Effects Of Nitrogen Application On Nitrogen Loss And Rice Nitrogen Threshold In Rice Field

n application rate;ammonia volatilization;runoff;leaching;nitrogen thresholdIn the agricultural non-point source pollution,the high application of nitrogen fertilizer to form a low utilization rate.The loss of serious situation makes the nitrogen pollution more prominent.In China,the long-term use of chemical fertilizers in a long time makes the physical structure of the soil decreased,land consolidation,soil fertility decreased,crop yields decreased,nitrogen utilization is much lower than the average level of developed countries.Agricultural non-point source pollution has become a lake water body eutrophication,land fertility decline,groundwater and surface runoff pollution and other issues,of which the lake water pollution is particularly serious.In China’s major water systems,the overall water quality has reached a moderate degree of pollution,individual lake pollution phase serious.The application of a large number of chemical fertilizers and pesticides in the yield also led to the increase of Chaohu load,water eutrophication can not be ignored.In order to study the relationship between nitrogen fertilizer loss and nitrogen loss in rice and wheat field in Chaohu Lake Basin,this paper studied the nitrogen loss in farmland and reduced the nitrogen emission to farmland.In this study,field experiment was conducted.In this study,Set the test area,set different levels of nitrogen,and the corresponding construction of runoff pool.The effects of ammonia volatilization,field water,leaching water,runoff water after each rainfall,and grain straw and surface soil after harvest were analyzed by analyzing the ammonia volatiles,the surface water and 0-90cm leaching.Water content and concentration,rice yield and so on.The changes of field water concentration in paddy field,the dynamic change of ammonia volatiles in paddy field and the proportion of ammonia volatilization to nitrogen application were studied.The runoff loss and runoff coefficient,20cm,40 cm,60 cm and 90 cm soil layers,as well as the rational nitrogen input based on food safety and environmental safety,the response of ammonia volatilization and farm runoff loss to nitrogen application rate Rate of Nitrogen Application in Rice Field of Rice-wheat Rotation in Chaohu Lake Watershed.The main findings are as follows:(1)The nitrogen concentration of paddy field surface water reached its peak immediately after fertilization,except for the control treatment concentration of 2.74mg/L,the other treatment between 36.49-58.55mg/L,reached the surface water inferior V class standard.After a week down to the control level.There was a significant positive correlation between water nitrogen concentration and nitrogen application rate,and the concentration was:basal fertilizer>tillering fertilizer>panicle fertilizer.The concentration of water and nitrogen in the control surface was kept at a low level,while the other treatments treated with high nitrogen treatment were significantly higher than those of low nitrogen treatment.Therefore,one week after fertilization is a critical period of controlling nitrogen loss in paddy fields.(2)The application of nitrogen fertilizer increased the risk of ammonia volatilization in paddy field to a certain extent,significantly increased the amount of ammonia volatilization,and the total amount of ammonia volatilization increased withthe difference of total ammonia volatilization(P<0.05).The total loss of ammonia(N0-N5)was 28.62-155.32 kg/hm~2,and the loss rate was 34.5%-49.4%.Compared with runoff and leaching loss,ammonia volatilization loss is large,and the proportion of nitrogen fertilizer is higher,and ammonia volatilization loss is the most important way of nitrogen loss in this area.After three fertilization,the amount of ammonia volatiles was>tillering fertilizer>panicle fertilizer.The dynamic patterns of ammonia volatilization(N0-N5)were similar,and reached the peak in the third to fourth days after fertilization,and then gradually decreased to the 7th day,which was close to the control level.A week after fertilization is a critical period of controlling the volatilization of ammonia in paddy fields.(3)The runoff loss of nitrogen in paddy field increased with the increase of nitrogen application rate.(N0-N5),the total nitrogen loss was 3.4-13.86kg/hm2,and the wastage rate was 0.42%-2.32%.The loss of nitrate(N0-N5)was 2.13-7.15kg/hm~2,(0.30%-1.11%).The wastage of N0-N5 is 0.16-2.54kg/hm~2 and the wastage rate is 0.02%-0.53%.The nitrogen runoff loss in paddy field is mainly nitrate nitrogen,and the loss of nitrate nitrogen accounts for 52%-77%of total nitrogen.(4)Nitrogen fertilizer significantly increased the concentration of nitrogen in various forms of leaching water,and the regularity showed that the concentration of tri-state nitrogen increased with the increase of nitrogen application rate.The leaching depth of each form was different:the concentration of nitrogen in 20-40 cm soil layer was larger and the lower concentration was lower;the nitrate nitrogen was leached to the deeper soil layer,the concentration of 90 cm soil layer Larger,increased from top to bottom concentration.Therefore,the loss of nitrogen in paddy field is mainly in the form of nitrate nitrogen.The concentration of total nitrogen reached the maximum at about five days after each fertilization,and then began to decrease.Three times of fertilization leaching water nitrogen concentration:base fertilizer>tillering fertilizer>panicle fertilizer.(5)Nitrogen fertilizer can significantly increase rice yield.The yield of rice increased first and then decreased with the increase of nitrogen application rate.The yield of rice was 150%N>125%N>100%N>200%N>75%N>blank N,150%N(ie,when nitrogen fertilizer was 337.5kg/hm2),Reaching 10478kg/hm~2.The yield of 316.625 kg/hm~2was the highest,which was 9923.14 kg/hm~2.Excessive nitrogen input not only failed to achieve the expected yield,but will reduce the yield.(6)when the nitrogen content exceeds rice 225.75kg/hm~2,the total amount of ammonia volatilization surge,food security and environmental factors based on ammonia volatilization,nitrogen paddy rice Rotation of Eco Chaohu Basin threshold 225.75kg/hm~2-229 kg/hm~2.(7)When the nitrogen application rate was 135 kg/hm~2,the runoff loss was the smallest and the environmental damage was the smallest,and the corresponding rice yield was 8594.53 kg/hm~2.The amount of nitrogen applied at 135 kg/hm~2 was the amount of nitrogen applied in the paddy field.