Long-term effect of organic and inorganic Fertilizers on soil physico-chemical properties of a silty clay loam soil under rice-wheat cropping system in Tarai region of Uttarakhand

The long-term impact of chemical fertilizers on soils and environment is harmful. Use of unbalanced nutrients in the soils may be harmful in the long run causing soils an unproductive one. It is true that sustainable production of crops cannot be maintained by using only chemical fertilizers and similarly it is not possible to obtain higher crop yield by using organic manure alone. Proper identification and management of soil fertility problems are prerequisite for boosting crop production and sustaining higher yields over a long period of time. So use of organic manure in integration with inorganic fertilizers is very important in improving soil fertility and crop productivity. In order to study the long-term effect of organic and inorganic fertilizers on soil physico-chemical properties of a silty clay loam soil under rice-wheat cropping system in tarai region of Uttarakhand, a field experiment was conducted at Norman E. Borlaug Crop Research Centre of the Govind Ballabh Pant University of Agriculture and Technology, Pantnagar during 2014-2015. The soil pH, EC, bulk density and Organic carbon ranged from 7.24 to 7.64, 0.26 to 0.32 dSm-1, 1.28 to 1.33 Mgm-3 and 0.58 to 1.12 percent, respectively at the surface layer and 7.58 to 7.77, 0.19 to 0.24 dSm-1, 1.34 to 1.41 Mgm-3 and 0.27 to 0.61 percent, respectively at the sub-surface layer. The application of NPK along with organic residues increased the pH, EC, organic carbon. The content of available S and Ca improved significantly over the control. The content of S and Ca ranged from 16.87 to 30.41ppm and 141.87 to 268.53 ppm, respectively at the surface layer and 15.07 to 22.51 ppm and 108.21 to 308.61 ppm, respectively at the sub-surface layer. The partial replacement of N through FYM, wheat straw and mung straw caused significant improvement in soil physico-chemical properties. In all the treatments of sub-subsurface layer nutrient status decreased as compared to surface layer except in case of pH, bulk density and Calcium. The treatment T7 where 25 percent N was applied through FYM and 75 percent through NPK fertilizer and T10 where 50 percent N was applied through mung straw and 50 percent through NPK were found best among all the treatments.