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Title: Cover crop, nitrogen, and variety effects on greenhouse gas emissions from organic rice production in southeast texas

item STORLIEN, J - Texas A&M University
item DOU, F - Texas A&M University
item STORLIEN, Y - Yangzhou University
item Torbert, Henry - Allen
item HONS, F - Texas A&M University
item WIGHT, J - Texas A&M University

Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/13/2014
Publication Date: 9/13/2014
Citation: Storlien, J.O., Dou, F., Storlien, Y., Torbert III, H.A., Hons, F.M., Wight, J.P. 2014. Cover crop, nitrogen, and variety effects on greenhouse gas emissions from organic rice production in southeast texas [abstract]. Rice Technical Working Group Meeting Proceedings. CDROM.

Interpretive Summary:

Technical Abstract: Increased demand for organic rice (Oryza sativa L.) has incentivized producer conversion from conventional to organically-managed rice production in the U.S. However, the impact of organic rice management practices on nutrient cycling and environmental sustainability is unclear. A field experiment was conducted at the Texas A&M AgriLife Research and Extension Center at Beaumont, Texas to assess and compare emissions of CO2, CH4, and N2O from different organically managed rice production scenarios. Specifically, the impacts of rice variety (Presidio, CLXL723, and Tesanai), nitrogen source (Rhizogen and Nature Safe), and nitrogen application rate (0, 150, and 210 kg N ha-1) on greenhouse gas (GHG) emissions were evaluated within three different fallow systems [ryegrass (Lolium multiflorum L.), clover (Trifolium repens L.), and weedy fallow]. Greenhouse gas fluxes were measured via static chamber-based methods for a period of 67 days (05/17/2013 through 07/23/2013) while fields remained under flooded conditions. As anticipated, N2O emissions remained low to non-detectable under the anaerobic conditions during this time period. Across all production scenarios, cumulative CO2 and CH4 emissions averaged 133 g CO2-C m-2 and 12 g CH4-C m-2, respectively. While direct CH4 emissions were much smaller than CO2, CH4 was the most dominant GHG when its global warming potential was considered (~360 g CO2-eq m-2). A temporal trend in flux rates between CO2 and CH4 was observed, with CH4 fluxes peaking (~13 mg CH4-C m-2 h-1) in mid-June, while CO2 fluxes peaked (~140 mg CO2-C m-2 h-1) in mid-July. Rice variety and N rate had little impact on the emissions of CO2 and CH4 in this study, while nitrogen source significantly influenced emissions. Rhizogen organic fertilizer increased emissions compared to Nature Safe fertilizer. Nearly double the mass of Rhizogen fertilizer was applied to supply the same amount of nitrogen as the Nature Safe fertilizer, which may partially explain the observed differences in GHG emissions. This work provided important preliminary information on GHG emissions from organic rice production and will continue as an ongoing effort to identify management practices which maximize rice yield while simultaneously minimizing GHG emissions.