EFFECTS OF TILLAGE, ROW WIDTH, AND CULTIVAR ON FOLIAR DISEASES OF DOUBLE-CROP SOYBEAN

Experiments were conducted over two years, 1985 and 1986, to determine the effect of tillage systems, row widths, and soybean cultivars on foliar diseases in double-crop soybean. The soybean cultivars Pershing, susceptible to bacterial blight, and Avery, resistant to bacterial blight, were each planted in 38-cm and 75-cm row widths in soil under conventional tillage or no-tillage following winter wheat. There was a significant interaction (P = 0.0001) between tillage and cultivar for the severity of bacterial blight and a significant interaction (P = 0.001) for tillage, cultivar, and year for the severity of brown spot. Tillage did not influence bacterial blight severity on Avery; however, disease severity was higher on Pershing soybean in tilled plots. Generally, brown spot severity was higher in 1986 than in 1985, lower on Avery than Pershing in both years, and higher in tilled than no-tilled conditions. Row width did not affect the severity of these diseases.