Organic no-till for vegetable production?
It can be done--Virginia Tech professor Ron Morse has been trialing a wide range of cover crop species for no-till planting of organic brassicas, cucurbits, solanaceae and more

By Mark Schonbeck

For more information on this research and on no-till cover crop mulch systems for organic vegetable production, contact: Dr. Ron Morse, Professor of Horticulture, Virginia Tech., Blacksburg, VA 24061; tel. 540-231-6724; e-mail morser@vt.edu.

Why and how organic no-till got started

Weed control is often cited as the single greatest challenge in organic crop production. In relying on tillage and cultivation rather than chemical herbicides to manage weeds, organic growers risk greater soil degradation, organic matter loss and erosion. Cover crops suppress weeds, add organic matter and nitrogen, mobilize nutrients, hold and improve the soil, and harbor beneficial insects. However, when the cover crop is turned under prior to planting the primary crop, the tillage required to prepare a seedbed burns up organic matter, degrades tilth and stimulates weeds to emerge—which means yet more cultivation and associated costs.

Since the mid 1980s, researchers at the New Alchemy Institute, The Rodale Institute Experimental Farm, and several land-grant universities have experimented with managing winter annual cover crops such as rye, hairy vetch, and crimson clover without tillage prior to planting a vegetable crop. These cover crops can be killed mechanically by mowing or rolling after they begin to flower and shed pollen (usually in mid to late May), and the resulting mulch can suppress weeds for six weeks or more. During this time, tomatoes, broccoli or other vegetables can be transplanted and established so that later-emerging weeds have little impact on yield.

We look forward to learning more about the effects of no-till on the soil, crop yields, weed and pest levels, and net economic returns to the farmer. Stayed tuned to www.newfarm.org for updates on project findings over the next few years.

The pros and cons of no-till cover crop management

The potential advantages of this system include greater cover crop biomass production (since it is allowed to grow until a week or so before vegetable planting), and much less loss of organic matter through tillage. Together, these can greatly enhance annual organic inputs and thereby support higher levels of 'active organic matter,' which correlates closely with soil quality. In addition, the cover crop mulch conserves soil moisture, curbs weed seed germination, and provides habitat for ground-dwelling predators of insect pests.

On the other hand, continuous no-till can eventually lead to perennial weed problems or cause some soils to become somewhat compacted. Thus organic growers may need to practice 'rotational tillage,' working the soil before planting cover crops in some years. Research results at The Rodale Institute Experimental Farm suggest that this may be the case. How often tillage is needed and whether soil quality can still improve under rotational tillage are two of the questions Morse’s research will address.

One other possible drawback is that the cover crop mulch will keep soil temperatures lower so that the system may not work where early harvests are desired, especially for warm season crops. However, later plantings of the same crops may benefit from the soil-cooling and moisture-conserving effects of mulch, especially in hot climates or in drought years.

“The one thing I want to accomplish before I retire is to establish workable systems for organic no-till vegetable production using cover crops,” Dr. Ron Morse told me in one of our first meetings. A professor of horticulture at Virginia Tech, in Blacksburg, Va., Morse has been working for upwards of two decades on soil-conserving systems for vegetable production in hilly Appalachia. Using high-biomass cover crop mixtures like winter rye and hairy vetch killed to form an in situ mulch, he has helped growers save tons of soil and reduce weed control costs. More recently, he has worked on herbicide-free systems for organic growers.

Morse was born and raised on a family farm in Utah. He worked with his father and three brothers in their 10-cow dairy, where “we did everything together, which taught us a strong ethic of cooperation and responsibility.” He went to college at Utah State, then earned a Ph.D. in Horticulture at Michigan State. His professional commitment to making farming more sustainable for both land and grower led naturally to no-till cover crop systems.

Morse began this line of research in the winter of 1978-79, when he received a letter from an extension agent in mountainous Carroll County, Va., with a photo of U.S. Route 58 blocked by a mass of soil washed away from an adjacent cabbage field. The caption read simply, “Help!” Morse knew the first step was to stop plowing. So he put a graduate student to work at Virginia Tech’s experimental farm, growing rye cover crops for no-till vegetable planting. Initially, they planted by hand, digging holes to plant cabbage through herbicide-killed rye. It worked!

The next hurdle was to mechanize the transplanting. At first, researchers modified a Holland transplanter by adding a front coulter to slice through cover crop residues, which worked well in moist, mellow soils. Farmers got interested fast—but then a drought struck, and the Holland planter repeatedly broke when pulled through dry, untilled soils. So Morse and a team of others built the first Sub-Surface Tiller-Transplanter (SST-T) in 1990. The front component is a durable sub-surface tiller that prepares a narrow strip of soil, loosening as deep as 8 inches. The second is a no-till transplanter that sets transplants into the prepared strip. It has a double-disk opener ahead of the planting shoe, and the press wheels are modified so that they close the untilled soil around the plant. By 1996, improved versions of the SST-T could lay drip tape, apply organic or conventional fertilizer (in-row or side-band), and water in the transplant. Different attachments can be used for a variety of vegetable starts, seed potatoes or large seeds like beans.

If you build it, they will come

When word of early successes got out, Morse received an avalanche of calls from farmers and extension agents wanting to see demonstrations and try the SST-T themselves. Many calls came from organic farmers and sustainable agriculture organizations interested in better weed control with less soil-damaging tillage. So the herbicides had to go—and winter annual cover crops can be killed mechanically. Morse uses a flail mower or a roller-crimper to convert a live, standing cover crop into a mulch through which the SST-T can easily operate. (A bush-hog or a sicklebar mower leaves the cover crop stems helter-skelter, which can jam the planter.) Broccoli, potatoes, tomatoes and other vegetables have been successfully planted into flail-mowed cover crops at Virginia Tech’s Kentland Agricultural Research Farm (hardiness zone 6b) and on several organic farms in the region. “The key to success is to grow really good cover crops,” Morse emphasizes, “at least three tons dry matter per acre. I like the rye and vetch [mixture] to be five or six feet high, and nice and thick. Otherwise, you don’t get weed control.”

Morse and his colleagues are also experimenting with other cover crops and planting seasons. Frost-tender annuals like German or foxtail millet, pearl millet, sorghum-sudan hybrid (sudex), cowpeas, forage soybean, sunn hemp, or lablab bean can be planted in early summer and mowed in August for no-till fall brassicas, or planted later in summer and grown until killed by fall frost. Sudex produces tremendous biomass, and suppresses weeds through competition and allelopathy (the release of substances that inhibit weed growth). Mowing sudex when it is chest high stimulates roots to penetrate deeper, which opens the subsoil and may enhance allelopathy. Morse mixes stiff-stemmed grasses or sunn hemp with more succulent legumes to maximize biomass and ground cover, and to balance the carbon to nitrogen ratio. Fall broccoli planted no-till into a flail-mowed cowpea and sunn hemp mixture gave yields similar to conventional-till broccoli.

Oats, lana vetch and berseem clover tolerate frosts to 20 degrees but do not over-winter, so they can be planted in late summer to create a winter-killed mulch for no-till planting of brassicas or other early spring crops the next year. When frost kills the cover crop, mowing is not needed.

Cover crop systems are limited only by your imagination

The possibilities are limited only by the imagination, of which Morse has plenty. He grows self-seeding winter cover crops such as little barley (considered a weed by some) and subterranean clover, which die down in early summer and come back from seed in the fall. In mid July 2003, he planted ‘Arcadia’ broccoli no-till into a little barley and sub clover residue. Recently, he began experimenting with garlic, which is normally planted in October and immediately mulched with hay or straw. This fall, he planted garlic no-till into frost-killed sudex, sunn hemp and lablab beans.

For no-till vegetables, Morse usually forms a raised bed just before planting the cover crop. At Kentland Farm, he plants “companion grass,” a mixture of dwarf perennial ryegrass and creeping red fescue, in the alleys between beds and up the bed shoulders. This grass mixture requires only two or three mowings a season, effectively suppresses weeds, and stabilizes the beds so they can be used for several years without re-forming. In the future, he may augment this combination with low-growing perennial clovers to provide long-term habitat for beneficial insects.

No-till, no-herbicide cover crop management and vegetable planting offer a vital soil-building weed management strategy for organic growers and a practical solution to the kind of soil loss that prompted the Carroll County extension agent’s original call for help. Recent trials suggest that this approach may find broad application in diversified vegetable production. The SST-T, manufactured by B & B No-Till in Laurel Fork, Va., costs between $5,000 and $10,000 for a one-row planter (depending on whether a fertilizer hopper and/or drip tape layer are included). However, some 25 regional Soil and Water Conservation Districts have purchased these planters and make them available to growers on a rental basis. Morse is also working on other ways to make this system available to small-scale growers who cannot afford to purchase the SST-T.

Future work will reach out to more growers

Morse’s work thus far has attracted support for a new round of soil-saving experiments over the next three years. During 2002-03, Morse was awarded grants from the Southern Region SARE program and the USDA Cooperative State Research, Education and Extension Service (CSREES) to conduct further studies on no-till organic broccoli, potato, pepper and summer squash. He hopes to extend no-till cover crop management to a wider range of cover crops, vegetable species, and planting seasons, and to incorporate state-of-the-art biological pest management practices into an integrated organic production system. (Editor’s note: The author, Mark Schonbeck was also invited to participate in two of these projects as farm outreach coordinator in Virginia.)

Dr. Richard McDonald, one of the region’s foremost consultants in bio-control, will help implement 'farmscaping,' or planting strips of flowers and herbs to provide forage and habitat for natural enemies of key vegetable pests. The experiments will compare no-till management of the cover crop with the traditional practice of turning the cover crop under as a green manure several weeks before planting. They will measure cover crop biomass, weed suppression, pest and disease levels, marketable crop yields, and soil biological and physical properties in the two systems.

In addition to research at Virginia Tech and University of Georgia, the projects will include an outreach component in which organic farmers in Virginia, North Carolina and Georgia will participate in on-farm trials comparing no-till cover crop management with the growers’ normal practices within a three-year vegetable rotation. Field days will be held during the 2004 and 2005 seasons, and the host farmers will also participate in project presentations at conferences.

Extremely wet weather during spring and summer of 2003 delayed the establishment of many of these experiments. Morse and his colleagues waited for weeks on end for the soil to get dry enough to plant cover crops. We finally got a break this fall, and cover crops have been successfully established on six acres of organic-transition land at Kentland Farm. On-farm trials also got a late start, but soil samples have now been taken and cover crops sown for vegetable planting in the 2004 season.

Mark Schonbeck coordinates the outreach component of SARE- and CSREES- funded organic no-till research projects in Virginia. He is also editor of The Virginia Biological Farmer, the 12-page quarterly newsletter of the Virginia Association for Biological Farming. You can contact Mark at 540-745-4130, mark@abundantdawn.org. For more information on VABF, write to VABF, P.O. Box 1003, Lexington, VA 24450; visit the web site www.vabf.org, or contact our office manager, Linda Davis at 540-463-6363.