@article{muwamba_amatya_chescheir_nettles_appelboom_tollner_ssegane_youssef_birgand_callahan_2020, title={Response of Drainage Water Quality to Fertilizer Applications on a Switchgrass Intercropped Coastal Pine Forest}, volume={12}, ISSN={["2073-4441"]}, DOI={10.3390/w12051265}, abstractNote={The objectives of this study were (1) to test the hypothesis that fertilizer applications do not increase nutrient fluxes on a switchgrass/pine forest (IC) when compared to a mature pine forest (MP) and (2) to evaluate post-fertilization (post-fert, 2014–2016) fluxes of nitrogen (N) and phosphorus (P) on IC and compare them to those observed during switchgrass growth prior to fertilization (pre-fert, 2012–2014) and site preparation for switchgrass establishment (site prep, 2009–2012). Nitrogen and P were applied to IC, a paired pure switchgrass site (SG), and MP, each about 25 ha in size, in June 2014, and again in June 2015 for the IC and SG sites only. Nitrogen and P concentrations were measured biweekly and rainfall and drainage outflow were measured continuously. During post-fert, the mean N concentrations and total loads were lower (p < 0.05) in IC than in SG and MP. The mean NO3-N concentration and loads in IC were lower during post-fert than during site prep. The post-fert phosphate concentrations in IC were lower than they were during pre-fert and site prep. Frequent N and P applications in IC did not significantly (α = 0.05) increase N and P fluxes, likely due to plant uptake and sorption on the acidic site.}, number={5}, journal={WATER}, author={Muwamba, Augustine and Amatya, Devendra M. and Chescheir, George M. and Nettles, Jamie E. and Appelboom, Timothy and Tollner, Ernest W. and Ssegane, Hebert and Youssef, Mohamed A. and Birgand, Francois and Callahan, Timothy}, year={2020}, month={May} }
 @article{muwamba_amatya_ssegane_chescheir_appelboom_nettles_tollner_youssef_walega_birgand_2020, title={Response of Nutrients and Sediment to Hydrologic Variables in Switchgrass Intercropped Pine Forest Ecosystems on Poorly Drained Soil}, volume={231}, ISSN={["1573-2932"]}, DOI={10.1007/s11270-020-04808-3}, number={9}, journal={WATER AIR AND SOIL POLLUTION}, author={Muwamba, Augustine and Amatya, Devendra M. and Ssegane, Herbert and Chescheir, George M. and Appelboom, Timothy and Nettles, Jamie E. and Tollner, Ernest W. and Youssef, Mohamed A. and Walega, Andrzej and Birgand, Francois}, year={2020}, month={Aug} }
 @article{liu_youssef_chescheir_appelboom_poole_arellano_skaggs_2019, title={Effect of controlled drainage on nitrogen fate and transport for a subsurface drained grass field receiving liquid swine lagoon effluent}, volume={217}, ISSN={["1873-2283"]}, DOI={10.1016/j.agwat.2019.02.018}, abstractNote={Application of livestock manure has become a principal nutrient source in groundwater and surface water. The goal of this research was to investigate the effect of controlled drainage (CD) on nitrogen (N) fate and transport for a subsurface drained grass field receiving liquid swine lagoon effluent (SLE). A four-year field experiment was conducted on a naturally poorly drained pasture in eastern North Carolina. The 1.25 ha experimental field was artificially drained by subsurface drains installed at 1.0 m depth and 12.5 m spacing. Two treatments, replicated twice were implemented: conventional drainage (FD) and CD. The CD management protocol was more intensive compared to previous studies. The drain outlets of CD plot were set at 36 cm below soil surface all year round except several days before irrigation application when water table depth was shallower than 65 cm below surface. Controlled drainage significantly reduced drainage flow and TN loading via subsurface drain lines by an average of 397 mm yr−1 (93%) and 34.5 kg N ha−1 yr−1 (94%), respectively. DRAINMOD hydrologic simulations indicated that 96% of the reduction in predicted drain flow was attributed to increased lateral seepage. The nitrogen that did not drain from the field in response to CD was lost via enhanced denitrification (67%) and lateral seepage to adjacent fields (33%). This study clearly demonstrated how CD management affects the N fate and transport through seepage and denitrification process.}, journal={AGRICULTURAL WATER MANAGEMENT}, author={Liu, Yu and Youssef, Mohamed A. and Chescheir, George M. and Appelboom, Timothy W. and Poole, Chad A. and Arellano, Consuelo and Skaggs, R. Wayne}, year={2019}, month={May}, pages={440–451} }
 @article{ssegane_amatya_muwamba_chescheir_appelboom_tollner_nettles_youssef_birgand_skaggs_et al._2017, title={Calibration of paired watersheds: Utility of moving sums in presence of externalities}, volume={31}, ISSN={0885-6087}, url={http://dx.doi.org/10.1002/hyp.11248}, DOI={10.1002/hyp.11248}, abstractNote={Abstract}, number={20}, journal={Hydrological Processes}, publisher={Wiley}, author={Ssegane, H. and Amatya, D. M. and Muwamba, A. and Chescheir, G. M. and Appelboom, T. and Tollner, E. W. and Nettles, J. E. and Youssef, M. A. and Birgand, François and Skaggs, R. W. and et al.}, year={2017}, month={Sep}, pages={3458–3471} }
 @article{muwamba_amatya_chescheir_nettles_appelboom_ssegane_tollner_youssef_birgand_skaggs_et al._2017, title={Water Quality Effects of Switchgrass Intercropping on Pine Forest in Coastal North Carolina}, volume={60}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/trans.12181}, DOI={10.13031/trans.12181}, abstractNote={Abstract.}, number={5}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Muwamba, Augustine and Amatya, Devendra M. and Chescheir, George M. and Nettles, Jami E. and Appelboom, Timothy and Ssegane, Herbert and Tollner, Ernest E and Youssef, Mohamed A. and Birgand, Francois and Skaggs, R. Wayne and et al.}, year={2017}, pages={1607–1620} }
 @article{birgand_lellouche_appelboom_2013, title={Measuring flow in non-ideal conditions for short-term projects: Uncertainties associated with the use of stage-discharge rating curves}, volume={503}, ISSN={0022-1694}, url={http://dx.doi.org/10.1016/j.jhydrol.2013.09.007}, DOI={10.1016/j.jhydrol.2013.09.007}, abstractNote={The vast majority of hydrological stations are set up such that discharge can be estimated from the sole measurement of water height or stage above a local datum. Hydraulics laws show that in the right conditions there may be a unique and stable relationship between stage and discharge, which can be described by a rating curve. For short-term projects where there may be little choice for station location and time to construct a detailed rating curve, conditions for the use of rating curves may be less than ideal, potentially yielding high uncertainties on hydrologic measurements. This article evaluates uncertainties induced on instantaneous flow rates and cumulative annual flow volumes by the use of one-segmented rating curves in small streams. Uncertainty distributions were obtained by simulating rating curves calculated from random sampling of reference flow and stage data obtained with Doppler flowmeters. Factors tested included the number of manual gauged points, the type of rating curve (power vs polynomial), the use or not of the observed stage-of-zero flow, the spread of gauged points along flow range, and the measurement errors during gauging. Results could vary widely depending on the scenarios tested and sometimes yielded very high uncertainties. The best scenario yielded significant uncertainties on annual cumulative flow volume included between −13% and +14% for the low gradient streams and between −5% and +7% for the higher gradient streams, and for 22 manual gauged points per year. Our results show that, even in the best scenario, very significant uncertainty can result from using one-segmented rating curve in non-ideal situations in the field.}, journal={Journal of Hydrology}, publisher={Elsevier BV}, author={Birgand, François and Lellouche, Guillaume and Appelboom, T.W.}, year={2013}, month={Oct}, pages={186–195} }
 @article{birgand_appelboom_chescheir_skaggs_2011, title={Estimating Nitrogen, Phosphorus, and Carbon Fluxes in Forested and Mixed-Use Watersheds of the Lower Coastal Plain of North Carolina: Uncertainties Associated with Infrequent Sampling}, volume={54}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/2013.40668}, DOI={10.13031/2013.40668}, abstractNote={Assessing the impact of a land use change or the water quality improvement provided by a treatment system almost always involves computation of the difference in nutrient loads before and after implementation, or upstream and downstream of the system studied. Reporting meaningful values on mass balance or differences in nutrient loads implies that the uncertainty in the computed loads is several times smaller than the difference itself. This may imply very small uncertainties for the nutrient load measurements. The level of uncertainty induced by infrequent sampling on annual loads was investigated for a suite of nutrients in runoff from a forested watershed and a mixed land use watershed in the lower coastal plain of North Carolina. Reference data were used to simulate discrete sampling and to calculate new annual load estimators, which were then compared to the reference loads to calculate the level of uncertainty. Uncertainties depended on the watershed and the nutrients and other constituents, but their level was generally found to be high, around ±20% and ±40% or more for weekly and monthly sampling for most nutrients. This was generally attributed to the short periods of active flow in these watersheds and the flashiness of flow associated with subsurface drainage. The results suggest that to obtain uncertainties of ±2% or ±5% for nitrogen forms, 100 or more than 200 samples over six months of the year might be necessary in the forested and mixed-use watersheds of the lower coastal plain.}, number={6}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Birgand, F. and Appelboom, T. W. and Chescheir, G. M. and Skaggs, R. W.}, year={2011}, pages={2099–2110} }
 @article{appelboom_chescheir_birgand_skaggs_gilliam_amatya_2010, title={Temperature Coefficient for Modeling Denitrification in Surface Water Sediments Using the Mass Transfer Coefficient}, volume={53}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/2013.29578}, DOI={10.13031/2013.29578}, abstractNote={Watershed modeling has become an important tool for researchers. Modeling nitrate transport within drainage networks requires quantifying the denitrification within the sediments in canals and streams. In a previous study, several of the authors developed an equation using a term called a mass transfer coefficient to mathematically describe sediment denitrification. This equation takes into account the effect that water column nitrate concentration and flow depth have on denitrification in the sediments. Water column temperature also has a marked effect on the rate of denitrification in the sediments. In the present study, a relationship between denitrification rate and temperature was developed. This relationship was inserted into the original mathematical relationship to improve its ability to predict nitrate removal due to denitrification within drainage networks. The modified equation was tested by comparing predicted and measured nitrate concentrations over time in denitrification tanks at various temperatures. Results show that the modified equation increased the accuracy of predicting nitrate removal by denitrification in drainage canals. Overall Nash-Sutcliffe model efficiency values ranged from 0.72 to 0.76 for the original equation and from 0.90 to 0.97 for the equation developed in this study. The effective temperature range for the equation is 0°C to 40°C. The equation has also only been tested under stagnant/low-flow conditions.}, number={2}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Appelboom, T. W. and Chescheir, G. M. and Birgand, F. and Skaggs, R. W. and Gilliam, J. W. and Amatya, D.}, year={2010}, pages={465–474} }
 @inproceedings{appelboom_chescheir_skaggs_gilliam_amatya_2008, title={Nitrogen balance for a plantation forest drainage canal on the North Carolina coastal plain}, volume={51}, DOI={10.13031/2013.25239}, abstractNote={Human alteration of the nitrogen cycle has led to increased riverine nitrogen loads, contributing to the eutrophication of lakes, streams, estuaries, and near-coastal oceans. These riverine nitrogen loads are usually less than the total nitrogen inputs to the system, indicating nitrogen removal during transport through the drainage network. A two-year monitoring study quantified the ammonium, nitrate, and organic-N inputs, outputs, and inferred in-stream processes responsible for nitrogen transformations and removal in a 1900 m reach of a drainage canal located in a managed pine plantation. Total nitrogen inputs to the canal section were 527.8 kg in 2001 and 1422.7 kg in 2002. Total nitrogen discharge at the outlet was 502 kg in 2001 and 1458 kg in 2002. The mass balance of nitrogen inputs and outputs indicated a loss of 25.8 kg (5.1%) of total nitrogen from the system in 2001, and a gain of 35.3 kg (2.4%) of total nitrogen to the system in 2002. Variability in the input and output estimates was high, especially for groundwater exchange. Different hydrologic and nitrogen inputs and outputs were identified and quantified, but measurement variability obscured any potential nitrogen removal from the system.}, number={4}, booktitle={Transactions of the ASABE}, author={Appelboom, T. W. and Chescheir, G. M. and Skaggs, R. W. and Gilliam, J. W. and Amatya, D. M.}, year={2008}, pages={1215–1233} }
 @article{appelboom_chescheir_skaggs_hesterberg_2002, title={Management practices for sediment reduction from forest roads in the coastal plains}, volume={45}, DOI={10.13031/2013.8529}, abstractNote={Sediment has been identified as one of the most important non-point source pollutants of surface waters. In forested areas, the predominant source of sediment is from the construction and maintenance of access roads, which contribute as much as 90% of the total eroded sediments. Seven different road management practices were studied to determine their effectiveness in reducing sediment production from forest roads on nearly flat lands in the lower coastal plains of North Carolina. One practice utilized a continuous berm along the roadside, while the other six practices had a non-continuous berm with different combinations of road surface gravel and roadside vegetative strips. Runoff samples collected during eleven different rainfall events of varying intensity and duration were analyzed for sediment content. The rainfall amount, intensity, infiltration, and antecedent rainfall conditions were combined into a single energy rating to assist in the overall analysis. The results of the study showed that a continuous berm maintained along the edge of a forest road can reduce total sediment loss by an average of 99% compared to the same type road without the presence of a continuous berm. When a continuous berm is not present, graveling the road surface can reduce the total loss of sediment from roads by an average of 61% compared to a non-graveled road surface. A 90 cm wide grass strip on the edge of the driving surface can reduce total sediment loss by an average of 56% compared to a road without a grass strip.}, number={2}, journal={Transactions of the ASAE}, author={Appelboom, T. W. and Chescheir, G. M. and Skaggs, R. W. and Hesterberg, Dean}, year={2002}, pages={337–344} }