Surface and groundwater quality impacts of conservation tillage practices on burley tobacco production systems in Southwest Virginia
Laird, Megan K.
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This study measured sediment, nutrient and pesticide edge-of-field and deep percolation losses from conventional tillage (CT), strip tillage (ST), and no-till (NT) treatments in a burley tobacco production system. The field experiment results show that the CT treatment yielded more total runoff, 93.6 mm, than ST and NT. Compared to the CT treatment, ST reduced the total mass loss of NO₃⁻ by 37 percent, NH₃ by 54 percent, PO₄³⁻ by 12 percent, TP by 65 percent and TSS by 64 percent. The NT treatment reduced the total mass of NO₃⁻ by 49 percent, NH₃ by 46 percent, PO₄³⁻ by 17 percent, TP by 73 percent and TSS by 77 percent. Field experiment results showed that, respectively, the ST and NT treatments yielded 77 and 82 percent less chlorpyrifos, an insecticide, mass loss in runoff compared to CT. With respect to flumetralin loss, a growth inhibitor, the NT treatment yielded 30 percent less and ST yielded 6.8 percent more flumetralin mass, compared to CT. The percolated water results show that compared to the CT treatment, ST resulted in 33 percent less NH₃, 7.5 percent less TKN, and 39 percent less PO₄³⁻ total mass. The NT treatment yielded 41 percent less NH₃ and 20 percent less TKN total mass loss compared to the CT treatment. The NT treatment had the most NO₃⁻, PO₄³⁻, and TP mass loss below the root zone, however NT also had the most percolated water by 53 mm (838 L). The ST treatment yielded 77 percent less, and NT yielded 82 percent less chlorpyrifos mass loss compared to the CT treatment. Compared to CT, the NT treatment resulted in 30 percent less and ST yielded 7 percent more flumetralin mass in percolated water. The GLEAMS model was used to simulate runoff, nutrient, sediment and pesticide losses from the same three tillage practices evaluated in the field experiment. The model results showed that for runoff volume, TSS, nitrogen, chlorpyrifos and flumetralin in runoff, the conventional tillage practice generated greater losses than the conservation tillage practices. Compared to the field experiment results, GLEAMS under predicted nitrogen and phosphorus in percolated water. The conservation tillage practices simulated in GLEAMS were effective in minimizing the loss of agricultural pollutants.
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