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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #81136

Title: POLYACRYLAMIDE AS A TOOL FOR CONTROLLING SEDIMENT RUNOFF AND IMPROVING INFILTRATION UNDER FURROW IRRIGATION

Author
item ROSS, CRAIG - LANDCARE RESEARCH NZ LTD.
item Sojka, Robert
item Lentz, Rodrick

Submitted to: Australian/New Zealand National Soils Conference
Publication Type: Proceedings
Publication Acceptance Date: 4/24/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Water-soluble anionic polyacrylamide (PAM) has been shown to be effective in controlling topsoil erosion, preventing sedimentation of waterways, and simultaneously improving infiltration rates for furrow irrigation in the western USA (Lentz et al. 1992; Lentz and Sojka 1994). PAM injected as a pulse into the irrigation stream as the water advances has a stabilizing effect on the surface soil in the furrow. Controlling sediment runoff under intensive irrigation has the dual advantage of conserving fertile topsoil and reducing downstream pollution from sediments in waterways, particularly suspended sediments. Topsoil losses of 5 - 50 tonnes per ha per year have been reported from irrigated fields on erodible soils in the US Pacific Northwest. Polymers provide farmers with a practical and economic management tool for conserving soil and preventing sedimentation of waterways from irrigated fields. Increased net infiltration, which translates to more efficient water use, is a secondary benefit, especially for semi-arid and environments where water supplies are limited. Results from field experiments on a highly erodible Portneuf silt loam (Durixerollic Calciorthid) in southern Idaho are presented comparing the efficacy of three different molecular weights of PAM for controlling sediment runoff and infiltration rates. Some potential environmental impacts of PAM applications under furrow irrigation are briefly discussed.

Technical Abstract: Research the USDA-Agricultural Research Service since 1991 using high molecular weight (12-15 Mg/mole) moderately anionic (18% negative charge density) polyacrylamides (PAMs) halts 80-99% of erosion in furrow irrigated fields of silt loam soil. PAM is an environmentally safe industrial flocculent. On freshly cultivated furrows, 0.7 kg/ha or more PAM, applied at 10 ppm in advancing furrow irrigation water (only), mean outflow sediment-loss from furrow irrigation of 1-1.5% slopes was reduced 94% in four years of field experiments. Water flowing after the completion of the advance was untreated. Sediment loss comparisons are for the total duration of irrigations. Infiltration increased an average of 15%. PAM doubled infiltration at 40 or 100mm tension. PAM treatment also greatly reduced biological oxygen demand (BOD) and total phosphorus of return flows. PAM cost to farmers ranges from about $US 7.80-12.13 per kg, and seasonal PAM application requirements for >90% erosion control typically vary from 2.1-4.9 kg/ha, depending on number irrigations on disturbed soil. PAM costs are offset by retention of soil (and applied inputs), resulting in fewer cultivations, less frequent sediment pond cleaning (or pond removal), and decreased labor.