About

Jennifer Weld is an Assistant Research Professor and the Director of PAOneStop at the Department of Ecosystem Science and Management at Pennsylvania State University. She holds a B.S. from Cornell University, an M.S. and a Ph.D.. from Penn State. Her areas of expertise include agricultural erosion and sedimentation planning, farm mapping, phosphorus cycling and management, and nutrient management planning. Her academic appointment involves a combination of extension, teaching, and administrative responsibilities, with courses such as Environmental Geographic Information Systems and Case Studies in Ecosystem Management. Her research contributions focus on improving the understanding and simulation of phosphorus loss in agricultural landscapes, nutrient management, and hydrological modeling, with a particular emphasis on phosphorus dynamics and environmental quality.

Research topics

• Environmental science
• Agronomy
• Business
• Environmental resource management
• Water resource management

Selected publications

• Analyzing Within‐County Hydrogeomorphological Characteristics as a Precursor to Phosphorus Index Modifications

  Journal of Environmental Quality · 2017-08-10 · 6 citations

  articleOpen access

  Phosphorus (P) site assessment is used nationally and internationally to assess the vulnerability of agricultural fields to P loss and identify high-risk areas controlling watershed P export. Current efforts to update P site assessment tools must ensure that these tools are representative of the range of conditions to which they will be applied. We sought to identify key parameters available in public GIS data that are descriptive of potential source areas in Pennsylvania and that ensure that modifications of the P Index span all feasible parameter combinations. Relevant soil and topographic variables were compiled for Pennsylvania at 30-m resolution, and areas within 90 m of permanent streams were extracted. Within each county, -means and classification trees were used to identify and create classification rules for topoedaphic groups. Within counties, two to five groups adequately represented near-stream complexity, with available water capacity, hydraulic conductivity, and organic matter being the most important environmental variables. Discontinuities across soil survey boundaries made it impossible to develop clusterings beyond the county level. For county-scale research and management efforts, these groupings provide a manageable approach to identifying representative sites for near-stream agricultural lands. The full set of representative sites across the state enables evaluation of the P Index throughout the full hydrogeomorphic diversity of Pennsylvania. In future work, we can then combine a set of reasonable management practices with each of the main hydrogeomorphological regions resulting from this study and verify the revised P Index against expert knowledge and simulation results.

  PublisherDOI

• Evaluation of Phosphorus Site Assessment Tools: Lessons from the USA

  Journal of Environmental Quality · 2017-08-03 · 51 citations

  articleOpen accessSenior authorCorresponding

  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 in a given geographic area, making evaluation extremely difficult. In general, evaluation with in-field monitoring data has been limited, focusing primarily on corroborating manure and fertilizer "source" factors. Thus, a multiregional effort (Chesapeake Bay, Heartland, and Southern States) was undertaken to evaluate P Indices using a combination of limited field data, as well as output from simulation models (i.e., Agricultural Policy Environmental eXtender, Annual P Loss Estimator, Soil and Water Assessment Tool [SWAT], and Texas Best Management Practice Evaluation Tool [TBET]) to compare against P Index ratings. These comparisons show promise for advancing the weighting and formulation of qualitative P Index components but require careful vetting of the simulation models. Differences among regional conclusions highlight model strengths and weaknesses. For example, the Southern States region found that, although models could simulate the effects of nutrient management on P runoff, they often more accurately predicted hydrology than total P loads. Furthermore, SWAT and TBET overpredicted particulate P and underpredicted dissolved P, resulting in correct total P predictions but for the wrong reasons. Experience in the United States supports expanded regional approaches to P site assessment, assuming closely coordinated efforts that engage science, policy, and implementation communities, but limited scientific validity exists for uniform national P site assessment tools at the present time.

  PublisherOA PDFDOI

• Nutrient management planners' feedback on New York and Pennsylvania phosphorus indices

  Journal of Soil and Water Conservation · 2016-07-01 · 11 citations

  articleOpen access

  State phosphorus indices (PIs) are being evaluated across the United States due to variability in phosphorus (P) management recommendations and questions about the lack of water quality improvement in some watersheds. Nutrient management planners in New York (NY) and Pennsylvania (PA) were surveyed via two separate “but related” questionnaires to document perspectives on the current NY-PI and PA-PI and to obtain recommendations for improvements. Many planners were content with the current versions of the PIs but felt improvements could be made to more strongly discourage application of manure under conditions of high P loss potential and better promote certain best management practices. The NY planners felt that the NY-PI should discourage manure application during winter and to fields near streams, and should more strongly promote manure incorporation or injection, establishment of cover crops, ground coverage with crop residues, and implementation of setbacks and vegetated buffers. Similarly, the PA planners felt that the PA-PI should more strongly discourage manure application to fields with insufficient ground cover, near subsurface drainage and surface inlets, and during winter. In addition, the PA planners said the PA-PI should more strongly encourage soil conservation practices such as no-till, use of cover crops, and vegetated buffers. Results of the survey suggest common experiences and viewpoints among planners in NY and PA, resulting in a valuable on-the-ground assessment of the PIs as a nutrient management planning tool in both states, and the potential for development of a single, physiographic region PI.

  PublisherOA PDFDOI

• Improved Simulation of Edaphic and Manure Phosphorus Loss in SWAT

  Journal of Environmental Quality · 2016-04-22 · 49 citations

  articleOpen access

  Watershed models such as the Soil Water Assessment Tool (SWAT) and the Agricultural Policy Environmental EXtender (APEX) are widely used to assess the fate and transport of agricultural nutrient management practices on soluble and particulate phosphorus (P) loss in runoff. Soil P-cycling routines used in SWAT2012 revision 586, however, do not simulate the short-term effects of applying a concentrated source of soluble P, such as manure, to the soil surface where it is most vulnerable to runoff. We added a new set of soil P routines to SWAT2012 revision 586 to simulate surface-applied manure at field and subwatershed scales within Mahantango Creek watershed in south-central Pennsylvania. We corroborated the new P routines and standard P routines in two versions of SWAT (conventional SWAT, and a topographically driven variation called TopoSWAT) for a total of four modeling "treatments". All modeling treatments included 5 yr of measured data under field-specific, historical management information. Short-term "wash off" processes resulting from precipitation immediately following surface application of manures were captured with the new P routine whereas the standard routines resulted in losses regardless of manure application. The new routines improved sensitivity to key factors in nutrient management (i.e., timing, rate, method, and form of P application). Only the new P routines indicated decreases in soluble P losses for dairy manure applications at 1, 5, and 10 d before a storm event. The new P routines also resulted in more variable P losses when applying manure versus commercial fertilizer and represented increases in total P losses, as compared with standard P routines, with rate increases in dairy manure application (56,000 to 84,000 L ha). The new P routines exhibited greater than 50% variation among proportions of organic, particulate, and soluble P corresponding to spreading method. In contrast, proportions of P forms under the standard P routines varied less than 20%. Results suggest similar revisions to other agroecosystem watershed models would be appropriate.

  PublisherOA PDFDOI

• Phosphorus and nitrogen losses from poultry litter stacks and leaching through soils

  Nutrient Cycling in Agroecosystems · 2015-09-01 · 6 citations

  article
  PublisherDOI

• Predicting phosphorus dynamics in complex terrains using a variable source area hydrology model INTRODUCTION

  2015-01-01

  article

• Predicting phosphorus dynamics in complex terrains using a variable source area hydrology model

  Hydrological Processes · 2014-02-24 · 62 citations

  article

  Phosphorus (P) loss from agricultural watersheds has long been a critical water quality problem, the control of which has been the focus of considerable research and investment. Preventing P loss depends on accurately representing the hydrological and chemical processes governing P mobilization and transport. The Soil and Water Assessment Tool (SWAT) is a watershed model commonly used to predict run-off and non-point source pollution transport. SWAT simulates run-off employing either the curve number (CN) or the Green and Ampt methods, both assume infiltration-excess run-off, although shallow soils underlain by a restricting layer commonly generate saturation-excess run-off from variable source areas (VSA). In this study, we compared traditional SWAT with a re-conceptualized version, SWAT-VSA, that represents VSA hydrology, in a complex agricultural watershed in east central Pennsylvania. The objectives of this research were to provide further evidence of SWAT-VSA's integrated and distributed predictive capabilities against measured surface run-off and stream P loads and to highlight the model's ability to drive sub-field management of P. Thus, we relied on a detailed field management database to parameterize the models. SWAT and SWAT-VSA predicted discharge similarly well (daily Nash–Sutcliffe efficiencies of 0.61 and 0.66, respectively), but SWAT-VSA outperformed SWAT in predicting P export from the watershed. SWAT estimated lower P loss (0.0–0.25 kg ha−1) from agricultural fields than SWAT-VSA (0.0–1.0+ kg ha−1), which also identified critical source areas – those areas generating large run-off and P losses at the sub-field level. These results support the use of SWAT-VSA in predicting watershed-scale P losses and identifying critical source areas of P loss in landscapes with VSA hydrology. Copyright © 2014 John Wiley & Sons, Ltd.

  PublisherDOI

• Profile of the Equine Industry's Environmental, Best Management Practices and Variations in Pennsylvania

  Journal of Equine Veterinary Science · 2011-05-01 · 6 citations

  article
  PublisherDOI

• Horse Manure and Bedding Disposal Practices, Variations and Magnitude

  Journal of Equine Veterinary Science · 2009-05-01 · 2 citations

  article
  PublisherDOI

• Integrating Contributing Areas and Indexing Phosphorus Loss from Agricultural Watersheds

  Journal of Environmental Quality · 2008-06-23 · 40 citations

  article

  Most states in the USA have adopted P Indexing to guide P-based management of agricultural fields by identifying the relative risk of P loss at farm and watershed scales. To a large extent, this risk is based on hydrologic principles that frequently occurring storms can initiate surface runoff from fields. Once initiated, this hydrological pathway has a high potential to transport P to the stream. In regions where hydrologically active areas of watersheds vary in time and space, surface runoff generation by "saturation excess" has been linked to distance from stream, with larger events resulting in larger contributing distances. Thus, storm-return period and P loss from a 39.5-ha mixed-land-use watershed in Pennsylvania was evaluated to relate return-period thresholds and distances contributing P to streams. Of 248 storm flows between 1997 and 2006, 93% had a return period of 1 yr, contributing 47% of total P (TP) export, while the largest two storms (10-yr return period) accounted for 23% of TP export. Contributing distance thresholds for the watershed were determined (50-150 m) for a range of storm-return periods (1-10 yr) from hydrograph analysis. By modifying storm-return period thresholds in the P Index and thereby contributing distance, it is possible to account for greater risk of P loss during large storms. For instance, increasing return period threshold from 1 (current P indices) to 5 yr, which accounted for 67% of TP export, increased the P-management restricted area from 20 to 58% of the watershed. An increase in impacted area relative to a decreased risk of P loss creates a management-policy dilemma that cannot be ignored.

  PublisherDOI

Frequent coauthors

• Peter J. A. Kleinman

  Agricultural Research Service

  19 shared

• Andrew N. Sharpley

  University of Arkansas at Fayetteville

  17 shared

• D. B. Beegle

  Pennsylvania State University

  8 shared

• Douglas B. Beegle

  Pennsylvania State University

  6 shared

• Tamie L. Veith

  6 shared

• William J. Gburek

  5 shared

• Ray B. Bryant

  Agricultural Research Service

  5 shared

• Zachary M. Easton

  4 shared

Education

• Ph.D., Soil Science

  University of California, Berkeley

  2006

• M.S., Soil Science

  University of California, Berkeley

  2001

• B.S., Soil Science

  University of California, Davis

  1998