Effect On Water And Salt Transpotr And Water Repellency Of Soil Under Reclaimed Water Irrigation

According to statistics, our country sewage emissions has amounted to76.3billion m3in2007, and it was still increasing in recent years. After Sewage was secondary treated, theReclaimed water was used for agricultural irrigation, not only improve water quality, reduceprocessing cost, and can make use of recycled water containing needed for crop growth of ni-trogen, phosphorus, potassium and other nutrients, promote green plant growth and improvethe production. It caused quality degradation of the arable soil that the produce and distribu-tion of soil salinity, water repellency. Drip irrigation as a kind of advanced irrigation tech-nology can not only save water, but also provide a good salt water environment for farmlandcrops.In this paper, vertical soil column and three-dimensional soil box was carried out to wa-ter infiltration and drip irrigation experiment, studies distribution regularities of soil water-saltand water repellencyunder different irrigation quota and different dripdischarges with rec-laimed water irrigation. Based on the experiments, the soil water repellency and the move-ment characteristics of soil water and salt were discussed. The main conclusions are as fol-lows:（1）The results showed that: after reclaimed water irrigation, Water repellency of allfour types of soils on surface was stronger than the subsoils. Lou soil and Saline-alkaline soilindicated repellency of0-2and1-3degrees, respectively; whereas both sand soil and Shajiangblack soil displayed repellency of degree0. Soil water repellency increased with the increaseof reclaimed water irrigation quantity and irrigation time dramatically, and the larger the irri-gation quota, the more notable the differences of soil water repellency. OM of the all fourtypes of soil had positive correlations with soil difference of water droplet penetration timeTR, while Cl-and EC presented negative correlation with soil difference of water dropletpenetration time TR. Compared with the three other types of soils, it’s available for sand soilirrigating with reclaimed water.（2）Principal component analysis (pca) results show that in the recycled water irrigationcondition, effect of the Lou soil salt content on soil water repellency is obvious, mainly in Cl-,EC in influencing Lou soil was a larger proportion of the principal component analysis ofwater repellency, the pH, times OM content taked second place, the most unsignificantly ef- fect on water repellency Lou soil was COD. Reclaimed water irrigation maked Lou soil par-ticle viscosity larger，water repellency increase, capacity of soil water infiltration to reduce.Alkaline of Lou soil increased significantly.(3) Sandy soil and Saline alkaline soil horizontal and vertical wetting front and timeaccorded with good power function in freshwater and reclaimed water irrigation under differ-ent dripper discharges. Compared with freshwater irrigation, Reclaimed water drip irrigationeffected soil water infiltration basically same. Sandy soil infiltration area indicated salt de-position area in the condition of two types of water with three dripper discharges. Saline alka-line soil were irrigated with both reclaimed water and freshwater, the horizontal desalinationarea radius was largest, while vertical desalination radius is minimal when the dripper dis-charge was biggest. Saline alkaline soil moist body salt content and distance from waterdropper was in line with the good relations of second order polynomial.(4) Sandy soil and saline alkaline soil in the condition of reclaimed water irrigaton andthe contrl water test, soil water repellency in the soil profile were enhanced, saline alkalinesoil water repellency performanced most obviously and distributed repellency level1~3, thesandy soil water repellency were0level. Difference of dripper discharges maked the sandysoil water repellency produces different difference, the larger the dripper discharges, thegreater the saline alkaline soil water repellency. Pearson coefficient of rank correlation me-thod and multiple regression analysis showed that sandy soil and saline alkaline soil watercontent are positively correlated with soil water repellency under the condition of two kindsof water drip irrigation, salt content and soil water repellency has a negative relationship.Compared with freshwater irrigation, reclaimed water irrigation increased the viscosity of soilparticles effect is more obviously, water repellency increased and capacity of soil infiltrationdecreased. Saline alkaline soil with high clay content suffered the effect of reclaimed water ir-rigation larger than sandy soil with low clay, so it was more suitable for sandy soil with rec-laimed water irrigation.