Research ArticleENVIRONMENTAL STUDIES

Genetically engineered crops and pesticide use in U.S. maize and soybeans

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Science Advances  31 Aug 2016:
Vol. 2, no. 8, e1600850
DOI: 10.1126/sciadv.1600850
  • Fig. 1 GE variety adoption and pesticide use, maize and soybeans in the United States, 1998–2011.

    (A) Adoption rates of GT soybeans, GT maize, and Bt maize (embedding one or more genes from Bacillus thuringiensis). (B) Insecticide use in maize (kg/ha and EIQ weights). (C) Herbicide use in soybeans (kg/ha and EIQ weights). (D) Herbicide use in maize (kg/ha and EIQ weights). Adoption rates and active ingredient (a.i.) use (kg/ha) are reported in tables S12 and S13.

  • Fig. 2 Estimated βt parameters from the fixed-effects model.

    (A) Year-specific impacts of GT soybeans on herbicide use (kg/ha and EIQ weights). (B) Year-specific impacts of GT maize on herbicide use (kg/ha and EIQ weights). (C) Year-specific impacts of Bt maize on insecticide use (kg/ha and EIQ weights). For all panels, vertical bars denote 95% confidence intervals.

  • Fig. 3 Estimated αt parameters from the fixed-effects model.

    (A) Year-specific herbicide use by non-GT soybean adopters (kg/ha and EIQ weights). (B) Year-specific herbicide use by non-GT maize adopters (kg/ha and EIQ weights). (C) Year-specific insecticide use by non-Bt maize adopters (kg/ha and EIQ weights). For all panels, vertical bars denote 95% confidence intervals.

  • Fig. 4 Decomposition of year-specific impacts of GE variety adoption.

    (A) Differences in herbicide use between GT soybean adopters and nonadopters (kg/ha) (red bars, glyphosate; blue bars, all other herbicides). (B) Differences in herbicide use between GT maize adopters and nonadopters (kg/ha) (red bars, glyphosate; blue bars, all other herbicides). (C) Fraction of hectares planted to GT varieties that use exclusively glyphosate.

  • Table 1 Estimated impact of GE varieties on pesticide use, average impact over 1998–2011 (assumes βt = β, ∀ t).

    N = number of observations. SEs (in parentheses) are clustered at the farmer level. The model includes time fixed effects, CRD-specific time trends, and individual (farmer) fixed effects. *P < 0.05, **P < 0.01, ***P < 0.001. a.i., active ingredient.

    Soybean herbicidesMaize herbicidesMaize insecticides
    a.i. kg/haEIQ kg/haa.i. kg/haEIQ kg/haa.i. kg/haEIQ kg/ha
    Gi0.3021***0.0045−0.0329*−0.2590***−0.0129***−0.0122***
    (0.0097)(0.0122)(0.0150)(0.0156)(0.0014)(0.0014)
    N86,73686,736134,264134,264134,264134,264
    R20.0670.0280.0220.0270.0390.051
  • Table 2 Estimated impact of GE varieties on the farmer, consumer, and ecology components of EIQ-weighted pesticide use, average impact over 1998–2011 (assumes βt = β, ∀ t).

    N = number of observations. SEs (in parentheses) are clustered at the farmer level. The model includes time fixed effects, CRD-specific time trends, and individual (farmer) fixed effects. *P < 0.05, **P < 0.01, ***P < 0.001.

    Soybean herbicide EIQMaize herbicide EIQMaize insecticide EIQ
    FarmerConsumerEcologyFarmerConsumerEcologyFarmerConsumerEcology
    Gi−0.0081***−0.0281***0.0407***−0.0301***−0.0534***−0.1755***−0.0019***−0.0003***−0.0100***
    (0.0021)(0.0013)(0.0091)(0.0024)(0.0017)(0.0116)(0.0003)(0.0001)(0.0011)
    N86,73686,73686,736134,264134,264134,264134,264134,264134,264
    R20.0340.0510.0270.0290.0480.0250.0410.0270.053

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/8/e1600850/DC1

    Supplementary Text

    fig. S1. Number of years sampled for growers in AgroTrak data set.

    fig. S2. Maize herbicide use by non-GT adopters (selected herbicides, kg/ha).

    fig. S3. Crop reporting districts.

    fig. S4. Trends in glyphosate and expected crop output prices, 1998–2011.

    table S1. Summary statistics for AgroTrak data set.

    table S2. Full results corresponding to Table 1.

    table S3. Full results corresponding to Figs. 2 and 3.

    table S4. Random effects replace farmers fixed effects.

    table S5. Model estimates with the no-till binary variable included.

    table S6. Targeted weeds and impact of GE variety adoption on herbicide use (kg/ha of active ingredient).

    table S7. Model excludes growers that plant both GE and non-GE varieties within a given year.

    table S8. Model excludes growers that plant both GE and non-GE varieties within a given year.

    table S9. Model excludes farmers that never used pesticides (on any of their plots).

    table S10. Model excludes farmers that never used pesticides (on any of their plots).

    table S11. Full set of results corresponding to Fig. 4.

    table S12. GE adoption rates (% of planted hectares), 1998–2011.

    table S13. Pesticide rates (kg/ha), 1998–2011.

    table S14. Correlation between state-level GE adoption rates from USDA and GfK data.

    table S15. Summary statistics by adoption choice.

    References (3545)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • fig. S1. Number of years sampled for growers in AgroTrak data set.
    • fig. S2. Maize herbicide use by non-GT adopters (selected herbicides, kg/ha).
    • fig. S3. Crop reporting districts.
    • fig. S4. Trends in glyphosate and expected crop output prices, 1998–2011.
    • table S1. Summary statistics for AgroTrak data set.
    • table S2. Full results corresponding to Table 1.
    • table S3. Full results corresponding to Figs. 2 and 3.
    • table S4. Random effects replace farmers fixed effects.
    • table S5. Model estimates with the no-till binary variable included.
    • table S6. Targeted weeds and impact of GE variety adoption on herbicide use (kg/ha of active ingredient).
    • table S7. Model excludes growers that plant both GE and non-GE varieties within a given year.
    • table S8. Model excludes growers that plant both GE and non-GE varieties within a given year.
    • table S9. Model excludes farmers that never used pesticides (on any of their plots).
    • table S10. Model excludes farmers that never used pesticides (on any of their plots).
    • table S11. Full set of results corresponding to Fig. 4.
    • table S12. GE adoption rates (% of planted hectares), 1998–2011.
    • table S13. Pesticide rates (kg/ha), 1998–2011.
    • table S14. Correlation between state-level GE adoption rates from USDA and GfK data.
    • table S15. Summary statistics by adoption choice.
    • References (3545)

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