Subsurface Water Retaining Membranes for More Efficient Surface and Subsurface Drip Irrigation in Sandy Soils.

Drip irrigation improves water use efficiency by precise control of water content in the root zone and therefore minimization of deep infiltration losses. Yet high water demands by corn and low water retention by sandy soils may still result in considerable losses of both precipitation and irrigation water. The subsurface water retention technology (SWRT) is a relatively new long-term approach that increases water retention capacities of highly permeable soils resulting in sustainable crop production. It has been shown experimentally that layers of polymer membranes installed in sand-filled lysimeters significantly reduced losses of water from corn root zone under overhead irrigation. The objective of this study was to evaluate efficiency of the SWRT for surface and subsurface drip irrigation. Specifically how irrigation rates and water losses can be optimized by modifying geometry and spatial location of SWRT membranes. HYDRUS-2D model, that describes two-dimensional water flow in unsaturated soil, was calibrated and validated on data from the sand-filled lysimeter with SWRT membranes installed at three depths with two aspect ratios. The model adequately reproduced soil water content dynamics measured at 12 locations inside the sand profile. Then HYDRUS-2D simulations were repeated for surface and subsurface irrigated sand profiles altered by SWRT membranes with, 3:1, and 5:1 aspect ratios and different spatial locations. The irrigation was triggered at soil pressure head of 30 cm at a depth of 15 cm. The results of simulations showed that maximum water use efficiency for both surface and subsurface irrigations can be archived using two membranes with 2:1 aspect ratios, installed at depths of 20 cm and 30 cm without space in horizontal direction.