Drip Irrigation Salinity Management for Row Crops

Abstract

In the past, California farmers have commonly used furrow and sprinkle irrigation to irrigate row crop plantings. More recently drip irrigation has come into increasing use in many other areas, including California's coastal valleys and the west side of the San Joaquin Valley. Growers in some of these areas encounter high soil salinity caused either by irrigation with saline water (in the coastal valleys) or upward flow of saline ground water (in many parts of the San Joaquin Valley). Drip irrigation has the potential to increase crop yields with less irrigation water, and under saline conditions it has additional advantages over furrow and sprinkle irrigation systems. First, drip causes no foliar accumulation of salts during irrigation. Second, soil in the wetted area around emitters is mostly leached of salts, and that is often where root density is the highest, particularly for row crops. Third, high-frequency drip irrigation applications can maintain a relatively constant soil water content and soil salinity level over time near the drip lines. A disadvantage of drip irrigation is that salt accumulates near the periphery of the wetted area. This salt accumulation can be a matter of concern if the emitter placement does not coincide reasonably well with the location of the plant row, particularly for crops that are sensitive or moderately sensitive to soil salinity. Salt accumulation above buried drip lines also is a concern. Drip irrigation has been successful in the saline soils of the San Joaquin Valley. Experiments in commercial fields have proven subsurface drip irrigation of processing tomatoes to be a highly profitable practice (Hanson and May 2003, 2004), but if you want to reap the benefits of subsurface drip, you must also implement adequate salinity control. In this publication, we present guidelines for controlling salinity under drip irrigation.