About

Professor Ray Weil is an internationally recognized expert on soil science, nutrient cycling, soil organic matter, and cover crop systems for soil health and water quality. His methods for soil microbial biomass and active carbon (POXC) are adopted by USDA/NRCS and researchers worldwide. His research on multi-purpose cover crops and ecological approaches to soil management is used by landscape managers and farms, large and small. He has advised on food security and soil management in Africa and other developing regions. Weil teaches undergraduate and graduate courses in soil science, soil fertility, and sustainable agriculture, and has developed and taught courses such as Soil and Environmental Quality, Fundamentals of Soil Science, Principles of Soil Fertility, Issues in Sustainable Agriculture, and Advanced Soil-Plant Relationships. His program at the University of Maryland integrates teaching, extension, and research, aiming to benefit all three. Weil's research focuses on organic matter management for soil health, sustainable farming systems, and soil management for improved nutrient cycling and water quality, with a particular emphasis on cover crop management. He has contributed significantly to promoting sustainable agricultural practices and ecological soil management, and his textbook, The Nature and Properties of Soils, is the most widely used soils textbook in the US and around the world.

Research topics

• Agronomy
• Environmental science
• Economics
• Biology
• Business
• Mathematics
• Agricultural economics
• Ecology
• Finance
• Economic growth
• Chemistry

Selected publications

• Assessing the topographic distribution of legacy soil phosphorus in agricultural fields of the Delmarva Peninsula, Mid‐Atlantic Coastal Plain, USA

  Journal of Environmental Quality · 2025-11-29

  articleOpen access

  Abstract Phosphorus (P) management remains a challenge in agricultural watersheds. The Choptank River Conservation Effects Assessment Project watershed, located in Maryland and Delaware and draining to the Chesapeake Bay, contains legacy soil P from historical dairy and poultry manure applications. These practices elevated soil P beyond crop needs, contributing to persistent P export to aquatic ecosystems. We assessed spatial P distribution and analyzed GIS (Geographic Information Systems)‐derived landscape features driving legacy P movement on a farm (47 ha). We hypothesized that P accumulates in drained lowlands and depressional areas due to gravity‐driven processes that accelerate P‐enriched water to receiving waters via overland flow. In collaboration with the US Department of Agriculture Legacy P project, we collected 105 soil samples (0‐ to 5‐cm and 5‐ to 15‐cm depths) and 14 ditch sediment samples across five topographic openness classes from a farm with >100 years of dairy manure application. Average Mehlich‐III P concentrations were 218 and 179 mg kg −1 at 0‐ to 5‐cm and 5‐ to 15‐cm depths, respectively, with legacy areas defined by P content > 100 mg kg −1 . Soil P and clay particle size were positively correlated ( r = 0.42, p < 0.05), increased as landscape openness decreased, and were negatively correlated with topographic openness (ranging from −0.2 to −0.4, p < 0.05), indicating accumulation of P and clay in low‐lying areas. These patterns suggest that historical field‐level managements have primarily shaped P distribution, while hydrologic and landscape properties further influence its redistribution via transport pathways and drainage. These findings support the development of landscape models to map critical source areas in low‐relief watersheds and guide targeted mitigation in high‐risk P export zones.

  PublisherOA PDFDOI

• Sulphur nutrition management in Sub-Saharan Africa crop production: a systematic review

  Frontiers in Agronomy · 2025-11-26

  articleOpen accessSenior author

  Sulphur (S) deficiency in Sub-Saharan Africa (SSA), driven by soil degradation and S-free fertilisers, threatens crop yield and protein quality. This systematic review synthesises four decades of studies (1980–2024) to assess soil S status, analysis methods, management challenges, and recommended rates for effective fertilisation to improve sustainable productivity. A systematic literature review was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) framework to synthesise available evidence on S nutrient management in agricultural soils across SSA. The review revealed that S concentrations were generally higher in surface horizons compared to sub-surface layers, with vertical distribution influenced by soil texture, pedogenic processes, organic matter content, and fertiliser inputs. In highly weathered soils, S depletion was pronounced, contributing to widespread deficiencies across SSA’s agricultural landscapes. Analysis of S fertilisation practices showed a research cereal crop (s) emphasis, accounting for 65% of studies, followed by legumes with 25% and oilseeds with 10%. Most of the cereal studies have reported S application rates between 0 and 30 kg S/ha, with 71% of studies applying ≤20 kg S/ha. Legumes, by contrast, received higher rates (21–40 kg S/ha), typically through potassium sulphate or nitrogen-phosphorus-sulphur (NPS) blended fertilisers. Yield responses to S application varied significantly by crop type. Maize exhibited the higher yield increase, ranging from 20% to 260% depending on the fertiliser application rate, followed by wheat and rice. Legumes such as soybeans showed more modest increase of 25%, while oilseeds like canola and sesame responded minimally, even under higher S inputs. These findings underscore the need for crop- and site-specific S management strategies in SSA. The adoption of soil testing and decision-making frameworks such as the 4R nutrient stewardship (right source, rate, time, and place) is recommended to optimise crop yield and reduce environmental risks associated with nutrient mismanagement.

  PublisherOA PDFDOI

• Learning to See More: UAS-Guided Super-Resolution of Satellite Imagery for Precision Agriculture

  ArXiv.org · 2025-05-27

  preprintOpen accessSenior author

  Unmanned Aircraft Systems (UAS) and satellites are key data sources for precision agriculture, yet each presents trade-offs. Satellite data offer broad spatial, temporal, and spectral coverage but lack the resolution needed for many precision farming applications, while UAS provide high spatial detail but are limited by coverage and cost, especially for hyperspectral data. This study presents a novel framework that fuses satellite and UAS imagery using super-resolution methods. By integrating data across spatial, spectral, and temporal domains, we leverage the strengths of both platforms cost-effectively. We use estimation of cover crop biomass and nitrogen (N) as a case study to evaluate our approach. By spectrally extending UAS RGB data to the vegetation red edge and near-infrared regions, we generate high-resolution Sentinel-2 imagery and improve biomass and N estimation accuracy by 18% and 31%, respectively. Our results show that UAS data need only be collected from a subset of fields and time points. Farmers can then 1) enhance the spectral detail of UAS RGB imagery; 2) increase the spatial resolution by using satellite data; and 3) extend these enhancements spatially and across the growing season at the frequency of the satellite flights. Our SRCNN-based spectral extension model shows considerable promise for model transferability over other cropping systems in the Upper and Lower Chesapeake Bay regions. Additionally, it remains effective even when cloud-free satellite data are unavailable, relying solely on the UAS RGB input. The spatial extension model produces better biomass and N predictions than models built on raw UAS RGB images. Once trained with targeted UAS RGB data, the spatial extension model allows farmers to stop repeated UAS flights. While we introduce super-resolution advances, the core contribution is a lightweight and scalable system for affordable on-farm use.

  PublisherOA PDFDOI

• Delta yield predicts nitrogen fertilizer requirements for corn in US production systems

  Agronomy Journal · 2025-09-01

  articleOpen access

  Abstract Predicting crop nitrogen (N) fertilizer needs is a major challenge in contemporary agriculture. Despite the success of current N recommendation tools, environmental concerns over N pollution from agriculture, and the adoption of improved corn ( Zea mays L.) technologies with enhanced N efficiencies highlight the need for more accurate N fertilizer recommendation systems. Here, we aimed to develop a methodology to predict corn N requirements based on delta yield (dY = maximum yield−unfertilized yield). To develop this delta yield‐based nitrogen (dY‐based N) tool, we selected 486 quadratic‐plateau corn yield response to N curves (from 732 N rate trials across northern US) to calculate dY and N fertilizer required to reach the yield plateau (N x ). The economic optimum nitrogen rate (EONR) was calculated using different fertilizer:crop price ratios (PR). The response curve outputs were then partitioned into calibration and validation sets. The calibration set was used to select linear models to predict N x based on dY, resulting in nine state, agroecosystem region, and irrigation‐specific sub‐models. These sub‐models predicted N x of the validation set with a mean absolute error (MAE) of 33.0 kg N ha −1 . Predicted values from the site‐year quadratic‐plateau response fits were used to improve further predictions’ outcomes. Predictions of EONR based on dY had a lower MAE than the predictions of N x , ranging between 19.9 and 25.4 kg N ha −1 depending on the PR, highlighting the system's predictive power. The exclusion of non‐responsive and linear‐response trials in our proposed dY‐based approach enables future model refinement to improve EONR prediction accuracy across a broader range of yield responses to fertilizer‐N rates. The proposed dY‐based N system, which integrates both economic and agronomic inputs (including management, environmental effects on soil N supply, and maximum yields), could help to reduce N losses and provide functional benefits for N optimization.

  PublisherOA PDFDOI

• Cover Crop Management to Reduce Nitrogen Leaching from Cropland: A Decade of Research in the Mid-Atlantic USA

  Progress in soil science · 2025-01-01

  book-chapter1st authorCorresponding
  PublisherDOI

• Soil texture, fertilization, cover crop species and management affect nitrous oxide emissions from no-till cropland

  The Science of The Total Environment · 2024-01-10 · 16 citations

  articleOpen accessSenior author

  Cover crops reduce nitrate leached, but effects on nitrous oxide (N2O) emissions are mixed. Cover crops can reduce N2O emissions by reducing levels of mineral nitrogen (N) and surface soil moisture during spring. Cover crops can also increase N2O emissions by adding organic substrates, releasing N during decomposition, or increasing summer soil water content. Winter-killed cover crops can increase soluble organic C and N during periods of typically low microbial activity. We hypothesized that planting a cover crop mix of radish (Raphanus sativus)-crimson clover (Trifolium incarnatum)-rye (Secale cereale) would increase direct N2O emissions relative to no cover crop, and result in lower direct and indirect N2O emissions than planting radish alone. We also hypothesized that extending the cover crop growing season, by planting earlier and killing later, would increase direct N2O emissions during winter, decrease direct N2O emissions during summer, and decrease indirect N2O emissions. To address these hypotheses, we conducted two field experiments (on sandy and silty soils) over four site-years. We measured cover crop biomass and N content, soil mineral N concentrations, soil moisture, green canopy cover, soil porewater nitrate, direct N2O emissions, and estimated indirect N2O emissions. Nitrous oxide emissions were ~ 7.8 times greater at the silty than the sandy sites due to greater soil moisture retention. Site-years with high radish biomass exhibited greater direct N2O emissions than sites with low radish biomass following winter-kill. Indirect N2O emissions were decreased ~7 % by planting cover crops and by ~70 % by planting cover crops early. Fertilizer induced emission peaks were 8.2 times greater than all previous N2O emissions combined at a silty site. Our results suggested that soil texture and fertilization played an important role in direct N2O emissions, while cover crop species, biomass, and timing played a more important role in NO3 leached, and thus, indirect N2O emissions.

  PublisherDOI

• Radish cover crop and manure alter organic carbon characteristics and improve soil physicochemical properties as well as wolfberry yields

  Agriculture Ecosystems & Environment · 2024-05-25 · 10 citations

  article
  PublisherDOI

• Soil Organic Carbon in Mid-Atlantic Region Forest Soils: Stocks and Vertical Distribution

  Forests · 2024-07-19 · 1 citations

  articleOpen accessSenior author

  Over a period of 10 years, 418 forested plots within the US National Capital Region parks were visited for morphological descriptions and to inventory carbon (C) stocks. Samples were collected from organic horizons, the loose leaf litter, and, using a hand auger, from each mineral horizon to a depth of 1 m. Soil C concentration was determined using high-temperature combustion, and organic carbon (OC) stocks were then calculated for each master horizon. Soil bulk density (Db) was determined using the core method for O and A horizons. For deeper mineral horizons, a strong linear relationship between NRCS SSURGO representative values and measured Db values averaged according to soil series (R2 = 0.75) was observed. Thus, the NRCS SSURGO representative Db values were used for mineral horizons below the A horizon. An average of 0.5 ± 0.0 kg C m−2 was contained in the loose leaf litter. For plots with O horizons, the organic layer contained 2.9 ± 0.3 kg C m−2. An average of 4.6 ± 0.2 kg C m−2 was stored in the A horizon, down to an average lower boundary of 18.8 cm. The mineral horizons below the A horizon averaged 8.5 kg C m−2. In these forested soil profiles, 52.8% of the TOC is found below the A horizon and 18.0% of the TOC is in the organic horizons. The predictive strength of the thickness of and SOC in the A horizon was also evaluated in terms of explaining and predicting TOC in the profile and in the subsoil. The thickness and SOC in the A horizon explained 54% of the variation in TOC stock; however, it was a poor predictor of OC stored in the subsoil (R2 = 0.04). This study demonstrates the importance of deeper sampling to encompass more of the rooting depth when investigating SOC stocks.

  PublisherOA PDFDOI

• Soil lead, zinc, and copper in two urban forests as influenced by highway proximity

  Journal of Environmental Quality · 2024-10-21 · 6 citations

  articleOpen accessSenior author

  Abstract Heavy metals emitted by vehicles have the potential to accumulate in soil near roadways, threatening the health of soil, plants, animals, and humans. This study evaluates Pb, Zn, and Cu levels in forest O‐horizons, mineral soil, and earthworms near busy roadways in the metro‐Washington, DC area. The study sites comprised road‐edge environments within urban parks. Six transects were sampled in each park, collecting mineral soil at 1‐ to 30‐m distances from the road edge and dividing it into eight depth increments (0–30 cm). O‐horizon plant litter and earthworm samples were also collected at these locations. All samples underwent total Pb, Zn, and Cu X‐ray fluorescence analysis. Generally, Pb concentrations (in upper 0–10 cm) were 1–4.8 times higher at 3 m compared to 30 m from the road, with less consistent gradients for Zn and Cu. Concentrations peaked near the soil surface, with lower levels in the O‐horizon above and deeper soil layers. Leaded vehicle fuel was phased out by the early 1980s, but legacy Pb contamination persisted in roadside forests, averaging 365 mg kg −1 in the upper 10 cm within 3 m of the roadway (< EPA action level of 1200 mg kg −1 for non‐play areas). Zinc, often present in vehicle tires, accumulated in earthworms to 192–592 mg kg −1 , concentrations exceeding those in the soil, while Pb and Cu were less concentrated in earthworms than in either O‐horizon or mineral soil. Factors such as plant uptake, erosion, wind, soil texture, and metal solubility influence how heavy metals redistribute and bioaccumulate in the O‐horizon, mineral soil, and soil fauna.

  PublisherOA PDFDOI

• Physicochemical fractionation reveals increased soil organic carbon storage in a wolfberry orchard under cover cropping

  Plant and Soil · 2024-11-19 · 3 citations

  article
  PublisherDOI

Frequent coauthors

• K. R. Islam

  The Ohio State University

  10 shared

• Michel A. Cavigelli

  Beltsville Agricultural Research Center

  9 shared

• Nyle C. Brady

  6 shared

• Cheryl Palm

  6 shared

• Brian A. Needelman

  University of Maryland, College Park

  5 shared

• Katherine L. Tully

  University of Maryland, College Park

  5 shared

• Xiongxiong Nan

  5 shared

• Pedro A. Sánchez

  5 shared

Labs

• Soil Quality LabPI

Awards & honors

• FoodShot Global Groundbreaker Prize (2022)