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Publications
Publications (127)
Soil testing is the foundation of fertilizer recommendations in the United States. Fertilizer recommendations have primarily been developed by land‐grant universities with limited coordination among programs. The individual state approach to developing fertilizer recommendations has resulted in discrepancies in recommended soil sampling protocols,...
Conservation practices that reduce nutrient and soil loss from agricultural lands to water are fundamental to watershed management programs. Avoiding trade-offs of conservation practices is essential to the successful mitigation of watershed phosphorus (P) losses. We review documented trade-offs associated with conservation practices, particularly...
The Fertilizer Recommendation Support Tool (FRST) will perform correlations between soil nutrient concentrations and crop response to fertilization from user‐selected datasets in the FRST national database. Yield response for the nutrient of interest in a particular site‐year is presented as relative yield (RY), a ratio of unfertilized yield to the...
Soil‐test correlation and calibration data are essential to modern agriculture, and their continued relevance is underscored by the expansion of precision farming and the persistence of sustainable soil management priorities. In support of transparent, science‐based fertilizer recommendations, we seek to establish a core set of required and recomme...
Abstract As part of the Fertilizer Recommendation Support Tool (FRST) project, the FRST database was developed to consolidate and preserve U.S. soil test correlation and calibration data. Legacy phosphorus (P) and potassium (K) soil test data that met a minimum requirement were included in the database. The FRST database initially included over 1,2...
Soil testing is an important practice for nutrient management in agricultural production systems. In the United States, soil‐test methods and interpretations vary across state lines, making institutional collaborations challenging and crop fertilization guidelines inconsistent. Uniformity and transparency in P and K soil fertility testing and ferti...
Phosphorus (P) is essential for optimum agricultural production, but it also causes water quality degradation when lost through erosion (sediment-attached P), runoff (soluble reactive P; SRP), or leaching (sediment-attached P or SRP). Implementation of conservation practices (CP) affects P at the source (avoiding), during transport (controlling), o...
Soil organic matter (SOM) provides many beneficial soil ecosystem services for sustainable soil management, but it is unclear how results from different methods of measuring SOM should be compared when making soil management decisions. To compare different methods, we used 84 soil samples from long-term agronomic trials in the coastal plain, piedmo...
Computer models are commonly used for predicting risks of runoff P loss from agricultural fields by enabling simulation of various management practices and climatic scenarios. For P loss models to be useful tools, however, they must accurately predict P loss for a wide range of climatic, physiographic, and land management conditions. A complicating...
Nitrogen (N) and phosphorus (P) input and export rates were determined in six rural, predominantly agricultural watersheds located in the Piedmont and Coastal Plain regions of North Carolina. Water quality monitoring was conducted at the outlets for 2.3 to 8.0 years to determine the annual N and P export from each watershed. Total N and P input and...
Nitrogen limits crop production when insufficient and harms the environment when excessive. Tailoring N inputs to cropping systems remains a high priority to achieve production and environmental goals. We collected soils from 47 corn (Zea mays L.) production fields in North Carolina and Virginia at depths of 0 to 10, 10 to 20, and 20 to 30 cm and e...
A blended actual and hypothetical vertical ecosystem services stacking scenario is developed for a water quality trading (WQT) program in North Carolina. Demand is estimated for total nitrogen reduction and simulated for total phosphorous reduction. Nitrogen and phosphorus are complementary pollutants jointly produced by a single conservation pract...
Winter wheat (Triticum aestivum L.) field trials were conducted from 2013 to 2015 to evaluate effectiveness of Environmentally Smart Nitrogen (ESN) in two different physiographic regions in North Carolina: Coastal Plain and Piedmont. Trials were designed to (i) determine the effectiveness of ESN alone or in blend with ammonium sulfate compared with...
The Agricultural Policy Environmental eXtender (APEX) model has been widely applied to assess phosphorus (P) loss in runoff water and has been proposed as a model to support practical decisions regarding agricultural P management, as well as a model to evaluate tools such as the P Index. The aim of this study is to evaluate the performance of APEX...
A wide range of mathematical models are available for predicting phosphorus (P) losses from agricultural fields, ranging from simple, empirically based annual time-step models to more complex, process-based daily time-step models. In this study, we compare field-scale P-loss predictions between the Annual P Loss Estimator (APLE), an empirically bas...
Due to a shortage of available phosphorus (P)-loss datasets, simulated data from an accurate quantitative P transport model could be used to evaluate a P Index. The objective of this study was to compare predictions from the Texas Best Management Practice Evaluation Tool (TBET) against measured P-loss data to determine whether the model could be us...
Phosphorus (P) Indices in the southern United States frequently produce different recommendations for similar conditions. We compared risk ratings from 12 southern states (Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas) using data collected from benchmark sites i...
Critical source area identification through phosphorus (P) site assessment is a fundamental part of modern nutrient management planning in the United States, yet there has been only sparse testing of the many versions of the P Index that now exist. Each P site assessment tool was developed to be applicable across a range of field conditions found i...
Over the past 20 yr, there has been a proliferation of phosphorus (P) site assessment tools for nutrient management planning, particularly in the United States. The 19 papers that make up this special section on P site assessment include decision support tools ranging from the P Index to fate-and-transport models to weather-forecast-based risk calc...
To reduce environmental losses of N and increase crop use, it is critical to optimize N fertilization rates and determine if N-loss prevention amendments increase yields. Research objectives were to: (i) determine N-release patterns of three N-loss amendments (urea ammonium nitrate [UAN] treated with NBPT+DCD, nitrapyrin, or an organo-Ca) and UAN t...
Implementation of nutrient management plans should protect the environment, maintain crop productivity, and increase profitability. Nutrient management planning is a complex process requiring planners knowing what resources are available and what needs are to be met. The Natural Resources Conservation Service (NRCS) 590 standard sets the national m...
Water quality trading (WQT) is a popular policy for improving the quality of waterways across the United States by reducing water pollution. However, in established markets, few trades are happening, making environmental gains from WQT limited. Despite these trends, policy makers continue to implement this market-based approach to achieve clean wat...
A promising program to address water contamination from nutrients is water quality trading (WQT), whereby entities with high abatement costs purchase credits from entities with lower abatement costs. The concept has found some success with point source water pollution, but very few trades have occurred in over 50 programs in the United States (U.S....
Reducing the export of nitrogen (N), phosphorus (P), and sediment from agricultural land in water-supply watersheds is a continuing goal in central North Carolina. The objective of this project was to document the effectiveness of a combination of livestock exclusion fencing and nutrient management implemented on a beef cattle pasture located in th...
Agricultural contributions of nitrogen are a serious concern for many water resources and have spurred the implementation of riparian buffer zones to reduce groundwater nitrate (NO). The optimum design for buffers is subject to debate, and there are few long-term studies. The objective of this project was to determine the effectiveness over time (1...
Over half of lakes, reservoirs, and ponds in the United States are threatened or impaired, mostly by nutrients. One policy to improve water quality is water quality trading (WQT). While the concept is appealing, adoption of conservation practices in these programs has been anemic at best. Using a case study in the newly-formed WQT market in Jordan...
Synthetic nitrogen (N) fertilizer has enabled modern agriculture to greatly improve human nutrition during the twentieth century, but it has also created unintended human health and environmental pollution challenges for the twenty-first century. Averaged globally, about half of the fertilizer-N applied to farms is removed with the crops, while the...
Organic agricultural systems are often assumed to be more sustainable than conventional farming, yet there has been little work comparing surface water quality from organic and conventional production, especially under the same cropping sequence. Our objective was to compare nutrient and sediment losses, as well as sweet corn ( L. var. ) yield, fro...
Corn (Zea mays L.) nitrogen (N) rate trials conducted in North Carolina over a recent 10-year time frame (2001-2011) were reviewed to potentially adjust yield goals (realistic yield expectations [RYE]) and their associated N rate recommendations in the North Carolina RYE database. The analyzed trial data provided evidence that corn yields increased...
Lawn management practices that produce aesthetically appealing landscapes may also create environmental conditions that stimulate soil nitrous oxide (N2O) fluxes. The purpose of this exploratory study is to investigate the effects of lawn management practices on N2O fluxes from three non-replicated distinctly different residential landscapes: a hig...
Field testing of the Agricultural Policy/Environmental eXtender (APEX) model has been performed using data for runoff, sediment and P losses from small watersheds (6.8-26 ha) and plots (0.02-0.8 ha) in 8 generalized physiographic regions in 5 southern states. Initial uncalibrated predictions of APEX evidenced that model’s default settings underesti...
Topsoil losses through surface runoff have severe implications for farmers, as well as surrounding ecosystems and waterbodies. However, integrating management systems that enhance soil organic matter (SOM) can stabilize the soil surface from erosion. Little is known about how differences in both tillage and cropping system management affect carbon...
Riparian 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...
To integrate lessons from the U.S. Department of Agriculture (USDA), National Institute of Food and Agriculture–Conservation Effects Assessment Project (NIFA CEAP) program, key informant (KI) interviews were conducted in all 13 project areas. The purpose of these interviews was to supplement technical information about watersheds, their contaminant...
Phosphorus is a major nonpoint source pollutant that causes eutrophication in surface waters. Phosphorus (P) Indices are applied assessment tools used to identify agricultural fields most vulnerable to P loss by accounting for major source and transport factors controlling P movement. There is a wide range in formulation and management recommendati...
Interest in pasture-based pork products has increased significantly in recent years. However, nitrogen (N) losses resulting from these systems are common due to importation of feed, high stocking rates, and pig behavior. This study was conducted to evaluate soil inorganic N, soil-test phosphorus (STP), ground cover, and compaction changes as impact...
Nutrient enrichment of water resources has degraded coastal waters throughout the world, including in the United States (e.g., Chesapeake Bay, Gulf of Mexico, and Neuse Estuary). Agricultural nonpoint sources have significant impacts on water resources. As a result, nutrient management planning is the primary tool recommended to reduce nutrient los...
The Atlantic Coastal Plain region has had a long history of experimental and applied efforts to exclude phosphorus (P) from drainage waters. Early research focusing upon the chemical controls of soil and sediment P has given way to field studies aimed at refining our understanding of hydrologic pathways and sources of P in drainage effluent. To som...
safety, agricultural water use, and groundwater management. These four grand challenge areas were distilled from a listing of over 50 important issues related to agricultural water resource management identified at a workshop of university and government water scientists in November of 2011. Our over
Like many impacted coastal water systems, the Tar‐Pamlico River Basin and Jordan Lake watershed in North Carolina have had environmental rules implemented to reduce nitrogen and phosphorus loadings to their waters. Agriculture's contribution to nutrient loading in both basins was based on models, and no agricultural data were collected before rules...
Relatively narrow (<50 m) riparian buffers strategically reestablished in correct landscape positions have been shown to significantly reduce agricultural non-point source pollution to streams. Because of this, conservation programs have been established to encourage landowners to enroll lands near surface waters to improve water quality. Former cr...
Fertilizer additive products have recently been developed with the intention of reducing phosphate fixation and improving phosphorus plant availability. We conducted two experiments at multiple North Carolina locations from 2007-2009 to evaluate the effects of an organic copolymer phosphorus fertilizer additive, AVAIL Phosphorus Fertilizer Enhancer...
Many states have invested significant resources to identify components of their Phosphorus (P) Index that reliably estimate the relative risk of P loss and incentivize conservation management. However, differences in management recommendations and manure application guidelines for similar field conditions among state P Indices, coupled with minimal...
Forty-eight states in the United States use phosphorus (P) indices to meet the requirements of their Natural Resources Conservation Service (NRCS) Code 590 Standard, which provides national guidance for nutrient management of agricultural lands. The majority of states developed these indices without consultation or coordination with neighboring sta...
The Conservation Effects Assessment Project (CEAP) is an USDA initiative that involves the Agricultural Research Service, the National Institute for Food and Agriculture (NIFA), and the Natural Resources Conservation Service. The overall goal of CEAP is to provide scientifically credible estimates of the environmental benefits obtained from USDA co...
Non-point source pollution from agricultural systems is an ever growing concern and the removal of nitrogen, phosphorus, and sediment from agriculture land is not only crucial to our water quality but to the management and value of our agricultural products. The objective of this study is to compare nutrient and sediment losses, as well as yield, f...
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 near...
Denitrification is a critical biogeochemical process that results in the conversion of nitrate to volatile products, and thus is a major route of nitrogen loss from terrestrial environments. Riparian buffers are an important management tool that is widely utilized to protect water from non-point source pollution. However, riparian buffers vary in t...
Spence, Porchè L., Deanna L. Osmond, Wesley Childres, Joshua L. Heitman, and Wayne P. Robarge, 2012. Effects of Lawn Maintenance on Nutrient Losses Via Overland Flow During Natural Rainfall Events. Journal of the American Water Resources Association (JAWRA) 48(5): 909-924. DOI: 10.1111/j.1752-1688.2012.00658.x
Abstract: A sampling system was used t...
T he overall goals of the Oregon National Institute of Food and Agriculture–Conservation Effects Assessment Project (NIFA–CEAP), Assessing Trade-offs Between Crop Production and Ecological Services, were to quantify linkages between conservation practices and biophysical responses, including water quality and biological indicators, and to develop a...
Long-term application of phosphorus (P) to soils as fertilizer or manure can increase the potential for P loss to ground and surface waters. Vertical P transport was investigated in a sandy soil material receiving seven different P fertilizer sources: poultry compost, poultry litter, triple superphosphate [Ca(H(2)PO(4))(2)center dot H(2)O], dairy l...
Cucumbers require adequate nitrogen (N) for growth and development. This study was undertaken to determine the most effective tillage system and N rate for hand-picked, processing, cucumber (Cucumis sativus L.) production. Three tillage systems and five N fertilizer rates were compared for effects on yield, fertilizer N use efficiency (NUE), and ef...
"Interface" organizations are groups created to foster the use of science in environmental policy, management, and education. Here we compare interface organizations that differ in spatial scale, modes of operation, and intended audience to illustrate their diversity and importance in promoting the application of science to environmental issues. Th...
As natural gas, and thus N fertilizer, prices increase, farmers are looking for ways to decrease N costs in farming operations. To potentially alleviate this cost burden, alternative synthetic N fertilizers are available as potential management tools for increasing crop yields and N use efficiency, and decreasing volatilization. In North Carolina s...
The nitrogen (N) release from coated urea fertilizers (Arborite and ESN), traditional N fertilizers [urea, (NH2)2CO], and urea ammonium nitrate (UAN) [(NH2)2CO, NH4NO3] in three North Carolina (USA) soils was measured throughout a 12-week laboratory incubation. Treatments were N source and moisture level (60% and 80% of field capacity). In both the...
An assessment of the performance of four level spreader-vegetative filter strip (LS-VFS) systems designed to treat urban storm-water runoff was undertaken at two sites in the Piedmont of North Carolina. At each site, a 7.6-m grassed filter strip and a 15.2-m half-grassed, half-forested filter strip were examined. Monitored parameters included rainf...
While P sorption in mineral soils has been extensively studied, P sorption behavior in organic-rich soils is less known. This study was conducted to determine the relationships between Langmuir P sorption maxima (S{sub max}) and selected physicochemical properties of soils, with particular emphasis on organic matter (OM) content. The S{sub max} val...
Riparian buffers can be valuable refuge areas for wildlife in otherwise homogeneous agricultural landscapes. Government sponsored programs like the Cropland Reserve Program generally require the planting of specifi c vegetative spe-cies during buffer restoration, although the effectiveness of such an approach when compared to restoration by volunte...
Phosphorus from agricultural lands poses a problem in water resources. In 2003, more than 48% of soil samples submitted to the North Carolina Department of Agriculture and Consumer Services (NCDA&CS) soil testing laboratory tested very high in soil P (> 20 mg dm(-3) P). As soil test P increases, off-site P loss increases, through erosion, soluble P...
Phosphorus (P) regulations in North Carolina (NC) assume that organic soils have little ability to retain P, and losses of P from these soils are of concern for the health of aquatic ecosystems. However, recent research has indicated decreased water-soluble P (WSP) in organic soils in the presence of high Al concentrations. Our objectives were to d...
Slow release N fertilizers have potential to improve yield and nitrogen use efficiency (NUE) in winter wheat (Triticum aestivum L.) and maize (Zea mays L.). A slow release urea formaldehyde polymer (UFP) was compared with aqueous urea ammonium nitrate (UAN) [(NH2)2CO, NH 4NO3] during a 2-yr field experiment in North Carolina. Crops were grown on Ca...