About

Gurpal Toor is a Professor and Extension Specialist in the Department of Environmental Science & Technology at the University of Maryland. His expertise includes Nutrient Management, Soil Fertility, and Water Quality. He holds a Ph.D. in Environmental Soil Science from Lincoln University, New Zealand, and has held academic positions at the University of Florida, where he served as Assistant Professor, Associate Professor, and Full Professor from 2007 to 2017. Additionally, he has a Visiting Professorship at Northwest A&F University in China and an Affiliate Professorship at Mohammed VI Polytechnic University in Morocco. His research and extension programs focus on conducting basic and applied research to increase understanding of environmental issues related to agricultural and natural ecosystems, with a particular emphasis on solving environmental problems associated with nutrient pollution in water bodies, including the Chesapeake Bay. He has been appointed as a representative for the University of Maryland on the Maryland Nutrient Management Committee and the Phosphorus Management Tool Committee, and has served on the United States Environmental Protection Agency Chesapeake Bay Program Agriculture Workgroup committee. Dr. Toor serves as an academic editor for several scientific journals and has been actively involved in professional organizations, including serving on the Board of Directors of the American Society of Agronomy and chairing the international organization SERA-17, which works to minimize nutrient losses from agriculture. His research primarily focuses on understanding the processes, mechanisms, and pathways of nitrogen and phosphorus flows in soil-plant-water systems, aiming to develop solutions that manage nutrients in plant root zones to protect water quality while sustaining agricultural productivity.

Research topics

• Environmental science
• Ecology
• Environmental chemistry
• Chemistry
• Environmental engineering
• Engineering
• Organic chemistry
• Biology
• Water resource management
• Waste management

Selected publications

• Extreme rainfall redistributes and leaches nitrate accumulated in the soil profiles of an intensive agricultural region

  Soil and Tillage Research · 2026-01-13 · 5 citations

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  PublisherDOI

• Nitrogen loss from agricultural land to water: Pathways, drivers, and management implications

  Advances in agronomy · 2026-01-01

  book-chapterSenior authorCorresponding
  PublisherDOI

• Increased drought intensity stimulates the extracellular polymeric substance accumulation and their contribution to soil organic carbon rather than microbial necromass

  Soil Biology and Biochemistry · 2025-11-27 · 3 citations

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  PublisherDOI

• Optimizing nitrogen-water use efficiency for nitrate reduction: spatiotemporal strategies and potential of climate-smart kiwifruit agriculture across SSP scenarios

  Water Research · 2025-12-01 · 1 citations

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  PublisherDOI

• Mitigating soluble phosphorus loss in legacy phosphorus soils: Biosolids characterization and phosphorus-transformation studies

  Environmental Technology & Innovation · 2025-12-08

  articleOpen access1st authorCorresponding

  Legacy phosphorus (P) from agricultural soils continues to leak into surface waters. We investigated how biosolids treated with metals (Fe, Al, and Ca) immobilize soluble P (water-extractable P, WEP) in soils while maintaining plant-available P (Mehlich 3-P, M3-P). Two complementary incubations (3–8 weeks; 25 °C) in non-legacy and legacy-P soils (M3-P: 58–139 mg kg⁻¹; 230–953 mg kg⁻¹) tracked WEP, M3-P, and M3-P saturation ratio (M3-PSR). Poultry litter and compost produced the largest WEP and the highest M3-P time-weighted means (TWM: 0.31 and 0.21 mg kg⁻¹ per kg of P), reflecting rapid P release. Fe/Al-treated biosolids (e.g., Bloom ±WTR)) showed small or negative WEP and lower M3-P TWM that declined with increasing application rate (0.12–0.04 mg kg⁻¹ from 1x to 4x). Thermo-hydrolyzed biosolid (low Fe) had a mid-range M3-P TWM (∼0.19 mg kg⁻¹) but the largest delta (Δ) over 8 weeks, consistent with sustained mineralization. WEP i TWM was –0.002–0.027 across products; increasing Bloom rates reduced WEP i TWM ( 0.007 to –0.0002 mg kg⁻¹) and Δ (–0.007 to –0.0005 mg kg⁻¹), confirming Fe/Al control of P solubility. M3-PSR changes mirrored product chemistry, with ΔPSR near zero for Bloom and minimal or negative for Fe/Al-treatments. Overall, Fe/Al-treated biosolids effectively reduced soluble P, while some products (e.g., thermo-hydrolyzed, lime-stabilized+WTR) gradually increased plant-available P. We suggest prioritizing Fe/Al-treated biosolids (±WTR) on legacy-P or sandy soils to immobilize soluble P, and applying labile materials (poultry litter, compost, thermo-hydrolyzed biosolids) in split doses on P-deficient soils, guided by M3-P, texture, WEPᵢ, and pH. • Fe/Al-rich biosolids curb soluble P and stabilize P saturation ratio in legacy-P soils. • Compost and thermo-hydrolyzed biosolids (low Fe+Al) build plant-available P and limit short-term soluble P pulses. • Lime-stabilized and WTR blends (high Ca+Al) deliver slow-release P with minimal increases in soluble P. • Matching biosolid chemistry to soil P levels and texture is a key to reducing soluble P losses.

  PublisherDOI

• Soil organic carbon formation from plant and microbial residual carbon: Effects of home-field advantage and root litter quality

  CATENA · 2025-03-27 · 9 citations

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• 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

• Soil Organic Carbon Formation from Plant and Microbial Residual Carbon: Effects of Home-Field Advantage and Substrate Quality

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• Pairing Traditional Approaches with High-resolution In-situ Sensors to Advance the Science of Nutrient Fluxes from Agricultural Catchments 

  2024-03-09

  preprintOpen access1st authorCorresponding

  Agricultural catchments are hot spots of nutrient (nitrogen, phosphorus) fluxes to downstream watersheds. New tools are needed to disentangle flow pathways, hot spots, and the interplay of nutrient dynamics. Yet, the constraints (cost, labor) have limited our ability to use the new tools to understand nutrient dynamics from land to water. The traditional approaches of water quality monitoring (grab or composite samples collected with autosamplers) remain the gold standard for water quality monitoring, although they yield limited information on the mechanistic controls of nutrient losses. This presentation will discuss how pairing the traditional approaches (such as autosamplers) with in-situ nutrient sensors in agricultural catchments furthered our understanding of hot spots, pathways, and stoichiometric controls on nitrate and orthophosphate losses and advanced the science of water quality monitoring in agricultural catchments.

  PublisherDOI

• Long-term trajectories of nutrient budgets and changes in soils of two counties with contrasting land use changes: cereals vs fruit orchards

  2024-04-29

  preprintOpen access

  Land use change (LUC) is a key factor affecting nutrient budgets in agricultural soils. Comparing the long-term trajectories of nutrient budgets and changes in soils at a regional scale with contrasting LUC is critical to optimizing nutrient management and minimizing adverse environmental effects. We investigated the nutrient budgets and changes in soils in two counties in the south Loess Plateau, China, with contrasting LUCs from 1992 to 2017. Wugong County has cereals as the main crop, whereas Meixian County has the main cereal crops changed to kiwi orchards. We found that nitrogen (N), phosphorus (P), and potassium (K) inputs in two counties increased rapidly, and the nutrient outputs by crop harvests remained relatively stable. This resulted in increasing nutrient surpluses in the soils of two counties. Nutrient surplus in the orchard-dominated county was higher than that of the cereal-dominated county, and nutrient use efficiencies were contrasting. High N surplus in the orchard-dominated county resulted in high nitrate-N accumulation in deeper soil profiles of orchards. High P and K surpluses in the two counties significantly increased available P and K in 0-20 cm depth. Soil available P and K in the orchard-dominated county were significantly higher than in the cereal-dominated county, which was also significantly higher than the threshold values of available P and K contents in soils. We conclude that comprehensive measures should be taken to control nutrient surpluses, which will help to balance nutrient inputs and outputs and minimize nutrient losses in intensive horticultural crop systems.

  PublisherOA PDFDOI

Frequent coauthors

• Yun‐Ya Yang

  Alameda Hospital

  26 shared

• Mary G. Lusk

  25 shared

• J. T. Sims

  University of Delaware

  12 shared

• Ignacio A. Rodríguez‐Jorquera

  12 shared

• Jingbo Gao

  Northwest A&F University

  11 shared

• Maninder K. Chahal

  9 shared

• Mriganka De

  9 shared

• Amy L. Shober

  8 shared

Awards & honors

• Fellow of the Soil Science Society of America (2023)
• Fellow of the American Society of Agronomy (2025)