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Cited by 3Soil and Water Nutrient DynamicsSoil erosion and sediment transportHydrology and Watershed Management Studies

Nutrient Runoff From Agricultural Lands in North American Ecoregions

Open access
Hopkins, A. P., Harmel, R. D., Kleinman, P. J. A., Sahoo, D., Ippolito, J. A.·2025·JAWRA Journal of the American Water Resources Association
DOI 10.1111/1752-1688.70004
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Abstract

ABSTRACT Field‐scale runoff and water quality data are critical to understanding the fate of agricultural nutrients and mitigating their off‐site transport; however, regional influences such as precipitation, temperature, and prevailing cropping and management practices also impact nutrient runoff. In the present study, we used the recently updated MANAGE database to conduct meta‐type analyses of nitrogen (N) and phosphorus (P) in runoff from cropland and grasslands for North American ecoregions. Specifically, we analyzed annual N and P loads and the impact of land use, tillage, fertilizer timing, and fertilizer placement. Notable differences between ecoregions included: (1) the Temperate Prairies dominated by highly erodible cultivated land had significantly higher median annual total N loads (11.7 kg/ha) than the South Central Semiarid Prairies (2.4 kg/ha) dominated by grasslands; (2) corn production tended to produce higher N and P loads than other land uses in the Mixed Wood Plains, Southeastern USA Plains, and Ozark–Ouachita/Appalachian Forests; and (3) no‐till had the highest dissolved P loads in the Southeastern USA Plains and Temperate Prairies, but conventional tillage had the highest dissolved P loads in the Ozark–Ouachita/Appalachian Forests. These data—that have never before been analyzed by ecoregion—should prove valuable for improving regional understanding of nutrient fate and transport and informing field‐scale agricultural management decisions.

Integrity signals

Registry

Crossref · 10.1111/1752-1688.70004

Cites

31 of 31 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

7 of 26 cited sources checked · 1 supported · 0 flagged · accuracy not yet measured

  • Interpretationcitation

    The lower particulate N loads in Ozark-Ouachita/Appalachian Forests despite higher rainfall can be partially attributed to most particulate N load data from that ecoregion being from grasslands, whereas most data from Temperate Prairies are from potentially highly erodible cultivated lands in corn or small grain production.

    “These counterintuitive differences can be partially attributed to the fact that most of the particulate N load data from the Ozark-Ouachita/Appalachian Forests are from grasslands, whereas most of the data from the Temperate Prairies are from potentially highly erodible cultivated lands in corn or small grain production (Harmel et al. 2022) (Table 2).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Harmel et al. 2022 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
  • Interpretationcitation

    The higher particulate and total N and P loads for split application with surface placement and either incorporation or injection in the Southeastern USA Plains can be partially attributed to the prevalence of surface placement treatments on grassland sites with low erodibility in the Southeastern USA Plains.

    “which can be partially attributed to the prevalence of surface placement treatments on grassland sites with low erodibility in the Southeastern USA Plains (Harmel et al. 2022).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Harmel et al. 2022 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
  • Findingreasoning

    For total P, the Mississippi Alluvial/Southeast USA Coastal Plains had the highest annual total P loads (3.0 kg/ha).

    “For the seven ecoregions with > 25 site years, the Mississippi Alluvial/Southeast USA Coastal Plains had the highest annual total P loads (3.0 kg/ha) due to high rainfall (1403 mm/yr) and often tillage-intensive corn, cotton, and sugar cane production (Table 1, Figures 3 and 4).”
    Quote in the paperSubstantial claim
  • Findingreasoning

    Under conservation tillage, dissolved N and dissolved P loads were significantly greater for the South-Central Semiarid Prairies than for the Temperate Prairies.

    “Under conservation tillage, dissolved N and dissolved P loads were significantly greater for the South-Central Semiarid Prairies than for the Temperate Prairies, likely due to lower N and P application rates in the studies from the Temperate Prairies.”
    Quote in the paperSubstantial claim
  • Findingreasoning

    For total N, median annual total N loads were significantly higher in the Temperate Prairies (11.7 kg/ha) than in the South-Central Semiarid Prairies (2.4 kg/ha).

    “A notable significant difference in median annual total N loads occurred between the South-Central Semiarid Prairies (2.4 kg/ha) and the Temperate Prairies (11.7 kg/ha).”
    Quote in the paperSubstantial claim
  • May combine two claims. 27
  • Classified as probably not a substantial claim. 3

  • May combine two claims.

    Interpretationcitation

    The higher N and P runoff from wheat than grasslands in the South-Central Semiarid Prairies is likely because of increased erodibility due to tillage and because not all grasslands are fertilized annually.

    “For the South-Central Semiarid Prairies, wheat produced higher N and P runoff than grasslands, likely because of increased erodibility due to tillage (van Oost et al. 2006) and because not all grasslands are fertilized annually (Harmel et al. 2022).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites van Oost et al. 2006 source
    • cites Harmel et al. 2022 source

      The Dataset Summary (Table 2) identifies grassland and wheat as land uses in the South-Central Semi-Arid Prairies, and the surrounding text notes that some treatments did not receive fertilizer. It does not say those treatments were grasslands, establish how often grasslands were fertilized, or link fertilization to the runoff difference. The tillage explanation is attributed to a different citation. (LLM, conf=0.78)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Interpretationcitation

    The total N difference may be attributed to most total N load data for the South-Central Semiarid Prairies being from grasslands with perennial cover, while Temperate Prairies data represent potentially highly erodible cultivated land in corn, corn/soybean, and small grain rotations.

    “As with particulate N, this difference may be attributed to the fact that most of the total N load data for the South-Central Semiarid Prairies are from grasslands with perennial cover (Harmel et al. 2022).”
    • Also stated in: § 3.1 | Ecoregion Influence on N and P Runoff · hedged
      “In contrast, data from the Temperate Prairies represent potentially highly erodible cultivated land in corn, corn/soybean, and small grain rotations (Table 2).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Harmel et al. 2022 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Study design and conductcitation

    The recent MANAGE update added 27 studies representing an additional 1346 site years of data, and its use ensured the most comprehensive data set possible for the present analysis.

    “We used the recent MANAGE update (Harmel et al. 2022), which added 27 studies representing an additional 1346 site years of data, to complete the present analysis, ensuring the most comprehensive data set possible.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Harmel et al. 2022 source

  • May combine two claims.

    Interpretationcitation

    The higher P loads for grass with growing-season fertilizer application than cropland with at-planting application in Ozark-Ouachita/Appalachian Forests can be partially attributed to most cropland sites growing corn with winter cover crops and to higher P application rates on grasslands (avg = 255 kg/ha/yr) than cropland (avg = 40 kg/ha/yr).

    “In the Ozark-Ouachita/Appalachian Forests, however, all P loads were significantly higher for grass with fertilizer application in the growing season than for cropland with application at planting, which can be partially attributed to most of the cropland sites growing corn with winter cover crops and to higher P application rates on the grasslands (avg = 255 kg/ha/yr) than the cropland (avg.= 40”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Harmel et al. 2022 source

      Table 2 in the Dataset Summary lists corn and grazed grassland as dominant land uses in the Ozark-Ouachita/Appalachian Forests and reports regional median P runoff loads. It does not compare P loads by land use and fertilizer timing, establish a significant difference, or report winter cover crops, the stated P application rates, or the proposed explanation. (LLM, conf=0.78)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Interpretationcitation

    The higher dissolved and total P losses for fertilizer injection in the Temperate Prairies than in the Ozark-Ouachita/Appalachian Forests likely occurred because the injection treatments in the Ozark-Ouachita/Appalachian Forests were all in corn production with winter cover crops and because application occurred at planting, whereas the Temperate Prairies sites were in corn production withoutcover

    “This difference likely occurred because the injection treatments in the Ozark-Ouachita/Appalachian Forests were all in corn production with winter cover crops and because application occurred at planting, whereas the Temperate Prairies sites were in corn production without cover crops and were fertilized out of season (Harmel et al. 2022).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Harmel et al. 2022 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingreasoning

    For grasslands that are likely hayed instead of grazed, dissolved N loads were lower, but dissolved P loads were higher for the South-Central Semiarid Prairies than for the Southeastern USA Plains.

    “For grasslands that are likely hayed instead of grazed, dissolved N loads were lower, but dissolved P loads were higher for the South-Central Semiarid Prairies than for the Southeastern USA Plains.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For the Temperate Prairies, conventional tillage sites had higher median annual particulate N, total N, and particulate P loads, and a similar trend with higher particulate and total N and P loads was observed in the South-Central Semiarid Prairies.

    “For the Temperate Prairies, conventional tillage sites had higher median annual particulate N, total N, and particulate P loads, and a similar trend with higher particulate and total N and P loads was observed in the South-Central Semiarid Prairies.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    In the Southeastern USA Plains, fertilized grassland and cotton/peanut rotations tended to produce higher dissolved N loads but lower particulate and total N loads than corn production.

    “In the Southeastern USA Plains, fertilized grassland and cotton/peanut rotations tended to produce higher dissolved N loads but lower particulate and total N loads than corn production.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    For the Southeastern USA Plains and Temperate Prairies, no-till had the greatest dissolved P loads and conventional tillage the lowest.

    “For the Southeastern USA Plains and Temperate Prairies, no-till had the greatest dissolved P loads and conventional the lowest, which is consistent with prevailing science (e.g., Daryanto et al. 2017).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The lowest median annual total P loads occurred in the driest ecoregions (West-Central Semiarid Prairies, Mediterranean California); however, the Central USA Plains also had low total P runoff values.

    “The lowest median annual total P loads occurred in the driest ecoregions (West-Central Semiarid Prairies, Mediterranean California); however, the Central USA Plains also had low total P runoff values likely due to the prevalence of conservation tillage and no-till (King et al. 2018).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning

    For annual dissolved N loads, median annual dissolved N loads were significantly higher in the Mixed Wood Plains (3.0 kg/ha), Southeastern USA Plains (3.1 kg/ha), and Mississippi Alluvial/Southeast USA Coastal Plains (3.3 kg/ha) than in the South-Central Semiarid Prairies (0.78 kg/ha).

    “For the seven ecoregions with > 25 site years of data (Table 1), notable significant differences in median annual dissolved N loads occurred between the semiarid South-Central Semiarid Prairies (0.78 kg/ha) and the Mixed Wood Plains (3.0 kg/ha), Southeastern USA Plains (3.1 kg/ha), and Mississippi Alluvial/Southeast USA Coastal Plains (3.3 kg/ ha).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The highest annual dissolved P losses occurred in the Mississippi Alluvial/Southeast USA Coastal Plains (0.48 kg/ha) and Ozark-Ouachita/Appalachian Forests (0.80 kg/ha).

    “The highest annual dissolved P losses occurred in the Mississippi Alluvial/Southeast USA Coastal Plains (0.48 kg/ ha) and Ozark-Ouachita/Appalachian Forests (0.80 kg/ ha)”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    For the Southeastern USA Plains and Temperate Prairies, no-till had the highest dissolved P loads and conventional had the lowest.

    “For the Southeastern USA Plains and Temperate Prairies, no-till had the highest dissolved P loads and conventional had the lowest”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For fertilizer incorporation, the Temperate Prairies produced the highest particulate and total N and P loads but relatively low dissolved N and P loads.

    “with the Temperate Prairies producing the highest particulate and total N and P loads but relatively low dissolved N and P loads”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Only 31 site years total are available and only from the Marine West Coast Forest and Mediterranean California ecoregions.

    “Only 31 site years total are available and only from the Marine West Coast Forest and Mediterranean California ecoregions.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    Few data are available from west of the Rocky Mountains, even though many areas of the western US are major agricultural regions.

    “Few data are available from west of the Rocky Mountains, even though many areas of the western US are major agricultural regions”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    For split application (preplant and out-of-season), total N, dissolved P, and total P loads were higher for the Temperate Prairies than for the Central USA Plains, even though the Temperate Prairies are more arid (748 vs. 1042 mm/yr).

    “For split application (preplant and out-ofseason), total N, dissolved P, and total P loads were higher for the Temperate Prairies than for the Central USA Plains, even though the Temperate Prairies are more arid (748 vs. 1042 mm/ yr).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Nitrogen (N) and phosphorus (P) are often the limiting nutrients in algal growth in North American waterbodies, and offsite transport from agricultural watersheds is often a substantial contributor to accelerated eutrophication.

    “Nitrogen (N) and phosphorus (P) are often the limiting nutrients in algal growth in North American waterbodies, and offsite transport from agricultural watersheds is often a substantial contributor to accelerated eutrophication (Beman et al. 2005;White et al. 2014).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Beman et al. 2005

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites White et al. 2014 source

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductreasoning

    The present analysis used nonparametric Dunn tests with an a priori α = 0.05 significance level on median values weighted by site years because the data were not normally distributed.

    “Specifically, we conducted nonparametric Dunn tests with an a priori α = 0.05 significance level on median values weighted by the site years of data (R Core Team 2022) because the data were not normally distributed.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites R Core Team 2022

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationown data

    The high total P loads in the Mississippi Alluvial/Southeast USA Coastal Plains are due to high rainfall (1403 mm/yr) and often tillage-intensive corn, cotton, and sugar cane production.

    “For the seven ecoregions with > 25 site years, the Mississippi Alluvial/Southeast USA Coastal Plains had the highest annual total P loads (3.0 kg/ha) due to high rainfall (1403 mm/yr) and often tillage-intensive corn, cotton, and sugar cane production (Table 1, Figures 3 and 4).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductcitation

    The MANAGE update delineated the Level II EPA ecoregion for each study and presents annual N and P runoff load data for 11 of the 50 Level II ecoregions in the United States and Canada.

    “This update also delineated the Level II EPA ecoregion (Omernik 1987;Omernik and Griffith 2014) for each study, presenting annual N and P runoff load data for 11 of the 50 Level II ecoregions in the United States and Canada (Figures 1 and 2).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Omernik 1987 source
    • cites Omernik and Griffith 2014 source

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    The higher N and P loads with fertilizer incorporation in the South-Central Semiarid Prairies are possibly due to the tillage soil disturbance during fertilizer incorporation.

    “possibly due to the tillage soil disturbance during fertilizer incorporation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    The surprising result occurred even though preplant application for the studies in the Southeastern USA Plains tended to incorporate fertilizer with tillage and thus increased soil disturbance, which can increase erosion and particulate N and P losses.

    “This surprising result occurred even though preplant application for the studies in the Southeastern USA Plains tended to incorporate fertilizer with tillage (Endale et al. 2017) and thus increased soil disturbance, which can increase erosion and particulate N and P losses.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Endale et al. 2017 source

  • May combine two claims.

    Interpretationreasoning

    The higher dissolved N, total N, and dissolved P loads for incorporation than surface application in the Ozark-Ouachita/Appalachian Forests can be explained by higher N and P rates for the incorporated treatments (262 and 183 kg/ha/yr., respectively) and by many of the surface placement treatments occurring on grasslands with application during the growing season with active nutrient uptake.

    “This counterintuitive result, however, can be explained by higher N and P rates for the incorporated treatments (262 and 183 kg/ha/yr., respectively) and many of the surface placement treatments occurred on grasslands with application during the growing season with active nutrient uptake (Table 5).”
    • Also stated in: § 4 | Summary and Conclusions · plain
      “This seemingly counterintuitive result can be explained by higher N and P rates for the incorporated treatments and because many of the surface placement treatments occurred on grasslands with application in the growing season with active nutrient uptake.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The higher annual particulate N loads in the Temperate Prairies than in the Ozark-Ouachita/Appalachian Forests are likely because most of the Ozark-Ouachita/Appalachian Forests data were from grasslands, whereas most of the data from the Temperate Prairies were from potentially highly erodible cultivated lands.

    “likely because most of the Ozark-Ouachita/Appalachian Forests data were from grasslands, whereas most of the data from the Temperate Prairies were from potentially highly erodible cultivated lands.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    All results presented in the present study are based on single-factor analyses.

    “All results presented in the present study are based on single-factor analyses.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The higher P loads for fertilizer application to grass in the growing season than for cropland at planting in the Ozark-Ouachita/Appalachian Forests are likely due to the effectiveness of winter cover crops in reducing N and P losses in corn production and to higher P application rates on grassed lands (avg = 255 kg/ha) than on cropland (avg = 40 kg/ha).

    “This is likely due to the effectiveness of winter cover crops in reducing N and P losses in corn production and to higher P application rates on grassed lands (avg = 255 kg/ha) than on cropland (avg = 40 kg/ha).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The higher loads with split fertilizer application than preplant application in the Southeastern USA Plains are especially surprising since preplant application in this ecoregion tended to incorporate fertilizer with tillage, thus increasing erosion potential.

    “This counterintuitive result is especially surprising since preplant application in this ecoregion tended to incorporate fertilizer with tillage, thus increasing erosion potential.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The higher total N loads in Ozark-Ouachita/Appalachian Forests than South-Central Semiarid Prairies for growing-season grass fertilization are possibly due to higher precipitation (1287 vs. 684 mm/yr), higher fertilizer rates, and higher slopes.

    “Similarly, total N loads were significantly higher in the Ozark-Ouachita/Appalachian Forests than in the South-Central Semiarid Prairies, possibly due to higher precipitation (1287 vs. 684 mm/yr), higher fertilizer rates, and higher slopes.”
    Quote in the paperSubstantial claim
29 of 29

  • The paper relies on this without support.

    The dominant land uses based on studies in MANAGE are reasonable proxies for actual areal extents of those land uses.

    “Although these dominant land uses based on studies in MANAGE may differ from actual areal extents, they appear to be reasonable according to prevailing production practices as influenced by topography, soil, temperature, and rainfall.”
1 of 1

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • South-Central particulate N value differs from Table 1

    Minor

    The text gives 2.4 kg/ha for particulate N in the South-Central Semiarid Prairies, whereas Table 1 gives 2.2 kg/ha. The table's 2.4 kg/ha value is for total N.

  • Fertilizer-placement loads are called averages instead of medians

    Minor

    The section describes the Table 5 loads as averages, but the table caption identifies them as medians.

  • Ozark particulate P value changes in the summary

    Minor

    The summary reports 0.13 kg/ha for Ozark-Ouachita/Appalachian Forests particulate P, while the results report 0.15 kg/ha.

  • Temperate Prairies conventional-tillage total N differs from Table 3

    Minor

    The text reports 39.9 kg/ha, but Table 3 gives 35.95 kg/ha for the same ecoregion, tillage category, and constituent.

  • Particulate P is not significantly lower than in every other ecoregion

    Minor

    The text claims the Ozark-Ouachita/Appalachian Forests value is significantly lower than those of other ecoregions. Table 1 assigns it "b" and the Mixed Wood Plains "ab"; under the table's stated lettering rule, those two values are not significantly different.

5 of 5

Cites

Flagged first, then by citations

Research works printed but not linked: 3

  1. Beaulac M. N., 1980, Nutrient Export Coefficients: An Examination of Sampling Design and Natural Variability Within Differing Land Uses
  2. Mallarino A., 2019, Soil and Phosphorus Losses With Surface Runoff From Corn‐Soybean Rotations as Affected by Tillage, Cover Crops, and Phosphorus Placement Methods
  3. Reckhow K. H., 1980, Modeling Phosphorus Loading and Lake Response Under Uncertainty: A Manual and Compilation of Export Coefficients, 214

Cited by

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Related

Authors
Hopkins, A. P., Harmel, R. D., Kleinman, P. J. A., Sahoo, D., & Ippolito, J. A.
Affiliations
  • Colorado State University (US)
  • Agricultural Research Service (US)
  • Clemson University (US)
  • The Ohio State University (US)
Corresponding author
Harmel, R. D.
ORCID
Venue
JAWRA Journal of the American Water Resources Association
Publisher
Wiley
Published
2025-02
Volume
61
Issue
1
ISSN
  • 1093-474X (ISSN-L)
  • 1752-1688
DOI
10.1111/1752-1688.70004
OpenAlex
W4407779867
Cited by
3
References
27
Citations by year
2026: 3
FWCI
0.90
Type
journal article
Language
en
Open access
Licence
Locations
JAWRA Journal of the American Water Resources Association (publishedVersion, public-domain)
Funders
U.S. Department of Agriculture
Topics
  • Physical Sciences › Environmental Science › Environmental Chemistry › Soil and Water Nutrient Dynamics
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Soil erosion and sediment transport
  • Physical Sciences › Environmental Science › Water Science and Technology › Hydrology and Watershed Management Studies
Keywords
nutrient runoff, agricultural non-point source pollution, nitrogen loading, phosphorus loading, ecoregions, cropland, grassland, tillage, no-tillage, fertilizer application timing, fertilizer placement, maize production, dissolved phosphorus, water quality, North America

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