Submitted to: University of Idaho Miscellaneous Publication
Publication Type: Proceedings
Publication Acceptance Date: May 6, 1996
Publication Date: N/A
Interpretive Summary: Previous experiments have shown that an initial application of 5-10 ppm polyacrylamide (PAM) to furrow irrigation water can substantially reduce sediment loss and increase infiltration in treated furrows. We determined whether polyacrylamide characteristics that control the shape and size of the dissolved PAM molecules (ie. associated charge type, amount of charge, and molecular weight, MW) influence PAM's ability to control furrow erosion. Negatively charged PAMs were more effective than those with positive charge. PAMs with high to moderate associated charge (19-35%) were more effective than low charge counterparts. Among negatively charged PAMs, those with the largest MWs controlled erosion slightly more effectively than lower MW PAMs. In general, factors tested influenced furrow erosion processes differently than infiltration processes. These results indicate which PAMs perform best. This information assists farmers in selecting the most cost-effective treatments for their fields. In addition, PAM manufacturers can use these results to design polymers that better control furrow erosion and/or stabilize infiltration.
Technical Abstract: Application of 5-10 ppm water soluble anionic polyacrylamide (PAM) to furrow irrigation water during flow advance substantially reduces sediment loss and increases net infiltration. We hypothesized that characteristics related to PAM's dissolved molecular conformation influences PAM's irrigation-management efficacy. The study was conducted in Kimberly, Idaho, on Portneuf silt loam (coarse-silty, mixed, mesic, Durixerollic Calciorthid); and slope was 1.5%. Polyacrylamides with contrasting charge type (neutral, anionic, cationic), charge density (0, 8-10, 19-20, 30-35%), and molecular weight (anionic: 4-7, 12-15 and 14-17 Mg/mol) were employed in two studies. Inflow rate was 23 L/min (6 gpm) during furrow advance, and 15 L/min (4 gpm) for the remaining set. The effect of conformational parameters on furrow erosion processes differed from that for infiltration. The order of effectiveness for soil-loss control was anionic > neutral > cationic PAM, and efficacy increased with increasing charge density and/or molecular weight. The order of effectiveness for infiltration maintenance was neutral > high-charge anionic/cationic > low-charge anionic/cationic-PAMs. For a given charge type, infiltration maintenance increased with decreasing PAM molecular weight. The infiltration-response to changing molecular weight was the reverse of that observed for soil-loss control.