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 va riety of concerns, including water conservation, runoff, flooding, and eros ion. Although frozen soil infiltration is typically not associated with irr igation practices, winter and spring irrigation in northern and northwester n China is conducted mostly during the freeze-thaw period when water is ava ilable. The shortage of water resources is an important factor affecting an d restricting development of crop and livestock in northern and northwester n parts of China. Therefore, improving irrigation efficiency and determinin g irrigation parameters have become key problems for agricultural managemen t. This paper examines the infiltration characteristics during different fr eeze-thaw stages through the winter based on water infiltration in a green bean standing stubble field. The variation in 90-minute cumulative infiltra tion capacity and final infiltration rate were examined for the transient f reeze-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 t he thawing stage, cumulative infiltration and final infiltration rates incr eased with the increase in thaw depth. The exchanges of water and heat betw een surface soil and atmosphere and the phase change of soil water were the main reasons for the variation in infiltration characteristics. Results fr om this study have practical significance for directing the winter and spri ng irrigation in seasonally frozen soil areas and also have hydrologic impl ications for predicting runoff and flooding associated with rainfall and sn owmelt on frozen soil.