间接地下滴灌条件下红黏土水分入渗特性试验研究

An Experimental Study on Water Infiltration Characteristics of Red Clay under Indirect Subsurface Drip Irrigation Condition

植物护坡效果与根系在土壤中的空间造型和分布(即根系构型)密切相关,研究不同土壤初始含水率和滴头流量对红黏土内水分运移的影响规律,对合理匹配土壤湿润体与植物根系分布情况,准确调控植物根系构型,提高植物边坡固土能力具有重要意义。采用室内试验的方法,在间接地下滴灌的条件下,观测土壤初始含水率和滴头流量对土壤湿润体特征值、湿润锋运移速度和含水率分布情况的影响。试验研究发现湿润锋运移的形状近似椭圆形,而湿润体的形状则近似为椭球体。随着土壤初始含水率的增加,湿润体水平方向对称轴不断下移,水分趋于垂直向下运移,随时间呈对数函数变化。在相同的滴灌量条件下,流量较小的湿润体的范围稍大于流量较大的湿润体范围,但湿润锋的半径均随时间呈幂函数变化。滴灌初期,同一时刻湿润锋运移速度随滴头流量的增大而增大,但随滴灌时间的延长,这一现象逐渐减弱。滴头流量大时,水分向水平方向运移的趋势明显,而滴头流量小时,水分向垂直方向运移的趋势更优。不同滴头流量和土壤初始含水率会形成不同形状和大小的湿润体,也会导致湿润体含水量分布不同。在调控所需的植物根系构型时,可通过控制滴头流量和土壤初始含水率来控制植物根系分布情况,提高植物根系固土的能力。

The plant slope protection effect is closely related to the spatial distribution of roots in soil.It is of great significance to study the effect of different initial soil moisture content and dropper flow rate on the water transport in red clay,so as to reasonably match the distribution of soil moisture and plant roots,accurately regulate the plant root configuration,and improve the soil fixation capacity of plant slope.Through an indoor experiment,under the condition of indirect subsurface drip irrigation,the effects of soil initial moisture content and dropper flow rate on the characteristic value of soil wetting body,the velocity of wetting front migration and the distribution of moisture content were observed.It was found that the shape of the wetting front was approximately ellipse,while the shape of the wetting body was approximately ellipsoid;With the increase of the initial soil moisture content,the symmetry axis of the wetted body moved down continuously in the horizontal direction,and the water tended to move vertically downward,which changed with time in a logarithmic function;under the same drip irrigation amount,the range of the wetted body with small flow was slightly larger than that of the wetted body with large flow,but the radius of the wetting front changed as a power function with time.At the early stage of drip irrigation,the migration velocity of the wetting front increased with the increase of the dropper flow rate at the same time,but this phenomenon gradually weakened with the extension of the drip irrigation time;when the dropper flow was large,the trend of water movement was obvious in the horizontal direction,while when the dropper flow was small,the trend of water movement in the vertical direction was better.Different dropper flow rate and initial soil moisture content would form different shapes and sizes of wetting bodies,which would also lead to different water content distribution of wetting bodies.During the regulation of the required plant root configuration,the distribution of plant root could be controlled by controlling the dropper flow and the initial water content of soil,so as to improve the ability of plant root to hold soil.