Effects Of Super Absorbent Polymers On Soil Water Moisture And Physical Properties

The water resources are regarded as prerequisite in the Agricultural development, inrecent years; drought and water shortage seriously restricts the agriculture development. Thetendency of modern agriculture development is the ecological agriculture mode of highefficient use of water resources. Super absorbent polymer that has the strong absorptioncapacity, wide material source and easy production can be used in wide range of applications.Application effect of super absorbent polymer is influenced by many factors, including itsown properties, physical and chemical characteristics of soil microorganisms, climaticconditions. The type and amount of super absorbent polymer as the starting point, researchedthe effect of super absorbent polymer on soil moisture and physical properties, analyzed theeffect and mechanism of super absorbent polymer, explored the persistent effect of superabsorbent polymer in soil and the effect on others soil physical properties, which provided atheoretical basis for the efficient use of water resources and the sustainable development ofagriculture.This paper selected the two textures of soil with poor water retention (sand soil, loessalsoil) and four kinds of super absorbent polymer in market, respectively put0.05%,0.1%and0.5%dosages into soil, studied the mechanism of super absorbent polymer on soil waterretention characteristics and the combined influence on soil physical characteristics, analysisthe ability of hold water again and the persistent of utility of super absorbent polymer aftersoil through alternation of wetting and drying, which provided a theoretical basis to establishthe system of efficiently water-saving technology and reasonable selection and application ofsuper absorbent polymer on agriculture. The main results are as follows:(1) Although super absorbent polymer absorb water through its molecule, it cansignificant increased the function of soil pore in the aspect of improved soil water-holdingability. Through researched soil water characteristic curve and its model parameter after usesuper absorbent polymer, got the conclusion that soil water-holding capacity varying degreesincreased and soil water-holding ability promoted after use super absorbent polymer. Superabsorbent polymer effectively increased soil water-holding capacity in the dehydrationprocess, especially improved the water-holding capacity during the middle and low suction segment. Soil water suction grows and water lose rate slow down when the soil begin to losswater, soil water-holding ability is further strengthen. Soil saturated water and field capacityof all treatments had significant increased, however permanent wilting coefficient had nosignificant change. Soil gravity water and available water had increased, soil unavailablewater had no significant change, these proved that super absorbent polymer had the functionof improve soil water-holding capacity and enhance the level of soil water absorbed by plant,and the effectiveness value of super absorbent polymer to improve soil water-holding ability.(2) Soil physical properties significant improved by super absorbent polymer of traceamounts. Soil is a system with more pores, soil structure direct influenced the size of soilbulk density, the quantity of soil pore and pore-size distribution. Due to the super absorbentpolymer volume expansion through absorbed water, soil volume became bigger and soilquality of unit volume reduced, then soil bulk density became smaller. The more dosage ofsuper absorbent polymer, the more water content and the more volume expansion of it, leadto the smaller soil bulk density. After the volume expansion, super absorbent polymer canenlarge the aperture of soil pore, lead the amount of soil bigger pore and the proportion ofsoil aeration porosity increased. During the process of water suction increasing, soil bulkdensity was Infinite close but not more than it of0%, though the increased extent of soil bulkdensity is bigger. These instructed that super absorbent polymer had the effect of loosen soilon compacted soil.(3) The effect of super absorbent polymer on two texture of soil was obviously different.Different soil texture type, the degree of response to the combined effect of super absorbentpolymer was different. After used super absorbent polymer, owing to the limited of soiltexture, the effect of super absorbent polymer on soil was different. For sandy soil and loessalsoil, two texture soil which used by experiment, saturated water content, field capacity andgravitational water increased after used super absorbent polymer, soil water-holding capacitysignificant increased during the process of absorbed water, these effectively increased thewater-holding ability by soil pore. However there are different expressions between two typesoil, including the shape of soil water characteristic curve, the rate of water loss, and thesuction range of rapid loss water. Meanwhile, with the amount of super absorbent polymerincreased, the growth of availability water and the degree of soil bulk density decline ofsandy soil are higher than loessal soil. Comprehensive analysis, the response to superabsorbent polymer of sandy soil are stronger than loessal soil.(4) Alternation of wetting and drying can affect the effect of super absorbent polymer,weakened this effect in different degrees. After alternation of wetting and drying repeatedly,soil water-holding capacity significantly reduced at low suction segment and soil saturated water content reduced; soil gravitational water had no significant change in the first threedehydration process, but it significant reduced in the fourth dehydration process; soil totalavailable water, easy available water and slow available water in four process of alternationof wetting and drying are different, but had no obvious regularity; with the process ofalternation of wetting and drying increased, soil bulk density increased, the proportion of soilaeration pore declined, the proportion of soil capillary pore and ineffective pore increased.Comprehensive analysis and comparison, after alternation of wetting and drying repeatedly,the capacity of super absorbent polymer had increased soil water-holding content reduced, thenumber of soil aeration pore and the capacity of soil pore water-holding declined, the contentof soil pore water-holding reduced, and had different influence for soil available water.