Tools & Practices (continued)

Tillage & Cultivation

Tillage and cultivation are tools that can accomplish a variety of objectives in farming systems: weed control, crop residue management, soil aeration, conservation of manures and other fertilizers, hardpan reduction, sanitation to destroy insect and disease habitat, etc.

While conventional farmers have grown to rely increasingly on chemicals to accomplish many of these objectives, organic growers have focused more on improving tillage and maximizing its benefits. Guidelines for primary tillage, for example, are intent on conserving crop residues and added manures in the upper, biologically active zones of the soil, rather than burying them deeply where decomposition is anaerobic (oxygen-starved). Leaving soils completely bare and vulnerable to erosion is discouraged; fall moldboard plowing is certainly frowned upon.

Cultivation in organic systems is often raised to the level of art. Row crop farmers frequently use blind cultivation—shallow tillage, which largely ignores the crop rows—beginning shortly after seeding until the plants are but a few inches in height. Rotary hoes, wire-tooth harrows, and similar equipment can be used for blind cultivation, delaying the first flush of weeds and giving the crop a head start.

After blind cultivation, subsequent weed control operations in larger-scale systems can make use of advances in tillage equipment such as rolling cultivators, finger weeders, and torsion weeders allow tilling close to the plant row. Smaller-scale operations often use wheel hoes, stirrup hoes, and other less capital-intensive hardware.

Determining the amount, the timing, and the kind of tillage to be done can be a balancing act for the organic grower, but experience and observation over time lead to proficiency.

There are downsides to tillage, however, and most organic growers are well aware of them. The most obvious of these is the dollar cost; organic farmers are as concerned as their conventional counterparts about costs of production and strive to minimize expensive field operations. There is also a cost to the soil and environment. Every tillage operation aerates the soil and speeds the decomposition of the organic fraction. While this may provide a boost to the current crop, it can be overdone and “burn up” the humus reserves in the soil. Excessive tillage can also be directly destructive to earthworms and their tunneling, reducing their benefits to the land. There is also the danger of compaction, even when field operations are well timed.

Organic agriculture is often characterized as addicted to maximum tillage—with growers using every opportunity to lay the land bare with shovel, plow, or rototiller. This image has been magnified through the popularity of small-scale organic systems like the French Intensive and Biointensive Mini Farming models that espouse double and triple-digging to create deep rooting beds for highly intensive crop culture. While appropriate to such intensive circumstances, this degree of cultivation is not characteristic of organic agriculture in general. It may surprise some to learn that a large number of organic producers are not only interested in conservation tillage, but have adopted it. They will be surprised because it is widely believed that conservation tillage always requires herbicides.

The interest in conservation tillage among organic producers in the Cornbelt was well documented in the mid-1970s by Washington University researchers. They noted that the vast majority of organic farmers participating in their studies had abandoned the moldboard plow for chisel plows. Plowing with a chisel implement is a form of mulch tillage, in which residues are mixed in the upper layers of the soil and a significant percentage remains on the soil surface to reduce erosion. Furthermore, a notable number of organic farmers had gone further to adopt ridge-tillage—a system with even greater potential to reduce erosion (3). It was especially interesting to note that the use of these conservation technologies was almost nil among neighboring conventional farms at this time. Organic growers were actually pioneers of conservation tillage in their communities.

Among the more well-known of these pioneers were Dick and Sharon Thompson of Boone, Iowa. Their experiences with ridge-tillage and sustainable agriculture became the focus of a series of publications titled Nature’s Ag School. These were published by the Regenerative Agriculture Association—the forerunner to the Rodale Institute. They are now, unfortunately, out of print.

Research continues to open up new possibilities in conservation tillage for organic farms. New strategies for mechanically killing winter cover crops and planting or transplanting into the residue without tillage are being explored by a number of USDA, land-grant, and farmer researchers. Notable among these is the work being done by Abdul-Baki and Teasdale at the USDA in Beltsville, Maryland—transplanting tomato and broccoli crops into mechanically killed hairy vetch and forage soybeans (27, 28). There are also the well-publicized efforts of Pennsylvania farmer Steve Groff, whose no-till system centers on the use of a rolling stalk chopper to kill cover crops prior to planting (29). Systems like Groff’s and Abdul-Baki’s are of particular interest because close to 100% of crop residue remains on the soil surface—providing all the soil conservation and cultural benefits of a thick organic mulch.