Study On Influence Factors And Spatial Variability Of Soil Physical And Chemical Properties In Upper Reaches Of Heihe River Basin On Southern Slope Of Qilian Mountains

This paper takes the upper reaches of Heihe River on the southern slope of Qilian Mountain as the research area,and uses the combination of field experiment and indoor analysis to study the spatial distribution of soil pH,organic matter and conductivity in the upper reaches of Heihe River on the southern slope of Qilian Mountains by using classical statistical methods and geostatistics.Characteristics and variability,to analyze the main influencing factors affecting the surface soil pH,organic matter and electrical conductivity of the study area.By analyzing the soil organic matter content,soil acidity and alkalinity and salinization degree in the study area,this paper wants to provide a reference basis to make rational use of agricultural production and land resources in the region.The results of the study are as follows:?1?According to the average content of sampling points in the upper reaches of Heihe River on the southern slope of Qilian Mountain,and the grading standards for salinized soil salinization index in semi-humid and semi-arid regions of China as well as the second national soil census nutrient content,the average pH value of soil in 0-40 cm was 7.6,which was consistent with the alkaline soil of arid and semi-arid area in northwest China;the average organic matter content of 0-40 cm soil organic matter was 69.23 g·kg^-1,and the soil was fertile;the average electrical conductivity in 0-40 cm soil was 95.46 us·cm^-1,and there is no salinization in the soil at the sampling point.The pH value increased from the surface layer to the deep layer,and the organic matter and electrical conductivity values were opposite.From the variability,pH was a weak variability,but organic matter and conductivity were moderate variability.The variation intensity was soil organic matter>conductivity>soil pH.?2?Analysis of factors affecting soil pH,organic matter and conductivity in0-10 cm in the study area,soil pH and NDVI,topographic relief,soil volumetric water content,total porosity,saturated water storage,Soil bulk density and very fine sand were significantly correlated?P<0.01?;soil organic matter and NDVI,topographic relief,silt,soil mass water content,total porosity,saturated water storage capacity,soil bulk density,fine sand were extremely significant Correlation?P<0.01?and soil organic matte was significantly correlated with clay,volumetric water content,elevation,and slope variability?P<0.05?;soil conductivity and soil mass water content,total porosity and saturated water storage,and soil bulk density were a extremely significant correlation?P<0.01?and soil conductivity was significantly correlated with plane curvature,slope variability,altitude,and fine sand?P<0.05?.?3?Pearson correlation analysis and path analysis showed that the correlation coefficient between soil volumetric water content and pH was the largest,and the direct path coefficient was also the largest,therefore,the soil volumetric water content was used as the auxiliary variable W₁ for pH synergy interpolation;the correlation coefficient between soil saturated water storage capacity and organic matter and electrical conductivity was the largest,and the direct path coefficient was also the largest,therefore,the soil saturated water storage capacity was used as the auxiliary variable W₁ to perform intercalation of organic matter and conductivity synergistic Kriging.?4?Soil pH,organic matter and conductivity are moderately spatially correlated in the study area,and spatial variability is affected by structural factors and random factors.The soil pH value in the study area was interval distribution of high-value and low-value from the northwest to the southeast.The spatial distribution of soil organic matter was plaque-like and strip-like,and the soil organic matter content showed a decreasing trend from southeast to northwest.The soil electrical conductivity showed a strip-like distribution in the spatial distribution,and the soil EC value showed that it was higher in the northwest than in the middle.By comparing the accuracy of three model interpolation,the accuracy of COK_PCACA model was higher than that of the other two models.