| In recent years,the agricultural non-point source pollution in Chaohu River Basin has attracted wide attention.The ecological environment problems caused by the loss of nutrients in the planting industry are becoming more and more serious.The excessive application of phosphate fertilizer in the farmland of Chaohu basin resulted in the loss of phosphate fertilizer and the decrease of utilization rate,which caused the pollution of water environment.This experiment carried out positioning and monitoring points in Chaohu Lake Basin Tongyang town in view of the current situation.The test set four different P fertilizer application treatments,including phosphorus blank,optimal phosphorus,optimal phosphorus of 200% and optimal phosphorus of 400%.Through the field monitoring of three years of 2012-2014,the loss of phosphorus and the utilization of phosphate fertilizer were studied under the rice wheat rotation cropping pattern,which provided the basic parameters for the accurate calculation of the phosphorus loss load in the Chaohu River Basin.And based on the fertilizer effect,with crop yield and soil available phosphorus and phosphorus use efficiency as determined P input constraint threshold,going in quest of input threshold of phosphate fertilizer for crop production and environmental friendly.The following conclusions can be obtained by analyzing the datas of 3 years of monitoring:(1)In rice wheat rotation cropping pattern,the amount of P uptake by rice was higher than that of wheat,and the amount of phosphorus uptake by grain was higher than that of straw.With the increase of phosphorus fertilizer application amount,the amount of phosphorus uptake by rice and wheat increased.In 2012-014,uptake of phosphorus in wheat were 8.74~28.45 kg/ha,10.38~33.03 kg/ha and 12.02~36.44 kg/ha,uptake of phosphorus in rice were 12.85~38.95 kg/ha,18.89~42.42 kg/ha and 25.44~29.15 kg/ha.(2)The utilization ratio of phosphate fertilizer was low,the utilization ratio of phosphate fertilizer in wheat was 12.57% ~5.47%,the utilization ratio of phosphate fertilizer in rice was 19.50%~8.34%.(3)The total phosphorus concentration in the surface water reached the peak after first days of fertilization,and then with the increase in the number of days of fertilization occasionally fluctuated,but the overall trend was gradually decreased.On the first day after fertilization,with the increase of phosphorus application rate,the greater the total phosphorus concentration in surface water reached the peak,the maximum peak of 2012-2014 years to reach respectively 16.64,5.64 and 43.72 mg/L.And the key period of controlling phosphorus loss was two weeks after fertilization.(4)The runoff coefficient in wheat and rice season were 28.08% and 23.12% in 2013,and were respectively 30.39% and 30.87% in 2014.The TP loss of wheat season were respectively 0.097~0.345 kg/ha and 0.115~0.228 kg/ha in 2013 and 2014 under different phosphorus levels,the TP loss of rice season were respectively 0.664~1.368 kg/ha and 0.592~1.015 kg/ha.With the increase of phosphorus fertilizer,phosphorus loss amount increases gradually.Overall,the annual total phosphorus loss was from the rice season,the total phosphorus loss in the rice season accounted for about 80.59%~85.56%.The loss rates of phosphate fertilizer in wheat and rice were 0.05% and 0.23% respectively.(5)During the whole growing period of rice,the total phosphorus concentration in the soil leakage water decreased with the increase of the number of days of fertilization.In the fifth day after the application of phosphorus fertilizer,phosphorus concentration in the leakage water got the highest.TP concentration in 20,40,60,90 cm depth were respectively 0.668~1.219 mg/L,0.577~1.021mg/L,0.324~0.784 mg/L,0.282~0.503 mg/L,soluble total phosphorus concentrations in 20,40,60,90 cm depth were respectively 0.095~0.396 mg/L,0.133~0.274 mg/L,0.108~0.202 mg/L,0.089~0.162 mg/L.P concentration decreased in afluctuation way after fifth day.On the whole,the total phosphorus concentration and leaching amount of water leakage is proportional to the amount of phosphorus,and is inversely related to the depth of soil.The amount of leaching in paddy field were 0.112~0.178 kg/ha in 2014.(6)The content of Olsen-P in soil was higher than that of rice in wheat season,and the content of Olsen-P was directly proportional to the phosphorus application amount.And the content of Olsen-P in soil was increased significantly compared with that in non phosphorus treatment.In wheat season,10.48~19.63 mg/kg,18.72~26.26 mg/kg and 28.43~42.67 mg/kg were increased respectively by the P fertilizer treatments than the blank treatment.In rice season,12.41~16.81 mg/kg,19.85~24.64 mg/kg and 27.21~30.26 mg/kg were increased respectively by the P fertilizer treatments than the blank treatment.From 2012 to 2014,the content of Olsen-P in the soil without phosphate fertilizer was decreased year by year,and the content of Olsen-P in the soil with phosphate fertilizer was increased year by year,which showed that the accumulation of phosphorus in excess phosphorus fertilizer could occur.(7)The yield increasing effect of increasing the amount of phosphorus fertilizer applied in wheat season was better than that of rice.The difference between the application of phosphate fertilizer and crop yield are not significant.So the phosphorus fertilizer did not significantly increase the crop yield.According to the fitting relationship between the yield and the amount of phosphorus in the crop of 3 years,the maximum yield of wheat were respectively 4953.0 kg/ha,4081.1kg/ha,4414.9 kg/ha.The phosphate fertilizer application rate of attaining the highest wheat yield were respectively 239.9,273.2 a,300.2 kg/ha.The maximum yield of rice were respectively 11824.2,7860.1,8570.6kg/ha.The phosphate fertilizer application rate of attaining the highest rice yield were respectively 155.8,175.8,147.8kg/ha.(8)The phosphorus application amount applied to wheat yield stability was 167.84~264.77 kg/ha.The least phosphorus application amount for the wheat yield stability and minimize emissions to the environment was 167.84 kg/ha.When the phosphorus content was the lowest,the soil Olsen-P was 28.69~37.86 mg/kg,the total phosphorus loss was 0.195~0.243 kg/ha.The phosphorus application amount applied to rice yield stability was 79.49~158.85 kg/ha.The least phosphorus application amount for the rice yield stability and minimize emissions to the environment was 79.49 kg/ha.When the phosphorus content was the lowest,the soil Olsen-P content was 20.00~28.56 mg/kg,the total phosphorus loss was 0.957~1.140 kg/ha. |
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