Cotton plants in Southern California can produce more cotton fiber if they take smaller, more frequent sips of the same amount of irrigation water they would normally get during July.

Scientists with USDA’s Agricultural Research Service developed and tested the new approach in California’s Imperial Valley.

In their three-year test, they applied just over 1-1/2 inches of water every five days during July, resulting in increased cotton yields by five to 11 percent. The new technique used no more water than traditional July regimens of three inches every 10 days, or 5 inches every 15 days.

Some growers and others have believed the traditional regimen is necessary to flush away salt that can damage crops if it accumulates in the soil. But the scientists found that no salt accumulated in the top 6 inches of soil during the study.

Why irrigate more often in July? The scientists say July is the peak time when cotton buds open up in the valley, and stresses such as inadequate water can strike yields especially hard.

The scientists found that small, frequent irrigations keep plants in peak condition with lower leaf temperatures, high leaf moisture content and higher leaf transpiration rate.

Scientific contact: Chang Chi Chu, USDA-ARS Irrigated Desert Research Station, Brawley, Calif., phone (619) 344-4184