Effect of Long Term Conjunctive Nutrient Management Practices on Soil Quality Indicators and Indices in Oxisol Soils under Rice (Oryza sativa L.)-Black gram (Vigna radiata L.) Cropping System in Ranchi Region

A long term study was conducted for 8 years (from 1998–2005) to quantify the influence of conjunctive nutrient management practices on soil quality indicators and indices. The experiment was laid out in a randomized block design with nine treatments in three replications under rice (Oryza sativa L.)-black gram (Vigna radiata L.) rotation. The nutrient management treatments selected for soil quality assessment studies comprised of T1: Control, T2: 100% recommended N (40 kg N/ha through inorganic), T3: 50% recommended N (20 kg N/ha through inorganic), T4: 25 kg N through compost, T5: 15 kg N/ha (compost) + 10 kg N/ha (inorganic), T6: 15 kg N/ha (compost) + 20 kg N/ha (inorganic), T7: 15 kg N/ha (green leaf) + 10 kg N/ha (inorganic), T8: 15 kg N/ha (green leaf) + 20 kg N/ha (inorganic). After 7 years of experimentation, the results of the study revealed that the application of 15 kg N Green leaf + 20 kg N inorganic (1.57), 15 kg N Green leaf + 10 kg N inorganic (1.56), and the application of 100% recommended N (40 kg through inorganic) significantly influenced the soil quality (SQI 1.58) compared to other treatments and maintained relatively higher soil quality indices. The indicators which emerged as key soil quality indicators and which substantially contributed towards soil quality were: EC (7%), OC (20%), available K (10%), available B (8%), DHA (15%), BD (23%) and MWD (17%). Bulk density was found to have maximum contribution towards aggrading the soil quality followed by organic carbon in these soils. The results of the present study will be highly useful to researchers, land managers, students and other stake holders associated with soil and land management.