Preventing Irrigation Furrow Erosion with Small Applications of Polymers

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Abstract
Soil erosion is a serious problem threatening sustainability of agriculture globally and contaminating surface waters. The objective of this study was to determine whether low concentrations of anionic polymers in irrigation water would appreciably reduce irrigation furrow erosion on Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthid), a highly erodible soil. Furrow slope was 1.6%, furrow length was 175 m, and irrigation rates ranged from 15 to 23 L min−1. Inflow during the first 1 to 2 h of the first 8‐h irrigation was treated. Subsequent irrigations were untreated. Polyacrylamide (PAM) or starch copolymer solutions were injected into irrigation water entering furrows at concentrations of 0, 5, 10, and 20 g m−3. Sediment loss from polymer‐treated furrows was significantly less than that of control furrows in the first (treated) and second (untreated) irrigations, but not in the fourth (untreated). The PAM provided better erosion control than the starch copolymer. Efficacy of PAM treatments varied depending on its concentration, duration of furrow exposure, and water flow rate. In the initial (treated) irrigation and at low flow rates, 10 g m−3 PAM reduced mean sediment load by 97% compared with untreated furrows. Residual erosion abatement in a subsequent irrigation, without further addition of PAM, was approximately 50%. The PAM increased net infiltration and promoted greater lateral infiltration. Effective erosion control was achievable for a material cost below $3 ha−1 irrigation−1.

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