Effects Of Phosphorus Fertilizer Amounts On Phosphorus Uptake In Cotton Under Film Drip Irrigation And Soil Microbial Community Structure

In the process of cotton production,long-term application of phosphorus fertilizer is required,which leads to the continuous accumulation of phosphorus in the soil,resulting in the waste of resources and the risk of crop yield reduction.In this study,a field experiment was carried out for two consecutive years with cotton under the film drip irrigation in Xinjiang,and five treatments with different phosphorus application levels were set up.:0 kg hm^-2（P0）;75 kg hm^-2（P1）;150 kg hm^-2（P2）;300 kg hm^-2（P3）and 450 kg hm^-2（P4）,Analyse soil nutrient changes,cotton growth,nutrient absorption and accumulation rules,and soil microbial community characteristics under different long-term phosphorus application levels,and explore the response of soil microorganisms to phosphorus application and the mechanism of efficient phosphorus absorption in cotton.Provide theoretical support for microbial functions to promote green agricultural production.The main findings are as follows:（1）The application of phosphorus fertilizer can reduce the soil p H and increase the electrical conductivity,and the electrical conductivity tends to decrease with the later of the cotton growth period.With the increase of the depth of the soil layer,the content of available phosphorus showed a downward trend;in 2020 and 2021,the total soil phosphorus increased significantly in the P3 and P4 treatments,respectively,and increased by 21.1%and 32.7%compared with the P0 treatment,respectively.With the increase of the soil layer depth Soil total phosphorus showed a downward trend.For two consecutive years,soil total nitrogen content reached its peak in P3 treatment,and both alkaline hydrolyzable nitrogen and organic matter increased significantly in P2 treatment.Compared with P0 treatment,the contents of total nitrogen,alkaline hydrolyzable nitrogen and organic matter were average increased by 42.1%,51.8%and31.4%;the content of Ca₁₀-P in soil inorganic phosphorus forms was the highest under different phosphorus application treatments during the cotton growth period for two consecutive years,and it was relatively stable and did not change significantly during the growth period.The treatment reached the highest,which increased by 56.3%and 60.2%respectively compared with the P0 treatment.The O-P and Ca₈-P contents also reached their peaks in the P4 treatment,and the Al-P and Fe-P contents,which were moderately effective phosphorus sources,were the highest in the P2 and P4 treatments,respectively.（2）Different phosphorus application levels had significant effects on cotton dry matter quality and yield components.In 2020 and 2021,the single boll weight was the highest under the P3 and P2 treatments,respectively,and increased by 8.1%and 11.9%on average compared with the P0 treatment.The number of bolls was the highest under the P2 treatment,which increased by 16.5%and 44.1%respectively compared with the P0 treatment;the cotton yield reached the highest value in the P2 treatment,and the yield increased by 19.7%and 13.5%compared with the P0 treatment,respectively.The distribution of phosphorus in various organs of cotton plants under different phosphorus fertilization treatments is roughly in the order of boll>stem>leaf>root.,compared with the P0 treatment,it increased by 6.2%,42.5%and55.5%in each period respectively;the overall pattern of phosphorus distribution in cotton plants in 2021was basically the same as that in 2020,and the phosphorus accumulation in the whole plant during the growth period increased significantly in the P2 treatment.Compared with the P0 treatment,each period increased by 53.5%,60.2%and 43.4%,respectively.The overall law of nitrogen distribution in cotton is similar to that of phosphorus.The nitrogen accumulation of the whole plant during the cotton growth period for two consecutive years increased significantly under the P3 treatment.Compared with the P0treatment,the average increase in each period was 46.5%,49.1%and 54.1%.（3）Compared with P0 treatment,increasing P fertilizer increased soil microbial C and P contents,and soil microbial C and P contents in different cotton growth stages in 2020 and 2021 were significantly increased under P2 and P3 treatments.In bacteria advantage bacterium group,detect the two dominant fungi door deformation bacteria were 59.7%（average relative abundance）and actinomycetes（14.1%average relative abundance）,three advantages are gamma phylum deformation phylum,alpha and beta phylum deformation,three dominant fungi genera are respectively the rhizobia,sugar more bacteria and Streptomyces.In the fungal dominant flora,three dominant phyla were identified as ascomycota（average relative abundance 86.7%）,basidiomycota and Morphospora,three dominant phyla were ascomycota,malegloglota and ascomycota,and two dominant genera were cephalomycota and Pseudopycota.According to the diversity analysis,phosphorus fertilizer can increase the richness and diversity of soil bacterial and fungal communities,but the effect is not significant.RDA analysis showed that soil p H,available nitrogen and phosphorus content and total nitrogen and phosphorus content were important environmental factors affecting soil microbial community structure.