Date of Graduation

8-2022

Document Type

Thesis

Degree Name

Master of Science in Biological Engineering (MS)

Degree Level

Graduate

Department

Biological and Agricultural Engineering

Advisor/Mentor

Benjamin Runkle

Committee Member

Kusum Naithani

Second Committee Member

Brian Haggard

Third Committee Member

Michele Reba

Keywords

eddy covariance, emissions, irrigation, methane, ratoon, rice

Abstract

Sustainable intensification of rice farming is crucial to meeting human food needs while reducing environmental impacts. Rice produces 8% of all anthropogenic CH4, which is a potent greenhouse gas. CH4 emissions can potentially be reduced by cultivation practices that minimize the number of days the fields are saturated, such as dry-seeding instead of water-seeding and irrigation using the alternate wetting and drying (AWD) technique instead of delayed, continuous flooding (DF). Ratoon cropping, wherein a second crop of rice is grown from the harvested stubble of the first crop, can be used to produce additional yield with minimal labor, but may generate more CH4 than single cropping. The objective of this study was to test different seeding methods and water management regimes for their impact on yield and CH4 emissions, as well as to determine if ratoon cropping was a viable method of sustainable intensification for rice in Arkansas. Adjacent fields in Lonoke County, Arkansas were compared under different seeding and irrigation treatments from 2015 through 2020; the 2020 season also included a ratoon crop. Field-scale CH4 emissions were measured using the eddy covariance method at each field. AWD reduced CH4 emissions by 79.5% on average in comparison to DF for the main seasons. CH4 emissions from the main crop ranged from 11.0 to 40.7 kg ha-1, while CH4 emissions from the ratoon crop ranged from 39.7-50.7 kg ha-1, up to a 3.6-fold increase in emissions relative to the main crop. CH4 emissions from the ratoon crop in this study were much lower than those found in previous ratoon studies, suggesting that ratoon cropping combined with AWD might be a viable option for sustainable intensification if the ratoon yield could be improved. The ratoon crop yield was 13% that of the main crop yield on average but there was no significant difference in yield between treatments for the main seasons. Seeding method had no discernable impact on CH4 emissions or yield.

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