Effects Of Phosphorus Fertilizer Application And Different Optimized Measures On Rhizosphere Process,Yield And Phosphorus Use Efficiency Of Winter Wheat In Dryland

In the Loess Plateau of China,the soils have high p H and calcium carbonate content,therefore,the applied phosphate fertilizers are easily fixed by the soils,making it difficult for crops to absorb and use phosphorus（P）.Therefore,it is important to explore the regulation measure and its mechanism,which is a key measure to achieve high-efficient use of P.In this study,based on a long-term field experiment with different P application rates（with P₂O₅0,50,100,150,and 200 kg/ha）,wheat rhizosphere soil bacteria were sequenced to study the effects of long-term phosphorus fertilization on the diversity and composition of bacterial community structure and its relationship with soil properties.Meanwhile,a two-year field experiment with different optimized fertilization/cultivation measures was conducted to study the mechanism of high P use efficiency.The main results are as follows.1.The results of 16S rRNA and pho D gene sequencing showed that the application of P fertilizer changed the wheat rhizosphere soil bacterial community structures.The bacterial community structure of 16S rRNA gene was sensitive to P fertilizer application,and high P input（P200）treatment significantly reduced the number of OTUs and Shannon index;The top five dominant bacterial phyla in each treatment were Proteobacteria,Actinobacteria,Acidobacteria,Bacteroidota,Chloroflexi,and the top five dominant genera were Massilia,RB41,Sphingomonas,Pedobacter,and Arthrobacter.The result of redundancy analysis（RDA）showed that soil organic C,available P,organic P,total P and alkaline phosphatase（ALP）were closely related to the community structure of based on16S rRNA gene bacteria.The dominant phyla in all soil samples of pho D gene bacteria were Proteobacteria,Cyanobacteria,Firmicutes,Planctomycetes,and the top five dominant genera were Bacillus,Nostoc,Pirellula,Gloeocapsa,and Pseudomonas.There was no significant correlation between the pho D gene bacterial community and soil properties,and there were also no significant differences in OTUs,Chao1 and Shannon index among the treatments.2.Compared with the treatment of farmer’practice（FP,P₂O₅120 kg/ha,broadcasted application）,the reduced fertilization treatment（RP,P₂O₅70 kg/ha,broadcasted application）decreased the total root length by 20.1%-29.6%,root surface area by 19.8%-22.7%,and total root length in the range of 0-0.5 mm by 19.4%-31.6%at jointing stage and heading stage,respectively,but alkaline phosphatase activity increased by 8.5%and6.2%,respectively;At maturity stage of wheat,the grain phosphorus content was significantly decreased by 5.8%,but the partial productivity of phosphate fertilizer was significantly increased by 70.8%,and the differences of grain yield and biomass were not significant.3.Compared with the RP treatment,the banded fertilization treatment（BF,P₂O₅70kg/ha,banded application）increased available P content by 5.5%and 11.6%,decreased alkaline phosphatase activity by 12.8%and 7.2%,and decreased mycorrhizal infection rate by 12.7%and 16.0%at jointing and heading stages,respectively.At maturity stage,grain phosphorus content was increased by 4.7%,but grain yield and biomass were decreased by5.0%and 6.6%,respectively.4.Compared with the RP treatment,the RM+BF treatment（P₂O₅70 kg/ha with banded application and plastic film mulching in furrows）increased alkaline phosphatase activity by 12.7%and 8.4%at jointing stage and heading stage,respectively,and decreased total root length and total root length in the range of 0-0.5 mm by 35.7%and 38.7%at heading stage respectively;The spike number per hectare was increased by 6.3%at maturity stage,and the grain yield,biomass,water use efficiency and partial productivity of phosphorus fertilizer were significantly increased by 19.6%,18.0%,15.7%and 19.6%,respectively.Meanwhile,the accumulation of nitrogen,phosphorus and potassium in shoots were significantly increased by 15.7%,21.3%and 19.3%,respectively.In conclusion,long-term high phosphorus fertilizer application reduced the biodiversity of soil bacterial community.It is feasible to reduce the amount of P fertilizer input from P2O5 120 kg/ha to P2O5 70 kg/ha.On the basis of the reduction of P fertilizer,the grain yield,biomass,partial productivity of P fertilizer,P use efficiency,water use efficiency were significantly improved by the optimized regulation measure with film mulching and banded P fertilizer application（RM+BF）.At the same time,the grain P content of winter wheat was not decreased and the P accumulation in wheat shoots was increased and as well as the high use efficiency of phosphorus.Therefore,the combination of reduction of P fertilizer input and film mulch and banded P fertilizer application can be widely used in the local winter wheat production.