Effects of Nitrogen and Phosphorous Fertilisation on Nitrous Oxide Emission and Nitrogen Loss in an Irrigated Rice Field

Nitrous oxide is an important greenhouse gas which contributes to stratospheric ozone destruction, but still little is known about emission of this trace gas from paddy rice fields treated with N and P fertilisation and how it is affected by irrigation. Therefore, a field experiment was conducted to measure nitrous oxide (N2O) emissions and nitrogen loss through the emission froin irrigated rice fields treated with different nitrogen and phosphorous fertilisers. Emissions of nitrous oxide (N2O) were ineasured by the closed chamber method during the vegetative period (6 July to 8 August) of the paddy plant in ShuangQiao farm in the northern part of Zhejiang Province in the Southeast coastal area of China. Jia-9312 rice variety was used for rice cultivation. Treatments of five nitrogen rates (0, 90, 180, 270, 360 kg N ha(-1)) and three phosphorous rates (0, 40 and 60 kg P ha(-1)) were laid out in a randomised block design with 3 replications in 45 plots. Submerging the rice field by continuous flooding irrigation at 7 cm depth up to maturity caused a remarkable reduction in N2O emission. First and second peaks of emission were observed iininediately after basal and top dressing of fertiliser addition due to nitrification and denitrification process. The study indicates that 180 kg N ha incorporation with 40 kg P ha may be practised in mitigation of N2O emissions from irrigated paddy rice fields. The amount of total N2O emission froin different N and P treatments ranged from 431.89 to 1181.21 g N ha(-1) which was a N loss of 0.10 to 1.18% through emission of applied nitrogen.