Dependence of DTPA‐extractable Zn, Fe, Mn, and Cu availability on organic carbon presence in arid and semiarid soils of Punjab

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Abstract
Surface (0–15 cm) soil samples (906) collected from arid and semi‐arid regions of the Punjab state, India, were analyzed for DTPA‐(diethylenetriaminepentaacetic acid) extractable micronutrient cations of Zn, Fe, Mn, and Cu, and other soil properties. The textural classes of soils were loamy sand, sandy loam, and loam. The majority of soils were free of any salt problems and their pH values ranged from 7.0 to 10.5. The content of DTPA‐extractable Fe, Mn, and Cu was directly related to soil texture. The finer the texture, the higher was the content of these micronutrients. There was a significant positive correlation between soil organic carbon and DTPA‐extractable micronutrients. Polynomial regressions of 1st to 3rd degree best defined the relationship between soil organic carbon and DTPA‐extractable ions. In these arid and semiarid soils, the micronutrient cations are likely to constrain crop production in coarse‐textured soils having low levels of soil organic carbon.