Acta Geographica Sinica ›› 1993, Vol. 48 ›› Issue (5): 447-456.

### SPATIAL STRUCTURE OF SOIL WATER CONTENT AND SAMPLING NUMBER DETERMINATION IN THE FIELD

Yang Shixiu, Lei Zhidong

1. Hydraulic Enginerring Department, Tsinghua University, Beijing 100084
• Online:1993-09-15 Published:1993-09-15

Abstract: This paper deals with spatial variation and spatial structure of soil一water content based on the test data in the field. 100 sampling sites were arranged along a line with one meter interval locat-ed at the Experimental Station of Guan County in Shandong Province. 505 samples were taken at depths of lOcm，3Ocm，5Ocm，7Ocm，9Ocm，89 samples for bulk density were taken in correspon-deuce with the samples for soil-water content. The analysis of statistical parameter，autocor-relation，and semivariogram have been done for the soil-water contents at different depths the avarage 0-100cm soil-water contente Field data obtained form the study area show that the co- efficient of soil-water content CVs is about 0. 1一0. 25. The values are similar to the CVs from 78 series(5000 samples)，which we were taken form Shanxi，Inner Mongolia，and Hebei Provences. The coefficient of avarage soil-water content CV at 0一1 OOcm is smaller than that of the soil-water content CVs at different depths. 1t is possible to calculate soil-water storage capaci-ty for one meter depth by using average soil-water content and average bulk density. The spatial relationship among the field soil-water contents is of little Significance. Samples which have a certain distance can be treated as random variables. Then the number of samples necessary for various probability level (or confidence level) PI and specified limit (or certain es- timation error )\Can be determined. A method of computer-similitude have been applied to check the necessary number of samples otained form the table. In general ,sampling for soil-water content with specified limit of A=10一l5% at confide-nce level of PI=90一95% is acceptable in practic.