EFFECT OF CROP-ROTATION AND TILLAGE ON NEMATODE DENSITIES IN TROPICAL CORN

Effects of tillage and crop rotation on nematode densities in tropical corn (Zee mays N. Pioneer X304C) were examined in a factorial experiment with two rotation craps and two tillage practices (no-till vs. conventional-till), conducted in each of three seasons (1990-1992) in north Florida. The rotation treatments consisted of sorghum (Sorghum bicolor cv. DeKalb BR64) or soybean (Glycine max) grown during the 1989 season. Densities of Meloidogyne incognita (race 1) remained lower throughout the growing season in corn following sorghum than in corn plots following soybean. This effect was observed clearly even in the third consecutive corn crop. In 1990, densities of Criconemella spp. were initially higher in plots planted to sorghum the previous year, but by the end of the subsequent corn crop, no differences were evident. Paratrichodorus minor and Pratylenchus spp. (primarily P. scribneri) were mostly unaffected by the crop rotation treatments, but in a felv instances, Pratylenchus spp. densities were higher in conventional than in no-till plots. In general, tillage had little effect on densities of most nematodes examined, and rotation appears to be more important than tillage for managing plant-parasitic nematodes under these conditions.