Study On Water-saving And Emission Reduction Technology Of Paddy Field In Southern Plain Irrigation Area

In order to reveal the effect of water and nitrogen regulation on water saving and emission reduction of rice in the southern plain area,two irrigation modes,namely no nitrogen(N0,0kg/hm~2),reduced nitrogen(N1,135kg/hm~2)and conventional nitrogen(N2,180kg/hm~2).Based on the experimental results,a water-nitrogen coupling model was constructed to set two nitrogen application levels,N3(108kg/hm~2)and N4(162kg/hm~2),to analyze the effects of water saving,yield increase,pollution control and emission reduction of rice under different water and nitrogen regulation schemes.The optimal paddy water and nitrogen model was obtained by principal component analysis.The results showed that:(1)Intermittent irrigation could reduce the number of ineffective tillers,irrigation amount,displacement,leakage,surface and underground nitrogen discharge loads,nitrogen harvest index and nitrogen use efficiency of rice,improve soil fertility retention and irrigation water productivity,but increase ammonia volatilization loss.(2)Nitrogen reduction fertilization was beneficial to reduce surface and subsurface nitrogen discharge loads,ammonia volatilization loss and soil denitrification,and there was no significant difference between yield and nitrogen use efficiency in paddy field.(3)Based on the results of field experiments and nitrogen input and output items,a daily scale water and nitrogen balance model was established in the paddy field.The model could simulate 11 nitrogen migration and transformation processes under different water and nitrogen treatments,including urea hydrolysis,nitrogen intake by irrigation,wet deposition,field drainage,leaching loss,ammonia volatilization rate,and nitrogen uptake by plants.The verification results show that the significance P of the simulated value and the measured value are greater than 0.05,and the correlation coefficients are above 0.8,indicating a good verification effect.(4)Principal component analysis was used to analyze the factors of water balance,yield and nitrogen input and output under different interaction models of water and nitrogen in the experiment and simulation.It was concluded that W1N1 model was the most suitable water and nitrogen model in the irrigated area of the southern plain,which reduced irrigation,drainage and leakage by 24.54%,15.03%and 5.42%compared with the local W0N2 model.Surface and leakage loads were reduced by 25.67%and 55.78%,irrigation water productivity and crop nitrogen absorption efficiency were increased by28.4%and 8.59%.