Comparison of field management strategies for preventing iron deficiency chlorosis in soybean

Iron deficiency chlorosis (IDC) is a serious management issue for soybean [Glycine max (L.) Merr.] grown on calcareous soils. Strip trials were established on calcareous Mollisols to study the effects of Fe-ethylene diamine-N,N¢-bis (hydroxy phenyl) acetic acid (EDDHA) in-furrow (IF-Fe) and of an oat (Avena sativa L.) companion crop on two soybean varieties either tolerant or susceptible to IDC. The severity of IDC varied from low to severe within sites. The susceptible variety produced the highest yield in the absence of IDC. In-furrow Fe increased the yield of a variety susceptible to IDC under moderate to severe IDC. The oat companion crop increased yield consistently for the susceptible variety under severe IDC and sometimes reduced yield when oat grew beyond 25 cm in height. The tolerant variety without IDC management produced yields similar to those of the susceptible variety with IF-Fe or an oat companion crop. Oat reduced trifoliate nitrate N and Fe concentration regardless of IDC severity. Trifoliate Fe concentration lowered with IF-Fe, but only when oat was not planted. Grain protein and oil concentration were affected by variety, but were not affected by IDC management. Soil test factors such as soil organic matter (SOM), pH, electrical conductivity (EC), or diethylene triamine phentaacetic acid Fe (Fe-DTPA) were poor predictors of the severity of IDC. Variety selection is the most important strategy for lessening the severity of IDC. In-furrow application of Fe-EDDHA provides a solution for mitigating moderate to severe IDC and provides less risk than an oat companion crop.