Indigenous Soil Properties Influencing the Availability of Iron in Calcareous Soils

Abstract

Abstract Iron chlorosis in plants is commonly associated with calcareous soils; however, soil factors other than total carbonate may also influence the plant's ability to obtain adequate Fe for growth. Twenty‐four calcareous soils, which represent the expected ranges of clay, CaCO 3 , Fe oxide, and organic matter contents of agronomically important soils in Texas, were sampled and examined extensively with respect to these phases along with extractable ion and soil solution composition. [ Sorghum bicolor (L.) Moench] was grown under greenhouse conditions to evaluate chlorosis and Fe uptake. Although total CaCO 3 content was important in influencing availability of Fe, the quantity, mineralogy, and crystallinity of the Fe oxide phase assumed a dominant role. Clay and organic matter contents were positively correlated with plant available Fe. The influence of these phases may be attributed to stabilization of a poorly crystalline Fe oxide phase. The contents of solution phase and exchangeable Mg 2+ were also positively correlated with the incidence of Fe chlorosis due to the influence of this ion on soil alkalinity.