Spatial Variability of Soil Water and Salt in Field and their Estimations by the CoKriging

The soils at ninety-eight observing points by a square of 10×10 (m 2) were sampled in a wheat field (approximately 1 ha). The soil water and salt of each point in the layers of 0-20cm and 80-100cm were measured at different time. The results indicated that the soil water content under two layers at different time showed a normal distribution, the soil salt content in bottom soil showed a lognormal distribution and the soil salt content in surface soil showed an uncertain distribution. The variability coefficients of soil water and salt respectively belonged to the low and middle intensity. The semivariance analysis was used and found that the soil water and salt were correlated in a given spatial range. Preliminary analysis was made for the spatial dynamic variability of soil water and salt in different time. The CoKriging method was also used to estimate soil water and salt content, the estimated variance could be decreased by 136.3% comparing with ordinary Kriging.