Comparison of Crop Rotation and Fallow for Management of Heterodera glycines and Meloidogyne spp. in Soybean.

The effects of cropping systems (fallow, rotation with sorghum-sudangrass hybrid [Sorghum bicolor x S. sudanense], and continuous soybean [Glycine max]), nematicide (aldicarb) treatment, and soybean cultivar on yield and nematode population densities were studied in a field infested with a mixture of Meloidogyne spp. and Heterodera glycines. Soybean following sorghum-sudangrass yielded 111 kg/ha more than soybean following fallow and 600 kg/ha more than continuous soybean. Aldicarb treatment increased yield by 428 kg/ha, regardless of previous crop. Cultivars interacted significantly with nematicide treatment and previous crop with respect to yield. Sorghum-sudangrass reduced numbers of Meloidogyne spp. compared with fallow and continuous soybean, but cropping system did not affect H. glycines numbers. The cultivar x previous crop and cultivar x nematicide interactions were significant for numbers of Meloidogyne spp. and H. glycines. We concluded that sorghum-sudangrass hybrid and fallow are effective in reducing yield losses caused by mixed populations of Meloidogyne and H. glycines. Highest yields were obtained using crop rotation and cultivars with the highest levels of resistance to both nematodes.