Polyacrylamide for Surface Irrigation to Increase Nutrient-use Efficiency and Protectwater Quality

Furrow irrigation systems have a greater application capacity, are less costly, and use less energy than sprinkler systems but furrow irrigation produces greater runoff, erosion, and deep percolation losses. Phosphorus (P) and nitrogen (N) losses are associated with runoff sediment, and can be minimized by eliminating irrigationinduced erosion. Excessive leaching of inorganic and organic solutes commonly occurs at the inflow region of furrow irrigated fields where infiltration opportunity times are longer. In one conservation practice, a high molecular weight, anionic polyacrylamide (PAM) is applied to advancing furrow stream flows at a concentration of 10 mg L 1. Because PAM stabilizes furrow soil and flocculates suspended sediment, we hypothesized that this treatment would reduce runoff losses of sediment, molybdate reactive P (MRP), total P, NO3-N, and chemical oxygen demand (COD). Polyacrylamide treatment may increase furrow infiltration in some soils. However, we hypothesized that because it permits higher initial inflows, PAM would not increase NO3-N or Cl leaching rela-