Advantages and Disadvantages of Subsurface Drip Irrigation

Subsurface drip irrigation (SDI) applies water directly to the crop root zone using buried polyethy­ lene tubing, also known as a dripline, dripperline, or drip tape (Figure 1). Driplines come in varying diam­ eters and thicknesses in order to maintain acceptable irrigation uniformity for different field lengths. Smaller diameter driplines are used when short lateral lengths are required. As lateral length increases, a larger diameter dripline must be selected to maintain ade­ quate irrigation uniformity. to irrigate high value crops. Thicker driplines are used for permanent installations. The thicker driplines can also withstand higher operating pressures. The cost of the dripline is directly related to both diameter and thickness. Small holes called emitters are usually spaced every 8 to 24 inches along the length of the dripline. During irrigation, pressure forces the water out of the emitters drop by drop. Once the water is in the soil, its move­ ment and wetting pattern will depend on the physical characteristics of the soil. In a fine-textured soil, for instance, water will tend to move laterally and upward, compared with a sandy soil where water tends to move mainly downward. The amount of water that can be delivered through a drip system depends on dripline diameter and spacing, emitter spacing, operating pres­ sure, emitter size, and emitter design. A variety of drip­ lines are now available from different manufacturers to fit the specific design requirements for different soils, crops and weather conditions.