Modeling Approaches for Determining Appropriate Depth of Subsurface Drip Irrigation Tubing in Alfalfa

Alfalfa provides high-energy feed for dairy cows and other livestock. This crop is also known for its high water-use efficiency. Subsurface drip irrigation (SDI) is an ideal method for meeting crops' water demands. A major design issue in SDI systems is determining the appropriate dripline depth of placement to provide adequate irrigation. The presented approach used HYDRUS 2D/3D to simulate spatial and temporal distributions of soil moisture content, root water uptake, and drainage of an SDI system commonly used for alfalfa production in Holtville, California, in late summer. The scheme presented supports the design and management of SDI systems for alfalfa by preventing a wet soil surface at harvesting time, maintaining trafficability, delivering the required crop water, and minimizing water loss at the same time. Based on the simulation results and after a sensitivity analysis, a dripline depth of 50 cm is recommended to ensure a drier soil surface at harvesting times, with a run time of 12 h every three days, which satisfies daily crop water needs and minimizes water loss.