Soil quality indexing of an acid Alfisol under rice wheat cropping system based on continuous integrated plant nutrient supply in mid hills of Himachal Pradesh

Abstract

newline Present investigation was carried out in a long-term integrated nutrient management experiment with rice wheat cropping sequence initiated in kharif 1991 at Padhiyarkhar research farm of College of Agriculture, Palampur, District Kangra. Twelve treatments comprising of T1-Control (no fertilizer, no manure), T2-50% NPK to both rice and wheat, T3-50% NPK to rice and 100% NPK to wheat, T4-75% NPK to both rice and wheat,T5-100% NPK to both rice and wheat, T6-50% NPK + 50% N through FYM to rice and 100% NPK to wheat, T7-75% NPK + 25% N (FYM) to rice and 75% NPK to wheat, T8-50% NPK + 50% N through wheat straw to rice and 100% NPK to wheat, T9-75% NPK + 25% N (wheat straw) to rice and 75% NPK to wheat, T10-50% NPK + 50% N through Dhaincha green manure to rice and 100% NPK to wheat, T11-75% NPK + 25% N (Dhaincha green manure) to rice and 75% NPK to wheat and T12-Farmers Practice (40% NPK + FYM at 5 t ha-1 to both the crops) were evaluated in a randomized block design with four replications. Surface (0 0.15 m) and sub-surface (0.15 0.30 m) soil samples were collected after the harvest of wheat crop during 2016-17 and analyzed for various soil physical, chemical and biological properties. Integrated use of organics and inorganics has sustained the crop productivity and significantly improved the soil properties. Sustainable yield index (SYI) was found lowest (0.33) in the treatment where no fertilizer or manure was applied (T1) and highest (0.66) where 50 per cent NPK through fertilizers and 50 per cent N through FYM to rice was followed by 100 per cent NPK to wheat (T6). Available nitrogen and potassium declined over the years in all the treatments whereas significant build-up in available phosphorus was observed through integrated use of organics and fertilizers over the respective initial values. Saturated hydraulic conductivity, pH, organic carbon, labile carbon, microbial biomass nitrogen and dehydrogenase activity were found to be the key minimum data set (MDS) indicators in this study. Multiple regression evaluated the efficacy of MDS taking SYI as goal (r2 =0.91 for surface and 0.88 for sub-surface soil). The soil quality index (SQI) was calculated by using weighting factors derived from principal component analysis for each scored MDS variable. The highest SQI values (2.81 for surface and 2.78 for sub-surface soil) were found in T6 followed by T10 (2.41 for surface and 2.56 for sub-surface soil) and the lowest (1.16 for surface and 1.23 for sub-surface soil) in T1. Application of 50% NPK through chemical fertilizers + 50% N through FYM in rice followed by 100% NPK in wheat (T6) was found to be better than other treatments in sustaining crop productivity as well as maintaining soil quality under rice-wheat cropping sequence.