Impact of integrated nutrient management options on GHG emission, N loss and N use efficiency of low land rice

Abstract

Emerging challenges of fertilizer use in intensive rice cultivation system such as nutrient mining, nutrient imbalance and environmental pollution etc. warrant for a rationalized nutrient management strategy combining both organic and inorganic sources. Field trials were conducted with rice cultivar Naveen during wet and dry seasons of 2015-16 to measure greenhouse gas (GHG) emission, nitrogen (N) loss and N use efficiency in low land rice under different integrated nutrient management (INM) options. Six treatments including 0 N, 100 % N from urea, 50 % N from urea + 50 % N from farm yard manure (FYM), 50 % N from urea + 50 % N from poultry manure (PM), 50 % N from urea + 25 % N from rice straw + 25 % N from FYM, and 50 % N from urea + 25 % N from blue green algae (BGA) + 25 % N from FYM were replicated thrice in randomized block design. Results revealed that 11–24% and 13–27 % reduction in nitrous oxide (N2O) and ammonia (NH3) emission respectively, in INM treatments as compared to urea alone. However, increase in methane (CH4) emission in INM treatments due to inclusion of organics led to overall increase in global warming potential (GWP). Yield reduction to the extent of 9.8–20.0 % in INM treatments as compared to urea alone resulted in higher greenhouse gas intensity (GHGI) in the former. Among different INM treatments, urea + PM and urea + FYM + BGA performed better in terms of yield and GWP than others. Enhancement of labile carbon (C) fractions and enzymatic activities in INM plots indicated the potential of combined application of organics manure and inorganic fertilizer in increasing fertility of soil in long run. Different organic amendments differ among themselves in relation to their effects on soil C and N dynamics and rice yield, which need to be taken into consideration while devising standard INM package for low land rice.