| With pressure on food security bigger because of factors such as population growth, new land resources must be opened up to seek new point of grain growth, at the same, the existing cultivated land resources should be excavated, and the development and utilization of saline-alkali soil especially primary saline-alkali wasteland is a feasible way.Based on high underground water level in primary saline-alkali wasteland in the article, the water-permeability plastic film was comprehensive covered in primary saline-alkali wasteland surface as this new agronomic measures, through used the local limited rainfall resource. The surface soil moisture evaporation was limited by the elastic water resistance, and the surface salt accumulation was suppressed. The soil salinity of plough layer was reduced gradually by rainfall stack leaching using its unidirectional pervious. Compared with other methods of saline-alkali soil governance, the greatest advantage of ideas was that the locally finite controllability fleshwater resources are not consumed. Therefore, the research results have important practical significance for the development and utilization of saline-alkali wasteland resources to increase the area of arable land, but also could be provided some scientific reference for the rich soil management theory.The innovation points were studied in this article including that:①The salinity of surface soil was accumulated by the pulling effect of water evaporation in primary saline-alkali wasteland, but its content is maximum. The reasons were that the inhibitory effect of dry soil on surface to salt accumulation, the discreting action of soil pores by sodium ion to delay salt accumulation, the polymeric zero flux of water movement in soil profile to inhibit salt surface accumulation, the diffusion and diffusion in solute potential gradient to reduce surface salinity.②The method was put forward that comprehensive coverage of water-permeability plastic film to improve saline-alkali soil, then the field engineering measures were supplemented to control the use of surface runoff. The surface soil original structure could be kept, because the water-permeability plastic membrane mulching could avoid direct hit of rain. After intermittent rain falling film, water could through film into the soil in soil suction effect. Then, the surface soil matric potential closed zero. The moisture could migrate to the lower layer under water potential gradient effect, and the soil salt would follow the moisture into the lower layer. The plough layer soil would realize desalting under the repeat effect of intermittent leaching.③The water and salt movement was divided two stages according to the characteristics of the water-permeability plastic film mulching, which were having water and no water on plastic film. When water was on the film, soil water flux was equal to the amount of infiltration on the water. When water was not on the film, soil evaporation could be assumed to be zero because of suppressed. Then, the water and salt transport process could be solved by simultanenously soluted moisture transport equation and solute transport one. And the simulation results showed that numerical calculation method is feasible.Of course, the conclusion and results were drawn in the article that only discussion about soil moisture and salt movement feature, and soil salt accumulation and migration regularity of water-permeability plastic film mulching, and its conclusion should be verified and supplied further. The simulation calculation methods need to be further validated and practice. Overall, this method of water-permeability plastic film mulching improved primary saline-alkali wasteland could provide reference, for development and utilization of tens of millions acres of saline-alkali wasteland in the northern arid and semi-arid region, and for low-yield secondary salinization. It also is a kind of new method and ideas to development land resource which was not consumed controllable freshwater resources. |
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