Nitrate Transport In The Unsaturated Zone

Abundance of nitrate in the soil is a basic issue in agricultural land-use regions, causing eutrophication and pollution of water bodies. The study focuses on the role of a saturated buffer zone (SBZ) to remove nitrate from the groundwater resulting from agricultural activities. The study area is herbaceous SBZ located in central Illinois (40.614382ºN, -89.023542ºW), which lies between a stream and a farm located upgradient. The SBZ has been outfitted with an agricultural runoff treatment system that diverts tile drainage into the subsurface of the SBZ rather than discharging into the stream. Within the SBZ three experimental areas composed of two plots were established; one plot allowed the plants, Switchgrass (Panicum virgatum L.) to grow, and the other plot served as the control, with no plant growth. The main objective of this research was to understand the role of plants in the transport and fate of nitrate in the unsaturated by addressing two hypotheses 1) during the growing season nitrate removal will be greater in the presence of plants than where plants are absent and 2) following a growing season, nitrate concentration in the soils underlying a barren plot (no plants) will be less than in the soils underlying a plot with plants. Statistical comparison between the NO3--N among the treatments, Pre-growing season, Plot with Plants, and Barren plot, and among the different depths, 30 cm, 60 cm, and 90 cm were significantly different. The presence of plants provided a mechanism to withdraw NO3--N in the vadose zone. The plots with plants experienced a reduction NO3--N from the soil and vadose waters due to plant uptake and denitrification. NO3--N concentration in the soils underlying the barren plot were high because the plants materials decomposed to increase the NO3--N concentration in the vadose. The low NO3--N concentration observed in the soil within the SBZ were similar to what was observed four years prior, suggesting that the NO3--N concentration in the vadose remains stable year-to-year. The study established temporal removal of NO3--N in the vadose zone of the SBZ and the SBZ serve as a short-term sink