Sampling Optimization Of Reclaimed Soil Nutrient Management

Due to the reclaimed soil is affected by the environment and its physical and chemical properties,it is difficult to recover to the desired level in a short time.The Regulations on Land Reclamation clearly stipulate that the effect of land reclamation should be tracked and evaluated within five years after reclamation for agricultural land,and suggestions and measures for improving land quality are put forward.How to determine the number and location of sample points is the key to ensure the accuracy of soil information,to match the follow-up measures with the variation characteristics of soil nutrients,and to improve the reclamation efficiency.Therefore,it is of great practical significance to study the sampling of reclaimed soil nutrients.Based on 81 soil samples gathered in 2017 in Antaibao Coal Mine,the contents of Soil Organic Matter(SOM),Total nitrogen(TN),Soil Available kalium(SAK)and soil available phosphorus(SAP)in soil nutrients were selected as the objects to analyze the level and distribution of soil nutrients in the dump.Cochran formula,stratified sampling method and cross-validation method were used to calculate the reasonable sampling number of soil nutrients at different depths,and a sampling point layout scheme based on spatial simulated annealing method was proposed.The following conclusions were drawn:(1)The soil nutrients in the study area were at a lower level in the whole country;the distribution trend of soil nutrients in different depths was basically the same,and the variation was similar.The coefficients between 0.1 and 1 are in the middle variation level;(2)The number of sampling points in existence satisfies the requirements of SOM,SAK and SAP for 95% relative error at confidence level of 10%,TN for 5% relative error at the same confidence level;the volume quality method of stratified sampling can reduce the number of sampling points on the basis of Cochran formula,and the optimum allocation method considers the correlation between regions.The reasonable sampling numbers of SOM,TN,SAK and SAP from shallow to deep are 50,50,50,20,40,50,50,50,50 and 50 respectively,which can better reflect the spatial distribution of the area.The representative areas of the dump content are located in the central and northeastern regions when the sample points are laid out,and the spatial simulated annealing is used to follow the Cochran formula.Based on the cross validation of reasonable sample points,the point distribution reflecting the spatial distribution characteristics with small average Kriging variance was obtained,which was basically consistent with the direction distribution of the larger variation degree of nutrients.The sample points could highlight the variability of nutrient content distribution to a certain extent.