Nematode populations as affected by residue and water management in a long-term wheat-soybean double-crop system in eastern Arkansas

Soybeans (Glycine max L.) are one of the major row crops in the United States, particularly in Arkansas. The soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is one of the most damaging pests that can cause major economic losses in soybeans. Little is known concerning the combined effects of tillage [conventional tillage (CT) and no tillage (NT)], water management (irrigation and non-irrigation), residue burning (burn and no burn), and wheat residue level (high and low) on nematodes. The objective of this study was to evaluate the effects of the combination of agronomic practices (tillage, water management, burning, and residue level) on natural nematode population densities and change over the growing season in a long-term wheat (Triticum aestivum L.)-soybean rotation on a silt-loam soil in Arkansas. A suite of 10 nematode genera were measured in the top 10 cm in July, August, and October in 2017 and 2018. Averaged across all other treatment factors, SCN egg concentration was 17.9 times greater at the end of the growing season in October than in July and August. The SCN second-stage juvenile (J2) population densities were 3.4 times greater in the CT-burn than in the CT-noburn and NT-burn treatment combinations. In contrast to under CT, SCN J2 population densities were 3.8 times greater in the NT-no-burn than under the NT-burn treatment combinations. Lance, lesion, spiral, and stunt nematode population densities were also affected by various field treatment combinations. Traditional (i.e., tillage, residue burning, and irrigation) and alternative (i.e., non-tillage, no burning, and dryland) wheat-soybean management practices can influence nematode population densities even in non-problematic fields, thus potentially affecting long-term strategies to maximize soybean profitability.