Study Of Alternate Drying And Wetting Irrigation With Reduced Phosphorus On Rice Yield In Paddy Field

Water and phosphate?P?fertilizer are the important factors for the rice yield.Different water strategies have great influence on the soil phosphorus concentration,but it is unclear that the mechanism of irrigations on soil phosphorus concentration.In this study,the field plot experiments were conducted by combining different irrigation regimes?continuously flooded:CF,0 kPa;frequently alternate wetting and drying:FAWD,-15 kPa;and alternate wetting and severe drying:AWSD,-30 kpa?and phosphorus treatments(normal phosphorus application:NP,90 kg ha^-1;reduced phosphorus application:RP,45kg ha^-1;and no phosphorus application:LP,0 kg ha^-1)with Zhongjiazao17 rice to research rice yield by alternate drying and wetting irrigation.The main results are as follows:1.Under RP and LP treatments,grain yield of rice at FAWD showed the highest among the three irrigation regimes?CF?FAWD?AWSD,respectively?,and AWSD was the lowest.However,under NP treatment,the yield of rice at CF and FAWD displayed significantly higher than AWSD,and CF and FAWD were not significantly different from each other;Among FAWD and AWSD treatments,the yield of rice at RP was the highest,while the yield of rice increased significantly with the increase of phosphorus application amount under the CF regime.The panicles and spikelet number per panicle had no significant difference among CF combined with NP,FAWD combined with NP and FAWD combined with RP,but they were significantly higher than other treatments,and the yield of rice under FAWD combined with RP was the highest.Under the same phosphorus treatment,compared with CF regime,the water use efficiency of rice was significantly increased by FAWD regime,and by 33.3%,40.1%and 38.8%under NP?RP and LP treatment,respectively.Under the same irrigation regime,compared with NP treatment,the phosphorus grain production efficiency of rice under RP treatment increased by 73.4%,99.9%and 92.2%in CF,FAWD and AWSD regime,respectively.Similarly,the phosphorus use efficiency was increased by 29.4%,66.7%and 14.4%,while the phosphorus harvest index was increased by 0.57%,2.8%and 1.9%,respectively;The results indicate that FAWD regime and reduced phosphate treatment can increase rice yield,water and phosphorus use efficiency.2.Under NP treatment,there was no significant difference on the availzble phosphorus concentration between AWSD and FAWD among the three irrigation regimes,but all of them were significantly higher than CF regime.Under RP treatment,AWSD was significantly higher than CF and FAWD,40.5%and 57.6%higher,respectively;but the difference between CF and FAWD was not significant.Under LP treatment,the available phosphorus concentration in AWSD regime was the highest,followed by FAWD,and the available phosphorus concentration in CF was the lowest,but AWSD was significantly higher than CF,about 82.4%higher.In order to further analyze the change of soil phosphorus composition,the soil phosphorus grading was determined.The results showed that Resin-Pi concentration was decreased with the decreaseed of phosphorus content in CF and AWSD regimes,and under FAWD regime,Resin-Pi concentration was increaseed significantly in RP treatment.In RP and LP treatment,NaHCO₃-Pi concentration was increased with the increased of soil drying degree,but in NP treatment,the concentration of FAWD was the highest among the three irrigation regimes,followed by AWSD and CF.Meanwhile,under NP and RP treatments,compared with CF and AWSD regimes,HCl-P concentration was decreased significantly at FAWD regime,but HCl-P concentration was decreased significantly with the increaseed of soil drying degree at LP treatment.The results showed that moderate alternate of drying and wetting could promote the transformation of insoluble phosphorus in soil to soluble phosphorus,thus increasing the concentration of available phosphorus in soil and promoting the absorption and utilization of available phosphorus in soil by plants.3.The decrease of phosphorus usage resulted in a remarkable increase in the population sizes of total bacteria,Delta-and Gamma Proteobacteria,Verrucomicrobia,which was consistent with the change trend of acid phosphatase activity in CF regime,but opposite to the content of available phosphorus in soil.However,the content of available phosphorus in soil treated with LP was significantly reduced,and the population size of Verrucomicrobia was significantly increased under LP regime.Therefore,rational fertilization under alternate of drying and wetting has a significant impact on the microbial population size in soil.In the study,frequently alternate wetting and dryin and reduced phosphorus can maintain rice yield,improve water and phosphorus use efficiency.In addition,frequently alternate wetting and dryin and reduce phosphorus can improve the soil soluble phosphorus concentration by promoting the transformation of soluble phosphorus and microbial diversity,so as to maintain the yield of rice,which is of great significance for us to further understand the efficient utilization mechanism of water and fertilizer from the perspective of water-saving irrigation.