|Lentz, Rodrick - UNIVERSITY OF IDAHO|
Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 1994
Publication Date: N/A
Interpretive Summary: There is great farmer and research interest in using polyacrylamide (PAM) in irrigation water to abate erosion. There is poor understanding of important PAM properties and use-considerations. The USDA/ARS North west Irrigaiton & Soils Research Lab at Kimberly, ID conducted a symposium at the 1993 Soil Science Society of America meeting in Cincinnati, OH to assemble the current information regarding PAM-use in irrigation water. The Kimberly ARS lab has logged >200 phone calls since Fall of 1993 seeking PAM information. The PAMs for this use are very high molecular weight (15 Mg/mole), 18% anionic polymers. They require slow addition to water with very aggressive mixing to properly dissolve. PAM is approved by EPA and FDA for sensitive food and environmental uses. Acrylamide monomer (a toxic manufacturing contaminant) is kept at safe levels (<0.05% by weight), degrades easily, and is not released by PAM decomposition. PAM is most effective when applied in irrigation water, halting 95% of irrigation-induced erosion and increasing infiltration by 15% or more. Typical seasonal application amounts are estimated at 3-7 lbs/acre @ about 3-5$ per pound, which compares very favorably for cost, ease of use, and effectiveness to other irrigation-induced erosion control methods.
Technical Abstract: PAMs have been used as soil conditioners since World War II incorporated into the soil at rates of 500-1000 pounds per acre. In 1991 the USDA/ARS Northwest Irrigation & Soils Research Lab in Kimberly, ID found that 1 pound per acre per irrigation of polyacrylamide (PAM) applied in irrigation water halts 95% furrow irrigation-induced erosion. PAM remains highly effective at slopes up 7%. This has stimulated a new wave of interest in soil conditioners. A number of key questions regarding this type of PAM-use were addressed in a symposium of nine papers presented at the 7-12 Nov., 1993 meeting of the Soil Science Society of America in Cincinnati, Ohio. This paper presents a brief background on PAM use in agriculture and presents the rationale for the symposium, outlining the main topics of concern. The new, very high molecular weight (15 Mg/mole), 18% anionic polymers are described. Their use for other sensitive applications including approval by EPA and FDA for environmental and food uses is noted. The issue of Acrylamide monomer (a toxic manufacturing contaminant) was addressed noting that it is restricted to safe levels (<0.05% by weight), degrades easily, and is not released by PAM decomposition. Effects of PAM on water management were noted. It increases infiltration by 15% or more, prolonging furrow water advance time. But since furrow water streams can be doubled without increase in erosion, better irrigation uniformity and reduced nitrate leaching potential are possible Typical seasonal application totals of 3-7 lbs/acre at about 3-5$ per pound, compares very favorably to other irrigation-induced erosion control methods for cost, ease of use, and effectiveness.