Leakage And Accumulation Of Nitrogen And Phosphorus In Soil By Mushroom Residue Under Rice-wheat Rotation System

The agricultural non-point source pollution problem is the main source of non-point source pollution in China at present,and China's agricultural organic waste has the characteristics of large quantity and low utilization efficiency.Based on the above two problems,this study carried out experiments on the effects of organic fertilizer slag returning on the loss and accumulation of nitrogen and phosphorus nutrient leakage in farmland in the rice-wheat rotation area of Chengdu Plain.The experiment set no fertilizer treatment?CK?;conventional fertilization treatment,no application of organic fertilizer?CF?;slag composting to the field treatment,the amount of fertilizer applied was 50%?T1?of conventional nitrogen fertilizer;slag compost was returned to the field,fertilization The amount is 100%?T2?of conventional nitrogen fertilizer;the slag compost is returned to the field,and the amount of fertilizer applied is 150%?T3?of conventional nitrogen fertilizer.The experiment was conducted to investigate the dynamic changes of leaching and the cumulative distribution of nitrogen and phosphorus leaching with different slag returning amount under the rice-wheat rotation system.The differences of leaching and accumulation of nitrogen and phosphorus leakage under different fields were compared.It provides a theoretical basis for the effective and rational application of organic fertilizers and the optimal management of nitrogen and phosphorus fertilizers and the reduction of agricultural non-point source pollution.The main conclusions are as follows:?1?In the rice season,the dynamic changes of water and nitrogen concentration in each soil layer decreased gradually,and the fertilizer treatment fluctuated greatly.About 6days after fertilization,it was the main period to control nitrogen loss.The slag could reduce the leakage water NH₄⁺-N.The concentration was negatively correlated with the amount of slag application;the concentration of NO₃^--N in the leakage of soil above 60 cm was positively correlated with the amount of slag application;with the increase of the amount of slag applied,the proportion of NH₄⁺-NTN in the soil leakage was gradually increased.Decrease,the ratio of NO₃^--N/TN gradually increases.The slag reduces the fluctuation range of phosphorus in leakage water;about 8 days after fertilization is the key period to control phosphorus leaching.The form of phosphorus in the leakage water is mainly dissolved phosphorus?DP?.As the amount of slag applied increases and the soil layer deepens,DP/TP increases and PP/TP decreases.According to the amount of nitrogen leaching,the NO₃^--N and TN leaching loss of T2in the 0-20cm soil layer was the lowest,2.48 kg/hm2,11.33 kg/hm2,respectively;the NH₄⁺-N leaching loss of T3 The minimum is 0.58 kg/hm2;the TN leaching rate T2treatment is 3.49%of the nitrogen application rate.In 60-90cm soil layer,the lowest leaching loss of NO₃^--N in T2 treatment was 1.01 kg/hm2;the lowest leaching loss of NH₄⁺-N and TN in T3 treatment was 0.12 kg/hm2,5.64 kg/hm2,respectively;TN leaching rate T3 The treatment was at least 0.73%?T3?of the amount of nitrogen applied.From the leaching loss of phosphorus?TP?,in the 0-20cm soil layer,the phosphorus percolation flow rate is 0.310⁰.867kg·hm-2,and the phosphorus leaching loss of T2 treatment is 0.42kg/hm2,TP leaching loss.It increases as the amount of slag applied increases.In the60-90cm soil layer,the phosphorus leaching loss was 0.134⁰.327 kg·hm-2,and the lowest phosphorus leaching loss in T3 treatment was 0.14 kg/hm2.?2?The main accumulation of soil nitrogen in the rice season was 0-60cm,and the main accumulation of phosphorus was in the 0-40cm soil layer.The addition of chemical fertilizer?T1?to the slag increased the accumulation of nitrogen and phosphorus nutrients;compared with CF,the single application of slag reduced the accumulation of nitrogen and phosphorus in the soil.The effect of wheat fertilization on soil nitrogen and phosphorus nutrients is mainly 0-40cm;the effect on soil nitrate nitrogen is mainly concentrated in0-60cm.The effect of slag combined with chemical fertilizer?T1?on soil nitrogen accumulation was higher than that of single slag?T2,T3?and conventional fertilization?CF?,which could improve soil available nitrogen supply in the late growth stage.The increase of the amount of slag applied will increase the soil available phosphorus supply capacity and soil TP content in the later season of wheat.There was a significant positive correlation between NO₃^--N and 0-360 soil NO₃^--N.The correlation between soil NH₄⁺-N and leakage water NH₄⁺-N decreased with soil depth.There was a significant positive correlation between soil Olsen-P content and leakage water TP.From the perspective of nitrogen accumulation,the soil T3-N accumulation T1treatment was higher than CF 4.54%,T2 and T3 were lower than CF 15.61%and 14.61%,respectively;the accumulation of NH₄⁺-N in slag treatment was higher than CF treatment57.14%,27.12%,24.21%.The combination of slag and chemical fertilizer treatment will increase the accumulation of NO₃^--N and NH₄⁺-N in the soil profile,and the effect of single slag treatment is smaller than that of T1.From the perspective of phosphorus accumulation,the sludge treatment T1,T2,T3 were higher than CF treatment 55.46%,1.01%,43.31%,and the slag compound fertilizer significantly increased the soil available phosphorus accumulation 0-90cm;The increase in the amount?T3?also increases the cumulative amount of available phosphorus in the 0-90 cm soil layer.When the amount of microbial application is increased,the phosphorus accumulation in the 20-40 cm soil layer will continue to approach?or even exceed?the surface phosphorus accumulation.