IRRIGATION TO INCREASE NUTRIENT-USE EFFICIENCY AND PROTECT WATER 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 irrigation-induced erosion. Excessive leaching of inorganic and organic sol-utes commonly occurs at the inflow region of furrow irrigated fields where infiltration opportunity times are longer. In one con-servation practice, a high molecular weight, anionic polyacryla-mide (PAM) is applied to advancing furrow stream flows at a con-centration of 10 mg L1. Because PAM stabilizes furrow soil and flocculates suspended sediment, we hypothesized that this treat-ment would reduce runoff losses of sediment, molybdate reactive P (MRP), total P, NO3-N, and chemical oxygen demand (COD)