Physiological effects of enhanced weathering with basalt on maize and soybean grown under increased carbon dioxide

Allen, Megan May

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https://hdl.handle.net/2142/129233 Copy

Description

Title

Physiological effects of enhanced weathering with basalt on maize and soybean grown under increased carbon dioxide

Author(s)

Allen, Megan May

Issue Date

2025-05-05

Director of Research (if dissertation) or Advisor (if thesis)

Ainsworth, Elizabeth A

Committee Member(s)

• Heaton, Emily A
• Villamil, Maria B

Department of Study

Crop Sciences

Discipline

Crop Sciences

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Enhanced weathering
• physiology
• FACE
• croplands

Abstract

Enhanced weathering (EW) is a carbon dioxide (CO2) removal technology in which silicate rocks, such as basalt, are finely ground and applied to land to accelerate natural weathering processes that capture and store atmospheric CO2 securely in the ocean. Croplands have been targeted for EW schemes because of the potential agricultural co-benefits of silicate powders, including improved soil pH and nutrient provision. The Midwestern United States could be an ideal region for integrating EW due to its large cropland area, mostly consisting of maize and soybean, and its existing infrastructure. If EW becomes more common place, it is important to consider factors that might affect the system in the future. If global CO2 emissions are not drastically cut, atmospheric CO2 concentrations will continue to rise, with potential implications for both crop production and EW rates. This study investigates how silicate powders might affect maize and soybean physiology and how changes in crop physiology might affect EW in a higher CO2 future. Aboveground physiological responses as well as soil moisture and respiration were measured over two growing seasons under ambient and increased CO2 levels in a fully open-air field setting. The application of basalt (40 t ha-1 year-1) did not significantly alter any aboveground physiological responses in maize or soybean under ambient or increased CO2 levels. This lack of response was likely due to the site’s relatively neutral starting pH, which reduced the potential of basalt to improve nutrient availability. In maize, increased CO2 enhanced photosynthesis during an early to mid-season drought, aligning with previous research showing that C4 crops experience CO2-related benefits only under drought stress. However, this did not translate to increased grain yield. In soybean, increased CO2 also did not improve seed yield, likely because a mid-season drought reduced the typical improvements to C3 photosynthesis observed under increased CO2. Increased CO2 also affected soil moisture at 10 – 50 cm depth in both cropping systems, with improvements to soil water only observed during non-drought periods. Basalt increased soil moisture at 40 – 50 cm across both crops, likely due to altered root dynamics, with a smaller effect under elevated CO2 in maize. In soybean, basalt also improved topsoil moisture, potentially through improvements to water-holding capacity, although further research is needed to confirm this. Neither basalt nor increased CO2 affected soil respiration rates. These findings show little evidence for interactions between basalt and increased CO2 on aboveground and belowground crop responses. It is possible, however, that under non-drought conditions, increased CO2 could improve Midwestern EW rates via greater soil moisture, although direct measures of EW were outside the scope of this study. This study also highlights the importance of initial soil conditions when assuming that basalt will stimulate crop productivity.

Graduation Semester

2025-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129233

Copyright and License Information

Copyright 2025 Megan Allen

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