Date of Award
Master of Science
AN ABSTRACT OF THE THESEIS OF JONATHAN W. STEWART, for the Master of Science degree in FORESTRY, presented on October 25, 2016, at Southern Illinois University Carbondale. TITLE: IMPACT OF VEGETATED BUFFER STRIPS ON SURFACE RUNOFF IN SOUTHERN ILLINOIS MAJOR PROFESSOR: Dr. Jon Schoonover Sediment and nutrient transport in agricultural surface runoff has been a challenge for watershed managers for decades. Excessive nutrient loading to streams and rivers has led to problems ranging from hypoxia in the Gulf of Mexico to drinking water contaminations throughout the world. In addition, these agricultural pollutants have impaired the water quality in many lakes and rivers which in turn have negatively affected both human and aquatic life. In order to reduce the environmental impacts from agricultural surface runoff many farmers, landowners, and land managers have implemented riparian buffers to reduce both sediment and nutrient loading in surface runoff. This study utilized fifteen 1x10 m flumes, with three replicates of each treatment, to determine the effectiveness of various riparian buffer species for their ability to attenuate nutrients and sediment from surface runoff. Treatments included, Kentucky bluegrass (Poa pratensis L.), Orchardgrass (Dactylis glomerata L.), giant cane (Arundinaria gigantea (Walt.) Muhl.), corn (Zea maize), and non-vegetated bare soil buffers (controls). Surface runoff samples were collected from every natural rainfall event that produced overland flow and were analyzed for sediment and a suite of nutrients. Giant cane, Kentucky bluegrass, and orchardgrass buffers were effective vegetated buffer species for reducing turbidity, total suspended solids, ammonium, and total phosphorus concentrations. The giant cane, Kentucky bluegrass, and orchardgrass buffers performed better than the corn and control buffers at removing turbidity, total suspended solids, and total phosphorus. When comparing the giant cane, Kentucky bluegrass, and orchardgrass buffers to the control buffer the removal of sediment was substantial. For example, giant cane, Kentucky bluegrass, and orchardgrass removed from 6 to 14 times more total suspended solids than the bare ground control treatment. Furthermore, the giant cane, Kentucky bluegrass, and orchardgrass also removed from 5 to 9 times more turbidity than the control treatment. The removal of nutrients was also significant for the giant cane, Kentucky bluegrass, and orchardgrass treatments. For example, giant cane, Kentucky bluegrass, and orchardgrass removed from 2 to 4 times more ammonium than the control and from 4 to 5 times more total phosphorus than the control treatment. The giant cane, Kentucky bluegrass, and orchardgrass did not remove dissolved reactive phosphorus better than the control treatment and they were less effective at removing nitrate levels when compared to the control treatment. The giant cane buffer proved to be a very effective riparian buffer species because it had significantly higher soil infiltration rates than that of the control, corn, Kentucky bluegrass, and orchardgrass buffers. Giant cane had an infiltration rate of 103.6 cm hr-1, while the infiltration rates of the control, corn, Kentucky bluegrass, and orchardgrass were 8.8 cm hr-1, 11.2 cm hr-1, 14.1 cm hr-1, and 24.9 cm hr-1, respectively. Data suggest that giant cane, Kentucky bluegrass, and orchardgrass buffers may be promising riparian buffer species for the removal of both sediment and nutrients in agricultural surface runoff.
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