By Mark Schonbeck

Souther SAWG participants visit an organic vegetable farm in Alachua county on January 25, 2004

Imagine that you farm in the South and are eager to learn how to do so with a lighter footprint on the earth and at the same time improve your bottom line. You arrive at the Paramount Resort Hotel in Gainesville, Florida on a Friday morning in late January and find yourself in the midst of nearly 500 other growers, agricultural professionals, educators and advocates united in a vision of sustainable agriculture and community food systems for the southern region. After registering, you catch a bus departing for one of four half-day tours of nearby organic farms, community gardens and research plots.

On the way, you peruse the program and find the next three days packed with exciting workshops on a gamut of topics from soil-plant microbiology, crop rotation, cover crops and sustainable soil management, to biological weed control, sustainable livestock, and poultry and meat processing. Other sessions cover direct and cooperative marketing, farm-to-school projects and other community food security programs, and how to access government programs that support earth-friendly farming. On Saturday morning, you’ll get to choose your own topic and exchange ideas with others at a “U-Pick” discussion session (who says farmers don’t have a sense of humor?).

Welcome to the annual conference of the Southern Sustainable Agriculture Working Group (Southern SAWG). This year’s event included an extensive track on community food systems, workshops on farm policy, and 35 practical sessions on sustainable production and marketing, including some led by each of 10 growers participating in Southern SAWG’s Experienced Organic Farmers’ Network (for more on this project, contact Jean Mills, jeanmills@aol.com). Top-notch presentations and field trips, state networking sessions at which participants meet others from their home states, time between sessions for informal conversation, and a Saturday evening banquet of locally-grown food followed by an uplifting keynote address all added up to a rich opportunity to learn, exchange ideas, and to help and inspire one another.

Community food systems

Duncan Hilchey of the Community Food and Agriculture Project at Cornell University opened the keynote address with statistics on the rapid growth of farmers markets, CSAs, and community food initiatives in the south, all of which he attributed in no small part to the work of Southern SAWG. A co-author of Growing Home: a Guide to Reconnecting Agriculture, Food and Communities (The Community, Food, and Agriculture Program, 2002), Hilchey encouraged those in attendance to keep on “growing home” by exploring new strategies such as community market gardens, local food restaurants, and value-added products from commodity crops.

Local producer Charlie Andrews of Hommock Hollow Herb Farms produces kale, lettuce many other different types of organic vegetables and herbs.

A team from the Sustainable Food Center of Austin, TX (www.sustainablefoodcenter.org) shared their experiences in a workshop entitled Securing a Circle of Fresh Food from Growing to Marketing to Cooking. Within a few years, the center has engaged 400 low-income families in community gardens, established a farmer’s market with 75 vendors and about 1300 customers per market day, and facilitated cooking classes where 500 people a year learn how to prepare simple, healthy, low-cost meals from locally grown ingredients. The CFSC also displayed written materials on its work and on the farm-to-cafeteria legislation now before Congress, legislation that would offer grants to help farm-to-school programs get started (visit the website for more details).

Getting to the root of plant health and disease

Jerzy Nowak, Ph.D., chair of the Virginia Tech Horticulture Department (where he is actively promoting organic horticultural research and education), gave a fascinating account of the importance of rhizosphere (root zone) microorganisms in sustainable soil management. He described a terrific diversity of microorganisms living near, on and even within plant roots, working together to create a functional whole. For example, mycorrhizal fungi that grow within and outside plant roots and promote nutrient and water uptake are themselves assisted by mycorrhizal helper bacteria. Plant roots typically exude 5 to 35 percent of the plant’s daily photosynthetic production as soluble substances that attract and nourish friendly microbes, Dr. Nowak explained. In return, he said, some of these organisms stimulate plant growth while others help prevent disease by enhancing plant resistance, out competing pathogens or releasing antibiotics. For more on astonishing mycorrhizae research here at our own farm in Pennsylvania, click here. Our research has lead to some immediate and practical field applications.

Rhizosphere organisms isolated from one crop or weed may either stimulate, inhibit, or not affect the growth of another plant species, Dr. Nowak explained. This, he said, may account for many of the favorable or adverse “rotation effects” that farmers and researchers have observed in the field. Rhizobia, the well-known nitrogen-fixing legume bacteria that makes its home in the root zone, also release hydrogen gas into the soil, Dr. Nowak said, which stimulates other bacteria beneficial to grain crops. When bits of mycorrhizal onion roots dramatically boosted potato growth in tissue culture, Dr. Nowak traced this to a new, mycorrhizal helper bacterium, Burkolderia phytofirmis, which reduces the release of ethylene (a plant stress hormone) and greatly improves heat and cold tolerance of vegetable crops. He also noted that excessive soil phosphorus levels can actually kill off the mycorrhizae.

Converting this fascinating research to practical application remains a challenge, Dr. Nowak said, since the micro-ecology is so complex and because indigenous soil organisms usually overwhelm single-species microbial inoculants added to the field. Dr. Nowak and others are working on techniques to introduce beneficial bacteria like B. phytofirmis into seed and plant tissues, where they are most effective. Some crop breeders are now “breeding for the rhizosphere,” he said, by selecting lines that interact positively with indigenous soil life. Another practical approach has been to stimulate soil organisms by providing air and food (in the form of a 0.1 percent sugar solution) via drip irrigation. Adding 12 percent air (by volume) to irrigation water through special capillary drip tubes (available through www.irrigro.com) laid 5 to 8 inches deep in the soil, has enhanced pepper yields by up to one third. (For more information, contact Dr. Nowak at jenowak@vt.edu or 540-231-5451.)

One of the “U-Pick” sessions on Saturday morning focused on strategies to deal with pest nematodes. We learned that velvetbean, sorghum-sudan hybrid, and bahiagrass each suppress some, but not all, harmful nematodes and that certain soil fungi and bacteria kill or inhibit these pests. One participant suggested that soil from a field in which nematode problems have disappeared might be used to inoculate other fields with its anti-nematode microbial complex. It was noted that, in the days before powdered inoculants, this was also how Rhizobia were moved into new fields and that the same strategy might work for introducing other desirable microorganisms.

Read your weeds and reap

Gary Zimmer, an organic farmer and consultant in Wisconsin, shared practical strategies for “reading” and managing weeds. Dandelions and chicory bring calcium up from the subsoil, he said, and if these are abundant and legumes are not thriving, this is an indication that the topsoil is low in calcium. Grass weed problems indicate tight soil, Zimmer said, and foxtails suggest compaction and low levels of calcium and sulfur. Gypsum may help correct the problem, he suggested. Velvetleaf, that bane of conventional row crops, tends to die out under organic management, Zimmer said, while pigweed and lambsquarters both indicate healthy, fertile soil.

Small-seeded weeds emerge from firmly packed soil, Zimmer said, so he minimizes tillage and rotovates a heavy cover crop just once in order to create a loose soil surface. Then he plants row crops in a shallow (4 to 5 inch) cleaned furrow for good seed-soil contact, leaving the rest of the soil surface loose so fewer weeds germinate. He rotary hoes twice, then cultivates (at an 8-inch crop height) with equipment that fills the furrow and buries within-row weeds. Zimmer recommended sudangrass or a sequence of buckwheat-buchwheat-rye to clean up weedy fields. His other key strategy is to “empower the crop,” with an extensive root system, promoted by loose, crumbly, aerated soils, fairly low NPK, and ample calcium and boron. A little extra phosphorous in planting furrows stimulates crop roots, as do kelp, fish and humate amendments, he said. Broadcast manure or soluble nitrogen will bring on a flush of weeds. “Fertilize the crop,” he emphasized, by placing nitrogen in the row after the crop is well established.

Cover cropping in the sometimes soggy South

Dr. Keith Baldwin of North Carolina A&T University discussed the benefits and best uses of various cover crops in the southern region, including winter rye, wheat, vetch, crimson clover, Austrian winter peas, and subclover, and the summer crops buckwheat, sudangrass, millet, cowpea, soybean, sunnhemp and velvetbean. “Cover crops are soil food,” Baldwin emphasized, “and they’re particularly important in the Southeast to help the soil absorb our summer thunderstorms.”

In the North Carolina Piedmont, winter cover crops yield maximum biomass, slow-release nitrogen and weed suppression when a grass-legume biculture is planted in fall and grown until May, Dr. Baldwin explained. Crimson clover matures earlier than hairy vetch, he said, and is less likely to clog rototiller tines. Baldwin showed some impressive slides of tomatoes planted no-till into vetch mulch (weed-free 45 days later) and edamame soybeans in strip-tilled crimson clover. For early spring vegetables, he recommended summer cover crops planted the previous July or August and allowed to winterkill. In research trials, Dr. Baldwin said, sunnhemp has accumulated 100 to 250 pounds of nitrogen within 45 days after planting, while sorghum-sudan hybrid gave the most biomass, at 4-5 tons per acre. For more on cover crops, visit www.ces.ncsu.edu/ag/SustgAg/covercrops, or www.attra.ncat.org, or contact Dr. Balwin at 336-334-7957, kbaldwin@ncat.edu. Also see Organic No-Till for Vegetable Production on The New Farm archives at http://www.newfarm.org/features/0104/no-till/index.shtml.

Crop rotation cycles for optimal fertility

Alex Hitt, who grows cut flowers and mixed vegetables with his wife, Betsy, led a workshop entitled Intricacies of Crop Rotation, at which he described in detail the eight-year crop rotation strategy in place at their Peregrine Farm. Since they use no manure, cover crops play a central role in fertility and organic matter and thus occupy about half of the rotation blocks at any season. Some heavy-feeding vegetables follow two successive cover crops (e.g. millet/cowpea, then oats/crimson), Hitt explained, whereas they sometimes grow two successive flower crops (which are light feeders). “The biggest observed benefit is weed control, resulting from shifting planting schedules, alternating warm season and cool season crops,” Hitt said.

According to Hitt, crop rotations can be designed on the basis of cash crops (keep members of same plant family at least three years apart; five to six years is ideal), cover crops (these should be rotated, too) or nutrient demands by different crops. To make rotations more workable, Hitt recommended a combined cash-crop/cover-crop approach, and “making rotation units (beds or blocks) all the same size. Leave some room for expansion, so that increasing a certain cash crop does not disrupt the rotation. If possible, group together crops that go in and come out at the same time.” He recommended two reference books: The New Organic Grower by Eliot Coleman (Chelsea Green, 1995) and Sustainable Vegetable Production from Startup to Market by Vern Grubinger (Natural Resource, Agriculture, and Engineering Service, 1999). Both are available in our online bookstore.