Experimental Research And Mathematic Simulation Of Water Movement And Salt Transfer Under Irrigation Condition In Loess Layer

The basic laws and primary influence factors of water movement and salt transfer in the loess were studied in allusion to the characteristics of loess through the theoretical analysis and simulation experiments on the basis of analysis and summing-up for research results about laws of water and salt transfer in the soil at home and abroad. At the same time, the simple mathematic model of water and salt transfer in the soil under one-dimension irrigation was ascertained according to experimental data.The water movement and salt transfer in the soil under different irrigation volume and fertilization volume were studied with the simulation model through the field experiments. The characteristics of the infiltration, salt concentration distribution, the influence of irrigation volume on the water and salt transfer processes in the soil and the quantificational relation between characteristics of water and salt coupling transfer were analyzed. Firstly, the results of water analysis indicated that in the process of water movement with time and depth, there are two obvious peak belts of moisture content which are distributed in the 1.6m~1.8m and 7.4m~7.8m respectively. The speed about micropore movement in loess is too slowly, so there is a widly humid zone in 1m~4m and it has little change during whole observation. Water movement rate increases with the increment of irrigation volume and the index function may be used describe the well relationships between them. Water flux increase with the increment of irrigation volume and the linear function may also be used describe the well relationships between them. The depth of humid peak transfer deepens with increment of irrigation volume and the logarithm function may be used describe the well relationships between them.Secondly, the results of salt analysis indicated that salt dissolved by irrigation water and precipitation can be absorbed in the low salinity area, and can be washed out in the high salinity area, so irrigation seepage water can adjust the adsorption ion in soil. The hydrolysis ion of carbamide can produce ion exchange and also increase soil salt. Shallow soil water evaporation can cause salt up-transfer, and increase salt in surface layer and seriously this result can cause soil salinification. The fine grain and micro pores of loess can improve the...