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Polymer Panacea?

Irrigation water flowing off a farmfield into a canal or river can be pretty murky stuff. But researchers in Stanislaus County are testing a substance that could mean less erosion and a corresponding drop in sediments clouding the Delta. The substance, polyacrylamide (PAM), is a synthetic polymer used in sewage treatment plants.

Researcher Phil Osterli of UC Cooperative Extension says PAM is injected into irrigation water at the head of the furrows. It bonds with soil particles in the water and causes them to settle out and remain behind in the field. Test results so far indicate the process reduces the amount of sediment leaving the furrow by more than 90 percent. "The water was clearer running down the furrow than it was at the source," says Osterli. The polymer also helps water penetrate the soil more thoroughly, which could allow farmers to cut back on irrigation water use by 10 percent. Pesticide residues may also stay behind in the furrows and out of runoff as chemicals often bind to soil particles.

Researchers used applications of 2.5 parts per million (ppm), although concentrations as low as 1 ppm give "pretty good results," says Osterli. He estimates the price of treating an acre foot of water to be about $10, although the cost could come down if the polymer gains wide acceptance among farmers. He's found no adverse environmental effects from using PAM so far.

Contact: Phil Osterli (209)525-6654

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