Effects of nitrogen fertiliser and wheat straw application on CH4 and N2O emissions from a paddy rice field

A 3-year field experiment was conducted to study the effects of nitrogen fertiliser and straw application on CH4 and N2O emissions from a paddy rice field in China from 2003 to 2005. Three rates of nitrogen fertiliser ( 0, 200, and 270 kg N/ha) and 2 levels of wheat straw ( 0 and 3.75 x 10(3) kg/ha) were adopted in this experiment. The effect of nitrogen fertiliser application on CH4 emission seemed to be affected by application rate. Nitrogen fertiliser decreased CH4 emission relative to the control when applied at a rate of 200 kg N/ha, but the effect lessened if the application rate was further increased to a rate of 270 kg N/ha. The depressive effect of nitrogen fertiliser application on CH4 emissions from rice fields became more pronounced when wheat straw was also incorporated with fertiliser, compared with nitrogen fertiliser application alone. Straw incorporation significantly enhanced CH4 emission by 3-11 times (P < 0.05). Nitrogen fertiliser application increased N2O emission by 5-6 times when applied at a rate of 200 kg N/ha and by 10-14 times when applied at a rate of 270 kg N/ha. On average, straw incorporation tended to decrease N2O emission by about 30% significant (P > 0.05). More than 50% of seasonal total amount of N2O was emitted within 11 days after fertiliser application at panicle initiation. The global warming potential caused by both CH4 and N2O emissions was affected by nitrogen fertiliser application rate and significantly stimulated by wheat straw incorporation. The global warming potential was lowest when nitrogen fertiliser was applied at a rate of 200 kg N/ha.