Abstract: To analyze the soil moisture characteristics and related affecting factors is of importance in improving agricultural production and rational land use in red soil regions. By using redundancy analysis method (RDA) and relevant data, this paper studied the relationships between the soil moisture (0-15, 15-30, 30-60, and 60-100 cm layers) variability and the meteorological factors (wind velocity, precipitation, vapor pressure, air temperature, relative humidity, and sunshine hours) on the low hill red soil slope in Yingtan of Jiangxi, China. The soil moisture in the study area had an obvious seasonal change, and was strongly affected by precipitation. The moisture in surface soil layer was most affected by precipitation. The effects of precipitation on soil moisture decreased with soil depth. The coefficient of variation (CV) of surface soil moisture was high, but the CV became smaller when the soil layer was deeper. RDA ordination diagram could well represent the relationships between the seasonal dynamics of soil moisture and the meteorological factors. Air temperature, precipitation, relative humidity, and vapor pressure were the main factors affecting the seasonal dynamics of soil moisture, and the main affecting factors in different months differed. In May and June, the main affecting factors were precipitation and relative humidity. In July and August, the main affecting factors were air temperature and sunshine hours. Therefore, the soil moisture variability was not only affected by the elevation, soil depth, land use patterns, and other environmental factors, but also by the precipitation, temperature, and other meteorological factors. The findings of this study could be used as a reference to further comprehensively analyze the affecting factors of the spatiotemporal variability of soil moisture, and also, as the basis for the timely regulation of the hillside soil moisture status and crop water conditions.

Key words: melon (Cucumis melo), melatonin, salt stress, Ca²⁺, alleviation effect.