Phosphorus Utilization Of Spring Maize With Optimizing Fertilization And Its Mechanism In Dryland

The Loess Plateau is a typical rainfed agricultural region in China,the improvement of phosphorus?P?utilization efficiency is limited because of the lack of water and high calcium carbonate content in soils.Optimizing fertilization measures can regulate the rhizosphere processes to improve absorption and utilization of phosphorus,to achieve efficient use of phosphorus.In this study,a field experiment with different fertilization regimes was conducted in the Changwu county,Shaanxi province on the Loess Plateau for three years,the spring maize root and shoot biomass and its phosphorus content were analyzed,as well as soil alkaline phosphatase activity,p H,available phosphorus,and arbuscular mycorrhizal infection rate,root morphology and bacterial community structure in the rhizosphere soil of maize.The aims were to explore the feasibility of reducing phosphorus fertilizer application in this rainfed agricultural area,to optimize fertilization methods,and to reveal the mechanisms of the high phosphorus use efficiency.This study might provide a basic understanding of efficient utilization of phosphate fertilizer in spring maize in this region.The main results were as follows.1. In this typical rainfed agricultural area,based on the current rate of phosphate fertilizer applied by farmers?P₂O₅ 120 kg/ha?,the application rate of phosphate fertilizer can be reduced by 42%?P₂O₅ 70 kg/ha?,which had no significant effect on the maize grain yield and aboveground biomass.The three-year average grain yield and biomass of spring maize under Farmers'practice?FP?were 12325 and 22381 kg/ha,respectively,in comparison with the values of 12171 and 21832 kg/ha under Reduced P fertilization pattern?RP,P₂O₅ 70kg/ha?,11992 and 21769 kg/ha under Banded P fertilization pattern?BF,P₂O₅ 70 kg/ha?,and12161 and 22103 kg/ha under Ammonium sulfate pattern?SA,P₂O₅ 70 kg/ha and urea was replaced by ammonium sulfate?,respectively.2. Compared with the FP treatment,the RP treatment significantly reduced the phosphorus content and phosphorus accumulation in maize grain,with the decreases of 9.5%and 11.4%,respectively.The RP treatment also decreased soil available phosphorus content in top soil in different growth stages of maize,the diversity and abundance of bacterial community,and the number of microbial groups at the genus level.However,RP significantly increased the partial productivity of phosphate fertilizer by 69.9%,and the P recovery rate by 4.3 per cent.Additionally,RP promoted the maize root growth at seedling stage and the AM fungal infection rate?by about 20%?and increased the relative abundance of phylum Firmicute,order Micrococcales,and genus Arthrobacter and Luteolibacter.3. Compared with the FP treatment,the BF treatment significantly increased the partial productivity of spring maize by 66.0%,and available phosphorus content in the top soil,bacterial Shannon index and the relative abundance of phylum Gemmatimonadetes,order Xanthomonadales and genus Luteolibacter.However,RP significantly decreased the phosphorus content in grain and phosphorus accumulation in maize by 13.0%and 17.3%,respectively.4. Compared with the FP treatment,the SA treatment significantly increased partial productivity of phosphate fertilizer by 68.9%,P recovery rate by 7.2 per cent,root length15.1%-15.8%,root surface area 42.2%-46.1%,and total root length in the range of 0-0.5mm 13.6%-18.1%,AM fungal infection rate by 16.3%-21.5%,as well as the relative abundance of order Betaproteobacteriales,Xanthomonadales,and genus Luteolibacter and Sphingomonas.In summary,in this rainfed agricultural area,the application rate of phosphorus fertilizer can be reduced to the amount of the maize phosphorus requirement,i.e.P₂O₅ 70-75kg/ha,which can maintain the maize grain yield and above-ground biomass and significantly increase the partial productivity of phosphate fertilizer.The fertilization regime of replacing urea with ammonium sulfate promoted root growth,increased AM fungal infection rate,and changed the relative abundances of dominant taxa in rhizosphere soil,thus ensured that the P content and P accumulation in maize grain did not decrease and high P use efficiency was achieved.Therefore,it might be used in the production of spring maize.