Effect of inorganic fertilizers (N, P, K) on methane emission from tropical rice field of India

In the tropical experimental rice field of Central Rice Research Institute, Odisha, India, an experiment was conducted during the dry season (January–April) and wet season (July–November) of rice cultivation to study the effect of nitrogen (N), phosphorus (P) and potassium (K) fertilizer application on grain yield and methane (CH4) emission. The experiment was carried out with five treatments (No fertilizer (control), N-fertilizer, P-fertilizer, K-fertilizer and N + P + K fertilizer) with three replicates of each under a completely randomized block design. Significantly higher CH4 emission was recorded from all plots during wet season. Among fertilizer applied plots, significantly higher CH4 emission was recorded from N-fertilizer applied plots (dry season: 80.27 kg ha−1; wet season: 451.27 kg ha−1), while significantly lower CH4 emission was recorded from N + P + K applied plots (dry season: 34.60 kg ha−1; wet season: 233.66 kg ha−1). Low cumulative CH4 emission to grain yield ratio was recorded from N + P + K applied plots during both seasons (83.57 kg Mg−1 grain yield during dry season and 77.14 kg Mg−1 grain yield during wet season). CH4 emission from different treatment was positively correlated with microbial biomass carbon (r = 0.516), readily mineralizable carbon (r = 0.621) and sugar (r = 0.340) content of the soil. Negative CH4 emission was recorded during the fallow period which may be attributed to higher methanotrophic bacterial population. Study suggests that the effects of P and K-fertilizer on CH4 emission from rice field along with the CH4 emission during the fallow period need to be considered to reduce the uncertainty in upscaling process.