@article{wherley_sinclair_dukes_schreffler_2011, title={Nitrogen and Cutting Height Influence Root Development during Warm-Season Turfgrass Sod Establishment}, volume={103}, ISSN={["0002-1962"]}, DOI={10.2134/agronj2011.0146}, abstractNote={Effective water conservation in the landscape requires identification of cultural management practices that maximize the genetic rooting potential of establishing turfgrass sod. Nitrogen is critical for successful turfgrass establishment; however, there has recently been debate over whether to restrict N fertilization during summer periods in parts of Florida and the United States. This study was undertaken to examine within four warm-season turfgrass species, the relative influences of cutting height and N fertility on the (i) rate of root extension and (ii) root biomass produced over a 10-wk period. ‘Tifway 419’ bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy), ‘Empire’ zoysiagrass (Zoysia japonica Steud.), ‘Argentine’ bahiagrass (Paspalum notatum Flugge), and ‘Floratam’ St. Augustinegrass (Stenotaphrum secundatum Walt. Kuntze) were established from 10-cm diam. by 5-cm deep plugs of turfgrass sod into 90-cm tall, clear acrylic tubes. Experimental treatments were arranged in a complete factorial that was repeated over two growing seasons. Rates of root extension were calculated from weekly measures of the deepest visible root in each column. Root extension rates ranged from ∼1.0 to 1.8 cm d−1 during the studies, with bahiagrass exhibiting the most rapid root extension of the four species. The results demonstrated that increasing N fertility during establishment increased rates of root extension into deep soil, particularly in bermudagrass. Height of cut had no effect on rate of root extension for most species, but higher cutting height did promote more rapid root extension in bermudagrass. Although not significantly accelerating vertical root extension in most species, maintaining sod at the higher cutting heights resulted in significantly greater root proliferation within both upper and lower soil depths for all species. The results emphasize the importance of proper N fertility and cutting heights for optimizing root development of different turfgrass species during sod establishment.}, number={6}, journal={AGRONOMY JOURNAL}, author={Wherley, B. G. and Sinclair, T. R. and Dukes, M. D. and Schreffler, A. K.}, year={2011}, pages={1629–1634} }
 @article{davis_dukes_miller_2009, title={Landscape irrigation by evapotranspiration-based irrigation controllers under dry conditions in Southwest Florida}, volume={96}, ISSN={["1873-2283"]}, DOI={10.1016/j.agwat.2009.08.005}, abstractNote={Due to high demand for aesthetically pleasing urban landscapes from continually increasing population in Florida, new methods must be explored for outdoor water conservation. Three brands of evapotranspiration (ET) controllers were selected based on positive water savings results in arid climates. ET controllers were evaluated on irrigation application compared to a time clock schedule intended to mimic homeowner irrigation schedules. Three ET controllers were tested: Toro Intelli-sense; ETwater Smart Controller 100; Weathermatic SL1600. Other time-based treatments were TIME, based on the historical net irrigation requirement and RTIME that was 60% of TIME. Each treatment was replicated four times for a total of twenty St. Augustinegrass plots which were irrigated through individual irrigation systems. Treatments were compared to each other and to a time-based schedule without rain sensor (TIME WORS) derived from TIME. The study period, August 2006 through November 2007, was dry compared to 30-year historical average rainfall. The ET controllers averaged 43% water savings compared to a time-based treatment without a rain sensor and were about twice as effective and reducing irrigation compared to a rain sensor alone. There were no differences in turfgrass quality across all treatments over the 15-month study. The controllers adjusted their irrigation schedules to the climatic demand effectively, with maximum savings of 60% during the winter 2006–2007 period and minimum savings of 9% during spring 2007 due to persistent dry conditions. RTIME had similar savings to the ET controllers compared to TIME WORS indicating that proper adjustment of time clocks could result in substantial irrigation savings. However, the ET controllers would offer consistent savings once programmed properly.}, number={12}, journal={AGRICULTURAL WATER MANAGEMENT}, author={Davis, S. L. and Dukes, M. D. and Miller, G. L.}, year={2009}, month={Dec}, pages={1828–1836} }
 @article{cardenas-lailhacar_dukes_miller_2008, title={Sensor-based automation of irrigation on bermudagrass, during wet weather conditions}, volume={134}, DOI={10.1061/(ASCE)0733-9437(2008)134:2(120)}, abstractNote={New technologies could improve irrigation efficiency of turfgrass, promoting water conservation and reducing environmental impacts. The objectives of this research were to quantify irrigation water use and to evaluate turf quality differences between (1) time-based scheduling with and without a rain sensor (RS); (2) a time-based schedule compared to a soil moisture sensor (SMS)-based irrigation system; and (3) different commercially available SMS systems. The experimental area consisted of common bermudagrass [Cynodon dactylon (L.) Pers.] plots (3.7m×3.7m), located in Gainesville, Fla. The monitoring period took place from July 20 to December 14, 2004, and from March 25 to August 31, 2005. SMS-based treatments consisted of irrigating one, two, or seven days a week, each with four different commercial SMS brands. Time-based treatments with or without RS and a nonirrigated treatment were also implemented. Significant differences in turfgrass quality among treatments were not detected due to the sustained wet weather conditions during the testing periods. The treatment with the rain sensor resulted in 34% less water applied than that without the rain sensor (2-WORS) treatment. Most SMS brands recorded irrigation water savings compared to 2-WORS, ranging from 69 to 92% for three of four SMSs tested, depending on the irrigation frequency. Therefore, SMS systems represent a promising technology because of the water savings that they can achieve during wet weather conditions while maintaining acceptable turfgrass quality.}, number={2}, journal={Journal of Irrigation and Drainage Engineering}, author={Cardenas-Lailhacar, B. and Dukes, M. D. and Miller, Grady}, year={2008}, pages={120–128} }
 @article{haley_dukes_miller_2007, title={Exact equations for critical depth in a trapezoidal canal - Discussion by Prabhata K. Swamee and Pushpa N. Rathie}, volume={133}, ISSN={["1943-4774"]}, DOI={10.1061/(ASCE)0733-9437}, number={5}, journal={JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING}, author={Haley, M. B. and Dukes, M. D. and Miller, Grady}, year={2007}, pages={509–509} }
 @article{dukes_evans_2006, title={Impact of agriculture on water quality in the North Carolina Middle Coastal Plain}, volume={132}, DOI={10.1061/(ASCE)0733-9437(2006)132:3(250)}, abstractNote={Water quality in the Middle Coastal Plain of North Carolina has been impacted by agriculture; however, the water quality impacts in these areas over time have not been studied in detail. The surface water quality of several streams in the Neuse River Watershed along the Middle Coastal Plain of North Carolina was monitored for approximately five years, while shallow groundwater in cropped fields and adjacent to drainage ditches was monitored for three years. Surface water samples were collected biweekly and analyzed for nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), total Kjeldahl nitrogen, orthophosphate (PO4-P), total phosphate, and total suspended solids, and approximately monthly groundwater samples were collected from wells and analyzed for NO3-N. Trends relating to seasonal changes in stream water quality as a function of land use and soil type were analyzed, as well as long term changes. Generally, upstream sampling points showed low levels of all constituents. Nutrient and sediment concentrations increased along the streams draining the agricultural lands. Trends in surface water quality did not change under row crops, and NO3-N averaged 3.4–4.1mg∕L, while NH4-N averaged 0.1mg∕L. Surface water was impacted dramatically by seepage from an anaerobic swine wastewater lagoon. NO3-N and NH4-N downstream from the seepage plume averaged 1.5 and 12.7mg∕L, respectively. Directly down gradient of the lagoon, groundwater samples averaged 121mg∕L for NH4-N. Groundwater NO3-N concentrations decreased 30–76% due to a reduced zone along many of the ditches. Biomass production in the drainage ditches resulted in substantial amounts of organic nitrogen in the ditches. Surface water nitrate concentration averaged at or above the limit for new wastewater treatment plants on the Neuse River. Groundwater nitrate concentration in the shallow groundwater averaged 4.6–9.3mg∕L; however, in several locations on the farm, groundwater nitrate nitrogen concentration was elevated above the 10mg∕L U.S. Environmental Protection Agency limit for drinking water due to fertilization of crops and pastures. Hurricanes in 1999 flushed nutrients out of the soil profile in areas that were flooded along the river.}, number={3}, journal={Journal of Irrigation and Drainage Engineering}, author={Dukes, M. D. and Evans, R. O.}, year={2006}, pages={250–262} }
 @article{dukes_evans_gilliam_kunickis_2003, title={Interactive effects of controlled drainage and riparian buffers on shallow groundwater qaulity}, volume={129}, DOI={10.1061/(ASCE)0733-9437(2003)129:2(82)}, abstractNote={As a result of recent surface water quality problems in North Carolina, riparian buffers and controlled drainage are being used to reduce the loss of nonpoint source nitrogen from agricultural fields. The effect of controlled drainage and riparian buffers as best management practices to reduce the loss of agricultural nonpoint source nitrogen from the middle coastal plain has not been well documented. The middle coastal plain is characterized by intensive agriculture on sandy soils with deeply incised or channelized streams. A 2-year study was conducted to determine the effectiveness of controlled drainage, riparian buffers, and a combination of both in the middle coastal plain of North Carolina. It was hypothesized that raising the water table near the ditch would enhance nitrate-nitrogen reduction through denitrification. On the sandy soils studied, controlled drainage did not effectively raise the water table near the ditch to a greater degree than observed on the free drainage treatment. Due to random treatment location, the free drainage treatment was installed along a ditch with a shallower impermeable layer compared to the impermeable layer on the controlled drainage treatments (2 m versus 3- to 4-m deep). This resulted in a perched or higher water table on the free drainage treatment. Over 17 storm events, the riparian buffer (free drainage) treatment had an average groundwater table depth of 0.92 m compared to 0.96 and 1.45 m for the combination (riparian buffer and controlled drainage) and controlled drainage treatments, respectively. Nitrate concentration decrease between the field wells and ditch edge wells averaged 29% (buffer only), 63% (buffer and controlled drainage), and 73% (controlled drainage only). Although apparently more nitrate was removed from the groundwater on the controlled drainage treatments, the controlled drainage treatment water table near the ditch was not raised closer to the ground surface compared to the free drainage treatment. Nitrate removal effectiveness was attributed to local soil and landscape properties, such as denitrification in deeper reduced zones of the soil profile.}, number={2}, journal={Journal of Irrigation and Drainage Engineering}, author={Dukes, M. D. and Evans, R. O. and Gilliam, J. W. and Kunickis, S. H.}, year={2003}, pages={82–92} }
 @article{dukes_evans_gilliam_kunickis_2002, title={Effect of riparian buffer width and vegetation type on shallow groundwater quality in the Middle Coastal Plain of North Carolina}, volume={45}, DOI={10.13031/2013.8528}, abstractNote={The effect of riparian buffer width and vegetation type on shallow groundwater quality has not been evaluated
in the Middle Coastal Plain of North Carolina. Four riparian buffer vegetation types and no–buffer (no–till corn and rye
rotation or pasture) were established at 8 and 15 m widths as follows: cool season grass (fescue), deep–rooted grass (switch
grass), forest (pine and mixed hardwood), and native vegetation. Nested groundwater monitoring wells were installed at the
field/buffer edge and the stream edge in the middle of each riparian buffer plot at three depths. Most deep, mid–depth, and
shallow wells were 3.0 m, 1.8 m, and 0.6 m deep from the ground surface to the top of the 0.6 m perforated section, respectively.
Wells were sampled for 23 months beginning July 1998. Although the ditch well nitrate–nitrogen concentrations at the middle
well depth were significantly lower in the 15 m wide plots compared to the 8 m plots over half the monitoring period, extreme
flooding as a result of a hurricane in the middle of the study confounded the results. The effect of vegetation was not significant
at any time, including the no–buffer cropped and fertilized plots. The effect of vegetation was minimized because at the early
stage in the buffer vegetation establishment, vegetative cover and root mass were not fully developed, the hurricane–induced
flooding forced the re–establishment of several vegetation types (forest and fescue), and there was likely some mixing of
groundwater flowing toward the vegetation plots. Establishment of buffers along streams where groundwater flowed away
from the stream did not result in lower groundwater nitrate levels.}, number={2}, journal={Transactions of the ASAE}, author={Dukes, M. D. and Evans, R. O. and Gilliam, J. W. and Kunickis, S. H.}, year={2002}, pages={327–336} }
 @article{dukes_ritter_2000, title={Validation of GLEAMS nutrient component for wastewater application in the Mid-Atlantic region}, volume={74}, ISSN={["0960-8524"]}, DOI={10.1016/S0960-8524(00)00010-9}, abstractNote={The nutrient portion of the Groundwater Loading Effects of Agricultural Management Practices (GLEAMS) model was analyzed under Mid-Atlantic conditions at a municipal wastewater land treatment facility. A sensitivity analysis was performed on soil nitrate concentration and crop nitrogen uptake over model input variables. Input variables having a relatively significant effect on the two outputs of interest were identified for adjustment during model calibration. Calibration was performed in an attempt to adjust model output as closely as possible to measured field data. GLEAMS was not satisfactorily calibrated for Mid-Atlantic conditions. Failure of the model to properly mineralize organic nitrogen was identified.}, number={2}, journal={BIORESOURCE TECHNOLOGY}, author={Dukes, MD and Ritter, WF}, year={2000}, month={Sep}, pages={89–102} }
 @article{dukes_ritter_1998, title={Modeling BMPs to optimize municipal wastewater land treatment system}, volume={124}, number={12}, journal={Journal of Environmental Engineering (New York, N.Y.)}, author={Dukes, M. D. and Ritter, W. F.}, year={1998}, pages={1178–1187} }