Leaf spot diseases on winter wheat influenced by nitrogen, tillage, and haying after a grass-alfalfa mixture in the Conservation Reserve Program

When contracts for the Conservation Reserve Program (CRP) expire, highly er odible land that had a long-term vegetative cover composed of grasses or gr ass-legume mixtures may be converted back to cropland. Considering that som e of the same leaf spot pathogens found on grasses can cause diseases on wh eat, the management practices used to convert these lands were evaluated fo r their effect on winter wheat leaf spot diseases. In a 3-year spring wheat -winter wheat-pea crop rotation, the major leaf spot diseases on winter whe at were tan spot and Stagonospora nodorum blotch. Removal of hay or leaving hay in the plots when converting grassland to cropland had no significant effect on leaf spot diseases, indicating that the residue from the grass-al falfa crop did not influence leaf spot diseases on winter wheat. Tillage tr eatments did not influence the amount of disease in 1996, but with higher p recipitation levels in 1999, higher disease severities were associated with the no tillage treatment. Higher levels of crop residue associated with th e no tillage treatment could potentially carry over plant pathogens from on e crop to the next. The severity of leaf spot diseases was consistently low er when nitrogen was applied, indicating the importance of nitrogen applica tion when converting grassland to cropland.