Evaluation Of Soil Fertility For Agricultural Cultivation In Arid Areas Based On Soil Nutrients

Soil is the loose surface layer of the earth's land,which can grow plants.It is also an indispensable material basis for human survival and development.Human agricultural planting activities lead to the disturbance of soil structure in the natural state,forming a cultivated soil of about 0-20 cm on the surface of the soil.Because of the harsh natural environment and human destruction,the soil quality in arid area is fragile and the anti-interference ability of ecosystem is weak,which is manifested by the decline of soil fertility quality and the insufficient fertility.According to this study,the central part of Changji City in Xinjiang was selected for soil fertility evaluation.The study area mainly includes Daxiqu Town,Sangong Town,Yushugou Town,Erliugong Town,Liugong Town,Tianba Town,Binhu Township.Military Farms,Communist Youth League Farm,Xiabahu Farm and Changji City.Based on the Chinese Soil Classification System in 1992,field sampling and laboratory experiment analysis of three soil types in the study area were carried out by GPS positioning.The eight indicators of organic matter,alkali-hydrolyzed nitrogen,available phosphorus,available potassium,available iron,available manganese,available copper and available zinc of 1421 soil samples in the study area were respectively mathematically and physically analyzed by combining classical statistics with geostatistics.Statistical and Kriging spatial interpolation were used to obtain the content characteristics,spatial variability and spatial distribution characteristics of each element.Soil fertility in the study area was graded and evaluated by principal component analysis.The results showed that:(1)According to the classification standard of soil properties in Xinjiang in the second national soil census,85.29%of the soil organic matter samples in the study area were mainly in grade 4(flat),and the organic matter content was in the middle level;50.81%of the soil alkali-hydrolyzed nitrogen samples were in Grade 5(deficiency),32.02%of simples were in grade 4,and the content of alkali-hydrolyzed nitrogen was mainly concentrated in grade 4-5,which was relatively scarce;41.10%of soil available phosphorus samples were in grade 4,34.60%of the samples were in grade 3(flat),mainly concentrated in grade 3-4,at medium level;49.89%of soil available potassium samples were in Grade 1(abundant),26.32%were in grade 2(abundant),mainly in grade 1-2,and the content of available potassium was relatively abundant;77.97%of the available iron was in the "flat" grade,and the total available iron content was in the middle level;99.93%of the available manganese was in the "deficient" grade,and the available manganese was relatively scarce;99.37%of the available copper was in the"abundant" grade,and the total available copper content was relatively rich:99.86%of the available zinc was in the "deficient" grade and relatively scarce.(2)The spatial variability of soil nutrient elements and trace elements in the study area was preliminarily understood by semi-variance function.As far as nutrient elements were concerned,the variation degree of available potassium was high,and the spatial autocorrelation of four nutrient elements was stronger.As far as the optimal model was concerned,organic matter and alkali-hydrolyzed nitrogen accorded with the exponential model,available phosphorus and available potassium accorded with the spherical model.As far as the spatial distribution of nutrient element content in the study area is concerned,the spatial distribution of organic matter content is east>west;the spatial distribution of alkali-hydrolyzed nitrogen content is southwest>northeast,and shows a decreasing trend;the spatial distribution of available phosphorus content is northeast>southwest,and the central content is low;the high-value area of available potassium content mainly concentrates in the north,and gradually decreases from north to south.As far as trace elements are concerned,the spatial variability of available zinc is the smallest,the variation of available manganese and available copper is constant,and the spatial autocorrelation of available iron and available zinc are strong.According to the determination coefficient,the available iron conforms to the exponential model,the available manganese and available copper conform to the linear model,and the available zinc conforms to the Gauss model.As far as the spatial distribution of trace elements is concerned,the content of available iron is higher in the north than in the south,higher in the east than in the west;the highest content of available manganese is in the eastern margin,lower in the middle and southwest;the content of available copper is quite abundant,lower in the middle and east,higher in the west,south and north;and the content of available zinc in the eastern part of the study area is higher than that in the western part.(3)Principal component analysis was used to calculate and classify the overall soil fertility in the study area.The soil fertility is 6.20%in "abundant"(grade 1 and grade 2);the soil fertility is 91.50%in "flat"(grade 3 and grade 4);and the soil fertility level is 2.30%in "deficient"(grade 5).It can be concluded that the overall soil fertility in the study area is at a medium level.