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. 2024 Feb 27;121(9):e2319436121.
doi: 10.1073/pnas.2319436121. Epub 2024 Feb 22.

Enhanced weathering in the US Corn Belt delivers carbon removal with agronomic benefits

David J Beerling  1 , Dimitar Z Epihov  1 , Ilsa B Kantola  2 , Michael D Masters  2 , Tom Reershemius  3 , Noah J Planavsky  3 , Christopher T Reinhard  4 , Jacob S Jordan  5 , Sarah J Thorne  1 , James Weber  1 , Maria Val Martin  1 , Robert P Freckleton  1 , Sue E Hartley  1 , Rachael H James  6 , Christopher R Pearce  7 , Evan H DeLucia  2 , Steven A Banwart  8   9
Affiliations

Enhanced weathering in the US Corn Belt delivers carbon removal with agronomic benefits

David J Beerling et al. Proc Natl Acad Sci U S A. .

Abstract

Terrestrial enhanced weathering (EW) of silicate rocks, such as crushed basalt, on farmlands is a promising scalable atmospheric carbon dioxide removal (CDR) strategy that urgently requires performance assessment with commercial farming practices. We report findings from a large-scale replicated EW field trial across a typical maize-soybean rotation on an experimental farm in the heart of the United Sates Corn Belt over 4 y (2016 to 2020). We show an average combined loss of major cations (Ca2+ and Mg2+) from crushed basalt applied each fall over 4 y (50 t ha-1 y-1) gave a conservative time-integrated cumulative CDR potential of 10.5 ± 3.8 t CO2 ha-1. Maize and soybean yields increased significantly (P < 0.05) by 12 to 16% with EW following improved soil fertility, decreased soil acidification, and upregulation of root nutrient transport genes. Yield enhancements with EW were achieved with significantly (P < 0.05) increased key micro- and macronutrient concentrations (including potassium, magnesium, manganese, phosphorus, and zinc), thus improving or maintaining crop nutritional status. We observed no significant increase in the content of trace metals in grains of maize or soybean or soil exchangeable pools relative to controls. Our findings suggest that widespread adoption of EW across farming sectors has the potential to contribute significantly to net-zero greenhouse gas emissions goals while simultaneously improving food and soil security.

Keywords: agricultural production; carbon removal; enhanced weathering; soil geochemistry.

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Conflict of interest statement

Competing interests statement:D.J.B. has a minority equity stake in Future Forest/Undo, and is a member of the Advisory Board of The Carbon Community, a UK carbon removal charity, and the Scientific Advisory Council of the non-profit Carbon Technology Research Foundation. J.S.J. is funded through the public benefit corporation, Mati Carbon, a subsidiary of the not for profit Swaniti Initiative. N.J.P and C.T.R were co-founders of the CDR company Lithos Carbon, but have no remaining financial ties to the company. The remaining authors declare that they have no competing interests.

Figures

Fig. 1.
Fig. 1.
Field trial CDR potential and soil biogeochemistry changes in response to EW. (A) Harvested corn acres across the US Corn Belt, shown as regional percent area (12). The field trial site is shown with an open circle. (B) Time-series of expected and observed soil calcium (Ca), (C) Mg cation concentrations in treated and control plots. (D) Cumulative CDR potential (CDRpot) over our 4-y trial in a Midwestern corn–soy rotation. Results show mean CDRpot across four sample blocks. The gray bar shows the pretreatment period (pre). The symbol “?” denotes a typical CDRpot rate for maize in 2019. (E) Soil pH increased significantly with EW at 0 to 10 cm and 10 to 30 cm depths. (F) Soil CEC increases with EW while exchangeable acidity decreases at 0 to 10 cm and 10 to 30 cm depths. Error bars are ± SEM. Statistical results shown for repeated measures two-way ANOVAs with basalt vs. control as the main factor, asterisks indicate significant difference (**P < 0.01, ***P < 0.001).
Fig. 2.
Fig. 2.
Field trial soil and crop biogeochemical responses to EW. (A) Total grain biomass nitrogen (N). (B) Plant NUE. (C) Measured P to Ti ratios in fresh and weathered basalt and calculated release of pf P. (D) Measured K to Ti ratios in fresh and weathered basalt and calculated release of P and K on a mass per unit area basis. (E) Total grain P and (F) K both increased significantly with EW. Error bars are ± SEM. Statistical results shown for repeated measures two-way ANOVAs with basalt vs. control as the main factor, asterisks indicate significant difference (**P < 0.01, ***P < 0.001).
Fig. 3.
Fig. 3.
Root transcriptional responses of crops to EW under field conditions. (A) Soybean and (B) maize root nutrient transporter and acid phosphatase transcriptional responses to EW. Responses are expressed as the percentage of significantly up- and down-regulated transporter genes (differential expression DESeq2 tests, P < 0.05) within all genes in a transporter group in response to EW (i.e., between basalt and control plants). (C) Heatmap of z-score normalized root expression levels of genes involved in different pathways (labeled I to X) of root nitrogen assimilatory metabolism and long-distance upward transport. The heatmap shows that a whole suite of genes is differentially expressed (DESeq2, P < 0.05; blue asterisks denote down-regulated and red asterisks up-regulated genes) in response to basalt in soybean, but not maize.
Fig. 4.
Fig. 4.
Grain yield responses of food and energy crops to EW and liming under field conditions. Results are averaged across hand-harvesting of large and small blocks. Error bars are ± SEM. Statistical results shown for two-way ANOVAs with basalt vs. control as the main factor, asterisks indicate significant difference (*P < 0.05).
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