Applying polymers to irrigation water: evaluating strategies for furrow erosion control

Adding dilute quantities of moderate-charge-density anionic polyacrylamide (PAM) to furrow irrigation water can greatly reduce runoff soil losses and, in some cases, increase net infiltration. We evaluated different strategies for adding PAM to irrigation water to determine which was most effective. The PAM was applied to irrigation water in gated irrigation pipe as dry granules, or to furrow inflows as a stock solution. Treatment efficacy varied primarily with irrigation inflow-rate, PAM concentration in irrigation water, duration of furrow exposure, and total PAM applied. The most effective erosion-control treatments either (1) applied an initial dose of PAM at 10 mg L-1 in irrigation inflows only during the furrow advance period; (2) applied an initial 5 mg L-1 dose, then reapplied PAM for 5 to 15 min episodically at similar concentrations; or (3) continually applied 1 to 2 mg L-1 to irrigation inflows. The full-advance treatment reduced sediment loss by 93%, compared to 60% for the continuous 0.25 mg L-1 PAM application when slopes were 1 to 2%. Dry and solution applications controlled erosion about equally. The PAM applications were economical and effective methods for controlling furrow-irrigation induced erosion, under a broad range of field conditions