Evaluation of sustainable nutrient management practices based on land degradation and rainfall effects on soybean yield and organic carbon and available N content in rainfed vertisols

Abstract

Long term experiments with nine organic and inorganic fertilizer treatments. Control, 20 kg N+13 kg P, 30 kg N+20 kg P, 40 kg N+26 kg P, 60 kg N+35 kg P, FYM 6 t/ha+20 kg N+13 kg P, soybean residue 5 t/ha+20 kg N+13 kg P, FYM 6 t/ha and soybean residue 5 t/ha were conducted in semi-arid vertisols at Indore, Madhya Pradesh, India, during 10 kharif seasons from 1992 to 2001 with the objective of identifying the most sustainable nutrient management practice for soybean (cv. JS-335) in the region. For this purpose, procedures of regression and sustainability index were used for evaluating the impact of integrated fertility management practices on soil health and crop productivity. There was a significant land degradation effect on the yield over the years as indicated by the negative slope of years in the regression model. The predictability of yield through land degradation variable ranged from 0.176 for control to 0.381 for 60 kg N+35 kg P per hectare treatment. Predictability of the yield through land degradation and rainfall was found to range between 0.277 for FYM 6 t/ha+20kg N+13 kg P to 0.507 for FYM 6 t/ha treatment. Using the treatment means, estimates of error and yield potential of the crop, i.e. the maximum yield of 3051 kg/ha obtained in kharif 1993. The study indicated that application of FYM 6 t /ha+20 kg N+13 kg P per hectare is highly sustainable followed by 60 kg N+35 kg P per hectare for attaining maximum yield of soybean and significant build up of organic carbon and available N and P status in the soil. The paper also presents the experimental evidence of the impact of joint use of in-situ and ex-situ residue application, vegetative barriers coupled with cost effective land treatments on checking the erosion of carbon and available nutrients from agricultural lands.