Chamber Size Effects on Methane Emissions from Rice Production

Alden D Smartt,Jarrod T Hardke,Richard J Norman,Edward E Gbur,Christopher W Rogers,Trent L Roberts,Kristofor R Brye

doi:10.4236/ojss.2015.510022

Alden D Smartt, Jarrod T Hardke + Show 5 more

Open Access

https://doi.org/10.4236/ojss.2015.510022

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Abstract

Quantifying methane (CH4) 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 CH4 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 CH4 fluxes and season-long emissions from rice grown on a clay soil in Arkansas. Chamber size did not affect (P > 0.05) CH4 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 CH4 emissions from optimally N-fertilized rice were 32.6 and 35.6 kg CH4-C ha&#451&#183season&#451, which did not differ, and from bare clay soil were 0.74 and 1.75 kg CH4-C ha&#451&#183season&#451, 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 CH4 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 CH4 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 CH4 emissions in this study.

Highlights

Rice (Oryza sativa L.) is one of the main staple food crops for much of the world’s population, with direct human consumption accounting for 85% of rice production compared to 72% and 19% for wheat (Triticum aestivum L.) and maize (Zea mays L.), respectively [1]
The objective of this study was to evaluate the effect of chamber size (15.2- and 30.4cm id) on CH4 fluxes and season-long emissions from rice grown on a clay soil in Arkansas
In the first few weeks after flood establishment, averaged across chamber size, CH4 fluxes were low and near zero in both treatments as the soil oxidation-reduction potential was decreasing due to the persistence of the flood

Summary

Introduction

Rice (Oryza sativa L.) is one of the main staple food crops for much of the world’s population, with direct human consumption accounting for 85% of rice production compared to 72% and 19% for wheat (Triticum aestivum L.) and maize (Zea mays L.), respectively [1]. Agriculture accounts for 47% of total anthropogenic methane (CH4) emissions, with 64% and 22% of agricultural CH4 emissions resulting from enteric fermentation and rice cultivation, respectively [2] [3]. Agricultural activities account for 33% of CH4 emissions in the United States (US), of which enteric fermentation is responsible for approximately 70% and rice cultivation is responsible for 3.7% [4]. Methane emissions from cultivated agricultural activities are significant since CH4 is a greenhouse gas and has a global warming potential that is 25 times greater than that of CO2 [5]. The 15.2-cm id has been suggested as the minimum chamber size to use in assessing trace gas emissions [7]. There is clearly no uniform chamber size associated with the enclosedheadspace chamber technique

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