Nitrous oxide and methane emissions during rice growth and through rice plants: effect of dicyandiamide and hydroquinone

There is growing interest in N2O and CH4 transport through rice plants, but very little information is available on the effects of inhibitors on these gaseous emissions during rice growth and through rice plants. The closed chamber technique was used to study the effect of the urease inhibitor hydroquinone (HQ) and the nitrification inhibitor dicyandiamide (DCD) on N2O and CH4 emissions. As rice plants grew, the N2O emission through rice plants was significantly reduced in all treatments; N2O emissions were always lower in the presence than in the absence of inhibitor(s). These variations paralleled those in NO3--N content of fresh rice plants. During the rice growth period, increasing NO3--N content in rice plants paralleled the increase in the N2O emission through rice plants. Hence, NO3--N in young rice plants can substantially contribute to the plant-mediated N2O flux. A substantial CH4 emission through rice plants occurred at their vigorous growth stage; CH4 emissions were always lower in the presence than in the absence of inhibitor(s). Under the experimental conditions, application of DCD, especially of DCD+HQ, could significantly improve the growth of rice, and reduce the emissions of N2O and CH4 during rice growth.