Date of Graduation

8-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Crop, Soil & Environmental Sciences (PhD)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Brye, Kristofor R.

Committee Member

Norman, Richard J.

Second Committee Member

Hardke, Jarrod T.

Third Committee Member

Nalley, Lawton L.

Fourth Committee Member

Runkle, Benjamin R.

Keywords

Greenhouse gas; methane; rice

Abstract

Methane (CH4) emissions from rice (Oryza sativa L.) production are a source of concern in the environmental and agricultural communities. New and/or revised agronomic methodologies will be needed to identify production practice combinations that reduce CH4 emissions without decreasing yields. The objective of this multi-year study was to evaluate the effects of water management (i.e., full-season flood and mid-season drain) (2015), cultivar (i.e., pure-line cultivar ‘LaKast’ and the RiceTec hybrid “XP753”) (2015), soil organic matter (SOM) concentration (2016), and tillage [conventional tillage (CT) and no-tillage (NT)] and urea-based fertilizers [N-(n-butyl) thiophosphoric triamide (NBPT)-coated urea and non-coated urea] (2017) on CH4 fluxes over the growing season, season-long emissions, and emissions intensity from rice grown in the direct-seeded, delayed-flood production system on silt-loam soils in east-central Arkansas. Vented, non-flow-through, non-steady-state chambers were used to collect gas samples over a 60-min sampling interval for weekly measurements of CH4 fluxes between flooding and harvest in each year of the study. During the 2015 sampling season, the full-season-flood (77.7 CH4-C ha-1season-1) produced the greatest (P < 0.01), while the mid-season-drain (42.8 kg CH4-C ha-1season-1) treatment produced the lowest season-long CH4 emissions. The mid-season-drain/hybrid combination exhibited the lowest (P < 0.05) emissions intensity (2.5 kg CH4-C Mg grain-1). In the 2016 growing season, rice grown in the soil with the largest SOM content, a managed grassland, produced the second largest CH4 emissions (1166 kg CH4-C ha-1 season-1). Methane emissions increased linearly (P < 0.05) with increasing SOM and total carbon concentrations (R2 = 0.81 and 0.85, respectively). In the 2017 study, CH4 fluxes differed (P < 0.01) between tillage treatments over time and when averaged across tillage, mean season-long CH4 emissions were 33.4 and 37.2 kg CH4-C ha-1 season-1 from NBPT-coated and non-coated urea, respectively, but were unaffected (P > 0.05) by fertilizer treatment. Properly matching water management scheme with cultivar selection and other agronomic management options and soil properties can provide a means to reduce CH4 emissions and reduce emissions intensity from rice production in the direct-seeded, delayed-flood production system on silt-loam soils.

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