Zinc pools and their availability to maize-wheat rotation

Abstract

SUMMARYIn a long-term experiment with maize-wheat rotation, no response to zinc application was observed, even after 13 years of cropping though the status of zinc had decreased to a deficient level (0.35 mg/kg; DTPA). A study was, therefore, planned to find the reasons for lack of response, and the zinc fractions in the soil were analysed to assess their contribution to plant growth. All the zinc fractions other than organic zinc decreased as a result of continuous cropping without zinc application. Depletion was from the 0-30 cm layer and mainly from acid-soluble and weakly adsorbed Zn fractions. Applied zinc remained mainly in the 0-30 cm layer as acid soluble and weakly adsorbed Zn pools. All the fractions were strongly related to each other. The acid-soluble zinc fraction contributed 54 % to zinc uptake by the crops. Thus release of zinc from this pool was perhaps the main reason for lack of response to zinc.