Submitted to: Soil and Water Conservation Society Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 1, 1999
Publication Date: N/A
Technical Abstract: Furrow irrigation systems are less costly and use less energy than sprinkler systems, but furrow irrigation produces greater runoff and more percolation. Furrow streams erode their channels and resulting sediment often leaves the field in runoff. Phosphorus (P) and nitrogen (N) losses are associated with eroded sediment in runoff, and can be reduced by eliminating irrigation-induced erosion. Excessive leaching of inorganic and organic solutes commonly occurs at the inflow region of furrow irrigated fields where infiltration opportunity times are longer. A convenient practice applies a high molecular weight, anionic polyacrylamide (PAM) to advancing furrow stream flows at a concentration of 10 mg/L. Because PAM stabilizes soil and flocculates suspended sediment, we hypothesized that this treatment would reduce runoff losses of ortho-P, total P, Nitrate-N, and chemical oxygen demand (COD). Since PAM often increases furrow infiltration we hypothesized that its use may increase Nitrate-N or Cl leaching, especially near inflow ends of furrows. Initial inflows were cut back from 23 or 45, to 15 L/min after furrow advance. Both irrigation runoff and percolation were sampled and analyzed. Total soil loss from four irrigations was 3.06 Mg/ha for control furrows vs 0.24 for PAM-treated furrows. PAM treatment reduced cumulative mass losses of sediment in runoff by 92%, ortho-P by 86%, total P by 91%, and COD by 83%, relative to control furrows. PAM had no field-wide, season-long effect on cumulative amounts of water, Nitrate-N or Cl leached. PAM-technology provides an effective means for decreasing N and P loads in surface waters receiving irrigation return flows.