Yellow soybean too early this season?
Since early August Iowa farmers have been reporting soybean fields or parts of fields with yellow or greenish-yellow leaves in the upper canopy which resemble early senescence and sometimes nitrogen (N) deficiency symptoms. The soybean growth stage is mainly R4 to R5. Several factors can cause these symptoms. Rainfall has been extremely variable this season in Iowa, with severe drought still persisting in some areas of the state. Yet, areas in southern and southeast Iowa have experienced normal to excessive rainfall.