Analysis Of Spatial Distribution Characteristics Of Soil Organic Matter In Cultivated Lands In Northwest China

Cultivated land is an irreplaceable important means of production for agricultural production and an important resource for maintaining the sustainable development of society and the national economy.The northwestern region is rich in land resources.However,due to the fragile ecological environment,most of the cultivated land is dry land.At present,the quality of cultivated land is declining and the ecological environment is deteriorating.As an important part of cultivated soil,soil organic matter is the main source of soil fertility,which can effectively improve the physical and chemical properties of soil and affect the growth of crops to some extent.Understanding the spatial distribution of soil organic matter and its relationship with climate,ecological conditions and related management factors has important practical significance for the analysis of the spatial variability of soil fertility and its driving mechanism.In this study,the soil organic matter content of 32029 soil sampling points in Northwest China was taken as the research object,based on the semi-variance function model theory of spatial variation of soil properties,using the combination of geostatistics method,traditional statistical method and GIS application.The spatial variability and distribution of organic matter in cultivated soils in five provinces of Shaanxi,Gansu,Qinghai,Xinjiang and Ningxia in Northwest China were explored,combined with geographical factors(topography,topography),meteorology(annual precipitation),and soil properties(The pH value,soil texture),management measures(irrigation method,film mulching method,straw returning)were analyzed for their relationship with soil organic matter content in different provinces.The results and conclusions are as follows:(1)The statistical analysis of soil organic matter content in 32029 soil sampling points in Northwest China showed that the average content of soil organic matter in cultivated land in Northwest China was 14.463 g·kg-1.In the cultivated soil in Northwest China,the average organic matter content in Qinghai Province was the highest.The average organic matter content of the autonomous region is the lowest.The degree of variation in each province is at a medium level.(2)From the macroscopic scale,the trend of soil organic matter content in cultivated land in the northwest region is not obvious along the longitude direction,but has a certain trend along the latitude direction.The spatial variance semi-variance results show that the exponential model is the optimal model for studying regional organic matter.And in the large scale,the autocorrelation of soil organic matter content and distribution is higher.(3)The distribution of soil organic matter content in cultivated land in Northwest China is relatively fragmented and has no obvious zonal law.Among them,the Xinjiang Uygur Autonomous Region and the Ningxia Hui Autonomous Region have low organic matter content.The content of organic matter in Shaanxi Province is rich and evenly distributed,and the content of organic matter gradually decreases from south to north.Gansu Province is rich in organic matter and gradually decreases from southeast to northwest.The organic matter content of Qinghai Province is relatively rich.(4)The relationship between the soil organic matter content in the northwestern region and the local geographical factors,meteorology,soil properties,management measures and other natural and human factors have more complex regional differences.Among them,there is a significant spatial correlation between soil pH and organic matter in Shaanxi Province;there is a significant spatial correlation between slope and organic matter content in Gansu Province;the elevation of Ningxia Hui Autonomous Region and Qinghai Province and the soil organic matter in this region are present.The correlation is the highest;there is a significant spatial correlation between precipitation and its organic matter content in Shaanxi Province.