Iron Deficiency of Soybean in the Upper Midwest and Associated Soil Properties

Iron deficiency chlorosis is a common, yield-limiting condition for soybean [Glycine max (L.) Merr.] grown in areas with high-pH, calcareous soils. The objectives of this study were to document the extent of chlorosis in an area of the upper Midwest, to understand producers' perceptions and management practices related to Fe deficiency chlorosis, and to investigate the soil properties associated with it. A survey tool evaluated the perceptions of soybean producers in western Minnesota regarding cause, extent, and management of chlorosis. A detailed field study in western Minnesota compared plant attributes and soil properties in severely chlorotic, moderately chlorotic, and nonchlorotic sites. Soybean producers indicated that Fe chlorosis is responsible for substantial yield loss on 24% of their crop even though the majority of the producers selected chlorosis-resistant varieties. Chlorotic plants had stunted growth and poor nodule development relative to nonchlorotic plants. Compared with nonchlorotic areas, soil in chlorotic areas had greater soil moisture content and concentrations of soluble salts, carbonates, and diethylenetriaminepentaacetic acid (DTPA)-Cr and had lesser concentrations of DTPA extractable Fe, Mn, Ni, and Cd. Discriminant analysis identified soluble salts, DTPA-Fe, DTPA-Cr, and soil moisture content as a set of significant predictors of chlorosis. This set of variables suggests that chlorosis occurs due to multiple stresses and not simply to limited available Fe. For a diagnostic soil test, a combination of DTPA-Fe and soluble salts predicted chlorosis expression. These observations should be considered in soybean variety screening so that variety tolerance can be matched with specific soil properties.