Date of Graduation

5-2025

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Brye, Kristofor R.

Committee Member

Roberts, Trenton L.

Second Committee Member

Fernandes, Samuel B.

Third Committee Member

Daniels, Michael B.

Keywords

Arkansas; biochar; conservation agriculture; greenhouse gases; reduced tillage

Abstract

Biochar application and reduced tillage (RT) are both practices within the conservation agriculture framework, but specific impacts of these practices on direct greenhouse gas (GHG) emissions still require investigation in varied agricultural systems. This research aimed to evaluate the effects of biochar source (i.e., powder- and pellet-sized) and application rate (i.e., 0, 2.5, and 5 Mg ha-1) on GHG production in simulated furrow-irrigated rice (Oryza sativa) in a greenhouse experiment, and to evaluate the effects of RT relative to conventional tillage (CT) on GHG production in soybean (Glycine max) in southeast Arkansas. Both studies evaluated carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes and season-long emissions, emissions intensity (EI), and global warming potential (GWP), as well as soil physical and chemical properties, and plant response, such as yield. Results showed an almost 10-fold reduction (P < 0.05) in N2O season-long emissions from the 5 Mg biochar ha-1 application rate of pellet-sized biochar (4.9 kg N2O ha-1 season-1) compared to the control (i.e., 0 Mg ha-1; 41.7 kg N2O ha-1 season-1), without any yield penalty, indicating the ability of pellet-sized wood chip biochar to mitigate N2O production in upland rice. In contrast, season-long N2O emissions did not differ (P > 0.05) among powder-sized biochar treatments. Bulk density was lower (P < 0.05) in the CT (1.29 g cm-3) than in the RT (1.44 g cm-3) treatment at the beginning of the growing season, but the greater bulk density in the RT treatment did not result in decreased yield compared to CT. Season-long CO2, CH4, and N2O emissions and EI, as well as GWP, did not differ (P > 0.05) between RT and CT, indicating that more time is needed after practice implementation to realize GHG mitigation benefits from RT. These results contribute to the wider knowledge of potential conservation agriculture benefits in Arkansas by quantifying direct climatic impacts of RT and biochar amendment.

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