Soybean and Soybean Cyst Nematode Response to Soil Water Content in Loam and Clay Soils

Soybean cyst nematode (Heterodera glycines Ichinohe) (SCN) a major pest of soybean [Glycine max (L.) Merr.] in the southeastern USA. The objective of this study was to determine the effect of wet and dry silt loam and clay soils on SCN development and corresponding soybean yield response in a greenhouse study. ‘Tracy-M’ soybean was grown in pots that contained either Dubbs silt loam(fine-silty, mixed, thermic Typic Hapludalf or Sharkey clay (very fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) surface soils that were watered to maintain adequate soil water potential (SWP) (−30 kPa SWP, wet treatment), or had water added at onehalf the rate of the adequate treatment (dry treatment). Nematode treatments were either infested or noninfested. Experiments were conducted in 1987, 1988, and 1989, and new soil was infested each year. Number of cysts increased significantly with time in the wet silt loam treatment, stayed the same as the initial infestation in the dry silt loam treatment, and declined significantly in both the wet and dry clay treatments in all years of the study. Infestation by SCN caused a reduction in seed yields in both soils, but the decrease was less in the clay soil. Soil water content in each soil interacted with level of SCN infestation to influence soybean yield. The interaction was not dependent on similar SCN infestation levels between soils, or similar differences in SCN infestation between wet and dry soil treatments within soil. Yield declines associated with SCN infestation were highly correlated with number of seed. These results indicate that SCN will not maintain populations in fine-textured clay soil under greenhouse conditions, nor result in the magnitude of yield decline that often is measured in coarse-textured soil.