Study On The Moisture Movement Law Of Farmland Soil In Northern Seasonal Frozen Soil Area

Water is the indispensable material basis for human survival and social development, and China is seriously shortage of water, which has seriously hampered the development of industrial and agricultural. Compared with the industrial, Agricultural water faces more serious situation. Because of China's national conditions, Water resources shortage and waste are all serious in using agricultural resources. Therefore, it is very important to improve agricultural water resources use efficiency, agricultural water-saving irrigation and efficient water use has been one of the major concern and attention issues.This paper adopts the modern data processing methods and combines with frozen soil observation test in winter to systemically study phase-change law, infiltration law and evaporation on the condition of seasonal frozen soil in northern cold area. The main research contents and production are presented as follows:(1) Surface temperature will not immediately affect the deep soil temperature, but lag some time, which increases with the depth in test cycle. Deep soil temperature basically unchanged throughout the thaw period. At the same time, in initial frozen period, the variation of surface soil phase-change is small in the horizontal direction and in the vertical direction it gradually changes weak as the depth increases, and there is no phase-change under the frozen layer. However, in frozen middle and later periods, the variation is bigger than that in initial frozen period not only in the horizontal direction but also in the vertical direction.(2) The difference between frozen soil and unfrozen soil is elaborated respectively. The results show that:compared with unfrozen soil, frozen soil infiltration process in different frozen depth conditions to achieve the relative stable time is quite different. The frozen soil infiltration capacity tends to decrease as the development of frozen depth in the same frozen depth, which has great influence on the infiltration capacity in early stage and relative weakening in later stage. At the same time, multiple regression method is used to set up frozen soil infiltration capacity simulation equation. Through accuracy testing, the model meet the requirements and can be used to simulate and forecast frozen soil infiltration capacity.(3) The characteristics of frozen soil evaporation is summarized, the time and rate for frozen soil evaporating at various phase is smaller than that of unfrozen soil. The methods of qualitative and quantitative are used to analyze and evaluate the factors of soil evaporation, and the result show that soil evaporation change in winter is induced by the action of multi factors. The main factors are ground temperature, air temperature, relative humidity, wind direction, air pressure and vapor pressure. BP artificial neutral network technology is used to fit the evaporation course and the results is effective.To sum up, it is very significant to study on the phase-change law, evaporation law and infiltration law of frozen-thawed soil and explorer scientific, reasonable and feasible measures for efficient utilization of soil water resources. It can not only provide technology support for solving water supply contradiction in northern arid and semi-arid cold region and promoting sustainable agricultural development, but also is of great significant to fully play the role of frozen storage moisture and rationally and efficiently use limited soil water resources.