Experimental study of infiltration into a bean stubble field during seasonal freeze-thaw period

Infiltration characteristics of frozen soils are of prime interest for a variety of concerns, including water conservation, runoff, flooding, and erosion. Although frozen soil infiltration is typically not associated with irrigation practices, winter and spring irrigation in northern and northwestern China is conducted mostly during the freeze-thaw period when water is available. The shortage of water resources is an important factor affecting and restricting development of crop and livestock in northern and northwestern parts of China. Therefore, improving irrigation efficiency and determining irrigation parameters have become key problems for agricultural management. This paper examines the infiltration characteristics during different freeze-thaw stages through the winter based on water infiltration in a green bean standing stubble field. The variation in 90-minute cumulative infiltration capacity and final infiltration rate were examined for the transient freeze-thaw stage, the steady freezing stage, and the thawing stage. Results showed that during the transient freezing stage, the effect of the frozen layer on infiltration characteristics was limited only at the beginning of infiltration, During the steady freezing stage, cumulative infiltration and final infiltration rates decreased as soil frost depth increased. During the thawing stage, cumulative infiltration and final infiltration rates increased with the increase in thaw depth. The exchanges of water and heat between surface soil and atmosphere and the phase change of soil water were the main reasons for the variation in infiltration characteristics. Results from this study have practical significance for directing the winter and spring irrigation in seasonally frozen soil areas and also have hydrologic implications for predicting runoff and flooding associated with rainfall and snowmelt on frozen soil.