Effect of water and nitrogen coupling on energy balance and production efficiency in rice production

This study evaluated the effects of water-nitrogen coupling on the energy balance and production efficiency of rice production in Hainan Province, a region of China with tropical climatic. Results showed that the effects of water and nitrogen fertilizer on the total energy output (Eo), net energy (NE), and energy production efficiency (EPE) of rice were coupled. The total energy input (Ei) for rice production increased with irrigation water and nitrogen fertilizer application. Rice production currently depends heavily on indirect and nonrenewable Eis. Diesel, machinery, and nitrogen fertilizer Eis accounted for more than 75 % of the total Eis for rice production. The highest total Eo and NE were observed in rice treated with F-N100 and AWD-N150, respectively. Except for the F-N150 treatment, the total Eo and NE of rice increased with nitrogen fertilizer application. Higher EPE was observed for rice treated with R-N100. In conclusion, the AWD-N150 treatment is suitable for rice production areas with good irrigation conditions, while the R-N100 treatment should be adopted as the preferred water and nitrogen management strategy in rice production areas with high rainfall. Furthermore, research on reducing Eis for irrigation, tillage, and nitrogen fertilizer application for rice production should be strengthened in the future.