[Applicability of cosmic-ray neutron sensing for monitoring soil moisture in farmland].

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 () and the root-mean-square error (RMSE) between CRNS-estimated soil moisture and measured soil moisture reached 0.64 and 0.05 cm·cm, 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.