Study On The Direction Of Nitrogen In Paddy Field Based On Pit Positioning Test

In order to ensure the high yield of paddy fields,we always input more fertilizer but excessive fertilizer input will lead to low nitrogen utilization in rice fields,resulting in a large amount of nitrogen loss.A large surplus of nitrogen is easily lost through runoff,leakage,ammonia volatilization and denitrification,causing a series of negative environmental problems such as groundwater nitrate pollution,water eutrophication and greenhouse effect.This paper mainly focus on the irrational application of nitrogen fertilizer in the suburbs of Shanghai.Three different fertilization treatments are set up,which are chemical fertilizer treatment(CT),organic fertilizer treatment(OT),organic fertilizer and chemical fertilizer mixed treatment(MT),and no fertilization treatment is set up as a control(CK)at the same time to compare nitrogen runoff loss,nitrogen leakage loss,ammonia volatilization loss,nitrogen soil storage,and nitrogen plant uptake in paddy fields under three different fertilization modes.On the basis of ensuring rice yield and quality,a fertilization method that can effectively utilize nitrogen fertilizers is sought to reduce the harm caused by fertilization to the environment.After two years of pit positioning experiments,the following conclusions have been obtained:(1)The results of different fertilization methods on nitrogen loss in paddy fields showed that the application of organic fertilizer could significantly reduce the nitrogen loss of rice paddy ecosystem.The nitrogen loss of chemical fertilizer treatment was the highest,followed by organic and inorganic application.In terms of total loss load,the annual average loss load of OT treatment is 14.05 kg N/hm~2,the average annual loss load of MT treatment is 15.94 kg N/hm~2,and the average annual loss load of CT treatment is 20.95 kg N/hm~2.Compared with the CT treatment,MT treatment and OT treatment reduced the total nitrogen loss of paddy fields by 23.91%and 32.94%,respectively.There was no significant difference in total nitrogen loss load,runoff loss load and leakage loss load between MT and OT treatment.(2)The results of different fertilization methods on ammonia volatilization in paddy fields showed that the volatile matter of single application of organic fertilizer was lower,and the ammonia volatilization of chemical fertilizer treatment and mixed fertilization treatment was higher.The ammonia volatilization loss rate of OT treatment,MT treatment and CT treatment accounted for 7.98%,13.15%and 15.87%.Compared with CT treatment,MT treatment and OT treatment can reduce the amount of ammonia volatilization loss by 17.16%and 49.72%,respectively.(3)The results of different fertilization methods on nitrogen in paddy soil showed that except for nitrogen deficiency in CK treatment,nitrogen in CT,MT and OT treatments were stored,and nitrogen storage was94.50~127.87 kg/hm~2.Soil nitrogen storage is a process of accumulation for many years.Although there is no significant difference in soil nitrogen storage between fertilization treatments in two years,from the perspective of soil nitrogen content after harvest,soil nitrogen content in OT treatment increased by 83.13%compared with CT treatment.This indicates that long-term application of organic fertilizer can increase soil nitrogen content.(4)The results of different fertilization methods on rice plant yield showed that the effect of mixed fertilization treatment was the best when the nitrogen application rate was the same.The average yield of MT treatment in the two-year trial was 7430 kg/hm~2,the average yield of CT treatment was 7210 kg/hm~2,the average yield of OT treatment was 6475kg/hm~2,and the average yield of CK treatment was 3993kg/hm~2.Compared with CK treatment,CT treatment,MT treatment and OT treatment increased output by 80.57%,86.08%and 62.16%,respectively.Fertilization can significantly increase the nitrogen uptake of rice plants,including CK treatment of 52.67 kg/hm~2,CT treatment of161.40 kg/hm~2,MT treatment of 172.24 kg/hm~2,and OT treatment of95.40 kg/hm~2.(5)The nitrogen destiny analysis of rice paddy ecosystem under different fertilization methods showed that the proportion of nitrogen absorbed by plants best was MT treatment of 41.45%,followed by CT treatment of 38.84%,and OT treatment was only 22.96%.The nitrogen used for MT treatment is more efficient.From the perspective of nitrogen soil storage,OT treatment was 30.78%,CT treatment was 30.05%,which was more than 22.74%of MT treatment.The more nitrogen stored in the soil,the higher the risk of nitrogen loss in the next season,indicating MT treatment risk of nitrogen loss is low.From the perspective of ammonia volatilization loss,the CT treatment was 11.46%,which was higher than9.49%for MT treatment and 5.76%for OT treatment.From the perspective of runoff leakage,the CT treatment was 5.04%,which was higher than 3.83%for MT treatment and 3.38%for OT treatment.It can be seen that the MT yield is the highest and the nitrogen utilization rate is the highest,and the risk of nitrogen loss is low.Therefore,MT treatment is recommended as the best fertilization method.