Effects Of Reduced Phosphorus Fertilizers On Phosphorus Loss Of Double Cropping Field Rice And Phosphorus Use Efficiency Of Rice

In this paper, a long-term experiment was carried out to study the application of different phosphate fertilizers in 2014 and 2015 for two years, which is related to the influence of constant application of phosphate fertilizer (PI), phosphate fertilizer reduction 10%(P2), phosphate fertilizer reduction 20%(P3), phosphate fertilizer reduction30%(P4) on double cropping rice phosphorus runoff and leakage loss, grain yield and utilization rate of phosphate fertilizer. The results are as follows:1. The thickness and loss amount of TP (total phosphorus), DP (Soluble phosphorus), and PP (Particulate phosphorus) in Paddy field runoff will rise with the increasing of the application amount of phosphate fertilizer. After the application of phosphorus, the longer the phosphorus application time is, the less the thickness and loss amount of TP, DP, and PP in field runoff will be. Phosphate fertilizer reduction by 10%-30% can considerably reduce the phosphorus loss from rice field. In 2014, compared with P1, the percentages of P2, P3 and P4 dealing with the runoff loss of TP, DP and PP are reduced by 18.91% to 36.84%?12.47% to 13.73% and 19.52% to 39.03% respectively. While in 2015, the percentages are reduced by 15.21% to 36.19%,2.31% to 13.03% and 15.95% to 37.52%. PP is the main form of phosphorus runoff loss in paddy fields. In 2014, the PP loss in runoff took up 84.52%?91.33% of the TP loss, and in 2015, the percentage varied between 89.12% and 94.56%.2. The thickness and loss of TP, DP, and PP in paddy field leakage rise with the increasing of Application amount of phosphate fertilizer. The longer the application time of the phosphorus fertilizer is, the less the thickness and loss of TP, DP, and PP in paddy field leakage will be. Phosphate fertilizer reduction by 10%-30% can considerably reduce the phosphorus loss in paddy field leakage. In 2014, compared with P1, the percentages of P2, P3 and P4 dealing with the loss of TP, DP and PP in leakage are reduced by 26.51% to 53.95%,29.28% to 56.65% and 21.86% to 49.43% respectively. While in 2015, the percentages are reduced by 28.57% to 53.82%,31.96% to 61.64% and 23.36% to 41.81%. The phosphorus loss in paddy field leakage is mainly in the form of DP. The percentage of loss of DP in leakage accounts for 50.29%-62.60% of loss of TP after applying the phosphorus fertilizer. Besides, the more the application amount of phosphorus fertilizer is, the more the percentage of loss of DP in leakage will be.3. The application of phosphorus fertilizer can effectively enhance the panicle number and plant height of rice, giving rise to the improvement of amount of rice grain and straw. The grain yield rises by 11.55% to 30.12% with the application of phosphorus fertilizer, compared to the application of CK. Meanwhile, the amount of rice straw rises by 11.47% to 25.87%. The rice yield will not be cut with a reduction by 10% or 20% in the application of phosphorus fertilizer, while the rice grain yield will considerably decrease when the application of phosphorus fertilizer is reduced by 30%.4. The utilization rate of phosphate fertilizer is not affected by the reduction of phosphate fertilizer by 10% to 20%, but the reduction can significantly improve the efficiency of agricultural use of phosphate fertilizer. In 2014, with the application of P2, early season rice fertilizer agronomic efficiency rises by 1.39 kg/kg compared with P1, while the efficiency rises by 2.36 kg/kg when using P3. As to late rice fertilizer agronomic efficiency, the growth number of the efficiency is 2.33 kg/kg and 4.27 kg/kg respectively when using P2 and P3. Therefore, with the use of P2 and P3, early season rice fertilizer agronomic efficiency and late rice fertilizer agronomic efficiency can both be notably improved when compared with the application of P1. In 2015, with the application of P2 and P3, early season rice fertilizer agronomic efficiency rises by 4.96 kg/kg and 1.14 kg/kg compared with P1. As to late rice fertilizer agronomic efficiency, the growth number of the efficiency is 3.27 kg/kg and 0.78 kg/kg respectively.5. Combined production, utilization of phosphate fertilizer, nutrient loss and other indicators, it is suggested that the amount of phosphate fertilizer in double cropping rice production be reduced by 10% to 20%, based on the present amount. Thereby, rice production will not be influenced while utilization rate of phosphate fertilizer, the loss of phosphate in paddy field runoff and leakage will be markedly reduced.