THE IMPACT OF REDUCED TILLAGE ON SOILBORNE PLANT-PATHOGENS

Farmers increasingly leave crop residues on the soil surface rather th an incorporating them into the soil. This practice helps reduce soil e rosion, conserve energy, increase soil moisture, and increase crop yie lds. However, many soilborne plant pathogens survive in the previous y ear's crop residue, making diseases more problematic under reduced-til lage conditions. Reduced tillage can favor pathogens by such mechanism s as protecting the pathogen's refuge in the residue from microbial de gradation, lowering soil temperature, increasing soil moisture, and le aving soil undisturbed. In order for reduced tillage to become more po pular, additional controls are needed for pathogens. The four major co ntrol tactics (disease-control chemicals, biological control, host res istance, and cultural controls) can be used to limit damage from disea ses. It is highly recommended, however, that crop rotation be coupled with reduced tillage. This practice controls many diseases and yet all ows as much of the crop residue as possible to be retained on the soil surface.