[Spatial variability of soil water content in field of Guanzhong Plain, Northwest China]

To clarify the spatial variability of soil water content at field scale, a reasonable sampling method was established to support precision irrigation in the field. Soil samples were collected from Caoxinzhuang experimental area in Yangling District, Shaanxi Province at seven different dates. The spatial variation of soil water content in different soil layers of 0-60 cm were analyzed with classical statistics and geostatistics methods. The results showed that spatial distribution of soil water content in field scale was weak and moderate. When soil water content was within the range of 11.7%-20.1%, soil water content was negatively correlated with spatial variability. Sampling interval signifi-cantly affected the calculation accuracy of the spatial variability of soil water content. The coefficient of variation of soil water content between the east-west direction spacing of 27 m and the north-south direction spacing of 9 m was about 3.3% higher than the east-west direction spacing of 9 m and the north-south direction spacing of 18 m. With increasing sampling density, the contour change of soil water content distribution increased, and the number of grids with the least spatial variability of soil water content at the field scale was 21 points. When the sampling spacing was 18 m in the east-west direction, 9 m in the north-south direction, soil water content at field scale had a high spatial distribution correlation with soil water content in the middle position being 3%-5% higher than the surrounding. Our results provided reference for reasonable sampling of soil water content in the Guanzhong Plain and could guide the precision irrigation in agriculture.