Cosmic-ray neutron sensing (CRNS) method was recently used to monitor soil moisture in farmland. But its spatial representation and accuracy needs further study. A field experiment was carried out to evaluate the applicability of CRNS for monitoring soil moisture in winter wheat farmland of the North China Plain. The spatial weight of CRNS detector was simulated by the ultra rapid adaptable neutron-only simulation for environmental research (URANOS) model and the CRNS-estimated soil moisture was compared with the measured soil moisture. The results showed that the CRNS detection radius obtained by URANOS simulation was 127-139 m, and that the weight distribution showed good agreement with the theoretical value. The determination coefficient (R2) and the root-mean-square error (RMSE) between CRNS-estimated soil moisture and measured soil moisture reached 0.64 and 0.05 cm3·cm-3, respectively. The CRNS-estimated soil moisture was sensitive to the changes of overall moisture in the detection area, with seasonal variation of measurement accuracy. In conclusion, cosmic-ray neutron sensing is a continuous and reliable method for monitoring total water content in winter wheat fields.
近年来,宇宙射线中子法(CRNS法)逐渐被应用到农田生态条件下的土壤水分监测领域,但其在田间应用时的空间代表性和测定精度还需进一步研究。本研究在华北平原冬小麦农田开展宇宙射线中子法应用效果的评价研究,采用超快速中子适应性(URANOS)模型计算CRNS法的空间权重,对CRNS法获得的土壤含水量与实测土壤含水量进行对比,以准确估算监测空间内的蓄水量。结果表明: 通过URANOS直接模拟得到的权重分布更符合理论值,测定半径在127~139 m。CRNS法估算的土壤含水量与实测土壤含水量的决定系数达到0.64,均方根误差达到0.05 cm3·cm-3。CRNS法所得土壤含水量对探测区域内总体水分的变化响应灵敏,测定准确度有季节性变化规律。宇宙射线中子法是一种可用于冬小麦农田的连续、可靠的区域总体水分监测方法。.
Keywords: cosmic-ray neutron sensing (CRNS); soil moisture; spatial weight; ultra rapid adaptable neutron-only simulation for environmental research (URANOS) model.