EFFECT OF WHEAT RESIDUE AND TILLAGE ON HETERODERA-GLYCINES AND YIELD OF DOUBLECROP SOYBEAN IN KENTUCKY

A study (1990 to 1992) was conducted in western Kentucky to determine the effects of wheat (Triticum aestivum 'Clark') residue and minimal- (two disking) or no-tillage on soybean cyst nematode (Heterodera glyci nes) cyst and egg population densities and yield of the H. glycines-su sceptible soybean (Glycine max) cultivar Pennyrile. In each year, cyst densities at soybean planting were unaffected by the presence of resi due from a prior winter wheat crop; however, harvest population densit ies were lower in plots with wheat residue compared with those without residue. Across residue treatments, tillage had no effect on harvest densities of cysts in any year. Differences in egg densities, determin ed only in 1992, were similar to differences detected in cyst densitie s for both residue and tillage. Minimum-tillage of wheat residue signi ficantly reduced the ''residue effect'' in 1990 and 1991; however, plo ts with wheat residue had fewer cysts at harvest than plots without re sidue in both years regardless of tillage method. Neither residue nor tillage affected soybean yields. Results indicate that producers who h ave the option to no-till doublecrop soybean following wheat may have an advantage in long-term management of H. glycines.