Effectiveness of vegetative filter strips in attenuating nutrient and sediment runoff from irrigated pastures

Abstract

Increasing concern about non-point source pollutants released from grazing livestock, a worldwide problem, motivated the present study on the effects of vegetative filter strips (VFS) for controlling pollutants (nutrients, micro-organisms and sediment loading) from grazed, irrigated pastures. Flood-irrigated pastures are an important source of forage for livestock during summer months in California, USA when the surrounding rangelands are dry and dormant. Significant amounts of runoff can be generated from these pastures during irrigation events.Nine plots on an irrigated pasture were assigned randomly to one of three treatments: Control (no VFS), Treatment VFS-1 (8·3×7 m, 0·0058 ha VFS) and Treatment VFS-2 (17·1×7 m, 0·012 ha VFS). In 2000, two grazing events (in April and June/July) occurred during the irrigation season prior to the experiment; further, the experimental plots were grazed between irrigations 2 and 3. Attenuation of runoff loads by VFS treatment was measured during four irrigation events (between 1 August and 3 October 2000) for total suspended solids (TSS), ortho-phosphate (Ortho-P), inorganic phosphate (Inorg-P), total phosphate (Total-P), organic phosphate (Org-P), polyphosphate (Poly-P), total Kjeldahl nitrogen (TKN), NH3, NO3 and presumptive faecal coliforms (FC).On average, approximately 0·43 of the applied water left the plots as runoff. Treatment effects approached significance for TSS and TKN and were significant (P<0·05) for Poly-P and NH3. Irrigation number effects were significant for all but TSS, NO3 and FC. The effects of VFS treatments were not consistent. Treatment VFS-2, although representing the largest buffer strip, did not always produce the lowest pollutant loads in runoff. Slope, relatively high runoff volumes and some channelled flow were probably responsible for the limited effectiveness of VFS in the present study. These results suggest that effectiveness of VFS for reducing sediment and nutrient transport from irrigated pastures may be questionable.

Man-made linear flow paths at catchment scale: Identification, factors and consequences for the efficiency of vegetated filter strips

“…A key parameter in this respect seems to be the extent of runoff convergence when entering buffer strips. Whenever surface runoff converges into buffer strips there is a reduction of the retention capacity of the VFS (Bach, Fabis, Frede, & Herzog, 1994a, 1994bDillaha et al, 1989;Dosskey, Helmers, Eisenhauer, Franti, & Hoagland, 2002;Hay, Pittroff, Tooman, & Meyer, 2006;LeedsHarrison et al, 1999;Verstraeten, Poesen, Gillijns, & Govers, 2006). Bach et al (1994a) pointed out the difficulties of linear structures, like plough furrows and ditches, leading to a reduced filter effect whenever concentrated surface flow enters buffer strips.…”

Livestock grazing and vegetative filter strip buffer effects on runoff sediment, nitrate, and phosphorus losses

“…Contaminant reduction also occurs through interception adsorption, infiltration, and degradation of pollutants dissolved in water (Hubbard et al 2003). Other researchers have reported on the effectiveness of vegetative buffers in treating agricultural runoff (Snyder et al 1998;Smith et al 2000;Bharati et al 2002;Gharabaghi et al 2001;Koelsch et al 2006) and consider them a best management practice for surface runoff pollutant removal (Dillaha et al 1989;Mickelson and Baker 1993;Gilley et al 2000;Lee et al 2000;Wang et al 2005;Hay et al 2006). Vegetative buffer studies also showed significant reductions of NO 3 -N, PO 4 -P, and total P in runoff (Patty et al 1997; Wenger et al 1999).…”

Effects of a livestock manure windrow composting site with a fly ash pad surface and vegetative filter strip buffers on sediment, nitrate, and phosphorus losses with runoff

“…These buffer strips provide erosionvia interception-adsorption, infiltration, and degradation of pollutants dissolved in water (Dillaha et al 1989). The VFS buffers are considered to be a best management practice that has been shown to reduce sediment and nutrient losses in a range of agricultural settings, including crop fields and feedlots (Dillaha et al 1985;Magette et al 1989;Mickelson and Baker 1993;Patty et al 1997;Lee et al 2000;Wang et al 2005;Hay et al 2006). These researchers also found that VFS buffers have potential for significantly improving the water quality of RO.…”