Education

Research Description

Ground water, water quality and hydrology

Honors and Awards

• ASABE President's Citation, 2009
• PEI Professional Engineer of the Year, 2010
• BAE Outstanding Teaching Award, 2011
• ASABE Certificate of Appreciation, 2012
• BAE Outstanding Teacher Award, 2015

Publications

Water Conservation Potential of Smart Irrigation Technologies in the Catawba-Wateree River Basin

Vick, R. L., Grabow, G. L., Miller, G. L., & Huffman, R. L. (2017), JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING, 143(2). https://doi.org/10.1061/(asce)ir.1943-4774.0001130

Residential Irrigation Water Use in the Central Piedmont of North Carolina. I: Measured Use and Water Requirements

Nautiyal, M., Grabow, G. L., Huffman, R. L., Miller, G. L., & Bowman, D. (2015), JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING, 141(4). https://doi.org/10.1061/(asce)ir.1943-4774.0000819

Residential Irrigation Water Use in the Central Piedmont of North Carolina. II: Evaluation of Smart Irrigation Technologies

Nautiyal, M., Grabow, G. L., Huffman, R. L., Miller, G. L., & Bowman, D. (2015), JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING, 141(4). https://doi.org/10.1061/(asce)ir.1943-4774.0000820

Water Application Efficiency and Adequacy of ET-Based and Soil Moisture-Based Irrigation Controllers for Turfgrass Irrigation

Grabow, G. L., Ghali, I. E., Huffman, R. L., Miller, G. L., Bowman, D., & Vasanth, A. (2013), JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING, 139(2), 113–123. https://doi.org/10.1061/(asce)ir.1943-4774.0000528

Factors affecting uniformity of irrigation-type manure application systems

Liu, Z., Grabow, G. L., Huffman, R. L., Osborne, J., & Evans, R. O. (2012), Applied Engineering in Agriculture, 28(1), 43–56. https://doi.org/10.13031/2013.41285

Using Variability within Digital Images to Improve Tall Fescue Color Characterization

Ghali, I. E., Miller, G. L., Grabow, G. L., & Huffman, R. L. (2012), CROP SCIENCE, 52(5), 2365–2374. https://doi.org/10.2135/cropsci2011.10.0553

Linking plant ecology and long-term hydrology to improve wetland restoration success

Caldwell, P. V., Vepraskas, M., Gregory, J. D., Skaggs, R. W., & Huffman, R. L. (2011), Transactions of the ASABE, 54(6), 2129–2137. https://doi.org/10.13031/2013.40662

Residential Irrigation and Water Conservation Potential of Smart Irrigation Technologies in the Catawba River Basin

Vick, Jr., R. L., Grabow, G. L., Huffman, R. L., & Miller, G. L. (2011), World Environmental and Water Resources Congress 2011. Presented at the World Environmental and Water Resources Congress 2011. https://doi.org/10.1061/41173(414)282

SDI Dripline Spacing Effect on Corn and Soybean Yield in a Piedmont Clay Soil

Grabow, G. L., Huffman, R. L., & Evans, R. O. (2011), JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING, 137(1), 27–36. https://doi.org/10.1061/(asce)ir.1943-4774.0000277

Leaching of Nutrients and Trace Elements from Stockpiled Turkey Litter into Soil

Shah, S. B., Hutchison, K. J., Hesterberg, D. L., Grabow, G. L., Huffman, R. L., Hardy, D. H., & Parsons, J. T. (2009), JOURNAL OF ENVIRONMENTAL QUALITY, 38(3), 1053–1065. https://doi.org/10.2134/jeq2007.0639

View all publications via NC State Libraries

Grants

Water Use Efficiency of Soil-Water-Sensor-Controlled Irrigation with a Subsurface Drip Irrigation System Contrasted with Center Pivot Irrigation in a Corn-Wheat-Soybean Crop Rotation

NC Soybean Producers Association, Inc.(3/01/11 - 11/30/14)

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Water Use Efficiency of Soil-Water-Sensor-Controlled Irrigation with a Subsurface Drip Irrigation System Contrasted with Center Pivot Irrigation in a Corn-Wheat-Soybean Crop Rotation

Sponsor: NC Soybean Producers Association, Inc.

Start Date: 3/01/11

End Date: 11/30/14

Abstract

Recurring drought in North Carolina has resulted in a need to increase water use efficiency in irrigated agriculture. The goals of the proposed research are to evaluate how well a commercially installed SDI system performs in a corn-winter wheat- soybean crop rotation, and to compare its relative performance to a center pivot system and a dryfarmed system. The objectives of the research to accomplish this goal are to: ? Compare crop yields in the two irrigation systems (SDI and pivot) ? Compare applied water and irrigation water use efficiencies of the two irrigation systems ? Implement and evaluate sensor-controlled irrigation in an SDI system ? Compare sensor-controlled scheduling to typical scheduling in terms of applied water and crop yield in an SDI irrigation system. ? Measure soil-water distribution from SDI driplines in a sandy loam soil to infer potential alternative dripline spacings An SDI system will be installed this fall or winter in Robeson County, North Carolina, using funds received from a conservation innovation grant (CIG). The soils located in the fields proposed for research include Nahunta very fine sandy loam, Trebloc loam, Aycock very fine sandy loam, and Exum very fine sandy loam. The production system is no-till with a corn-winter wheat-soybean crop rotation. A center pivot irrigation system was recently installed on the farm and the SDI system will be installed on land immediately adjacent to the pivot-irrigated land. The SDI system will irrigate approximately 25 acres immediately adjacent to the existing center pivot irrigation system, and both SDI and center pivots fields will be planted to the same crop. Corn will be planted in spring 2011, followed by wheat planted behind corn in September and harvested in May 2012. Soybeans will be planted in June 2012 and harvested in December 2012, and corn planting would follow in spring 2013. Funds received for research proposed herein will be used to monitor and control the SDI system, monitor soil water in the SDI, pivot and unirrigated fields, and to compare all three systems (SDI, pivot, unirrigated) with respect to crop yield, irrigation water use, and water use efficiency. Two irrigation water management strategies will be compared in the SDI system. One zone will be scheduled to apply 0.20 inch of water daily, but will use feedback from soil-moisture sensors to override the scheduled irrigation if soil moisture is sufficient. The other SDI system zone will be scheduled to apply the gross long-term irrigation requirements by crop growth stage. The center pivot system will also be scheduled to apply the long-term irrigation requirement by crop growth stage and will differ in applied water from the similarly scheduled SDI zone only by the difference in irrigation system efficiency. Weekly applied water will be compared between both SDI zones (irrigation treatments) and the center pivot. Fertilizer will be injected in both the drip and pivot systems at rates according to realistic yield expectations for the particular crop irrigated and soil type. Soil-moisture sensors will be used not only to control irrigation in one SDI zone, but to monitor soil-moisture in the other SDI zone, on the pivot irrigated field, and in the unirrigated field. In the SDI field, sensors will be placed at various distances and depths from the drip line to characterize water distribution from an SDI dripline in a fine sandy loam soil.

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Catawba River Basin Residential Irrigation Water Conservation Study

Duke Energy Carolinas, LLC (Duke Power)(2/10/09 - 3/31/12)

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Catawba River Basin Residential Irrigation Water Conservation Study

Sponsor: Duke Energy Carolinas, LLC (Duke Power)

Start Date: 2/10/09

End Date: 3/31/12

Abstract

NC State University is proposing to lead a water use study on Duke Energy lakes in the Catawba River Basin. The study will establish an estimate of water withdrawals by homeowners bordering the lake through installation of water meters at 36 properties during phase I of the study. Additional information about water use practices will be obtained through a survey instrument designed by NC State. Long-term estimates of irrigation water requirements will be generated using existing long-term data from local weather stations, and weather stations will be deployed at project lakes to estimate irrigation water requirements over the course of the study. During Phase II, two groups of cooperating homeowners will receive two types of ?smart? irrigation control technologies. One type of technology is weather based and the other is soil-moisture sensor based. A third group of homeowners will receive educational material and guidance on programming their existing irrigation controller and a fourth group will receives no intervention other than water use monitoring. Soil moisture will be recorded in all homes that receive the smart technologies. Weekly and seasonal water use of all groups will be compared between all four groups. Water use of the four groups will all be compared against irrigation requirements as estimated from the weather stations deployed at the Duke Energy lakes. Study results will be used to quantify the potential reduction of water withdrawals from the use of smart irrigation technologies, and an educational campaign aimed at property owners along Duke Energy lakes. Typical water withdrawal patterns (both current patterns and patterns associated with efficient irrigation management) will be used to evaluate the potential water savings.

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Historic Irrigation Water Use and Evaluation of two SMART Irrigation Technologies in the Town of Cary, NC

Cary, NC(12/01/08 - 5/31/10)

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Historic Irrigation Water Use and Evaluation of two SMART Irrigation Technologies in the Town of Cary, NC

Sponsor: Cary, NC

Start Date: 12/01/08

End Date: 5/31/10

Abstract

So-called ?Smart? Controllers and technologies hold promise for water conservation in urban settings. These technologies can be grouped into two basic categories; those that use weather data to estimate turf water use and replace that lost to evapotranspiration (ET) -generically called ET controllers - and those that use soil-moisture sensors to regulate irrigation. ET controllers have been tested in researched more than the sensor-based technologies, however most previous testing and research have not been done in the conditions of the southeastern United States nor have been done in typical operating conditions. The major objectives of this study are to -Quantify historic irrigation water use in Cary -Evaluate the performance of two types of smart controllers in a homeowner setting and contrast water use with a control group and against historical water usage Historical irrigation water use data from a sample of 120 homes will be collected to establish historic baseline water use rates. Estimated water requirements for the same period will be calculated used local weather data. This will help establish potential savings by "smart" controllers. Homeowner sites with in-ground irrigation systems will be selected to deploy two types of "smart" irrigation technologies (6 sites each); to receive educational information and guidance in programming existing controllers (6 sites); and finally 6 sites will be chosen as control sites (no intervention but having city required rain sensors). All selected sites would receive an irrigation audit to determine uniformity and system water application rate. All systems will be monitored for weekly water use and for turf health. Statistical analysis will be used to evaluate differences in average weekly water use for the different groups. Local weather data will be used to compare applied water to the estimated water requirements of turf.

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Multi-scale Analysis of Mechanisms and Impact of Phosphorus Mobilization in Wetland Soils Created from Drained Agricultural Fields

US Dept. of Agriculture (USDA)(9/01/09 - 8/31/13)

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Multi-scale Analysis of Mechanisms and Impact of Phosphorus Mobilization in Wetland Soils Created from Drained Agricultural Fields

Sponsor: US Dept. of Agriculture (USDA)

Start Date: 9/01/09

End Date: 8/31/13

Abstract

The goal of this research is to determine the cause and extent of phosphorus dissolution from restored wetland soils, particularly organic soils, and to make a regional assessment of whether wetland restoration activities will actually impair water quality (through P release) rather than improve it. By studying a large restored site, we will determine: 1) the magnitude of P released to surface waters, 2) the mechanisms by which it is released, and 3) the areal extent of surface waters that may be impacted by P released from similar restored wetlands. Work will be conducted in a Carolina Bay wetland that was previously drained for agriculture, but has now been restored into a wetland. The interdisciplinary research team has studied the soils, hydrology, and plants at this wetland for 5 years prior to its restoration. This research will build on that done earlier to evaluate the impacts of the restoration. Knowledge of the chemical processes controlling P dissolution in soils will be applied toward developing a way to predict reductive dissolution of P from a given soil. This will increase the probability of success for other wetland restoration efforts throughout the southeastern U.S through judicious selection of land for wetland restoration.

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Conservation Reserve Enhancement Program (CREP) Riparian Buffer Monitoring

NC Dept. of Natural & Cultural Resources formerly NC Dept of Env. & Natural Resources (DENR)(1/01/08 - 8/31/11)

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Conservation Reserve Enhancement Program (CREP) Riparian Buffer Monitoring

Sponsor: NC Dept. of Natural & Cultural Resources formerly NC Dept of Env. & Natural Resources (DENR)

Start Date: 1/01/08

End Date: 8/31/11

Abstract

High priority has been placed on protecting riparian buffers based on prior research that indicate that buffers are generally effective in reducing nutrient and sediment inputs to streams from upland sources, such as agriculture. Because of their effectiveness and sustainability, the N.C. Conservation Reserve Enhancement Program (CREP) intended to provide landowner incentives to establish these buffers to improve water quality and habitat in four targeted watersheds (Chowan, Neuse, and Tar-Pamlico River Basins, and the Jordan Lake watershed). Much is currently known about treatment of pollutants through buffers, and for the most part, we understand how to implement them to achieve some level of water quality benefit. However, with the economic implications of removing lands from agricultural production or from development in the name of water quality protection, it is of utmost importance that we strive to implement these systems properly with an improved understanding of such elements as width, hydrology, and soils. Within the next three years, the objectives of our multi-disciplinary team are to: 1. Produce a multi-year (5-12 years depending on the site) assessment of the water quality benefits of four distinctive riparian buffers (three enrolled in CREP in the Tar-Pamlico watershed, 1 at CEFS located within the Neuse target watershed) 2. Enhance the field of riparian buffer research by contributing to the understanding of the complex factors (hydrology, geology, soils, topography, etc.) that determine how well these areas transform and remove pollutants (particularly nitrate-nitrogen) in groundwater before discharging into streams or canals. 3. Incorporate data collected from the sites on geology, soils, hydrology, groundwater and surface water chemistry, topography, and vegetation into existing models or models under development to make long term predictions of the effect of these buffers on water quality improvement 4. Conclude 2-yr analysis to determine how buffer size and shape (which is expressed by a perimeter to area ratio value) and landscape context affect bird occupancy of buffers and the productivity of five focal bird species nesting in the buffers. 5. Continue to assist CREP staff in determining appropriate water quality criteria to apply to future enrollments

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A Rapid Assessment Tool For Determining Uniformity of Irrigation-Type Animal Waste Land Application Systems

NC Pork Council(7/01/07 - 9/30/09)

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A Rapid Assessment Tool For Determining Uniformity of Irrigation-Type Animal Waste Land Application Systems

Sponsor: NC Pork Council

Start Date: 7/01/07

End Date: 9/30/09

Abstract

The objective of this proposal is to develop a rapid uniformity assessment tool for irrigation-type land application equipment used in land application of swine waste. In order to accomplish this, several easily obtainable hydraulic measurements will be correlated to application uniformity. These measurements will include sprinkler or big gun operating pressure, sprinkler wetted diameter and lane (or sprinkler) spacing. Information will be gathered from three sources: previously done work that evaluated application uniformity in traveling guns and solid set sprinkler systems, controlled field trials at the Lake Wheeler Land Application and Demonstration Facility, and field trials at cooperating animal facilities. Several combinations of the factors measured will be correlated against uniformity as measured by the traditional catch can method. The measurements will be taken on traveling gun systems and stationary systems. The North Carolina Swine industry will benefit from the development of this tool through savings of time and human resources associated with measuring system uniformity by the catch can method. The catch can method is currently required as part of the 1217 guidance document, and is to be performed once every three years. If an alternate method, such as the one proposed, proves to be a good predictor of uniformity there is a strong possibility that the guidance may be changed to allow the easier method. The proposed method will also help determine if a system is operating correctly or is in need of maintenance or operational changes. An easily performed measurement of application uniformity will ensure that crops receiving animal waste receive nutrients uniformly, and that the environment is protected.

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Methodology to Assess Vegetation, Hydrologic, and Soil Parameters That Affect Wetland Restoration

NC Department of Transportation(8/01/07 - 6/30/09)

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Methodology to Assess Vegetation, Hydrologic, and Soil Parameters That Affect Wetland Restoration

Sponsor: NC Department of Transportation

Start Date: 8/01/07

End Date: 6/30/09

Abstract

Wetland restoration is a multimillion-dollar industry in North Carolina that has developed in response to state and federal laws. The most common way wetlands are restored in NC is to plug ditches in a field that was drained for agriculture, then plant trees found in a target natural wetland nearby, and let nature take its course. Failures are common because the hydrology needed for the plant communities to grow is not known, and so restored areas are frequently either too dry or too wet (ponded) for the planted vegetation to survive. In addition, some restored wetlands may be releasing phosphorus to nearby surface waters, and thereby inadvertently causing algae blooms in some areas. Algae blooms have led to fish kills in some areas. This study will find out how well four kinds of trees grow in soils that are ponded with water for different periods of time. The plants and ponding regimes were selected based on a prior study that showed pond pine trees are found in soils that pond for 14 days or less each year, while bay trees as well as baldcypress trees grow well in soils ponded for over 100 days each year. In the greenhouse, pond pine, baldcypress, sweet bay, and swamp chestnut oak trees will be grown in pots that are kept under ponding regimes ranging from 110 days to no ponding. Tree height and diameter will be measured weekly to assess growth, and photosynthetic rates will be measured as well. The effect of ponding on root growth will also be examined. In the field, similar tree species will be grown in a restored wetland to assess growth rates and survivability in ponded soils. Trees will be grown both on flat ground and raised beds to determine if bedding will increase a tree?s chance of surviving long-term ponding. In addition, we will monitor the phosphorus levels in the ground waters in the wetland as well as in surrounding areas, and also monitor phosphorus concentrations in a stream near the site. Previous laboratory experiments suggested that some phosphorus will be leaving the site, particularly where the organic soils are found. This is in part due chemical reactions occurring in the restored wetland soils that dissolve the phosphorus that remains in the soils that were heavily fertilized when used for agriculture. We hope this study will determine which trees grow best in wetlands that will be ponded with water for long (100 days or more) each year. These results will be used by wetland ecologists to select trees for their wetland restoration projects. We will also determine how much phosphorus is leaving the restoration site. Should the amounts be significant, we will also propose remediation methods that can be used to protect downstream waters from algae blooms and fish kills.

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Comparing Environmental Impacts and Agronomic Performance of a Subsurface Drip Irrigation System and a Traditional Spray System used for Land Application of Animal Waste

NCSU Animal and Poultry Waste Management Center(7/01/06 - 6/30/09)

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Comparing Environmental Impacts and Agronomic Performance of a Subsurface Drip Irrigation System and a Traditional Spray System used for Land Application of Animal Waste

Sponsor: NCSU Animal and Poultry Waste Management Center

Start Date: 7/01/06

End Date: 6/30/09

Abstract

Land application of animal manure (herein referred to as wastewater) is a common practice in North Carolina. Typical application methods include the use of hard hose traveling systems with big gun sprinklers, solid set sprinkler systems, and center pivot systems. Recently, hose drag systems have been increasingly used. Even with alternative treatment systems to the lagoon-sprayfield system, liquid waste streams will still need land application. New methods that reduce ammonia emissions and odor, and enhance agronomic value of treated wastewater need to be evaluated. One such method is application through a subsurface drip irrigation (SDI) system. The objectives of this study are 1) to evaluate the technical feasibility of applying animal (swine) wastewater through an SDI system, including operational requirements of an appropriate filtration system and comparison to traditional spray irrigation, and 2) to assess the beneficial environmental impact of an SDI system compared to the traditional method. In order to meet these objectives, a subsurface drip irrigation (SDI) system will be installed in North Carolina in a small field adjacent to a swine lagoon. Wastewater from the lagoon will be land applied through the SDI system. Wastewater will also be applied through a solid set sprinkler system (aluminum pipe with sprinklers on risers) to contrast with SDI impacts, and to contrast yields. Soil sampling will be performed prior to land application and at the end of the study period. Soil samples will be analyzed to infer movement of phosphorus (P). The analytes will be soluble P, Mehlich-3 P, and percent soil saturation with P. Soil water samplers will be installed and used to sample for total P and chloride. Ammonia volatilization will be characterized by surface sampling. Soil moisture sensors will be used to monitor wastewater movement from the drip lines.

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Methodology to Assess Soil, Hydrologic, and Site Parameters that Affect Wet Restoration

NC Department of Transportation(7/01/03 - 6/30/07)

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Methodology to Assess Soil, Hydrologic, and Site Parameters that Affect Wet Restoration

Sponsor: NC Department of Transportation

Start Date: 7/01/03

End Date: 6/30/07

Abstract

Restored wetlands must perform the hydrologic, biogeochemical, and plant community functions that are found in natural wetlands. Limited assessment of those functions is normally conducted in accordance with Corps permits that specify monitoring of certain parameters of hydrology, hydric soil indicators, and plant community structure. While wetlands may perform many ecological functions, the likelihood of their occurrence can be estimated by monitoring key soil and hydrologic properties. In current wetland restoration practice, there is often a lack of detailed pre- and post-restoration monitoring and assessment that documents the progress of the recovery of wetland functions on restoration sites. This leads to conflicts between agencies creating wetlands and those regulating them, and delays issuance of permits until the regulatory agencies are certain the restoration efforts will be successful. Research Objectives 1. Document the variability in the properties of soils and sediments and the water table regime across Juniper Bay and the reference bay that will affect restoration success. 2. Determine current groundwater flow paths and water table regime both inside and outside Juniper Bay, and identify a strategy for hydrologic restoration. 3. Assess the recovery rate of key hydrologic, biogeochemical, and plant community functions that are necessary for a sustainable wetland ecosystem. 4. Assess the usefulness of reference ecosystems for defining required hydrologic and soils factors and target vegetation composition necessary for long-term restoration success. 5. Identify soil chemical and physical properties and hydrologic requirements for optimum growth of Carolina Bay vegetation. 6. Test different restoration methodologies for establishing tree species in the restored site.

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