Long-term Integrated Nutrient Management for Enhancing Soil Quality and Crop Productivity under Intensive Cropping System on Vertisols

The present investigation was carried out to study the long-term effect of integrated nutrient management on properties of Vertisol under sorghum-wheat cropping system on the research farm of Mahatma Phule Krishi Vidyapeeth, Rahuri, Maharashtra at the end of 22nd cycle. The treatments of this long-term experiment comprised of levels of NPK fertilizers, combination of NPK fertilizers with organics viz., farmyard manure (FYM), wheat straw and green manure, 100% organics and unfertilized control laid out in randomized block design with four replications. Soil physical properties were improved due to continuous application of chemical fertilizers in conjunction with organics over only chemical fertilizers. Soil organic carbon showed profound influence in enhancing soil physical properties indicating their dynamic nature and dependence on soil management practices suggesting their usefulness as sensitive soil quality indicators. The integrated use of nutrient sources was beneficial to enhance soil properties by increasing labile soil C fractions and maintained the crop yields year after year while only chemical fertilizers showed decline in yield. Continuous intensive cropping without addition of organics led to gradual loss in soil quality. The integrated use of organics with chemical fertilizers recorded 31.8% increase in hydraulic conductivity, 5.5% increase in aggregate stability, 23.4% increase in available moisture, 15.1% increase in labile carbon and 6.9% reduction in bulk density over only chemical fertilizers under long-term period of 22 years. The improvement in permanganate oxidizable carbon due to more carbon sequestration from added organic manures and increase in root residues under integration enhanced soil quality. It can be concluded that building-up of the active carbon fractions in soil is essential under intensive agriculture for enhancing soil quality which necessitates addition of organic manures and crop residues in conjunction with chemical fertilizers in balanced form and these practices can be regarded as best management practices for better carbon sequestration in soils of semi-arid areas of central India.