California Agriculture 65(4):182-183. DOI: 10.3733/ca.v065n04p182. October-December 2011.
Leaching requirement guidelines published in the 1980s to help growers manage salt buildup in crop fields now need retooling, say workgroup members appointed by the UC Center for Water Resources. Workgroup chair John Letey, former director of the center, says the group found that current guidelines overestimate the leaching requirement and the negative effects of salinity.
Rather than issuing new recommendations for growers, however, the workgroup has proposed new guidelines for agencies that regulate the water quality of irrigation sources (table 1). They have shared them with California Agriculture, but plan no other formal report.
Salinity is a sensitive issue for agriculture. If salts in irrigation water (such as chloride, sulfate, bicarbonate, sodium, calcium and magnesium) build up in the root zone, plant growth and yields can be affected. In the worst cases, soils become too saline for agricultural use. Leaching is application of extra water to carry salts below the root zone. The leaching requirement (LR) guidelines specify how much extra water (the leaching fraction, LF) should be applied to maintain maximum crop yields.
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