Conservation Tillage

Building up and conserving soil organic matter is essential for the sustainability of organic agriculture.However, many organic farmers plow or rototill their soil to uproot weeds and expose the mineral soil as a seedbed. The problem with this it that it destroys the soil organic matter: as the soil is tilled, it is exposed to oxygen and as a result, bacteria in the soil quickly oxidize the soil organic matter, that is, convert it to carbon dioxide. Thus farmers that till their soil are destroying the very resource that they should be conserving. One way to avoid this is through a strategy of winter cover crops followed by “no-till planting”. In the fall, winter cover crops such as clovers, winter peas and rye are planted. By the first frost, these crops become established, and are able to survive the winter. They hold the soil in place during winter rains, and in the spring, they begin vigorous growth. Before they go to seed in early April, they are rolled flat with a roller fitted with angle irons that crimp the stems, thereby killing the crop and preventing resprouting. Then a no till planter is used to inject seeds or seedlings through the mulch of the winter cover crop. The mulch suppresses weeds and as it decomposes, it contributes to a build-up of soil organic matter. The photo shows vegetable starts (seedlings) being planted through mulch with the use of a no-till vegetable transplanter.

No-till planters are now often used in Southern Georgia for commodity crops such as cotton and peanuts that are planted on a large scale. However, there are no small scale planters commercially available for organic vegetable fields of an acre or less, typical of North-Georgia organic farms . The Agroecology Laboratory, in cooperation with the Instrument Shop of the University, built a no-till vegetable transplanter for planting vegetable seedlings that have been started in a greenhouse, and a no-till seed planter for planting larger seeds such as those of corn and squash. The seed planter can easily be modified for strip tillage, in which a narrow band of soil is exposed. Seeds are planted into this narrow band, while the rest of the bed is undisturbed.

Full Moon Farms, a commercial organic farm that occupies 7 acres of Spring Valley Ecofarms, uses a “spader” to prepare the seed bed. This is a tractor-driven machine that drives spade-like wedges into the soil to loosen it without turning it over. When compost is spread on the vegetable beds, the spader is used to drive the compost into the soil, closer to where the roots of the vegetable crops will grow. For the same reason, it also is used to drive a winter cover crop into the soil.