Strategies for soil conservation in no-tillage and organic farming systems

John R. Teasdale is a plant physiologist at the Sustainable Agricultural Systems Laboratory, USDA Agricultural Research Service, Beltsville, Maryland. N o-tillage cropping systems are known to provide many benefits to soils that can enhance production of grain crops. Many of the improvements to soils that result from no-tillage production such as increases in soil aggregation, water-holding capacity, nutrient cycling, and biological activity are related to increases in soil organic matter. Notillage systems are known to increase soil organic matter because of the absence of destructive tillage operations, the minimization of soil erosion losses, and the return of crop residue to the soil. Organic matter can be further enhanced by the addition of cover crops, perennial crops, and organic amendments into no-tillage rotations. Organic farmers share many of the same goals for building soil organic matter, fertility, and the capacity for supporting soil biological activity and productivity as no-tillage farmers. In organic farming this is achieved through integrated systems that maintain living vegetation cover, return vegetative residue back to soils, and add organic amendments from external sources as needed. The dilemma for organic farmers is that these approaches for increasing soil organic matter also require tillage. Specifically, tillage is required (1) to eliminate perennial legumes or winter annual cover crops before planting annual crops, (2) to incorporate manure to avoid nitrogen (N) runoff and volatilization losses, and (3) to prepare a seedbed and control weeds. Since an increase in tillage intensity and frequency has been shown to decrease soil matter, gains in organic matter by the addition of organic materials into the system may be offset by decreases in organic matter from tillage. Some authors have speculated that conventional no-tillage agriculture may provide superior soil improvement and potential environmental benefits compared with those of organic farming because of the tillage requirements of organic farming (Trewavas 2004). There is a need for long-term research to assess the relative merits of conventional no-tillage agriculture compared with those of organic farming (Macilwain 2004). Organic farmers share many of the same goals for building soil organic matter, fertility, and the capacity for supporting soil biological activity and productivity as no-tillage farmers.