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

Abstract

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 Ϫ1 . 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, NO 3 -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 NO 3 -N or Cl leaching rela- www.dekker.comThis article is a U.S. government work, and is not subject to copyright in the United States.tive to conventional, constant inflow irrigation. To test the first hypothesis, all treatments had the same inflow regime. For hypothesis two, control inflows were a constant 15 L min Ϫ1 ; PAM treated inflows were cut back from 45 to 15 L min Ϫ1 after furrow advance. Irrigation runoff and percolation waters were sampled and analyzed. Polyacrylamide increased infiltration and decreased runoff, particularly early in the irrigations. Mean cumulative runoff sediment loss over 12 h was 11.86 kg for each control furrow vs 1.15 kg for PAM-treated furrows. The PAM reduced 12-h cumulative sediment losses in runoff by 90%, MRP by 87%, total P by 92%, and COD by 85%, relative to control furrows. Polyacrylamide had no field-wide, season-long effect on cumulative amounts of water, NO 3 -N or Cl leached. The PAM-technology effectively prevented soil nutrient losses, increased nutrient-use efficiency, and decreased N and P loads in irrigation return flows and receiving surface waters.

Polyacrylamide preparations for protection of water quality threatened by agricultural runoff contaminants

“…The most significant environmental effect of PAM use is its erosion reduction, protecting surface waters from sediment and other contaminants washed from eroding fields. PAM greatly reduces nutrients, pesticides, and biological oxygen demand (BOD) of irrigation return flows (Agassi et al, 1995;Lentz et al, 1998Lentz et al, , 2001. In Australian tests of PAM, sediment, nutrient, and pesticide reductions exceeded levels achieved by traditional conservation farming methods (Waters et al, 1999a, b).…”

Erosion Control in Furrow Irrigation Using Polyacrylamide

“…Wetting fronts are broader and infiltration is higher in the rows treated with polyacrylamide as compared with those that are untreated (Yu et al, 2003). The use of PAM as alternative practice of soil conservation has been repeatedly proven to be an effective and viable (Bjorneberg et al, 2000;Santos et al, 2000;Lentz et al, 2001;Yu et al, 2003;Kornecki et al 2005;Shrestha et al, 2006;Chávez, 2007;Chavez et al, 2009). However, this effectiveness depends on the type and charge density and molecular weight (Green et al, 2001).…”

“…Several studies have shown that PAM dissolved in irrigation water at a rate of 10 kg ha -1 improves water infiltration (Leib et al, 2005;Chávez et al, 2010) and may be increased from 7 to 8 times the final infiltration as compared with the control (Ajwa & Trout, 2006). However, at rate of 20 kg ha -1 applied in granular was this has proven to be effective in controlling erosion (Lentz & Sojka, 2000;Chávez et al, 2009), if applied in the first 5 mm of soil, it will reduce runoff by up to 30% as compared with the control plot (Yu et al, 2003), and may be increased by up to 54% of the aggregates stability (Lentz et al, 2001;Shrestha et al, 2006). According to Leib et al (2005) polyacrylamide application prior to irrigation control the erosion caused by concentrated flow in furrow irrigation systems, reducing soil detachment caused by hydraulic shear stresses.…”

“…This has been as soil conditioning since 1950; however, the expansion of its use was not seen until the last decade (Green & Stott, 2001). When applied to soil it, increases the aggregate stability, reduce the release and transport of sediments, flocculate the suspended sediment, increases infiltration (Norton et al, 1993;Lentz et al, 2001;Leib et al 2005) and is a non-toxic product whose by mechanical interaction degrades into CO2, water and nitrogen. The PAM is a water soluble polymer with the ability to enhance soil stabilization.…”

“…The PAM is a water soluble polymer with the ability to enhance soil stabilization. It is grouped in a class of compounds formed by polymerization of acrylamide (Lentz et al, 2001). Pure PAM is a homopolymer of identical units to that of acrylamide.…”