EFFECTIVE SUSPENDED SEDIMENT AND SOLUBLE NUTRIENT LOAD MITIGATION IN IRRIGATED AGRICULTURAL RETURN FLOWS THROUGH THE USE OF VEGETATIVE FILTER STRIPS
Bodah, Brian William
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The use of vegetative filter strips (VFSs) in the mitigation of suspended sediment and soluble nutrient loads from agriculturally derived overland flows is a widespread practice. VFSs have been used in a wide variety of situations to treat runoff from croplands, feed lots, dairy operations, confined animal feeding operations, and roadsides, among other locations. While vegetative matter must regularly be removed from vegetative filter strips in an effort to prevent them from becoming nutrient load sources, very limited attempts have been made (with the exception of biofuel harvesting) to harvest that biomass for a useable purpose.This dissertation examines the novel approach of establishing vegetative filter strips on the ends of surface-irrigated, row-cropped fields with commonly utilized forage species for the direct mitigation of suspended sediment and soluble nutrient loads in overland flow while concurrently producing a marketable forage crop. A review of the pertinent literature is provided followed by a detailed overview of the experimental setup. Five commonly utilized forage crops were used to establish vegetative filter strips of varying lengths on the ends of furrow-irrigated, row-cropped fields in an arid environment. Vegetative filter strips of 3.05 (10 ft), 6.07 m (20 ft), and 9.14 m (30 ft) in width were found to have removal efficiencies exceeding 99% for: total inflow volume, total suspended solids, NO3-N, NH4-H, PO4-P and total P while yielding marketable forage biomass at a rates roughly comparable to average yields from regional hay farms. Statistical analyses on mean removal efficiencies showed a significant statistical difference among the performance of VFS width and vegetation cover type for mean suspended sediment removal efficiencies, and among vegetation cover type for NH4-N mean removal efficiencies. No significant statistical difference was shown among either vegetation cover types or VFS width for mean removal efficiencies of NO3-N, PO4-P or total P. NH4-N removal among differing VFS lengths was shown not to be statistically different.