横坡垄作措施下层状棕壤的积水入渗特征及其模拟

Ponding infiltration characteristic and its molding simulation for layered brown soil in contour ridge system

横坡垄作系统中雨水/灌溉水易在垄沟低洼处积聚,诱发积水入渗,使入渗特性有别于传统耕作系统。基于横坡垄作垄沟内积水特征,采用室内土柱供水实验,以层状棕壤为研究对象,分析5个积水深度(2、4、6、8和12 cm)下入渗率、湿润锋运移动态变化,并利用修正的Gree n-Ampt模型对积水入渗过程进行模拟。结果表明:1)耕层阶段,入渗率呈急剧下降后趋于稳定趋势;过渡阶段,入渗率稳定一定时段后逐渐降低;犁底层阶段,入渗率趋于稳定;2)积水深度的增加均促进湿润锋的运移,但未改变湿润锋运移过程;3)初始入渗率、稳定入渗率、平均入渗率、累积入渗量等入渗参数均随积水深度增加呈幂函数增大,其中积水深度12、8、6和4 cm下的平均入渗率较积水深度2 cm分别增加120.5%、65.4%、39.4%和29.9%;4)在解析积水深度(h)与饱和导水率(K_(s)(h))间呈线性正相关关系基础上(K_(s)(h)=0.092h+0.76),结合湿润锋处土壤吸力(25.61 cm),构建模拟积水入渗过程的修正Green-Ampt模型。积水深度的增加加快土壤水分入渗,可利用修正Green-Ampt模型对积水入渗过程进行模拟。研究结果可为横坡垄作措施下水分高效利用、水资源调控提供科学依据。

[Background]Contour ridging is an effectively agricultural practice applied worldwide that is conducted approximately perpendicular to the overland flow path on sloped land.In practices,the ridges are much too hard to precisely follow the contour of the ground on slopes,and thus results in the formation of low areas in furrows.Thus,rainwater from side slopes or irrigation water easily accumulates in these furrow areas,and then induces the occurrence of ponding infiltration.The ponding infiltration characteristic in contour ridge system differs that on traditional slope,such as flat tillage,downslope tillage.However,little attention has been paid to the ponding infiltration characteristic in contour ridge system.[Methods]Based on the ponding characteristic of water in contour ridge system,this study analyzed the temporal variation of infiltration rate and the advancement of wetting front for layered brown soil under five ponding depths,2,4,6,8 and 12 cm using the suppling water experiment(Mahalanobis)on soil column.Meanwhile,the layer brown soil was respectively packed with bulk density of 1.30 g/cm^(3)and 1.50 g/cm^(3)to simulate the infiltration process for plough layer and plow pan.Then,the ponding infiltration process was stimulated with the improved Gree n-Ampt model.[Results]1)The ponding infiltration process was divided into three phase:Plough layer phase,transition phase,and plow pan phase.During the plough layer phase,infiltration rate sharply decreased and then kept a stable state.However,during the transition phase,infiltration rate firstly changed slightly for a period of time until gradually decreasing.In addition,infiltration rate was closed to a constant during the plow pan phase.2)The increase of ponding depth enhanced the advancement of wetting front,but slightly changed the advanced process of wetting front.3)The relationship between infiltration parameter(the initial,average and stable infiltration rate,as well as cumulative infiltration)and ponding depth was fitted to the power function.Compared to ponding depth 2 cm,the average infiltration rate under ponding depth 12,8,6 and 4 cm increased by 120.5%,65.4%,39.4%and 29.9%,respectively.The linear relationship between infiltration rate and the inverse of wetting front depth at different ponding depths was used to calculate soil saturated hydraulic conductivity(K_(s)(h))and the suction at the wetting front.Based on the positively linear correlation between soil saturated hydraulic conductivity and ponding depth(K_(s)(h)=0.092h+0.76),combined the determination of suction at the wetting front(25.61 cm),the improved Gree n-Ampt model was established to simulate the ponding infiltration process.[Conclusions]The increase of ponding depth enhanced the infiltration capacity,while the increase influence was related to the range of ponding depth.The improved Gree n-Ampt model could simulate the infiltration process for varied ponding depths.These findings can supply scientific guidance for water use efficiency and water resources regulation in contour ridge system.