Salinity Control with Drip Irrigation

Drip irrigation has the potential of increased yield under saline soil conditions. Factors affecting root zone soil salinity under drip irrigation include the salinity of the irrigation water, amount of applied water, soil hydraulic characteristics, placement of drip lines relative to plant rows, subsurface vs. surface drip lines, and under saline, shallow ground water conditions, the ground water depth and salinity. The salt pattern reflects the water flow patterns under drip irrigation. The key to profitable drip irrigation under saline conditions is adequate salinity control by leaching salts from the root zone. Under drip irrigation, highly concentrated leaching, called localized leaching, occurs near drip lines. Leaching decreases with horizontal distance from drip lines. Larger amounts of applied water increase the volume of leached soil near drip lines. Salts accumulate above subsurface drip lines, which requires rainfall or sprinkle irrigation for leaching. The water balance method of estimating leaching fractions is inappropriate for drip irrigation and underestimates the actual leaching fractions. Water applications equal to crop evapotranspiration provide adequate localized leaching.