arsenic is a component of some feed medications or growth promoters used in commercial broiler operations. The majority of arsenic consumed by poultry is excreted and incorporated into the litter, leading to the potential for build-up in the soil and leaching from compost piles into lakes and streams. For more information, consult the ATTRA publication, Arsenic in Poultry Litter: Organic Regulations, by Bellows (2005).

Increasing use of copper in broiler and hog operations may result in manures with high concentrations of copper. Copper foot baths are also common in cattle production. While copper is a necessary plant nutrient, it can become toxic in very high concentrations. Sustained use of compost from these sources could contribute to copper build-up in the soil in the long-term, especially in operations that rely on copper as a pesticide.


The NOP regulations refer to production methods for compost in the context of managing plant and animal materials to maintain and improve soil organic matter content:

The producer must manage plant and animal materials to maintain or improve soil organic matter content in a manner that does not contribute to contamination of crops, soil, or water by plant nutrients, pathogenic organisms, heavy metals, or residues of prohibited substances. Animal and plant materials include:

   (2) Composted plant and animal materials produced though a process that:
      (i) Established an initial C:N ratio of between 25:1 and 40:1; and
      (ii) Maintained a temperature of between 131°F and 170°F for 3 days using an in-vessel or static aerated pile system; or
      (iii) Maintained a temperature of between 131°F and 170°F for 15 days using a windrow composting system, during which period, the materials must be turned a minimum of five times.

~ 7 CFR 205.203(c)(2), USDA, 2000

The NOP's draft guidance on compost and vermicompost in organic crop production (NOP, 2010b) identifies these processes as examples of methods for producing acceptable composts, and states that:

An example of another acceptable composting method is when:
   a. Compost is made from allowed feedstock materials (either nonsynthetic substances not
prohibited at §205.602, or synthetics approved for use as plant or soil amendments), and
   b. The compost pile is mixed or managed to ensure that all of the feedstock heats to the minimum of 131°F (55°C) for a minimum of three days. The monitoring of the above parameters must be documented in the Organic System Plan in accordance with §205.203(c) and submitted by the producer and verified during the site visit.

~ NOP, 2010b

NOP compost requirements can also be met by vermicompost (compost produced by the action of earthworms), so long as:

a. It is made from allowed feedstock materials (either nonsynthetic substances not prohibited at §205.602, or synthetics approved for use as plant or soil amendments);
b. Aerobicity is maintained by regular additions of thin layers of organic matter at 1–3 day intervals;
c. Moisture is maintained at 70–90%; and
d. The duration of vermicomposting is at 6–12 months for outdoor windrows, 2–4 months for indoor container systems, 2–4 months for angled wedge systems, or 30–60 days for continuous flow reactors.

~ NOP, 2010b

Compost production practices, including the type and source of all feedstock materials, temperature monitoring logs by date, and practices used to achieve uniform elevated temperatures, should be described in the organic system plan (OSP).


Compost made in accordance with the above production criteria may be applied in organic production systems without restriction on the time interval between application and crop harvest.

Composts that don't meet the above production criteria may still be used in organic farming. However, if they contain animal manure, they must be applied to agricultural land in accordance with NOP regulations for manure, which state that raw animal manure must be composted unless at least one of the following conditions is satisfied:

  • Applied to land used for a crop not intended for human consumption
  • Incorporated into the soil not less than 120 days prior to the harvest of a product whose edible portion has direct contact with the soil surface or soil particles
  • Incorporated into the soil not less than 90 days prior to the harvest of a product whose edible portion does not have direct contact with the soil surface or soil particles

~ 7 CFR 205.203(c)(1), USDA, 2000

Compost Quality

Compost quality varies depending on the raw organic materials (feedstocks), the composting process used, and the state of biological activity. Before using compost as a soil amendment, it is a good idea to evaluate its quality by determining moisture content, organic matter content, C:N ratio, and pH (Table 1).

Table 1. Qualities of compost for on-farm use and how to test (after Cooperband, 2002a). Quality Optimum How to test Source of organic matter Should have a good organic matter content (40-60%) Have organic matter tested by a soil lab Source of nitrogen 10–15:1 C:N ratio Have C:N ratio tested by a soil lab Neutral pH 6–8 Use soil pH kit at home or have pH tested by a soil lab Low soluble salts If compost will be spread in the fall, no test necessary N/A If compost will be spread before planting, levels should be below 10 dS Have soluble salts tested by a soil lab No phytotoxic compounds Good seed germination (>85%) Plant 10 seeds in a small pot Weed-free No or few weed seeds Moisten compost and watch for weed seedling growth Compost and Disease Suppression

Compost can be effective at controlling some soil-borne diseases, particularly root-rot diseases. By providing a favorable environment and food source, compost encourages the growth of microorganisms that compete with, parasitize, or produce natural antibiotics against plant pathogens. Additionally, increased plant vigor due to compost application can increase resistance to plant pathogens. For more information see the chapter on Compost and Disease Suppression in the ATTRA publication Sustainable Management of Soil-Borne Plant Diseases by Sullivan (2004). See a related article to learn how composting can reduce or eliminate weed seeds and plant pathogens in crop residues and other organic feedstocks.

Compost and Soil Fertility

Generally, compost can be considered more as a soil conditioner than as a fertilizer substitute because it improves plant productivity primarily by improving physical and biological soil properties and increasing soil organic matter, rather than by directly supplying significant amounts of plant-available nutrients. By increasing soil organic matter content, which fuels microbial activity and nutrient cycling, compost applications will increase overall soil fertility. Over subsequent growing seasons, the nitrogen applied in compost will become plant-available.

Compost Application Rates

Compost should be considered a slow-release source of nitrogen. Most nitrogen remaining after completion of the composting process is bound into organic forms and thus not available immediately for plant uptake. Compost routinely applied at rates high enough to meet immediate crop N requirements will almost always result in excess P and K application. Excess P can result in surface water pollution (and potentially threaten organic certification). In some cases, excess K can upset crop nutrition balance.

Compost application rates can be calculated using fertilizer recommendations from soil tests, compost nutrient analysis, and methods similar to those used to determine manure application rates. When using this method, nutrient availability in compost must also be taken into account. General guidelines suggest that 10 to 25% of compost N will be plant-available during the first year of application. Estimates for P and K availability in the first year are higher, 40% and 60% respectively. It is important to keep in mind that these are only estimates and actual availability will depend on the nature of the compost and—for N especially—conditions during the growing season that affect N mineralization. Composting on the Organic Farm, by Baldwin and Greenfield (2009), provides detailed instructions for calculating application rates.

This vegetable producer in Washington State built his own compost spreader from existing equipment.
Figure 4. This vegetable producer in Washington State built his own compost spreader from existing equipment. Photo credit: David Granatstein, Compost Education and Resources for Western Agriculture project, Washington State University.

References and Citations Additional Resources


This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 2880

How do you calibrate a manure spreader?

mar, 2012/08/07 - 10:38

Calibrating a manure spreader is critical to ensure that the appropriate rate of manure nutrients is being applied to a field. For some livestock operations, this practice may be a required practice as part of their permit. Calibration will differ depending on the equipment and type of manure being applied. If you know the capacity of the spreader, you need to determine the width of each pass and the distance it takes to empty the spreader to determine the rate of application. A measuring wheel is a useful tool and can often be borrowed from a local Cooperative Extension or Natural Resources Conservation Service (NRCS) office. After you have determined both of those measurements, use the charts in the publication linked below to determine application rate. If the capacity of the manure spreader is unknown and solid manure is being spread, you can use a process that involves setting out plastic sheets or tarps of known size and driving the manure spreader over them and weighing the amount of manure that is collected on the sheets. A 22-square-foot tarp is a convenient size because the net weight of the manure on the sheet will be equal to the application rate in tons per acre. A step-by-step guide on making these calculations for other size tarps is available in the publication linked below. Charts and step-by-step procedures for calibrating liquid or solid manure spreaders are available at: Manure Applicator Calibration Guide Author: Jill Heemstra, University of Nebraska Extension Educator

Maximizing Dry Matter Intake on Your Organic Dairy Pastures Webinar by eOrganic

ven, 2012/08/03 - 17:05

The presentation is available as a pdf file at the following link: http://cop.extension.org/mediawiki/files/0/0b/Maximizing_DMI.eOrganic_Webinar.pdf

About the Webinar

On February 12, 2010, the USDA National Organic Program (NOP) published a final rule that establishes pasture standards for organic livestock. The Access to Pasture rule specifies that organic milk and meat products come from organically-raised animals that are actively grazing on pasture. The rule requires that these animals' diets consist of at least 30% dry matter intake from pasture grazed during grazing season, and that the grazing season is at least 120 days.

In this webinar, recorded on September 16,  2010, USDA NRCS animal scientist Karen Hoffman describes how organic dairy farmers can maximize dry matter intake from the pasture. She describes the connection among milk production, a cow's rumen and pasture quality, including plant density, number of tillers/plant, pasture height, and species composition. She takes a look at protein and energy relationships in the pasture and ways to balance them to enhance dry matter intake and encourage high animal performance.

Find all eOrganic upcoming and archived webinars »

Presenter Karen Hoffman

Karen Hoffman is an animal scientist with USDA-NRCS in New York and is also the NY state coordinator for the Grazing Lands Conservation Initiative. Karen received her Bachelor of Science degree from the Animal Science Department at Cornell University and her Master of Science degree from the Department of Dairy and Animal Science at PennState where she studied grain feeding strategies to high producing dairy cows on a rotational grazing system. Karen has worked with dairy and other livestock producers on their grazing systems for more than 15 years including Cornell Cooperative Extension as a dairy management educator and now as animal scientist specializing in grazing nutrition for the USDA - Natural Resources Conservation Service.

About eOrganic

eOrganic is the Organic Agriculture Community of Practice at eXtension.org. Our website  at http:www.extension.org/organic_production contains articles, videos, and webinars for farmers, ranchers, agricultural professionals, certifiers, researchers and educators seeking reliable information on organic agriculture, published research results, farmer experiences, and certification. The content is collaboratively authored and reviewed by our community of University researchers and Extension personnel, agricultural professionals, farmers, and certifiers with experience and expertise in organic agriculture.

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 5412

Dairy Herd Performance Tools Available Online for Farmers

jeu, 2012/08/02 - 12:49

Released August 1, 2012
MADISON, Wis. — Dairy farmers have the opportunity to compare the health and production performance of their herd with other herds around the country as the result of a recent research project from the University of Wisconsin-Madison.

Approximately 200 organic and 100 size-matched conventional dairy farms across the U.S. were recruited to participate in a recent study examining the impact of organic management on animal health and well-being. Dr. Pamela Ruegg, UW Dairy Science professor and Extension milk quality specialist, and her research team visited each farm to collect herd health records, milk samples, body condition scores, disease treatments, usage of veterinarians, livestock housing, feed, and routine milking procedures.

Researchers selected indicators of animal health, such as somatic cell counts, and identified the management practices of the participating farms that were most closely associated with better herd health. The project team created individualized benchmark reports for each farm based on their scores. These reports collectively became the database for a new suite of interactive herd performance tools available online to all dairy farmers.

The online tools compare: somatic cell counts, milk production, percentages of milk fat and protein, clinical mastitis in the herd and culling rates. Any dairy farmer can use these tools and select a variety of management practices, herd characteristics and other farm criteria of which to compare his or her herd.

Farmers have the option of storing their herd’s information into the system. As more and more farmers do so, the database will dynamically grow from the original 300 dairy farms—continuously providing the most up-to-date results.

Creating a forum for dairy farmers to compare the performance of their herd to other herds is empowering since herd health can influence overall farm income. The peer benchmarking approach helps farmers identify areas of strength and weakness on their individual farms and set performance goals for their herd, such as improved diagnosis of future health-related problems and increased milk production.

The herd performance tools are featured on the UW Milk Quality website, http://milkquality.wisc.edu. UW Milk Quality is an online collaboration between Dr. Pamela Ruegg and Dr. Doug Reinemann, professor and director of the UW Milking Research and Instruction Lab, geared toward helping dairy producers best manage herd health and milking systems.


August 2012 eOrganic Newsletter

mer, 2012/08/01 - 18:52
In this issue
  • Organic Seed Finder Webinar on August 21st
  • Recently Published eOrganic Articles and Videos
  • NOP Adds Natural Resources Standard to their Accreditation Checklists
  • New Publication on GMO Contamination Prevention
  • New Book on Breeding for Organic Agriculture
Webinar on August 21st: Learn about the Organic Seed Finder

Sourcing Organic Seed Just Got Easier: An Introduction to Organic Seed Finder. This webinar will be presented on August 21st at 2PM Eastern Time (1PM Central, 12PM Mountain, 11AM Pacific Time). Join Chet Boruff of the Association of Offiial Seed Certifiying Agencies and Kristina Hubbard of the Organic Seed Alliance as they introduce the new Organic Seed Finder database, which will serve as a valuable tool for the organic community by providing reliable organic seed availability information. The webinar is free and open to the public. Advance registration is required. Find out more and register at http://www.extension.org/pages/64782

Recently Published eOrganic Articles and Videos

Soilborne Disease Management in Organic Vegetable Production, by Fulya Baysal-Gurel, Brian McSpadden Gardener, and Sally Miller, of the Department of Plant Pathology at The Ohio State University

Videos on Plant Propagation and Pest Management for Beginning Farmers from Penn State Extension. These farm profile videos, which are directed by Tianna DuPont and produced by Daniel Paashaus, are designed to give new farmers ideas and advice from experienced producers. They feature John Good of Quiet Creek Farm in Kutztown, PA.

NOP Adds Natural Resources Standard to Accreditation Checklists

The USDA National Organic Program (NOP) has updated two sections of their Accreditation Checklists to make sure that all NOP-accredited certification agencies are verifying that organic operations implement conservation practices and protect natural resources.

In the Witness Audit Checklist, the NOP now will verify that the certifiers are effectively implementing the requirement to “Maintain or improve natural resources" - standard §205.200. In the Certification File Review Checklist, the NOP now will verify that certifiers are requiring that their farmers, ranchers, wild crop harvesters, and handlers are addressing standard §205.200 in their Organic System Plans. For more information, see http://archive.constantcontact.com/fs054/1103777415326/archive/1110502812671.html

New Publication on GMO Contamination Prevention

Jim Riddle, Organic Outreach Coordinator for the University of Minnesota Southwest Research and Outreach Center, has released a newly revised and expanded publication, GMO Contamination Prevention – What Does It Take?

The publication describes best management practices for growers of GMO and non—GMO crops, including certified organic crops, to help minimize GMO contamination of non-GMO crops. The 8-page guide contains commonsense steps that producers can take to reduce risks of GMO contamination.

New Textbook: Organic Crop Breeding

The first textbook on organic crop breeding has been published by Edith T. Lammerts Van Bueren and James Myers. This comprehensive text provides readers a review of the latest efforts by crop breeders to develop improved varieties for organic production. The book opens with chapters looking at breeding efforts that focus on specific valuable traits such as quality, pest, and disease resistance, as well as the impacts improved breeding efforts can have on organic production. The second part of the book is a series of case studies from around the globe that look at breeding efforts underway in crops ranging from carrots to corn. Find out more at http://blog.seedalliance.org/2012/07/02/new-textbook-the-first-on-breeding-for-organic-agriculture/

eOrganic Mission

eOrganic is a web community where organic agriculture farmers, researchers, and educators network; exchange objective, research- and experience-based information; learn together; and communicate regionally, nationally, and internationally.

eOrganic Resources

Find all eOrganic articles, videos and webinars at http://extension.org/organic_production

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This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic 8080

Organic Vegetable Production Systems, Disease Management in Organic Farming Systems

mer, 2012/08/01 - 13:14

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.

eOrganic T879,876