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Response of Grain Sorghum to Iron Sources Applied Alone or with Fertilizers

Mortvedt, J. J., Giordano, P. M.
Agronomy journal 1971 v.63 no.5 pp. 758-761
Sorghum bicolor, application rate, calcareous soils, crops, dry matter accumulation, ferrous sulfate, fertilizer application, foliar spraying, forage yield, grain sorghum, greenhouses, iron, pH, phosphorus fertilizers, soil treatment, zinc, zinc sulfate
Soil applications of inorganic Fe sources are generally not effective for crops unless rather high rates are applied. Since previous results had indicated that these sources may be effective if applied at lower rates with fluid polyphosphate fertilizers, several greenhouse pot tests were conducted. Dry matter production and Fe uptake by grain sorghum (Sorghum bicolor) were higher with FeEDDHA than with FeSO₄ or Fe₂₍SO₄)₃ applied to Epping sil (pH 7.5), a calcareous soil low in available Fe. There was very little crop response to either inorganic Fe source applied alone to the soil at rates up to 24 ppm Fe. However, both sources were somewhat effective when applied with fluid polyphosphate fertilizers at the same rates. Seed and foliar spray applications were not as effective as soil application, probably because the rate of Fe was limited by the application method. Without applied Zn, crop response to FeEDDHA was limited. However, Zn uptake by sorghum decreased while forage yields increased with FeEDDHA application rate, even though ZnSO₄ was also applied to the soil. Evidence for a marked Fe-Zn interaction in sorghum was shown on this soil. Application of ZnSO₄ to the no-Fe check treatment reduced growth and Fe uptake, while high Fe applications reduced Zn uptake in the presence or absence of applied Zn.