Epsilon Archive for Student Projects

Abstract

Managed forage grazing alongside flood-irrigated rice cultivation is recognized as a significant contributor to GHG emissions into the atmosphere. Forage grazing releases large amounts of nitrous oxide emissions, which can be reduced using species such as koronivia grass (Brachiaria humidicola), a forage grass known for its biological nitrification inhibition capacity through the root exudate called brachialactone. Rice cultivation releases large amounts of methane into the atmosphere, which is why greenhouse gas emissions from flood-irrigated rice paddies have been extensively studied in Asia; however, few studies have been conducted in Latin America, including Colombia, highlighting the need to understand the topic in this region better.
Rice cultivation and forage grazing are two of Colombia's most important agricultural activities; therefore, assessing GHG emissions from these activities is of utmost importance since no GHG emission factors are available for these two cropping systems under Colombian conditions.
This study aims to provide insight into the key characteristics of greenhouse gas emissions and yield-related components of different rice and koronivia grass cultivars in Colombia through a field trial of two rice and two koronivia grass cultivars, contributing to a better understanding of the environmental effects of cultivation in tropical areas of South America. To achieve this goal, biomass and yield components were evaluated, along with CH4 and N2O emissions and emission factors, with a specific focus on differences in root biomass between cultivars.
The rice and koronivia grass field trials were conducted at the CIAT Research Center in Colombia, where soil samples were collected before the trial started. The experimental layout consisted of a randomized block design with three replications of each rice and koronivia grass cultivar. Within each replication, three closed static chambers were placed and used as subsamples, with gas concentrations quantified using gas chromatography. An automatic weather station was used to gather environmental data during the sampling period.
Rice cultivar HL23 had a higher grain yield and greater daily methane emissions during the beginning of the sampling period. Meanwhile, cultivar FE60 displayed a larger variance in daily CH4 emissions from flowering to the end of the sampling period. This study presents the first reported field-emitted methane emissions from a koronivia grass field experiment. The koronivia grass cultivar CI67 displayed a significantly higher variance in daily CH4 emissions during the beginning of the sampling period, and a trend was observed where cultivar CI67 had higher cumulative CH4 emissions. This study also provides insight into the key characteristics of CH4 and N2O emissions and yield-related components of different rice and koronivia grass cultivars.