The Infiltration Characterics Of Repellent Soil Under Different Irrigation Conditions

Existence of soil water repellency has an serious impact on soil water movement,whichwould influence the outpur of crop, and at the same time have an influence on environment ina certain degree. Abroad study of soil water repellency has been more mature, and hasformde the certain system. In China, in recent years the research of soil water repellency hasbeen underway in succession in Xinjiang, Inner Mongolia and so on. But the domestic studyof soil water and salt movement of water-repellent soil is still not mature at present to adefinite theoretical system, generally. This paper has performed the water ponding infiltrationexperiments by distilled water in3kinds of homogeneous soils under2different waterrepellent degrees, maked the water ponding infiltration experiments by brackish water in2kinds of homogeneous soils under2different water repellent degrees, carried out the waterponding experiment by alcohol in2kinds of homogeneous soils under5different waterrepellent degrees and the water ponding experiment by bracish water added to Nalidet P-40in the one kind of homogeneous soil.This paper had analysed the water-repellent-soil waterand salt movement laws and the study of modeling application in water-repellent-soilinfiltration. The conclusions were as follows:(1) From the experimental study of distilled water infiltration laws inwater-repellent-soil, existence of soil water repellency had an obvious impact on the soilinfiltration capacity. Take loutu soil for an example, cumulative infiltration volume was600mL with the time of wettable soil and repellent soil of274min and30400min.1st degreerepellent soil was used to performed the experiment, and the cumulative infiltration volumeof repellent soil was obvious smaller than that of wettable soil. With different water pondingdepths and water repellent degrees, the result of cumulative infiltration volume versus timefitted by Kostiakov equation was better than others models and the result fitted would changewith water repellent degree and so on. For example, the result fitted by Exponential equationin water repellent soil was better than that in wettable soil for the same kind of soil.(2) From the experimental study of brackish water infiltration laws in water-repellent-soil, the infiltration ability of non-water-repellent soils increased with theincrease of mineralization degrees. For the water repellent soils, the infiltration ability waslargest at mineral degree of1g/L, but decreased with the increase of mineralization degreewhen mineralization degree were larger than1g/L. Water content﹑salt content﹑Na+andCl-concentration in wetted soil profiles increased with the increase of mineralization degrees,and the soil water repellency could not change this trend, yet their contends would bereduced. To some extent, soil water repellency was caused after irrigated by brackish water.As to the specific auses still remain farther test and verify.(3) From the experimental study of alcohol infiltration laws in water-repellent-soil,therepellency index from the experimental datas were not the same as Tillman Et al, but theoverall similarity; the existence of soil water-repellency had some obvious impacts on the soilinfiltration property, but variations of the infiltration capacity among water-repellent soils ofdifferent water-repellent degrees, and the infiltration capacity in water-repellent soils waslower than one in wettable soils; the rinsed results of total salt and Cl-were more obvious inwater-repellent soils that those in wettable soils, and the maximum was reached at the wettingfront; Applicability of Kostiakov equation was well about the variations of the infiltrationrates versus time; There was good exponential relationship between infiltration rates and t-1/2.The process of infiltration based on alcohol solution was accelerated greatly compared todistilled water infiltration.(4) From the experimental study of brackish water added to Nalidet P-40infiltration lawsin water-repellent-soil, infiltration ability of saline-alkali soil was largest at mineral degree of3g/L, but decreased with the increase of mineralization degree when mineralization degreewere larger than1g/L. The rinsed results of total salt and Cl-increased with the increase ofmineralization degrees at the same wetting front, and the maximum was reached ahead of thewetting front. Water content in soil profiles was largest with3g/L of mineralization degrees,then5g/L,1g/L,0g/L came next.(5) Kostiakov equation could well described the variations of infiltration rate versus timecompared to other models, whether distilled water infiltration or brackish water infiltration oralcohol infiltration or brackish water infiltration added to Nalidet P-40. The change ofcumulative infiltration volume with the change of time can be expressed by power functionand there was good linear relationship between the amount of cumulative infiltration and thewetting front distance.