FIELD RESULTS USING POLYACRYLAMIDE TO MANAGE FURROW EROSION AND INFILTRATION

Furrow irrigation-induced soil erosion is a serious threat to sustaina ble irrigated agriculture globally. Recent field studies have demonstr ated that small concentrations of polymers dissolved in irrigation wat er appreciably reduce soil loss from irrigated furrows and increase ne t infiltration (total inflow - total outflow). This paper summarizes p olymer-related field studies conducted in Idaho on highly erodible sil t loam soils (Durixerollic Calciorthids, Xerollic Haplargids, Haploxer ollic 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 modera te-charge-density anionic polyacrylamide (PAM), highly effective for c ontrolling furrow sediment losses, was employed in the field trials. T reatment efficacy depended primarily on application rate, PAM concentr ation in irrigation water, duration of furrow exposure, and inflow rat e. Nontreated furrow soil loss in 75% of the irrigations exceeded soil loss tolerance (T) for these soils, whereas only 13% of the PAM-treat ed 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% (r ange: 80-99%) and increased net infiltration by 15% (range: -8-57%). O ne of the most effective treatments applied PAM at 10 g m-3 in irrigat ion inflows during the furrow advance period. This initial high-load t reatment 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-loa d treatment protected furrows with slopes ranging from 0.5 to 3.5%. PA M reduced total phosphorus (84% of control value), nitrate (83%), bioc hemical oxygen demand (72%), and sediment (57%) in treated runoff wate r.