| Nitrogenous fertilizer was added to agricultural production after the Haber process reaction was found.Through the use of chemical fertilizer,on the one hand,we have greatly promoted the production of crops,but also has a certain impact on the biogeochemical cycle of N and the ecological environment.However,the increase of crop yield is limited by chemical fertilizer.Many studies have proved that reasonable reduction of chemical fertilizer application will not reduce the yield,which provides ideas on how to solve the contradiction between agricultural development and environmental problems.A typical rice cowpea rotation system in Hainan was selected for field experiment.Based on the in-situ monitoring of N2O emission,the characteristics of N2O emission and the nitrogen loss process of N2O pathway were studied under different fertilization modes.By monitoring the leaching and runoff in the field,the effects of different fertilization modes on soil leaching and runoff path nitrogen loss in rotation system were explored.The experiment consisted of 5 treatments:conventional farming fertilization（CON）,optimized fertilization（OPT）,organic-inorganic fertilization（ORG）,slow-controlled optimization fertilization（SCOPT）and no nitrogen as control（CK）.The N2O emission was measured by static chamber-gas chromatography during the whole paddy-cowpea rotation seasons,and the GHGI and N2O emission coefficient were estimated.The leaching and runoff samples of the whole planting process were collected by leakage pool method,and the total nitrogen content was determined.The results show that:（1）During the rice cowpea rotation,the three optimized fertilization treatments can ensure the yield of rice and cowpea.The yield of two crops treated by scopt is higher than that of CON,and the yield of rice and cowpea reaches 6043 kg·hm-2and 23368 kg·hm-2respectively.（2）The peak value of N2O emission appeared after fertilization and concentrated in cowpea season.The cumulative N2O emission in rice growth season was 0.19-1.37 kg·hm-2.Compared with CON treatment,other treatments reduced N2O emission by 50%to 86%.And the cumulative N2O emission in cowpea growth season was 1.15-3.52 kg·hm-2,except for ORG increased by 30%,the other two treatments decreased by 7%and 29%.During the fallow period,the N2O emission was relatively stable,but the total accumulation could not be ignored.（3）The loss of leaching nitrogen was 1.04-3.30 kg·hm-2in rice season,0.80-2.18 kg·hm-2in fallow period and 0.88-2.19 kg·hm-2in cowpea season.Runoff nitrogen loss was7.86-17.87 kg·hm-2in rice season,4.94-12.76 kg·hm-2in fallow period,and no data in cowpea season.The loss of nitrogen in leaching and runoff of ORG treatment was significantly higher than that of OPT treatment.（4）Among the three optimized fertilization treatments,SCOPT treatment with NAM can increase the yield and reduce the N2O emission,leaching and runoff nitrogen loss,which is the optimal fertilization scheme. |
