Effects of bicarbonate, phosphorus, iron EDDHA, and nitrogen sources on soybeans grown in calcareous soil

Abstract

Abstract Hawkeye soybeans (Glycine max L.), an iron‐efficient cultivar when grown in calcareous Hacienda loam soil low in P and available Fe, did not respond to P, FeEDDHA, NH4+‐N or NO‐ 3‐N when applied singly nor to Fe + P together; but did give yield response for N + P + Fe applied together. Addition of HCO3 ‐ with N + P + Fe decreased yields by about 10% and decreased Fe in shoots also by 10%. The NH4+ source of N gave 12% higher leaf yield without HCO3 ‐ and 11% higher with HCO3 ‐ than did nitrate N. Bicarbonate alone caused severe damage to the Hawkeye soybeans, while P alone had little effect. In contrast, P was very damaging with less effect from HCO3 ‐ with iron‐inefficient PI‐54619–5–1 soybeans from a companion study. Addition of Fe decreased Zn and Mn concentrations in leaves, while addition of both Fe and P decreased Zn concentration even more. Bicarbonate contributed additionally to low Zn in leaves with treatments of Fe and Fe + P. These Fe‐efficient Hawk‐eye soybeans were less impaired by N...