ABSTRACT:
Efficiencies of surface irrigation systems are often limited by infiltration conditions. Treatments that decrease infiltration into unlined canals, reservoirs, and the inflow end of furrows relative to outflow ends would reduce seepage losses and improve application uniformity. Several laboratory studies evaluated effects of high molecular weight (10 to 15 Mg mol−1), water-soluble, anionic polyacrylamide (PAM), alone and combined with anionic surfactants, on the hydraulic conductivity (KSAT) of soils. Dry soils were treated with one or two treatment solutions and subjected to conditions that simulated those in an irrigation furrow or pond. The KSAT of soil packed in columns was measured with a constant head apparatus for 19 hours. PAM treatment concentrations > 125 mg L−1 applied to dry soils preceding flooding reduced KSAT by 25%, and a 10 mg-L−1 PAM + 29 k-mg-L−1 sodium-lauryl-sulfate surfactant application reduced KSAT by 70%, relative to controls. Miniflume tests then applied the treatments only to the inflow end of the mini-furrows. The 125 and 250 mg L−1 PAM treatments significantly improved water application uniformity: Cumulative infiltration was reduced in the upper half of miniflume furrows and increased in the lower, relative to controls. When applied to dry soils and allowed to dry overnight, as may be done when treating irrigation ponds, the 1,000 mg L−1 PAM solution reduced KSAT by 60% to > 90% in silt loam and clay loam soils. Either the single or combination treatments could potentially be used to increase the uniformity of furrow water applications and reduce seepage from unlined irrigation ponds and canals.
Footnotes
Rodrick D. Lentz is with the U.S. Department of Agriculture - Agricultural Research Service, Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho.
- Copyright 2003 by the Soil and Water Conservation Society
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