Rotations of soybean with tropical corn and sorghum for the management of nematodes.

The relative efficacy of rotations of soybean with sorghum and tropical corn for nematode management was studied for 2 years in a field infested with root-knot (Meloidogyne arenaria) and soybean cyst (Heterodera glycines, race 14) nematodes. Corn, sorghum, and soybean cv. Kirby were planted in 1989, and in 1990 the same areas were planted with seven soybean cultivars with and without at-plant application ofaldicarb. Corn and sorghum did not support H. glycines, but significant juvenile populations of the nematode in soil were associated with Kirby soybean. Numbers of H. glycines and M. arenaria juveniles in 1990 depended on cultivar and cropping system but were little affected by nematicide treatment. Lowest numbers of H. glycines juveniles were associated with Leflore soybean and the corn-soybean rotation. Numbers of M. arenaria juveniles were highest with Leflore and lowest with Braxton and Brim soybean. The sorghum-soybean rotation resulted in slightly higher numbers of M. arenaria juvenile populations than soybean monoculture or the corn-soybean rotation. Aldicarb increased yields of some cultivars, but its use was not justified economically. Yields of all cultivars were from 19-287% higher in rotation systems than in monoculture.