Iron deficiency of soybean in the north central US and associated soil properties

Despite extensive research and variety screening efforts, iron deficiency chlorosis is a common, yield-limiting condition for soybean [Glycine max (L.) Merr.] grown in areas with high pH, calcareous soils. In the North Central U.S., total land area where soybean is grown on high pH soils is approximately 1.8 million ha, with iron deficiency responsible for an estimated loss in soybean grain production of 340,000 Mg at a value of $120 million per annum. This is a significant increase in the extent of iron deficiency problems relative to the past because of an expansion of soybean production in the region. Soil properties associated with iron deficiency in this region compared to adjacent areas without iron deficiency include greater soil moisture content and concentrations of soluble salts, carbonates, and DTPA-Cr, and lesser concentrations of DTPA-Fe, Mn, Ni, and Cd. Iron deficiency occurs due to multiple stresses and not simply to limited available iron. Biotic and management factors such as pests and diseases, symbiotic nitrogen fixation, seeding rate, and herbicide application also interact with iron deficiency in the field. There is a need to better match varieties to the specific soil and environmental conditions to which they are adapted.