Yield and soil nutrient balance of a sugarcane plant–ratoon system with conventional and organic nutrient management in sub-tropical India

A 3-year field trial of sugarcane, comprising 11 treatment combinations of different organic manures with and without Gluconacetobacter diazotrophicus (Gd), NPK and an absolute control, on an inceptisol was conducted to assess the effect of these treatments on sugarcane total and economic yield, the benefit:cost ratio, nutrient balance and soil quality in a sugarcane plant–ratoon system. The highest cane yield (78.6 t ha−1) was recorded in the plant crop given vermicompost + Gd, whereas ratoon yields (first and second) were highest (80.8 and 74.9 t/ha−1, respectively) with sulphitation press mud cake (SPMC) + Gd. In both plant and ratoon crops, a number of different organic manures produced the highest cane yield that was also statistically similar to those obtained with using the recommended NPK levels (76.1, 78.2 and 71.7 t/ha for plant crop and subsequent two ratoons, respectively). The highest benefit:cost (B:C) ratio in the plant and two ratoon crops (1.28, 2.36, 2.03 respectively) were obtained with the addition of SPMC + Gd. The nutrient balance for NPK in the soil was highest in the SPMC + Gd treatment. The highest increase in organic C (94%) and total N (87%), in comparison to the initial level, and soil microbial biomass C (113%) and soil microbial biomass N (229%), in comparison to the control treatment, was recorded with the addition of SPMC + Gd. The maximum decrease in soil bulk density (BD) (12%) with an increase in soil aggregate (17%) and water infiltration rate (35%) was obtained with the addition of SPMC. Overall, the sugarcane crop responded well to different organic manures in a multiple ratooning system with a better economic output and improved soil quality. Strategic planning in terms of an integrated application of these manures with inorganic chemicals will not only sustain our soils but will also be beneficial for our farmers in terms of reducing their dependence and expenditure on chemical fertilizers.