Effect of combine application of organic manure and inorganic fertilizer on methane and nitrous oxide emissions from a tropical flooded soil planted to rice

- Cumulative CH4 emission was highest in rice straw + urea-N treatment
- Cumulative N2O emission was highest in poultry manure + urea-N treatment
- Global warming potential was highest in rice straw + urea-N treatment
- Compost + urea-N had lowest GHGI, highest CER and highest yield
- Compost + urea-N could be an effective option to mitigate CH4 and N2O emissions

Methane and nitrous oxide emissions, their global warming potential, carbon efficiency ratio and related biogeochemical properties of a tropical soil planted to rice were investigated under different N management [i.e. urea-N (120 kg N ha− 1), rice straw (RS) (30 kg N ha− 1) + urea-N (90 kg N ha− 1), compost (C) (30 kg N ha− 1) + urea-N (90 kg N ha− 1) and poultry manure (PM) (30 kg N ha− 1) + urea-N (90 kg N ha− 1)]. CH4 fluxes were increased by 82.7%, 65.1%, 63.4% and 31.9% in RS + urea-N, C + urea-N, PM + urea-N and urea-N, respectively whereas percentage increase in cumulative N2O emission was 390.6, 371.8, 315.6, and 253.1 in PM + urea-N, urea-N, C + urea-N and RS + urea-N, respectively over control (no fertilizer amendment). However, increase of GWPs in different manure + urea-N over that of control were 85.5%, 69.2%, 68.8% and 37.6% in RS + urea-N, C + urea-N, PM + urea-N and urea-N, respectively. Microbial biomass carbon (MBC), readily mineralizable carbon (RMC) and fluorescence diacetate (FDA) hydrolysis activity were significantly affected by integrated N-management and followed the order of C + urea-N > PM + urea-N > RS + urea-N > urea-N > control. With considerably high microbial biomass C and microbial activity, high C efficiency ratio, high yield and low greenhouse gas intensity, C + urea-N could be a better option to mitigate CH4 and N2O emissions and to maintain soil biological quality and yield in tropical paddy.