Water-soluble anionic polyacrylamide (PAM) has been shown to be effective in controlling topsoil erosion,
preventing sedimentation of waterways, and simultaneously improving infiltration rates for furrow irrigation in the
western USA (Lentz et al. 1992; Lentz and Sojka 1994). PAM injected as a pulse into the irrigation stream as the
water advances has a stabilizing effect on the surface soil in the furrow. Controlling sediment runoff under intensive
irrigation has the dual advantage of conserving fertile topsoil and reducing downstream pollution from sediments in
waterways, particularly suspended sediments. Topsoil losses of 5 - 50 tonnes ha' yr 4 have been reported from
irrigated fields on erodible soils in the US Pacific Northwest. Polymers provide farmers with a practical and
economic management tool for conserving soil and preventing sedimentation of waterways from irrigated fields.
Increased net infiltration, which translates to more efficient water use, is a secondary benefit, especially for semiarid
and arid environments where water supplies are limited.
Results from field experiments on a highly erodible Portneuf silt loam (Durixerollic Calciorthid) in southern
Idaho are presented comparing the efficacy of three different molecular weights of PAM for controlling sediment
runoff and infiltration rates. Some potential environmental impacts of PAM applications under furrow irrigation are
briefly discussed
