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

Kristofor R. Brye

Committee Member

Richard J. Norman

Second Committee Member

Jarrod Hardke

Third Committee Member

Lanier Nalley

Fourth Committee Member

Benjamin Runkle

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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