Effects Of Long-term Fertilization On Soil Microbial Characteristics Of Slope Farmland

Fertilization in agriculture is the main way to increase crop yields.Now,in view of the effects of long-term fertilization on soil properties,especially enzyme and microbial characteristics,it is not very clear.This study is based on the long-term(1995-2019)positioning fertilization test on the slope farmland at the Ansai Soil and Water Conservation Experimental Station of the Chinese Academy of Sciences,and studies the long-term nitrogen and phosphorus fertilization treatments(CK,N1,N2,N1P,N2P,and N1,N2:55.2,110.4 kg·hm^-2,P:90 kg·hm^-2)on the soil physical and chemical properties and microbial characteristics of slope farmland.The main results obtained are as follows:1.Compared with CK,the long-term single application of nitrogen fertilizer(N1,N2)in soil has increased the content of alkali-hydrolyzable nitrogen by 24.81%and39.92%,respectively;long-term combined application of nitrogen and phosphorus fertilizers(N1P,N2P)soil organic carbon,total phosphorus,The content of alkali hydrolyzable nitrogen and available phosphorus increased by 7.82%-16.81%,52.63%?58.18%,21.59%-22.89%,450.5%?660.3%,and soil p H decreased by0.04?0.08 units.2.Long-term single application of nitrogen fertilizer(N1,N2)increased the alkaline phosphatase activity by 3.90%?4.44%;long-term Nitrogen and Phosphorus Fertilizers(N1P,N2P)increased soil?1,4-N-acetylglucosaminidase With leucine aminopeptidase enzyme activity and glucosidase activity increased by 47.12%?59.94%,16.76%?71.01%respectively;long-term crop rotation and fertilization have significant effects on carbon source enzyme,nitrogen source enzyme and phosphorus source enzyme activity Improve the effect,and the stoichiometric ratio of soil enzymes in N1P treatment is closest to the steady state of 1:1:1.3.Compared with the beginning of the experiment,after 24 years of long-term fertilization,the single application of nitrogen fertilizer(N1,N2)increased the organic carbon and total nitrogen by 51.4%?77.3%,19.6%?30.3%,and the growth rates were respectively.0.09?0.13 g/(kg·a),0.02?0.04 g/(kg·a).Combined application of nitrogen and phosphorus fertilizers(N1P,N2P),soil organic carbon and total nitrogen increased by 38.5%?42.2%,18.9%?36.3%,and the growth rates were 0.07?0.08 g/(kg·a),0.02?0.03 g,respectively/(kg·a).4.Without fertilization,the microbial biomass phosphorus in millet rhizosphere soil was significantly higher than that in non-rhizosphere soil,and microbial biomass carbon and nitrogen were slightly lower than in non-rhizosphere soil.Under different fertilization conditions,MBC,MBN and MBP were slightly higher in rhizosphere soil than in non-rhizosphere soil.Compared with single application of nitrogen fertilizer,combined application of phosphate fertilizer treatments(N1P,N2P)significantly increased the?diversity of soil bacterial communities,and the number of dominant bacterial species was also greatly increased,which enriched the diversity of soil bacterial species composition and community structure.For rhizosphere soil bacteria,long-term nitrogen and phosphorus fertilization(N1P,N2P)will significantly increase the relative abundance of Soil Acidbacteria,Actinobacteria and Chloroflex and reduce the abundance of Cyanobacteria,but N2 fertilization treatment is just the opposite;N1P,N2P increase the soil Proteobacteria abundance,N1 and N2 are the opposite.Generally,the relative abundance of dominant bacteria in rhizosphere soil is higher than that in non-rhizosphere soil,but under N1 and N2 treatments,the relative abundance of soil bacteria is significantly reduced.In all treatments,Chloroflex is highly enriched in rhizosphere soil.5.Nitrogen and phosphorus balanced fertilization(N1P,N2P)has the most significant increase in root carbon and phosphorus content.The biomass of fertilization and transport roots increased by 106.67%?336.41%,and the biomass of absorbing roots was reduced by 35.20%?60.20%.Absorbing roots are sensitive to nutrient changes,and it is especially obvious in the combined application of nitrogen and phosphorus fertilizers.Fertilization increased the relative abundance of pathogenic bacteria in absorbing roots and increased the relative abundance of disease-resistant bacteria in transporting roots.The relative abundances of Ascomycota,Glomeromycota,Fusarium and Minimedusa in absorbing roots were significantly higher than those of transporting roots,while the relative abundances of Mortierellomycota,Basidiomycota and Mortierella,Bipolaris,and Cladosporium were significantly lower than those of transporting roots.6.Long-term fertilization increases the abundance of Actinomycetes by increasing TP in the soil.Fertilization increases the abundance of the Proteobacteria through SAP content,and reduces its abundance by increasing MBC and NO₃^--N.Fertilization increases microbial MBC,NO₃^--N and TP reduce the abundance of Cyanobacteria.Fertilization improves root biomass and changes the structure of the dominant flora of transporting roots.Fertilization improved plant PTC,TP,SAP,DON and promoted the changes in the structure of the dominant flora of the absorbing roots.Fertilization increased the relative abundance of pathogenic bacteria in absorbing roots and increased the relative abundance of disease-resistant bacteria in transporting roots.In short,long-term fertilization can promote the growth of millet plants.The effect of using nitrogen and phosphorus together is better than that of only applying nitrogen fertilizer.Low-nitrogen combined with phosphorus fertilizer(N:55.2 kg·hm^-2+P:90kg·hm^-2)has the best effect.good.Compared with the treatment without fertilization,the nitrogen and phosphorus content,soil enzyme activity,soil microbial biomass and yield in the treatment of low nitrogen combined with phosphate fertilizer(N1P)increased by 21.59%?58.18%,59.94%?71.01%,32.46%?218.10,respectively% And 227.62%.