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.
为了明确田块尺度土壤含水量的空间变异特征,制定合理准确的土壤采样方法,支持田间精准灌溉,分7个日期对陕西省杨凌区曹新庄试验区土壤样品进行采集,利用经典统计学和地统计学方法,分析了0～60 cm不同土层土壤含水量的空间变异特点。结果表明: 田块尺度土壤含水量空间分布呈弱变异或中等偏弱变异;土壤含水量在11.7%～20.1%时,其值越低,空间变异性越强。采样间距显著影响土壤含水量空间变异性的计算精度,采样间距设置为东西方向间距27 m和南北方向间距9 m时的土壤含水量变异系数比采样间距设置为东西方向间距9 m和南北方向间距18 m大3.3%。随着采样密度的增大,土壤含水量分布的等值线变化增大;表征田块尺度土壤含水量空间变异性最少的网格数量为21个点。采样间距为东西方向间距18 m和南北方向间距9 m时,田块尺度土壤含水量具有较高的空间相关性,田块中间位置的土壤含水量比四周高3%～5%。本研究可为关中平原田间测定土壤含水量确定合理的采样方法,并为实现农业精准灌溉提供参考。.
Keywords: field scale; sampling spacing; soil water content; spatial variability.