Why are wheat and barley diseases favored or not favored by zero-till or conservation tillage?
All root diseases of wheat and barley are favored by planting wheat and barley year after year, or at least every other year, on the same fields. In addition, take-all, Pythium root rot, and Rhizoctonia root rot, being favored by cool, moist soil, gain an additional advantage when harvest residues are left on or mulched into the soil surface. In other words, straw left on the soil surface helps to maintain the soil in an ideal condition for the activity of these three root pathogens. It is important to recognize that the root pathogens live mainly in the top 4-6 inches of soil–the first layer to dry and warm up after a rain or snow melt but less likely to dry and warm up if covered with straw. With take-all, for example, removing the straw by burning in a no-till experimental planting of winter wheat after winter wheat near Pullman, Washington, reduced the incidence of disease, but burning the straw and then returning fresh straw to cover the burned-over soil surface with fresh straw
