Distribution of zinc as influenced by long-term application of fertilizers and manure in a Vertisol

The present investigation was carried out under the ongoing All India Coordinated Research Project on Long-term Fertilizer Experiment with soybean-wheat cropping sequence at Jabalpur, Madhya Pradesh during 2010–11. The study was aimed to find out the effect of continuous application of inorganic fertilizers and organic manure on the depth wise distribution of Zn fractions under soybean-wheat cropping sequence in a Vertisol. Results revealed that the highest value of DTPA-Zn and its fractions (water soluble-Zn, exchangeable-Zn, complexed-Zn, organically bound-Zn, occluded-Zn and residual-Zn) were recorded in the treatment receiving 100%NPK + Zn, followed by 100% NPK +FYM; while the lowest values of DTPA-Zn and its fractions were noted in control plot. The available Zn and various Zn fractions were found to be higher in 0–20 cm soil depth which decreased with increasing soil depth in all the treatments. Zinc content in various fractions varied in the order of water soluble <exchangeable-Zn <complexed-Zn <organically bound-Zn <occluded-Zn <residual-Zn. In general, the significant positive relationship of water soluble-Zn was observed with pH, EC, OC and CaCO₃ contents at 0–20 cm soil depth.