| CH4 and N2O are two important greenhouse gases discharged in rice fields.Reducing greenhouse gas emissions from rice fields plays a crucial role in slowing global warming.Heilongjiang Province is an important commodity grain production base in China.The greenhouse gas emission of rice fields have increased due to lind large application of nitrogen fertilizer and conventional flooding,in order to improve rice production,thus low water and nitrogen utilization and greenhouse gas emission have become an urgent problem to be solved in production.Soil Moisture and nitrogen are two important factors affecting greenhouse gas emission in fields.This study sought to slow down the effects of CH4 and N2O emission by seeking reasonable water and nitrogen management model.In this experiment,the field testing method was adopted,and a japonica rice Longdao 21 was used as the material,and a two-factor split plot design was adopted.In the main area,there were three water management models of controlled irrigation?W1?,intermittent irrigation?W2?and flooding irrigation?W3?,and six nitrogen application levels(0,60,80,100,120,140 kg·hm-2 respectively).The CH4 and N2O emission rules of paddy fields under different water and nitrogen management were studied to clarify the influencing mechanism.Combined with rice yield,an environmentally friendly water and nitrogen transport model was preliminarily selected.The research results are as follows:?1?Water-saving irrigation?W1,W2?and nitrogen fertilization inhibited CH4 emission in rice field.During the growth period of rice,the emission of CH4 showed a single-peak curve,and reached a peak in the tillering stage.The emission of CH 4 was mainly concentrated in rice tillering and booting.Compared with flooding irrigation?W3?,cumulative emissions of CH4 from controlled irrigation?W1?decreased by 11.35%-29.94%,and intermittent irrigation?W2?decreased by 19.73%-30.02%;under the same water management,the CH4 cumulative emissions of high nitrogen?N4,N5?treatment were lower than those of medium nitrogen?N3?,low nitrogen?N1,N2?,and no nitrogen?N0?.?2?Water-saving irrigation?W1,W2?and nitrogen fertilization promoted N2O emission in rice fields.During the growth period of rice,N2O emission peaked in the jointing and booting stage,and the emission were mainly concentrated in this period.Compared with flooding irrigation?W3?,cumulative emission of N2O in controlled irrigation?W1?increased by 16.09%42.41%,and intermittent irrigation?W2?increased by 77.01%127.20%;under the same water management mode,cumulative emission of N2O increased with the increase of nitrogen fertilizer application amount,and the N2O emission tended to decrease when N application exceeded 120 kg·hm-2.?3?Water-saving irrigation mode?W1 W2?combined with appropriate nitrogen fertilizer could improve rice yield.Under the same nitrogen fertilizer condition,the rice yield showed as intermittent irrigation?W2?> controlled irrigation?W1?> flooding irrigation?W3?,and compared with flooding irrigation?W3?,intermittent irrigation?W2?increased yield by 5.91%12.67%;under the same irrigation treatment rice yield increased with the increase of nitrogen fertilizer application,but when N application wa s higher than 120 kg·hm-2 the yield decrease;water-nitrogen interaction affects rice yield by changing the effective tillers and grain number per spike.Biological straw yield have the same trend as rice grain yield,while the harvest index has no obvious regularity.?4?Water-saving irrigation models?W1 W2?combined with nitrogen fertilization reduced global warming potential?GWP?.The greenhouse effect of CH4 emission from rice field has a higher contribution rate to the GWP,accounting for 97.85%99.50% of the GWP,and N2O only accounts for 0.50%2.15%.Compared with flooding irrigation?W3?,controlled irrigation?W1?and intermittent irrigation?W2?were reduced by 11.12%29.52% and 18.68%29.38%,water-saving irrigation effectively reduces the global warming potential of rice fields.Under the same water management mode,the global warming potential of nitrogen treatment decreased with the increase of nitrogen fertilizer application.The yield-scaled global warming potential of different treatment is similar to the regularity of the GWP.?5?Overall,took three indicators of rice yield,warming potential and yield-scaled GWP into account.This study concluded that intermittent irrigation and 120 kg·hm-2?W2N4?combinationis the best water and fertilizer management measure for CH4 and N2O emission reduction in the rice fields of Heilongjiang Province. |
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