@article{grabow_2021, title={Discussion of "Cylindrical Central Baffle Flume for Flow Measurement in Open Channels" by Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar}, volume={147}, ISSN={["1943-4774"]}, DOI={10.1061/(ASCE)IR.1943-4774.0001582}, number={7}, journal={JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING}, author={Grabow, Garry}, year={2021}, month={Jul} }
 @article{pinnix_miller_bowman_grabow_2018, title={Color, Transfer, and Application Parameters of Turfgrass Colorants}, volume={110}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2017.03.0164}, abstractNote={Core Ideas
Turf colorants can be used as an alternative to winter overseeding, therefore saving turf managers resources.Multidimensional scaling analysis can be used to separate turf colorants into groups, allowing turf managers to better select products based on color parameters.Turf colorant transfer varies greatly among products and can result in severe staining.
Turfgrass colorants are primarily used as an alternative to winter overseeding. Information on colorants is limited in the scientific literature. The primary objective of this field study was to evaluate the effect turfgrass colorants had on color parameters (colorant intensity, color, and hue angle) of dormant bermudagrass (Cynodon sp.). Secondary objectives were to examine colorant transfer (wipe off) from the turfgrass surface to an absorbent material and to measure product viscosities. Twenty‐five colorants were applied at two spray volumes (75 and 112 mL m–2) on dormant bermudagrass at two heights of cut (0.3 and 1.5 cm). Multidimensional scaling and cluster analysis were used to separate colorants based on measured color parameters. Group 1 colorants maintained colorant intensity the longest, but colorant color was reduced at application due to the appearance of bright blue (e.g., Munsell 5BG/6/6) and bright green (e.g., Munsell 7.5GY/7/10) colors. Group 2 colorants provided the darkest green (e.g., Munsell 5GY/4/4) color, while Group 3 colorants provided minimal color change of dormant turfgrass. Among the Group 2 colorants, Green Lawnger, Lesco Green, Ultradwarf Super, Southwest Green, and Endurant provided a natural green color. Measurements of colorant transfer showed that Blue, Regreen, SprayMax, Green Dye Turf, Titan Green Turf, Solarogen, and Endurant have the highest propensity to disassociate from treated turfgrass. The use of multidimensional scaling and cluster analysis provided new information regarding a number of turf colorants. Grouping products by measured parameters indicated that products within Group 2 provided superior performance.}, number={1}, journal={AGRONOMY JOURNAL}, author={Pinnix, Garland D. and Miller, Grady L. and Bowman, Daniel C. and Grabow, Garry L.}, year={2018}, pages={66–76} }
 @article{vick_grabow_miller_huffman_2017, title={Water Conservation Potential of Smart Irrigation Technologies in the Catawba-Wateree River Basin}, volume={143}, ISSN={["1943-4774"]}, DOI={10.1061/(asce)ir.1943-4774.0001130}, abstractNote={AbstractA 3-year study was conducted in the Catawba-Wateree River Basin during the spring and summer months of 2009–2011 to evaluate the water savings potential of three smart irrigation controllers compared with standard timer-based irrigation controllers. Thirty-six residential sites, 12 on each of three Duke Energy lakes (Lake Norman, Lake Hickory, and Lake Wylie), were selected for the study. Each site had an automated, underground irrigation system that directly drew water from the Duke Energy lake that the property bordered. None of the systems had previously been metered and there was no charge to homeowners for withdrawing water from the bordering lake. All sites were instrumented with water meters in 2009 to monitor irrigation water withdrawals, and irrigation system audits were performed before installation of smart technologies. After collecting baseline water-use data in 2009, existing controllers were replaced with one of three smart controllers at 27 of the study sites in 2010, and irrigatio...}, number={2}, journal={JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING}, author={Vick, Robert L. and Grabow, Garry L. and Miller, Grady L. and Huffman, Rodney L.}, year={2017}, month={Feb} }
 @article{smolek_hunt_grabow_2015, title={Influence of Drawdown Period on Overflow Volume and Pollutant Treatment for Detention-Based Stormwater Control Measures in Raleigh, North Carolina}, volume={1}, ISSN={2379-6111 2379-6111}, url={http://dx.doi.org/10.1061/JSWBAY.0000798}, DOI={10.1061/JSWBAY.0000798}, abstractNote={AbstractThe drawdown rate of detention-based stormwater control measures (SCMs) influences both the treatment capability of the device and the volume of runoff that becomes untreated overflow. Currently, hydrologic design goals set by the North Carolina Department of Environmental and Natural Resources and other mid-Atlantic U.S. state agencies (e.g., those in Maryland, Virginia, and Pennsylvania) require stormwater practices to treat, e.g., 90% of stormwater runoff (or similar). This equates to a 10% overflow volume, defined as the percentage of inflow volume that bypasses the SCM and therefore receives minimal treatment. For detention-based SCMs, this design goal is met by sizing the outlet to release runoff generated from the water quality event (in North Carolina, either 25 or 38 mm) over a required minimum period of 2 days. Previous studies have not shown whether rainfall patterns in North Carolina and other east coast United States states justify a 2-day drawdown rate of the water quality event to l...}, number={2}, journal={Journal of Sustainable Water in the Built Environment}, publisher={American Society of Civil Engineers (ASCE)}, author={Smolek, Alessandra P. and Hunt, William F., III and Grabow, Garry L.}, year={2015}, month={May}, pages={05015001} }
 @article{nautiyal_grabow_huffman_miller_bowman_2015, title={Residential Irrigation Water Use in the Central Piedmont of North Carolina. I: Measured Use and Water Requirements}, volume={141}, ISSN={["1943-4774"]}, DOI={10.1061/(asce)ir.1943-4774.0000819}, abstractNote={AbstractIrrigation is the most common and standard practice for maintaining turfgrass and landscape plants in residential settings. The main objective of this study was to quantify the residential irrigation water use in Cary, North Carolina. A subobjective was to develop distributions of monthly reference evapotranspiration (ETo) and gross irrigation requirements (GIRs) for the area using long-term weather data. As part of the subobjective, an investigation was performed to compare daily measured solar radiation with two empirical methods of estimating solar radiation (Rs). The goal of this investigation was to determine the relative accuracy of these methods and to evaluate the impact of using Rs estimates in the computation of ETo and GIR for the Raleigh-Durham area, where Cary is located. Irrigation water use data from 2005 to 2007 for 120 randomly sampled residences were evaluated. The average lawn area of the sampled residences was 713  m2. None of the sampled households used drip irrigation. A nega...}, number={4}, journal={JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING}, author={Nautiyal, M. and Grabow, G. L. and Huffman, R. L. and Miller, G. L. and Bowman, D.}, year={2015}, month={Apr} }
 @article{nautiyal_grabow_huffman_miller_bowman_2015, title={Residential Irrigation Water Use in the Central Piedmont of North Carolina. II: Evaluation of Smart Irrigation Technologies}, volume={141}, ISSN={["1943-4774"]}, DOI={10.1061/(asce)ir.1943-4774.0000820}, abstractNote={AbstractA study was conducted in Cary, North Carolina, in the spring and summer of 2009 with the purpose of evaluating the effectiveness of two “smart irrigation” controllers based on the amount of irrigation applied and resulting turf quality in residential settings. Twenty-four residential sites were selected, in clusters of four, representing six geographical areas within the town. Each geographical cluster included one site of each treatment. The treatments were standard irrigation controller with an add-on soil moisture sensor system (SMS); standard irrigation controller with an add-on evapotranspiration-based adjustment system (ET); standard irrigation controller using seasonal runtimes based on historical climate data (ED); and a control group which used a standard irrigation controller with no intervention (CON). Weekly water usage was obtained from irrigation meter readings and turf quality was characterized using a visual rating and a normalized difference vegetation index (NDVI) meter. Maximum ...}, number={4}, journal={JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING}, author={Nautiyal, M. and Grabow, G. L. and Huffman, R. L. and Miller, G. L. and Bowman, D.}, year={2015}, month={Apr} }
 @article{jordan_johnson_grabow_corbett_2014, title={Corn, cotton, and peanut response to tillage and subsurface drip irrigation in north carolina}, volume={106}, DOI={10.2134/agronj13.0486}, abstractNote={Determining response of agronomic crops to subsurface drip irrigation (SDI) in conventional and reduced tillage systems is important in defining utility of SDI. Therefore, the objectives of this research were to define interactions of SDI and tillage with respect to yield and economic return of corn (Zea mays L.), cotton (Gossypium hirsutum L.), and peanut (Arachis hypogaea L.) planted in rotation. Research was conducted in two 4‐yr periods (2007–2010 and 2008–2011) in North Carolina using continuous strip tillage vs. continuous conventional tillage without irrigation or with SDI using a crop sequence of 1 yr of cotton, 2 yr of corn, followed by 1 yr of peanut. Corn, cotton, and peanut yields increased with SDI compared with no irrigation regardless of tillage system. Cotton and peanut yields were not affected by tillage system or the interaction of tillage and irrigation; corn yield was affected by this interaction. In the second year of corn, yield and economic return were higher in conventional tillage with SDI than strip tillage with SDI. Economic return for the sum of crops in the rotation was affected by the interaction of irrigation and tillage. Economic return was higher in both periods during each year corn was grown under SDI compared with non‐irrigated corn while higher economic returns for cotton and peanut under SDI were noted in one of two periods. When pooled over periods, crops, and tillage, economic return for SDI was US$1,552 ha−1 higher than non‐irrigated production over 4 yr.}, number={3}, journal={Agronomy Journal}, author={Jordan, D. L. and Johnson, P. D. and Grabow, G. L. and Corbett, T.}, year={2014}, pages={962–967} }
 @article{wiseman_burchell_grabow_osmond_messer_2014, title={GROUNDWATER NITRATE CONCENTRATION REDUCTIONS IN A RIPARIAN BUFFER ENROLLED IN THE NC CONSERVATION RESERVE ENHANCEMENT PROGRAM}, volume={50}, ISSN={["1752-1688"]}, DOI={10.1111/jawr.12209}, abstractNote={AbstractRiparian buffers have been used for many years as a best management practice to decrease the effects of nonpoint pollution from watersheds. The NC Conservation Reserve Enhancement Program (NC CREP) has established buffers to treat groundwater nitrate‐nitrogen (NO3−‐N) from agricultural sources in multiple river basins. A maturing 46 m wide riparian buffer enrolled in NC CREP was studied to determine its effectiveness in reducing groundwater NO3−‐N concentrations from a cattle pasture fertilized with poultry litter. Three monitoring blocks that included groundwater quality wells, water table wells, and soil redox probes, were established in the buffer. NO3−‐N concentrations decreased significantly across the buffer in all of the monitoring blocks with mean reductions of 76‐92%. Many biological processes, including denitrification and plant uptake, may have been responsible for the observed NO3−‐N reductions but could not be differentiated in this study. However, mean reductions in Cl− concentrations ranged from 48‐65% through the blocks, which indicated that dilution was an important factor in observed NO3−‐N reductions. These findings should be carefully considered for future buffer enrollments when assigning nitrogen removal credits.}, number={3}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Wiseman, Jacob D. and Burchell, Michael R. and Grabow, Garry L. and Osmond, Deanna L. and Messer, T. L.}, year={2014}, month={Jun}, pages={653–664} }
 @article{grabow_ghali_huffman_miller_bowman_vasanth_2013, title={Water Application Efficiency and Adequacy of ET-Based and Soil Moisture-Based Irrigation Controllers for Turfgrass Irrigation}, volume={139}, ISSN={["1943-4774"]}, DOI={10.1061/(asce)ir.1943-4774.0000528}, abstractNote={Abstract Increasing competition for water and the desire for high-quality turfgrass require sound irrigation water management. The main objective of this study was to evaluate two types of commercially available irrigation control technologies: one based on evapotranspiration (ET) estimates and the other based on feedback from a soil-moisture sensor (SMS). Irrigation treatments were combinations of controller technology: a timer-based standard controller system (TIM), an add-on (1 set point) SMS system (SMS1), and an evapotranspiration (ET)-based system (ETB), and watering frequency: weekly, twice per week, and daily (1, 2, and 7 days per week, respectively) plus a 10th treatment of an on-demand (2 set point) SMS system (SMS2). Both irrigation efficiency and adequacy were best for the SMS2 treatment when averaged over all three years. The SMS1 treatment provided good irrigation efficiency, but irrigation adequacy suffered, most noticeably with the twice per week treatment. The ET treatment provided good i...}, number={2}, journal={JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING}, author={Grabow, G. L. and Ghali, I. E. and Huffman, R. L. and Miller, G. L. and Bowman, D. and Vasanth, A.}, year={2013}, month={Feb}, pages={113–123} }
 @article{liu_grabow_huffman_osborne_evans_2012, title={Factors affecting uniformity of irrigation-type manure application systems}, volume={28}, DOI={10.13031/2013.41285}, abstractNote={Liquid manure is usually treated through application to agricultural land using irrigation systems. Land application of liquid manure needs to follow established guidelines in order to achieve economic goals as well as to protect the environment. Guidance at the time of this study in North Carolina suggested calibration of land application equipment be performed once every three years by the catch can method, a time- and labor-consuming method. The goals of this project were to investigate the relationship between liquid manure application uniformity by using data from historical uniformity assessment trials and from additional trials conducted during the study, and to use the results to provide guidance in developing a simplified field method for uniformity assessment. Trials were performed to test the liquid manure application uniformity for different irrigation system types, sprinkler types and models, nozzle types, nozzle diameters, and nozzle pressures. Wind speed during the trials was monitored. Different sprinkler overlaps were achieved by superposition, thereby allowing for assessment of multiple sprinkler spacings for each trial. Regression models were constructed using historic and study-period trial data and a process of main effect selection, collinearity checking, interaction term and quadratic term selection, parameter estimation, and normality testing of model residuals. The model for stationary systems performed well with an adjusted R2 of 0.72 and predicted application uniformity showed the expected tendencies with changes in predictive factors. The model for traveling gun systems did not perform as well as that for stationary systems; the adjusted R2 was only 0.33. The results of this study were used to amend uniformity assessment requirements to a simple procedure requiring measurement of sprinkler nozzle pressure, wetted diameter, and sprinkler spacing.}, number={1}, journal={Applied Engineering in Agriculture}, author={Liu, Z. and Grabow, G. L. and Huffman, R. L. and Osborne, J. and Evans, R. O.}, year={2012}, pages={43–56} }
 @article{messer_burchell_grabow_osmond_2012, title={Groundwater nitrate reductions within upstream and downstream sections of a riparian buffer}, volume={47}, ISSN={["1872-6992"]}, DOI={10.1016/j.ecoleng.2012.06.017}, abstractNote={The objective of this study was to evaluate the water quality benefits provided by a buffer enrolled in the North Carolina Conservation Reserve Enhancement Program (NC CREP). A 5-year study was conducted on two distinct buffer sections along the same stream to evaluate the hydrology and attenuation of groundwater nitrate (NO3−-N) entering from nearby agricultural fields. The average buffer widths were 60 m (Section 1, upstream) and 45 m (Section 2, downstream). Three transects of groundwater monitoring well nests within each buffer zone were installed to monitor water quality and water table depths for 5 years. Mean groundwater NO3−-N concentrations at the 1.5 m depth decreased from 4.5 mg L−1 to 1.7 mg L−1 and from 12.9 mg L−1 to 1.4 mg L−1 in buffer Sections 1 and 2 respectively. These differences were significant in both buffer sections (α = 0.05), but the wider Section 1 received significantly less NO3−-N than did Section 2 (P < 0.0001). Groundwater NO3−-N loads were reduced by 0.003 kg m−2 yr−1 (76% reduction) at the 1.5 m depth, while in Section 2 these loads were reduced by 0.02 kg m−2 yr−1 (94% reduction) and 0.04 kg m−2 yr−1 (86% reduction) at the 1.5 m and 3 m depths, respectively. Topography, water table and redox measurements, nitrate to chloride ratios, and deep groundwater cation analyses, indicated both sections were suitable for denitrification to proceed. However, the position of the wider Section 1 buffer in the landscape limited the amount of NO3−-N contaminated groundwater that entered from the agricultural fields, and thus could have been designed to be narrower. The effectiveness of NO3−-N reduction in riparian buffer systems is dependent on multiple landscape and biogeochemical factors and not buffer width alone. Findings provide design guidance for conservation buffer program managers as related to the influence of buffer landscape position on groundwater nitrate reduction.}, journal={ECOLOGICAL ENGINEERING}, author={Messer, Tiffany L. and Burchell, Michael R., II and Grabow, Garry L. and Osmond, Deanna L.}, year={2012}, month={Oct}, pages={297–307} }
 @article{lamm_bordovsky_schwankl_grabow_enciso-medina_peters_colaizzi_trooien_porter_2012, title={Subsurface drip irrigation: Status of the technology in 2010}, volume={55}, DOI={10.13031/2013.41387}, abstractNote={Subsurface drip irrigation (SDI), although a much smaller fraction of the microirrigated land area than sur- face drip irrigation, is growing at a much faster rate and is the subject of considerable research and educational efforts in the U.S. This article discusses the growth of SDI, highlights some of the research and extension efforts, and points out some of the challenges to SDI adoption and some of the future opportunities for SDI.}, number={2}, journal={Transactions of the ASABE}, author={Lamm, F. R. and Bordovsky, J. P. and Schwankl, L. J. and Grabow, G. L. and Enciso-Medina, J. and Peters, R. T. and Colaizzi, P. D. and Trooien, T. P. and Porter, D. O.}, year={2012}, pages={483–491} }
 @article{ghali_miller_grabow_huffman_2012, title={Using Variability within Digital Images to Improve Tall Fescue Color Characterization}, volume={52}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2011.10.0553}, abstractNote={ABSTRACTDigital image analysis (DIA) provides an accurate, nondestructive, and objective assessment of turf color. Previous research developed an index known as the dark green color index (DGCI) via DIA as an indicator of turf color. The objective of this study was to use DGCI variability to better predict a visual rating (VR) index used to evaluate tall fescue (Festuca arundinacea Schreb.) color under different irrigation treatments. To develop DGCI statistics, two freeware software packages (Image J and R) were used to extract and process information from digital images. The model to predict VR from DIA was developed and calibrated using candidate DGCI statistical moments from 120 images in a calibration data set using a multiple linear regression procedure. Fitness of calibration and validation models were verified using the adjusted coefficient of determination, root mean square error, and the Mallow's Cp statistic. The two‐variable model produced more precise estimates (adjusted R2 = 0.926 and 0.899) than the model that only used one term in predicting the VR values (adjusted R2 = 0.879 and 0.843) for calibration and validation sets, respectively. These data suggest incorporating a measure of color uniformity improves the use of DGCI in predicting VR values compared to using only the mean of DGCI values to predict VR values. Model refinements may be needed for other turf species, but current work suggests using additional statistical moments such as SD improves VR estimate precision and accuracy.}, number={5}, journal={CROP SCIENCE}, author={Ghali, Ihab E. and Miller, Grady L. and Grabow, Garry L. and Huffman, Rodney L.}, year={2012}, month={Sep}, pages={2365–2374} }
 @inproceedings{vick, jr._grabow_huffman_miller_2011, title={Residential Irrigation and Water Conservation Potential of Smart Irrigation Technologies in the Catawba River Basin}, ISBN={9780784411735}, url={http://dx.doi.org/10.1061/41173(414)282}, DOI={10.1061/41173(414)282}, abstractNote={A three year residential lake water use study in the Catawba River Basin was initiated in 2009 to assess current water withdrawals for landscape irrigation and the water conservation potential of "smart irrigation" technologies. The study is being conducted by North Carolina State University, on properties bordering Duke Energy managed lakes, in North Carolina and South Carolina, that withdraw lake water for landscape irrigation. Assessment of current irrigation water use began in 2009 with a survey to which over 1,400 residences responded (reflecting a 7.4% return rate). Survey results were used to select thirty-six residences (twelve on each of three lakes along the Catawba River) for further evaluation. Water meters with loggers were installed on the main lines of irrigation systems of the selected residences in the summer of 2009 to monitor lake water withdrawals for landscape irrigation under current practices. Two weather stations and four atmometers were also installed in the region to monitor reference evapotransporation during the study. Three types of smart irrigation technologies (two ET-based controllers and one soil-moisture sensor system) were installed at twenty-seven of the study sites at the beginning of the 2010 irrigation season. The technologies were distributed such that each lake had six sites with ET-based controllers, three sites with soil-moisture sensors, and three sites with no intervention, which would serve as a comparison group. Metering of irrigation water withdrawals continued throughout the 2010 irrigation season after installation of smart irrigation technologies. Turf quality assessments were made throughout the year using a visual turf quality rating and a Normalized Difference Vegetative Index (NDVI) obtained with a turf color meter. The study will conclude with data collected in the 2011 irrigation season.}, booktitle={World Environmental and Water Resources Congress 2011}, publisher={American Society of Civil Engineers}, author={Vick, Jr., R. L. and Grabow, G. L. and Huffman, R. L. and Miller, G. L.}, year={2011}, month={May} }
 @article{grabow_huffman_evans_2011, title={SDI Dripline Spacing Effect on Corn and Soybean Yield in a Piedmont Clay Soil}, volume={137}, ISSN={["1943-4774"]}, DOI={10.1061/(asce)ir.1943-4774.0000277}, abstractNote={A subsurface drip irrigation (SDI) system was installed in the Piedmont of North Carolina in a clay soil in the fall of 2001 to test the effect of dripline spacing on corn and soybean yield. The system was zoned into three sections; each section was cropped to either corn (Zea mays L.), full-season soybean [Glycine max (L.) Merr.], or winter wheat (Triticum aestivum) double cropped to soybean representing any year of a typical crop rotation in the region. Each section had four plots; two SDI plots with dripline spacing at either 1.52 or 2.28 m, an overhead sprinkler irrigated plot, and an unirrigated plot. There was no difference in average corn grain yield for 2002–2005 between dripline spacings or between either dripline spacing and sprinkler. Irrigation water use efficiency (IWUE) was greater for sprinkler irrigated corn than for either SDI treatment and there was no difference in IWUE in soybean. Water typically moved laterally from the driplines 0.38 to 0.50 m. SDI yield and IWUE increased relative t...}, number={1}, journal={JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING}, author={Grabow, G. L. and Huffman, R. L. and Evans, R. O.}, year={2011}, month={Jan}, pages={27–36} }
 @inproceedings{westerman_ogejo_grabow_2010, title={Swine anaerobic lagoon nutrient concentration variation with season, lagoon level, and rainfall}, volume={26}, DOI={10.13031/2013.29472}, abstractNote={Twenty swine anaerobic lagoons (8 finish, 6 nursery, and 6 sow) were monitored for lagoon liquid nutrient concentrations and liquid level above or below the stop-pump level. Weekly rainfall was also recorded. Significant differences in total nitrogen (N) concentrations existed between lagoons and also between types of farms. The N concentration varied within the same lagoon by a factor of two or more during the 4-yr study period and typically displayed a seasonal trend of decreasing during the summer and increasing during the winter. Years of operation (8 to 29 yr) were not a significant factor for mean N concentration over the 4-yr period. The lagoon liquid level was not a significant factor for N or total phosphorus (P) concentration. The finish farms displayed a decreasing trend of average annual nitrogen concentration with increase in annual rainfall.}, number={1}, booktitle={Applied Engineering in Agriculture}, author={Westerman, P. W. and Ogejo, J. A. and Grabow, G. L.}, year={2010}, pages={147–152} }
 @article{shah_balla_grabow_westerman_bailey_2009, title={Impact of land application method on ammonia loss from hog lagoon effluent}, volume={25}, DOI={10.13031/2013.29236}, abstractNote={Ammonia volatilization during land-application of hog lagoon effluent can adversely affect public health and the environment. Ammonia losses from hog lagoon effluent applied to Coastal Bermudagrass with the drag-hose (two applications) and traveling gun (three applications) were measured in spring and summer of 2006. Ammonia losses during application with the traveling gun were measured with acidified catch cans while losses during (traveling gun) or following (drag-hose) application for up to 96 h was measured with a micrometeorological method, the integrated horizontal flux (IHF) method; ammonia-N losses measured with the IHF method and catch cans are not additive. Ammonia-N losses during application with the traveling gun ranged between 3.8% to 9.2% of total ammoniacal nitrogen (TAN) applied, increasing with wind speed and decreasing relative humidity. For two applications, average ammonia loss with the drag-hose was <25% of the traveling gun. Ammonia-N losses from the traveling gun and drag-hose averaged 46.3% (n = 3) and 5.5% (n = 2), respectively, of the TAN applied. Ammonia-N loss during the first 4 h, as percent of total TAN loss was higher with the traveling gun. Whereas traveling gun ammonia losses were affected more by weather (e.g., relative humidity) and crop height, drag-hose losses were impacted more by effluent properties. Wind speed measurement contributed to <6% uncertainty in ammonia loss for both systems during one 4-h period. There are also other sources of uncertainty. Results from this study are comparable with published micrometeorological studies on hog lagoon effluent application.}, number={6}, journal={Applied Engineering in Agriculture}, author={Shah, Sanjay and Balla, B. K. and Grabow, G. L. and Westerman, P. W. and Bailey, D. E.}, year={2009}, pages={963–973} }
 @article{shah_hutchison_hesterberg_grabow_huffman_hardy_parsons_2009, title={Leaching of Nutrients and Trace Elements from Stockpiled Turkey Litter into Soil}, volume={38}, ISSN={["1537-2537"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-66649083862&partnerID=MN8TOARS}, DOI={10.2134/jeq2007.0639}, abstractNote={In addition to nutrients, poultry are fed trace elements (e.g., As) for therapeutic purposes. Although a large proportion of the nutrients are assimilated by the birds, nearly all of the As is excreted. Hence, turkey litter constituents can leach into the soil and contaminate shallow ground water when it is stockpiled uncovered on bare soil. This study quantified the leaching of turkey litter constituents from uncovered stockpiles into the underlying soil. Four stockpiles were placed on Orangeburg loamy sand in summer 2004 for 162 d; 14 d after their removal, four stockpiles were created over the same footprints and left over winter for 162 d. Soil samples at depths of 7.6 to 30.5 cm and 30.5 to 61 cm adjacent to and beneath the stockpiles were compared for pH, electrical conductivity, total C, dissolved organic C, N species, P, water‐extractable (WE)‐P, As, WE‐As, Cu, Mn, and Zn. All WE constituents affected the 7.6‐ to 30.5‐cm layer, and some leached deeper; for example, NH4+–N concentrations were 184 and 62 times higher in the shallow and deep layers, respectively. During winter stockpiling, WE‐As concentrations beneath the stockpiles tripled and doubled in the 7.6‐ to 30.5‐cm and 30.5‐ to 61‐cm layers, respectively, with WE‐As being primarily as As(V). Heavy dissolved organic C and WE‐P leaching likely increased solubilization of soil As, although WE‐As concentrations were low due to the Al‐rich soil and low‐As litter. When used as drinking water, shallow ground water should be monitored on farms with a history of litter stockpiling on bare soil; high litter As; and high soil As, Fe, and Mn concentrations.}, number={3}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Shah, Sanjay B. and Hutchison, Kimberly J. and Hesterberg, Dean L. and Grabow, Garry L. and Huffman, Rodney L. and Hardy, David H. and Parsons, James T.}, year={2009}, pages={1053–1065} }
 @inproceedings{grabow_dukes_thapa_2009, title={The Use of Soil-Water Sensors in Turf Irrigation Control — How Effective Are They?}, ISBN={9780784410363}, url={http://dx.doi.org/10.1061/41036(342)433}, DOI={10.1061/41036(342)433}, abstractNote={Soil-Water sensor controllers have been used since the mid-1990s to manage turf irrigation. While evapotranspriation (ET) based controllers have been more widely adopted for turf and landscape irrigation, soil-water-sensor based systems hold some distinct advantages, particularly in humid regions where rainfall contributes significantly to turf water requirements and is highly spatially variable. Some perceived disadvantages of soil-water-sensor based systems are representativeness of whole landscapes when only one sensor is used; sensor accuracy and repeatability, and proper setting of soil-water setpoints. Several studies involving soil-moisture sensors have been done in Florida, and one study in North Carolina is near completion. These studies have looked at soil-water sensor based systems of various manufacturers in similar settings; have compared results between different moisture setting thresholds; have contrasted water usage with ET based controller systems; and have monitored root zone soil-water status in plots irrigated by soil-water based systems. Soil-water data has also been collected for replicates of sensor-based treatments in an effort to address the question of repeatability and sensor placement representativeness. Preliminary data from these studies have shown that there is wide variability between different sensor systems with respect to both applied water and turf quality. The data has also shown that soil water sensor based systems may in some cases apply less water than ET controllers. Consistent relationships between soil-water-content and controller settings has been found to be problematic. Analysis of soil-water data indicates that while there are differences in soil-water between replications of soil-water-based sensor treatments, soil-water trends are generally consistent between replications and turf quality is generally not substantially different between replications.}, booktitle={World Environmental and Water Resources Congress 2009}, publisher={American Society of Civil Engineers}, author={Grabow, Garry L. and Dukes, Michael and Thapa, Bir}, year={2009}, month={May} }
 @inproceedings{grabow_vasanth_bowman_huffman_miller_2008, title={Evaluation of Evapotranspiration-Based and Soil-Moisture-Based Irrigation Control in Turf}, ISBN={9780784409763}, url={http://dx.doi.org/10.1061/40976(316)117}, DOI={10.1061/40976(316)117}, abstractNote={A study was initiated in Fall 2006 in Raleigh, North Carolina to compare two types of commercially available irrigation control technologies, one based on estimates of evapotranspiration (ET) and the other based on feedback from soil moisture sensors. Water applied and turf quality from one ET-based system and two sensor-based systems were compared to a system using a standard time-based irrigation schedule. The effect of irrigation frequency was also a part of the study. Estimates of turf ET were obtained from the Penman-Monteith equation using on-site weather data, and also from an atmometer. Results from the twenty week evaluation in 2007 showed that on average the “add-on” soil-moisture-based system evaluated applied the least amount of water while the ETbased system evaluated applied the most water. Weekly irrigation frequencies used the least amount of water, followed by bi-weekly and daily frequencies in increasing amounts when averaged across all technologies. Minimally acceptable turf quality was maintained by all technologies and frequencies through most of the study, but turf quality declined substantially the last month of the study for the add-on system and standard timer-based system. The “on-demand” sensor-based system resulted in the best combination of water efficiency and turf quality.}, booktitle={World Environmental and Water Resources Congress 2008}, publisher={American Society of Civil Engineers}, author={Grabow, Garry L. and Vasanth, Arjun and Bowman, Dan and Huffman, Rodney L. and Miller, Grady L.}, year={2008}, month={May} }
 @article{grabow_mccornick_2007, title={Planning for water allocation and water quality using a spreadsheet-based model}, volume={133}, DOI={10.1061/(ASCE)0733-9496(2007)133:6(560)}, abstractNote={An integrated planning activity was undertaken for the Amman-Zarqa Basin in Jordan to account for present and future uses of water resources including reclaimed water. Upgrades to existing wastewater treatment plants mean that new reclaimed water resources will be available in the future. To evaluate the impact of current and potential future uses on basin stakeholders, a spreadsheet-based model was developed to predict water quantity and quality at several key locations. The model consists of a flow component and a water quality component. The model was used to screen various water-use scenarios and to formulate feasible alternatives including the sequencing of future water demands. The use of a spreadsheet model allowed engineers and scientists within the Ministry of Water and Irrigation, and members of the consulting team who had limited modeling experience to be involved in the planning activity.}, number={6}, journal={Journal of Water Resources Planning and Management}, author={Grabow, G. L. and McCornick, P. G.}, year={2007}, pages={560–564} }
 @article{shah_grabow_westerman_2006, title={Ammonia adsorption in five types of flexible tubing materials}, volume={22}, DOI={10.13031/2013.22253}, abstractNote={Five different types of tubing materials, namely, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), high density polyethylene (HDPE), and polyvinyl chloride (PVC) were evaluated for ammonia adsorption at two nominal ammonia concentration values (1 and 10 ppm) at ~24°C. All tubing sections were 2.5 m in length and 4.76 mm in i.d. except the HDPE which had an i.d. of 4.32 mm. Mass balance was used to determine ammonia (as ammonium-nitrogen (N)) adsorbed on the inside of the tubing versus the total N recovered in the tubing plus the gas scrubbers (primary and secondary). No tubing significantly differed in N adsorption. Averaged for both ammonia concentrations, N adsorption as percent of total N ranged from 0.15% (PVC) to 1.69% (FEP). Hence, the least expensive PVC tubing may represent the best option under conditions similar to those used in this study. The gas scrubber design used in this study had excellent trapping efficiency (>99%).}, number={6}, journal={Applied Engineering in Agriculture}, author={Shah, Sanjay and Grabow, G. L. and Westerman, P. W.}, year={2006}, pages={919–923} }
 @article{grabow_huffman_evans_jordan_nuti_2006, title={Water distribution from a subsurface drip irrigation system and dripline spacing effect on cotton yield and water use efficiency in a coastal plain soil}, volume={49}, DOI={10.13031/2013.22303}, abstractNote={A subsurface drip irrigation (SDI) system was installed in 2001 in the Coastal Plain of North Carolina. Initially, four zones were installed, each with 0.91 m dripline spacing. In 2002, a fifth zone with 1.82 m dripline spacing was added. This system irrigated a cotton (Gossypium hirsutum L.) and peanut (Arachis hypogea L.) rotation on a Norfolk sandy loam soil. Seed cotton yield data was collected from 2001 to 2004. In addition to SDI, overhead sprinkler irrigation was applied to cotton plots from 2001 to 2003. This study was concurrent with another study that evaluated the effect of irrigation system type, cotton growth regulator (mepiquat chloride), herbicide (glyphosate) treatment, and planting date on lint yield and quality. Although the soil is classified as a sandy loam, water moved laterally to the midpoint of the 1.82 m spaced dripline; this was likely due to the pan layer found at about 0.3 m just below the dripline depth of 0.23 m. There was no difference in lateral water movement between the two dripline spacings. Seed cotton yield and irrigation water use efficiency was not statistically different between irrigation system type or dripline spacing over all years in the study. Seed cotton yield averaged 3.44 Mg ha-1 for the 0.91 m dripline spacing and 3.22 Mg ha-1 for the 1.82 m spacing for the three-year period 2002-2004 compared to an unirrigated average of 2.58 Mg ha-1 for the same period. Average irrigation water use efficiency was greater for the 0.91 m dripline spacing but not statistically different from the 1.82 m spacing. For 2001-2003, when sprinkler-irrigated plots existed, seed cotton yield averaged 3.55 Mg ha-1 for the 0.91 m dripline spacing, 3.35 Mg ha-1 for the sprinkler-irrigated plots, and 2.56 Mg ha-1 for the unirrigated plots. Drought conditions existed in 2002, when 258 mm of rain occurred between planting and final irrigation. The other growing seasons received relatively high amounts of rainfall: 524, 555, and 643 mm in 2001, 2003, and 2004, respectively.}, number={6}, journal={Transactions of the ASABE}, author={Grabow, G. L. and Huffman, R. L. and Evans, R. O. and Jordan, D. L. and Nuti, R. C.}, year={2006}, pages={1823–1835} }
 @inproceedings{grabow_harrison_dukes_vories_smith_zhu_khalilian_2005, title={Considerations for the Design and Installation of SDI Systems in Humid Areas}, ISBN={9780784407929}, url={http://dx.doi.org/10.1061/40792(173)518}, DOI={10.1061/40792(173)518}, abstractNote={Humid areas, such as the southeastern and midsouthern United States, have particular climate, topography, soils, cropping systems, and water sources that require special consideration when considering and implementing a subsurface drip irrigation (SDI) system. Design criteria are generally the same in humid areas as in arid or semi-arid areas, but these factors are normally different enough in value or type to result in a different system design. Irregularly shaped fields commonly found in humid areas can result in a system layout that differs greatly from a "normal" layout. Installation is best done when the soil moisture is within an optimal range, which may seriously limit installation windows in humid areas. As fewer systems have been installed in humid regions, availability of professional installers and installation equipment can be problematic. This paper presents both design and installation considerations for SDI systems, with particular emphasis placed on conditions found in humid areas. It is condensed from two publications in a series designed to provide guidance on SDI systems in humid regions in an "extension-like" format. Topics include: design criteria; pumps; filtration; chemical injection; valves; main and submain, dripline, and flush ing manifold design; instrumentation and control systems; design implementation; installation tips; and locating an installer.}, booktitle={Impacts of Global Climate Change}, publisher={American Society of Civil Engineers}, author={Grabow, Garry L. and Harrison, Kerry and Dukes, Michael D. and Vories, Earl and Smith, W. Bryan and Zhu, Heping and Khalilian, Ahmad}, year={2005}, month={Jul} }
 @article{lanier_jordan_barnes_matthews_grabow_griffin_bailey_johnson_spears_wells_2004, title={Disease management in overhead sprinkler and subsurface drip irrigation systems for peanut}, volume={96}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2004.1058}, abstractNote={Experiments were conducted during 2001 and 2002 at one location in North Carolina to compare development of early leaf spot (Cercospora arachidicola Hori), pod yield, and market grade characteristics when peanut (Arachis hypogea L.) was grown under overhead sprinkler irrigation (OSI) and subsurface drip irrigation (SDI) and fungicides were not applied or applied biweekly or based on weather advisories. Incidence of early leaf spot was lower when peanut was grown under SDI compared with OSI when fungicides were not applied. Fewer fungicide applications were needed when applications were based on weather advisories rather than when applied biweekly. There was no difference in early leaf spot control or leaf defoliation resulting from disease when fungicides were applied regardless of irrigation system or fungicide application approach. Pod yield was higher in 2001 under SDI compared with OSI when fungicides were not applied; yield was similar in 2002. Disease severity was much higher in 2001 than in 2002 and most likely explains differences in pod yield between years. No difference in yield was noted when fungicides were applied, regardless of irrigation system. The percentage of extra large kernels (%ELK) was lower in 1 of 2 yr under SDI compared with OSI. There were no differences in percentages of fancy pods (%FP), sound splits (%SS), and other kernels (%OK) among irrigation systems and fungicide programs. In a separate experiment where fungicides were applied biweekly, pod yield, %FP, and %ELK were similar under SDI and OSI but greater than nonirrigated peanut. The %OK was lower when peanut was irrigated.}, number={4}, journal={AGRONOMY JOURNAL}, author={Lanier, JE and Jordan, DL and Barnes, JS and Matthews, J and Grabow, GL and Griffin, WJ and Bailey, JE and Johnson, PD and Spears, JF and Wells, R}, year={2004}, pages={1058–1065} }
 @article{richards_grabow_2003, title={Detecting reductions in sediment loads associated with Ohio's conservation reserve enhancement program}, volume={39}, ISSN={["1093-474X"]}, DOI={10.1111/j.1752-1688.2003.tb03707.x}, abstractNote={ABSTRACT:  Small systematic changes in loads or concentrations of water quality constituents are difficult to detect against the background of short term fluctuations (“noise”) that result from weather and climate effects. Minimum Detectable Change Analysis (MDCA) uses prior knowledge of a water quality constituent to determine how much change must occur (e.g., from implementation of conservation practices) for the change to be statistically significant. In this paper we use MDCA to determine whether the goal of the Ohio Lake Erie Conservation Reserve Enhancement Program (CREP), to reduce sediment loads by an average of 6 percent over 10 years, represents a large enough change to be detected. We conclude that this amount of change is unlikely to be detected as statistically significant, even with the high frequency sampling program planned for evaluating it. The minimum detectable change ranges from about 7 to 9 percent for three different rivers.}, number={5}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Richards, RP and Grabow, GL}, year={2003}, month={Oct}, pages={1261–1268} }
 @article{ranki_grabow_mccornick_2001, title={Stream gauging of torrential rivers in eastern Eritrea: closure}, volume={6}, DOI={10.1061/(ASCE)1084-0699(2001)6:2(175)}, number={2}, journal={Journal of Hydrologic Engineering}, author={Ranki, J. G. and Grabow, G. L. and McCornick, P. G.}, year={2001}, pages={175–176} }
 @article{grabow_yoder_mote_2000, title={An empirically-based sequential ground water monitoring network design procedure}, volume={36}, ISSN={["1093-474X"]}, DOI={10.1111/j.1752-1688.2000.tb04286.x}, abstractNote={ABSTRACT:  A procedure using a simple, empirically‐based model that makes efficient use of available information has been developed for designing a ground water monitoring well network. A moving plume is described by siting wells in a sequential manner, relying upon two‐dimensional concentration data obtained from previously installed wells to determine the locations of future wells. Data sets from two well known, densely monitored natural gradient tracer studies were used to test the procedure. Plumes defined by all information in the original networks were compared to those defined by reduced networks designed by the new procedure. The new procedure tracked the plumes using only a portion of that information. The new procedure could have reduced the number of wells in the original tests by about 50 percent without appreciable loss of plume information as measured by plume location and extent and by tracer mass.}, number={3}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Grabow, G and Yoder, DC and Mote, CR}, year={2000}, month={Jun}, pages={549–566} }
 @article{grabow_mccornick_rankl_1998, title={Stream gaging of the torrential rivers of Eastern Eritrea}, volume={3}, DOI={10.1061/(asce)1084-0699(1998)3:3(211)}, abstractNote={To better evaluate the potential of projects in Eritrea, a national data collection network was established. Part of that network was two stream gauging stations located in the eastern slope region of the country. The design of these stations allowed for the lack of access in the area and for the flow regime, characterized by highly flashy and ephemeral sediment laden discharge. The stations consist of a pressure transducer housed in a well screen–type housing and solar-powered data logger. Stage and water temperature are logged every 20 min. Discharge is estimated from a stage-discharge curve generated from a survey of the channel and the use of a step-backwater approach in a numerical model. System operation has been transferred to the Eritrean Water Resources Department. After a year of evaluation, some modifications were made to the installations.}, number={3}, journal={Journal of Hydrologic Engineering}, author={Grabow, G. L. and McCornick, P. G. and Rankl, J. G.}, year={1998}, pages={211–214} }