Browsing by Author "Dr. Deanna Osmond, Committee Chair"

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Effect of Shrub Buffers, Tillage and Cropping Systems on Shallow Groundwater Nitrate-N in Eastern North Carolina
(2004-10-18) Wafer, Carrie Cathleen; Dr. Mike Vepraskas, Committee Member; Dr. Wendell Gilliam, Committee Member; Dr. Robert Evans, Committee Member; Dr. Deanna Osmond, Committee Chair
Water quality in the Neuse River, NC has decreased as a result of elevated nitrate-N (NO3--N) concentrations. The goal of this research was to examine the effectiveness of shrub buffers and no-till agricultural production to decrease shallow groundwater NO3--N concentrations and subsequently decrease the amount of NO3--N reaching surface waters. Groundwater NO3--N concentrations were measured 0-, 4.5- and 9-m drainage ditches with 1-, 4.5- and 9-m wide buffers at three different depths at the research site near Kinston, NC. The percent decrease of NO3--N at the intermediate (2.1 to 2.6 m) depth was calculated across the 4.5- and 9-m distances. The percent decrease across 9 m was significantly lower (p=0.05) in the 1-m buffer (67%) than in the 4.5-m (93%) and 9-m (91%) buffers, but no difference due to buffer width was found across the 4.5-m distance 1-m (66%), 4.5-m (79%) and 9-m (74%) buffers. Redox probes were used in conjunction with the deep (2.7 to 3.4 m) and shallow (0.6 to 0.9 m) groundwater data to determine if denitrification was responsible for decreased NO3--N concentrations. Groundwater and redox data indicated that conditions favored denitrification and was likely responsible for the decreased NO3--N concentrations. Groundwater NO3--N was examined in a no-till (NT) field on Wickham soils (NT-Wi), and in two fields on predominantly Nixonton soils - a conventional till (CT) field (CT-Ni) and an NT field (NT-Ni) at the research site near Goldsboro, NC. Wheat was grown as a small grain and cover crop on NT-Wi, as a small grain on CT-Ni and rye was grown as a small grain and cover crop on NT-Ni, within the corn – small grain – soybean – cover crop/bare soil cropping system. Nitrate-N concentrations and crop yields were compared between fields during each of the cropping periods (corn, small grain, soybean and cover crop/bare soil) because the cropping system periodically changed during the study period (1996 – 2003). The groundwater NO3--N concentrations averaged over the entire study period were similar in NT-Wi (5.5 mg N L-1) and CT-Ni (5.8 mg N L-1), but were lower in NT-Ni (2.4 mg N L-1). This pattern was also evident during individual cropping periods. Crop yields were also examined between the three fields and no significant yield differences were found, except during a drought year; soybean yields were much higher in NT-Ni (1,709 kg ha-1) (cover crop) than in CT-Ni (971 kg ha-1) (no cover crop) and NT-Wi (601 kg ha-1) (cover crop) during 2002. This data suggests that soybean production benefited from NT production in soils with greater water holding capacity during periods of drought. The results from this study indicate that NT production alone will not result in decreased groundwater NO3--N concentrations. The successfulness of NT to reduce groundwater NO3--N concentrations was also dependent upon crop fertilization rate, the use of cover crops and soil properties.
Nitrogen Use Efficiency and Yield Effects of Urea Formaldehyde Polymer (UFP) Fertilizer in Winter Wheat and Maize
(2007-01-30) Cahill, Sheri; Dr. Randy Weisz, Committee Member; Dr. Deanna Osmond, Committee Chair; Dr. Carl Crozier, Committee Member
The potential for improved fertilizer nitrogen (N) use efficiency (NUE) and yield in winter wheat (Triticum aestivum L.) and maize (Zea mays L.) was tested using a new, controlled release urea formaldehyde polymer (UFP). This polymer was compared with conventional aqueous urea-ammonium nitrate (UAN) [(NH2)2CO—NH4NO3] fertilizer during a two-year field experiment in North Carolina from 2004 to 2006. The crops were grown on three soils: Candor (sandy, siliceous, thermic Grossarenic Kandiudult), Portsmouth (fine-loamy over sandy or sandy-skeletal, mixed, semiactive, thermic Typic Umbraquult) and Cape Fear (fine, mixed, semiactive, thermic Typic Umbraquult). The sandy soil was irrigated as needed to avoid drought stress. Treatments were N source (UAN and UFP) and N rate (0, 50, 78, 106, 134, 162, and 190 kg N ha-1 or 0, 45, 70, 95, 120, 145, and 170 lb ac-1 for wheat and 0, 39, 78, 118, 157, 196, and 235 kg N ha-1 or 0, 35, 70, 105, 140, 175, and 210 lb ac-1 for maize) arranged as randomized complete blocks with four replications. The UAN and UFP were applied as a split application for wheat, while maize received UFP at planting and split UAN. Timing of the materials was determined either by label (UFP) or prior experimental experience (UAN). Harvest biomass, grain, and mid-season soil sampling were performed to assess N availability. For both crops, UAN performed statistically similar to or better than UFP at both sites with regards to yields and NUE. Also, soil sampling and incubation results showed no consistent difference between N sources, implying the slow release properties of the UFP were not seen under the site and laboratory conditions. The release time for both sources at both sites was approximately 14 days (2 weeks). Since the cost of UFP is substantially greater than UAN and form did not significantly affect yield, UFP may not be as economical as UAN, depending on pricing of the different fertilizers.
Polyacrylamide Use for Erosion and Turbidity Control on Construction Sites
(2003-07-07) Hayes, Sara; Dr. Gary Grabow, Committee Member; Dr. Deanna Osmond, Committee Chair; Dr. Rich McLaughlin, Committee Co-Chair
Sediment is the most widespread pollutant of streams and rivers in North Carolina. Construction sites are a source of accelerated erosion contributing to the sediment problem. This study was conducted to determine if the application of polyacrylamide (PAM) to soil surfaces on construction sites reduces erosion and turbidity. Polyacrylamide has been demonstrated to greatly reduce erosion in furrow irrigation, and there is limited evidence it controls erosion when applied to bare soil. Two PAM products applied at manufacturers recommended rates (11.2 and 1.68 kg ha-1) and one half the recommended rates (5.6 and 0.84 kg ha-1) with and without grass seeding and mulching were tested on three North Carolina Department of Transportation construction sites in Raleigh and near Fayetteville. Runoff volumes, turbidity levels, and eroded sediment data were collected after natural rain events. On a 2:1 cut slope, turbidity and sediment loss were significantly decreased with application of seed/mulch. Erosion rates were 20 times greater on bare soil after seven rain events, with or without PAM, compared to treatments receiving seed/mulch. Polyacrylamide applied with seed/mulch produced slight reductions in turbidity and sediment loss in early rain events. At the higher rate, PAM applied directly on a more moderate, 4:1 fill slope decreased sediment loss and turbidity in the first few rain events following application compared to bare soil, with decreases diminishing over time. A sandy fill slope had inconsistent results between PAM treatments but reductions in turbidity and sediment from seed/mulch applications.