Soil Water Infiltration Characteristics for Drip Irrigation of Seedlings to Reduce Aeolian Erosion of Sandy Soils

A vertical tube surface drip irrigation system was designed to address the damage caused by soil drought and high surface temperature to sand-fixing seedlings in a plant sand-fixation area. Numerical simulation and experimental verification were used to study soil water movement with vertical tube infiltration and surface drip irrigation for four aeolian sandy soils with different hydraulic conductivity ($K_s$), drip discharge ($Q$), vertical tube diameter ($D$), and vertical tube buried depth ($B$). The results show that a power function relationship exists between the soil-stable infiltration rate ($i_f$) and $K_s$, $D$, and $B$ given the condition of vertical tube water accumulated infiltration, and its coefficient is 0.17. The power function indices of $K_s$, $D$, and $B$ are 0.87, 1.89, and $-0.37$, respectively. The $i_f$ can be used to determine the maximum drip discharge ($Q_{\max }$) of the dripper in the vertical tube to ensure that the sand-fixing plants are not submerged during drip irrigation through the vertical tube ($Q_{\max }=i_f$). The wetting front transport distance in the three directions increased with increasing $K_s$ and $Q$ but decreased with increasing $D$ and $B$. After determining the time required for water to reach the bottom of the vertical tube, an estimation model of soil wetting body transport for vertical tube surface drip irrigation, including $K_s$, $Q$, $D$, and $B$, was constructed. Compared with the experimental data, the root mean square error (RMSE) is between 0.17 and 0.42 cm, and the Nash–Sutcliffe efficiency (NSE) is at least 0.88. Therefore, the model is appropriate and can provide valuable practical tools for the design of vertical tube surface drip irrigation in different plant sand fixation areas.

A surface drip irrigation system and pipe protection technology were combined to form a vertical tube surface drip irrigation system to address the damage caused by soil drought and high surface temperature to sand-fixing seedlings. However, this irrigation technology has the problem that it is difficult to quantify the matching of drip discharge and pipe parameters (vertical tube diameter and burial depth), wetted soil volume, and plant roots due to the single soil sample used in the laboratory experiments. This paper considers the influence of soil differences in diverse plant sand-fixing areas and establishes a stable infiltration rate model to determine the maximum drip discharge. Additionally, a soil wetted volume prediction model was developed by combining HYDRUS-2D simulations and experimental verification. The model is simple and has high prediction accuracy, which is convenient for designers to determine the appropriate vertical tube parameters for different plant sand-fixation areas.