AbstractsChemistry

newline ABSTRACT newlineThe present investigation was carried out to study the effect of integrated nutrient supply on transformation of sulphur, zinc and copper into various chemical pools in the on going long-term fertilizer experiment initiated during 1991 at Bhadiarkhar farm of College of Agriculture, CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur in randomized block design with twelve treatments replicated four times. The soil of the experimental site was silty clay loam and classified taxonomically as Typic Hapludalf with acidic reaction, medium in organic carbon, high in available N, medium in P and K at the initiation of the experiment. Surface (0-0.15 m) and sub surface (0.15-0.30 m) soil samples taken after the harvest of wheat (2010-11) were analyzed for different forms of sulphur, zinc and copper. Besides, pH, organic carbon, CEC, available N, P, K and S and micronutrient cations were also determined in surface soil samples taken before rice (2010 and 2011) and wheat (2010-11 and 2011-12) using standard methods of analysis. Zero fertilization led to decline in the levels of all the forms of sulphur at both the depths as compared to the buffer plots while, application of sulphur containing fertilizers and organics increased all the sulphur fractions in soil compared to control. Organic sulphur was found to be the most dominant fraction (about 96%) of sulphur. All the fractions of sulphur were highly correlated with organic carbon and CEC. Heat soluble S and organic S was found to play major role in supply of sulphur in rice and wheat, respectively. The continuous use of chemical fertilizers alone for twenty years brought out marked depletion in the pools of Zn and Cu compared to buffer plots while, integrated application of organics and chemical fertilizers recorded relatively higher content of pools of Zn and Cu over chemically treated plots. Residual Zn and Cu were the most dominant forms of zinc and copper contributing about 55 and 67 per cent to total Zn and Cu, respectively. Zn-I (non-specifically adsorbed exchangeable Zn) and Cu-I (soil solution and exchangeable Cu) were the most important fractions of zinc and copper contributing towards DTPA-Zn and Cu, respectively. There was a significant increase in organic carbon, CEC and available phosphorus content, respectively, through integrated use of organics and inorganics for the last twenty years over its initial value while available N and K declined over the years in all the treatments. Integrated use of inorganic fertilizers along with organics enhanced the productivity and NPK uptake by rice and wheat significantly. Application of 50 per cent NPK + 50 per cent N through FYM to rice followed by 100 per cent NPK to wheat recorded highest net returns in rice-wheat cropping sequence while application of 100 per cent NPK through chemical fertilizers recorded highest benefit cost ratio. newline%%%