FIELD RESULTS USING POLYACRYLAMIDE TO MANAGE FURROW EROSION AND INFILTRATION

Furrow irrigation-induced soil erosion is a serious threat to sustainable irrigated agriculture globally. Recent field studies have demonstrated that small concentrations of polymers dissolved in irrigation water appreciably reduce soil loss from irrigated furrows and increase net infiltration (total inflow - total outflow). This paper summarizes polymer-related field studies conducted in Idaho on highly erodible silt loam soils (Durixerollic Calciorthids, Xerollic Haplargids, Haploxerollic Durargids). A range of furrow lengths (163–264 m), slopes (0.5–7%), and inflows (15–38 L min−1) were included in the studies. A moderate-charge-density anionic polyacrylamide (PAM), highly effective for controlling furrow sediment losses, was employed in the field trials. Treatment efficacy depended primarily on application rate, PAM concentration in irrigation water, duration of furrow exposure, and inflow rate. Nontreated furrow soil loss in 75% of the irrigations exceeded soil loss tolerance (T) for these soils, whereas only 13% of the PAM-treated irrigations exceeded T. Those treatments that applied at least 0.7 kg ha−1 PAM (mean, 1.3 kg ha−1) reduced furrow sediment loss by 94% (range: 80–99%) and increased not infiltration by 15% (range: −8–57%). One of the most effective treatments applied PAM at 10 g m3 in irrigation inflows during the furrow advance period. This initial high-load treatment was nearly twice as effective as a continuous 0.25 g m−3 PAM application on these soils when slopes were 1–2%. The initial high-load treatment protected furrows with slopes ranging from 0.5 to 3.5%. PAM reduced total phosphorus (84% of control value), nitrate (83%), biochemical oxygen demand (72%), and sediment (57%) in treated runoff water