Experimental study of wetted soil volumes in a sandy loam under subsurface drip irrigation in the East Sandy Land of the Yellow River

摘要

Subsurface drip irrigation is a technology commonly used for improving the use efficiency of irrigation water. This technique is more desirable in an !arid and semi-arid region, because of cutting down soil surface evaporation and deep percolation ofthe soil moisture. However, it is even more important to save the irrigation requirements in an arid and semi-arid region in comparison with the other traditional irrigation methods. Before the design of the underground drip irrigation, the dimension ofsoil wetting pattern is one of the main factors used to identify the vertical and horizontal spacing of emitters. This study was carried out to determine experimentally the infiltration laws of the different emitter discharges (2010, 1810,1290, 1050mm/min) and different hydraulic heads (1.5, 1.25, 1, 0.8, 0.5 m) in a sandy loam soil under point-source drip irrigation. Three sets of parallel experiments were conducted to measure the infiltration rate and cumulative infiltration of the sandy loam soil andthe dimension of the wetted soil volume throughout the whole infiltration process. Averages of the measured data taken from these experiments were analyzed to study wetting patterns in the soil under point-source drip irrigation. The results showed thatthe infiltration rate gradually decreased as the infiltration time increased, and it approached a stable value in the end. The changes in the infiltration rate versus time can be described by a power function. Conversely, the cumulative infiltration progressively increased as the infiltration time increased during the whole process of infiltration. Finally, it closed to a stable value as well as the infiltration rate. Similarly, the changes in the cumulative infiltration versus time can be described bya logarithmic paction. During the experiment process, the wetting front in the horizontal and vertical direction constantly increased as the infiltration time increased. The difference was that the wetting front in the horizontal direction was greater than in the vertical direction throughout the experiments. Those results can help in designing subsurface drip irrigation systems and improving the water-use efficiency.