Evaluation of fertilizer and water management effect on rice performance and greenhouse gas intensity in different seasonal weather of tropical climate.

Intensively double cropping rice increases greenhouse gas (GHG) emission in tropical countries, and hence, finding better management practices is imperative for reducing global warming potential (GWP), while sustaining rice yield. This study demonstrated an efficient fertilizer and water management practice targeting seasonal weather conditions effects on rice productivity, nitrogen use efficiency (NUE), GWP, and GHG intensity (GHGI). Two-season experiments were conducted with two pot-scale experiments using urea and urea+cattle manure (CM) under continuous flooding (CF) during the wet season (2013WS), and urea with/without CaSiO3 application under alternate wetting and drying (AWD) during the dry season (2014DS). In 2013WS, 120kgNha-1 of urea fertilizer resulted in lower CH4 emission and similar rice production compared to urea+CM. In 2014DS, CaSiO3 application showed no difference in yields and led to significant reduction of N2 O emission, but increased CH4 emission and GWP. Due to significant increases in GHG emissions in urea+CM and CaSiO3 application, we compared a seasonal difference in a local rice cultivation to test two water management practices. CF was adopted during 2013WS while AWD was adopted during 2014DS. Greater grain yields and yield components and NUE were obtained in 2014DS than in 2013WS. Furthermore, higher grain yields contributed to similar values of GHGI although GWP of cumulative GHG emissions was increased in 2014DS. Thus, utilizing urea only application under AWD is a preferred practice to minimize GWP without yield decline for double cropping rice in tropical countries.