Abstract:

Based on soil gravimetric water content data at depths of 0−50cm collected during crop growth stages at the Wuwei Desert Ecological and Agricultural Meteorological Experiment Station over the past 12 years (March 2011-July 2022), contour plots were employed to analyze the spatial and temporal distribution in soil moisture derived from both automatic and manual observations in farmland of arid region, the differences and correlations between these methods were quantified using statistical indices such as root mean square error(RMSE) and absolute error(E), employing statistical indices such as RMSE, absolute error(E), and relative error(RE), comparative analysis of the differences and correlations between the methodologies was conducted, and this study identified the dynamic changes in soil moisture using different measurement methods, and corrected the automatically observed soil moisture data using regression equations. The results showed these were some differences in the spatial and temporal variation of soil moisture between automatic and manual observations. However, the overall change trend in soil moisture was roughly the same. The soil gravimetric water content of automatic observation was lower than manual observation, and the mean absolute error (E) was 2.4 percent points(PP). From the perspective of each soil layer, the average soil gravimetric water content observed for many years was the largest in 0−10cm soil layer. The frequency of absolute difference E<5 percent points of soil gravimetric water content in 10−40cm soil layer could reach more than 80%, and the frequency of absolute difference E<5 percent points of soil gravimetric water content observed in 40−50cm soil layer was 73.3%. In addition, the error value in the soil gravimetric water content in 20−30cm soil layer was the smallest under many years of observation. By correcting the soil moisture data of automatic observation, the frequency of absolute difference E<5 percent points of soil gravimetric water content in each soil layer reached more than 80%, which improved the accuracy of agricultural meteorological automatic monitoring data in arid areas, and further provided certain technical support and theoretical basis for farmland soil moisture drought warning and monitoring.

Key words: Soil moisture, Automatic monitoring, Manual observation, Soil gravimetric water content, Comparative analysis of difference, Data revision