Study On The Biological Characteristics Of Dryland Soil Under Long-term Application Of Organic Fertilizer

Fertilization is an important measure in the management of loess and dryland agriculture fields.The application of organic or chemical fertilizers may result in differences in soil properties,and soil biological indicators can sensitively respond to changes in soil quality.Therefore,this study selected the long-term positioning experiment that has been running for37 years at the Shaanxi Changwu Loess Plateau Agricultural Ecological Experimental Station as a platform.Based on the winter wheat continuous cropping system,five treatments were selected,including the control group without fertilization,single application of organic fertilizer,single application of phosphorus fertilizer,nitrogen-phosphorus compound fertilizer,and nitrogen-phosphorus-organic compound fertilizer.The study focused on the long-term effects of organic fertilization on soil biological characteristics in loess and dryland areas,providing theoretical basis for soil fertility evaluation and achieving sustainable land use.The main results are as follows:(1)The long-term application of organic fertilisers(M,NPM)significantly increased the organic carbon,total nitrogen and alkaline nitrogen contents in the topsoil layer(0-20cm)and subsoil layer(20-40cm)compared to chemical fertilisers(P,NP),and the organic fertiliser with nitrogen and phosphorus(NPM)treatment was the best,this treatment also significantly increased the total and effective phosphorus contents of the soil.This treatment also significantly increased the total phosphorus and effective phosphorus content of the soil.In other words,the best improvement in all indicators was achieved by the NPM treatment,and the organic fertiliser treatment led to a more significant improvement in the nutrient content of the soil.(2)Long-term application of organic fertiliser had an effect on soil enzyme activity,and there were differences in the pattern of performance of different enzymes.The application of organic fertilisers reduced the sucrase activity in the top layer of the soil,while the opposite was true for the subsoil layer;long-term application of organic fertilisers significantly increased soil urease and alkaline phosphatase activities compared to chemical fertilisers;application of organic or inorganic fertilisers significantly reduced soil catalase activity compared to no fertilisers,but the differences between treatments were not significant.Correlation analysis further showed that there was a highly significant correlation between soil enzyme activities and between soil enzyme activities and soil physicochemical properties.(3)Long-term application of organic fertilizer will alter the diversity of soil bacterial and fungal community structure,as well as the relative abundance of dominant bacterial phyla.In the 0-20 cm soil layer,long-term application of organic fertilizer significantly increases the relative abundance of Proteobacteria and Bacteroidetes in bacteria,and Ascomycota in fungi,compared with chemical fertilizer.However,it decreases the relative abundance of bacterial phyla such as Acidobacteria,Chloroflexi,and Rokubacteria,as well as Basidiomycota in fungi.In the 20-40 cm soil layer,except for basic consistency with the relative abundance changes in related phyla observed in the 0-20 cm soil layer,long-term application of organic fertilizer also significantly reduces the relative abundance of Actinobacteria and Latescibacteria(bacteria),Mortierellomycota(fungi).LEf Se analysis also indicates that the application of organic fertilizer can affect the species composition of bacteria and fungi,changing the differential species enriched in different treatments.In summary,long-term application of organic fertilizer will alter the diversity of soil bacterial and fungal community structure,as well as the relative abundance of dominant bacterial phyla,which is significantly different from chemical fertilizer.(4)By constructing network diagrams of bacterial and fungal groups in different soil layers,the results show that there are complex interactions between bacteria and fungi,and most of them are positively correlated relationships.Spearman correlation analysis of key species and soil chemical properties and soil enzyme activity shows that in both soil layers,most soil key species are significantly correlated with soil SOC and TN,except that in the subsoil layer,a few bacterial phyla are also significantly negatively correlated with soil total phosphorus and available phosphorus.In the topsoil layer,they are significantly correlated with sucrase and catalase activity,while in the subsoil layer they are significantly correlated with catalase and phosphatase activity.This indicates that changes in soil carbon,nitrogen,and other properties may drive the changes in key species in the soil,and the subsoil layer may also have a limited role in phosphorus.Additionally,sucrase,catalase,and phosphatase activity also interact with soil key species.Through redundancy analysis,it was further discovered that the environmental factors affecting changes in bacterial community structure in the topsoil layer were soil SOC,TN,Olsen-P and TP,while in the subsoil layer,it was TP and TN.In other words,the main environmental factors driving changes in soil topsoil bacterial community structure are soil carbon,nitrogen,and phosphorus indicators,and for the subsoil layer,nitrogen and phosphorus indicators are the main factors.The changes in fungal community structure in the topsoil layer are significantly correlated with soil SOC and AlkaliN,while the main environmental factor driving changes in the fungal community structure in the deep soil layer is Olsen-P.In summary,by regulating relevant environmental factors,it is possible to achieve differences in bacterial and fungal communities in the soil.