Submitted to: University of Idaho Miscellaneous Publication
Publication Type: Other
Publication Acceptance Date: May 6, 1996
Publication Date: N/A
Interpretive Summary: Irrigation induced erosion is a serious pollution problem, and threatens the sustainability of Earth's most productive cropland. Polyacrylamides (PAMs) have been used as soil amendments since the early 1950's, but were applied directly to soil via spray application and incorporation. Rates of use were often 500 to 1000 pounds per acre to in achieve desired changes in soil structural properties. This was too expensive for all but the highest value cropping situations or for construction or other high value uses. Placing water soluble PAMs in furrow irrigation water at 10 ppm during initial advance of water across the field (only) eliminates 94% of sediment loss. Phosphorus and Nitrogen fertilizer, soil incorporated pesticides, and BOD are all greatly reduced in return flows. Water net infiltration in improved 15%. Guidelines for PAM-use are specified in an NRCS application standard. This paper provides useful background information on PAM and gives practical tips for farmer use of PAM.
Technical Abstract: Erosion seriously threatens irrigation's ability to sustain its 2X yield advantage and 3X economic advantage over rainfed agriculture and risks serious environmental and food security consequences. Furrow irrigation-induced erosion is nearly eliminated by small additions of water-soluble polyacrylamide (PAM) to irrigation water. PAM is an environmentally safe industrial flocculent used in municipal water treatment, paper manufacturing, food processing and other sensitive applications. On freshly cultivated furrows, 1 lb/acre (1 kg/ha) of PAM applied in the inflow at 10 ppm (10 g/m3) during water advance (only), reduced sediment in runoff 94% and increased net infiltration 15% in 3 yrs of ARS tests on Portneuf silt loam soils (coarse-silty, mixed, mesic Durixerollic Calciorthids). PAM products are now registered throughout the western US. The Natural Resources Conservation Service published a PAM-use practice standard in Jan., 1995. In 1995, the first year of product sales, 50,000 acres (20,000 ha) of furrow irrigated land used PAM, halting an estimated 1 million tons (0.9 million metric tons) of erosion. PAM-use reduced irrigation return flow sediment, biochemical oxygen demand (BOD), total phosphorus, and various pesticides. Many irrigation farmers who have viewed traditional conservation practices as cumbersome, intrusive, or ineffectual, adopt PAM-use as an attractive inexpensive alternative. The typical $15 to $35/acre per crop ($37-$88/ha) operations, improved infiltration, water conservation, or crop responses.