Chamber Size Effects on Methane Emissions from Rice Production

Abstract

Quantifying methane (CH 4 ) emissions from cultivated rice ( Oryza sativa L.) production in the field has received increased attention recently due to methane’s importance as a greenhouse gas. The enclosed-headspace chamber technique is the standard methodology for field assessments of trace gas emissions. However, to our knowledge, no direct comparisons of measured CH 4 fluxes and emissions from field-grown rice among differing chamber sizes have been reported. Therefore, the objective of this study was to evaluate the effect of chamber size [15.2- and 30.4-cm inside diameter (id)] on CH 4 fluxes and season-long emissions from rice grown on a clay soil in Arkansas. Chamber size did not affect ( P > 0.05) CH 4 fluxes on 10 sampling dates during the flooded portion of the rice growing season and only affected fluxes on one of four sampling dates after flood release. Total season-long CH 4 emissions from optimally N-fertilized rice were 32.6 and 35.6 kg CH 4 -C ha &#45 1 &#183 season &#45 1 , which did not differ, and from bare clay soil were 0.74 and 1.75 kg CH 4 -C ha &#45 1 &#183 season &#45 1 , which also did not differ, from the 15.2- and 30.4-cm chambers, respectively. Chamber size ( i.e ., 15.2- or 30.4-cm id) did not result in differences in cumulative CH 4 emissions from this flooded-rice study that was conducted on a Sharkey clay soil in northeast Arkansas. Results indicate that both 15.2- and 30.4-cm diameter chambers were similarly adequate for measuring CH 4 fluxes and emissions from the clay soil investigated. The similarity in emissions results between chamber sizes also indicates that the 15.2-cm diameter chambers adequately facilitated the quantification of CH 4 emissions in this study.