Iron availability as influenced by phosphate and ferrous‐and ferric‐sulfate fertilizers

Abstract

Abstract Ferrous‐and ferric‐sulfate was banded alone or with phosphate fertilizers [urea phosphate (10–30–0), urea sulfate phosphate (10–30–0‐7S), diammonium phosphate (DAP), and mono calcium phosphate (MCP) in an Fe‐deficient soil in a greenhouse experiment The Fe rates were 0, 25, and 50 mg/kg, and P rates were 0 and 50 mg/kg. Dry matter yield and nutrient uptake by sorghum plants were measured and the residual effects were determined on a second crop. The Fe application alone had little effect, but when banded together with P fertilizers, it more effectively increased dry matter yield, and the uptake of Fe, Mn, and Zn. Addition of P fertilizers with FeSO4 increased the DTPA‐extractable soil Fe in the following order: DAP>10–30–0 >10–30–0‐7S>MCP. The addition of P fertilizers also increased NaHCO3‐extractable soil P, but decreased the DTPA extractable soil Mn and Zn. The ferrous‐Fe source generally was more effective than was the ferric‐Fe source. Ferrous and ferric sulfate availability was enhanced by ...