Study On Nitrogen And Phosphorus Emission Reduction Fertilization Model Of Rice-wheat Rotation In Chao Lake Basin

In order to reduce the pollution of Chao Lake from agricultural surface sources of nitrogen and phosphorus,this thesis takes the rice-wheat rotation in Chao Lake Basin as the research object and studies the concentration of nitrogen and phosphorus loss,crop yield,fertilizer utilization rate and economic benefits under different fertilizer application patterns through field plot experiments in order to screen out the optimal fertilizer application pattern suitable for the source emission reduction of nitrogen and phosphorus in the rice and wheat rotation in Chao Lake Basin and provide scientific basis for the management of agricultural surface source pollution in Chao Lake Basin.The main findings are as follows:(1)Nitrogen and phosphorus concentrations in paddy field drainage around Chao Lake were sampled and measured,and the results showed that the total nitrogen concentration in paddy field drainage water ranged 1.31 mg/L ～ 14.16 mg/L and total phosphorus concentration ranged 0.09 mg/L～0.65 mg/L,which were higher than the critical values of total nitrogen and total phosphorus concentrations in eutrophic water bodies and the total nitrogen and total phosphorus concentrations in Class III water quality standards.(2)Fertilizer application can significantly increase nitrogen and phosphorus concentrations in wheat field runoff and rice field drainage,while optimized fertilizer application can reduce nitrogen and phosphorus concentrations in wheat field runoff and rice field drainage.Compared with conventional fertilization,the total nitrogen concentration was reduced by 33.35%～38.73% and the total phosphorus concentration was reduced by22.95%～34.43% in wheat season: four optimized fertilization treatments of soil testing and formulated fertilization,chemical fertilizer reduction + organic fertilizer,chemical fertilizer reduction + biochar,and controlled release fertilizer;rice season: soil testing and formulated fertilization,chemical fertilizer reduction of 20% + organic fertilizer,chemical fertilizer reduction of 30% + organic fertilizer,controlled-release fertilizer four optimal fertilization treatments of total nitrogen average concentration reduction of 24.19%～39.35%,total phosphorus average concentration reduction of 22.22%～44.44%.(3)Laboratory experiments simulating the release of nitrogen and phosphorus from rainfall on wheat field soils showed that the release patterns of fertilized soil nitrogen and phosphorus were basically consistent with the concentration patterns of nitrogen and phosphorus loss from wheat field runoff.The concentrations of nitrate nitrogen in wheat field runoff ranged 0.38 mg/L～1.89 mg/L and ammonium nitrogen 0.19 mg/L～1.42 mg/L.The concentrations of ammonium nitrogen in paddy field drainage ranged 0.06 mg/L～0.22mg/L and nitrate nitrogen from 0.01 mg/L～0.08 mg/L.The concentration of nitrate nitrogen in wheat field runoff was higher than that of ammonium nitrogen,while the concentration of ammonium nitrogen in rice field drainage was higher than that of nitrate nitrogen,which may be related to soil nitrification and denitrification.As rice grows,the concentration of nitrogen and phosphorus in paddy drainage gradually decreases,therefore,trying not to drain early can effectively reduce the loss of nitrogen and phosphorus from paddy fields.(4)The theoretical yield measurement results showed that the theoretical yields of wheat and rice in the fertilize treatment were significantly higher than the theoretical yields of wheat and rice in the non-fertilizer treatment,and compared with the conventional fertilizer treatment,the controlled-release fertilizer treatment reduced the yield of wheat by 0.89%and rice by 1.52%,and the crop yield was reduced the least,which could achieve the effect of fertilizer reduction without yield reduction.Changes in soil nutrient content indicate that optimized fertilization can mitigate soil acidification.(5)Optimizing fertilizer application can improve fertilizer utilization and fertilizer bias productivity.Compared with conventional fertilization,in wheat season: four optimized fertilization treatments of soil testing and formulated fertilization,chemical fertilizer reduction + organic fertilizer,chemical fertilizer reduction + biochar,and controlled-release fertilizer increased nitrogen fertilizer utilization by 6.89%～14.47%,nitrogen fertilizer bias productivity by 5.71%～12.37%,phosphorus fertilizer utilization by 16.39%～31.71%,and phosphorus fertilizer bias productivity by 21.18%～23.88%;rice season: four optimal fertilization treatments of soil testing and formulated fertilization,chemical fertilizer reduction of 20% + organic fertilizer,chemical fertilizer reduction of 30% + organic fertilizer,and controlled-release fertilizer increased nitrogen fertilizer utilization by 2.21%～5.45%,the bias productivity of nitrogen fertilizer by 1.19% ～ 32.59%,phosphorus fertilizer utilization by 9.21% ～ 26.31%,and the bias productivity of phosphorus fertilizer by17.52%～47.72%.Appropriate reduction of fertilizer application can improve fertilizer utilization and fertilizer bias productivity and reduce fertilizer loss and waste.(6)Compared with the net production value of conventional fertilizer application,the net production value of optimized fertilizer application treatments was affected to some extent.Among the four optimized fertilizer application treatments,the controlled-release fertilizer treatment increased the net production value of wheat by 0.02% and reduced the net production value of rice by 2.57%,which had the least effect on the economic efficiency of the crop.Considering the environmental and economic benefits of different fertilizer models,the controlled-release fertilizer treatment is more advantageous as a fertilization model for rice and wheat rotation in the Chao Lake Basin and can effectively reduce the pollution of agricultural surface sources of nitrogen and phosphorus in the Chao Lake Basin.