Management Strategies for Chlorotic Soybeans in Western Kansas.

Iron deficiency chlorosis is a common yield-limiting factor for soybean grown on high pH, calcareous soils, like those in Western Kansas. The causes of iron chlorosis are complex, which makes chlorosis difficult to manage.  Foliar iron application, iron chelate seed coating, and varietal selection of iron chlorosis tolerant soybeans have all been proven effective in past studies in the Great Plains.  Our objectives for this study were to (i) evaluate the effect of different iron fertilizer applications strategies on soybean yield on iron deficiency chlorosis potential soils and evaluate economic returns to iron fertilizer applications and varietal resistance selection. Plots were arranged in the field in a randomized complete block design with four replications. Two soybean varieties with different genetic tolerance to iron chlorosis: AG2905, with a very good chlorosis tolerance, and AG3205, with low tolerance. Iron chelated (FeEDDHA 6%) was used for seed coating at 0.5 lb Fe/acre. Two different iron chelates (Fe-EDDHA or Fe-HEDTA) was applied as foliar treatment at 0.1 lb Fe/acre. Foliar application seemed to improve “greenness”, but created no statistically significant increase in plant yield in 2009. But seed coating provides the yield increases of 57% in the chlorosis tolerant variety and a 25% increase in the susceptible variety  across locations. Selection of a soybean variety that is tolerant to iron deficiency chlorosis seems to provide significant improvements for chlorosis management.