The impact of reduced tillage on soilborne plant pathogens.

Farmers increasingly leave crop residues on the soil surface rather than incorporating them into the soil. This practice helps reduce soil erosion, conserve energy, increase soil moisture, and increase crop yields. However, many soilborne plant pathogens survive in the previous year's crop residue, making diseases more problematic under reduced-tillage conditions. Reduced tillage can favor pathogens by such mechanisms as protecting the pathogen's refuge in the residue from microbial degradation, lowering soil temperature, increasing soil moisture, and leaving soil undisturbed. In order for reduced tillage to become more popular, additional controls are needed for pathogens. The four major control tactics (disease-control chemicals, biological control, host resistance, and cultural controls) can be used to limit damage from diseases. It is highly recommended, however, that crop rotation be coupled with reduced tillage. This practice controls many diseases and yet allows as much of the crop residue as possible to be retained on the soil surface.