Abstract
The burgeoning demand for rice in Latin America and Caribbean (LAC) exceeds supply, resulting in a rice deficit. To overcome this challenge, rice production should be increased, albeit sustainably. However, since rice production is associated with increases in the atmospheric concentration of two greenhouse gases (GHGs), namely methane (CH4) and nitrous oxide (N2O), the challenge is on ensuring that production increases are not associated with an increase in GHG emissions and thus do not cause an increase in GHG emission intensities. Based on current understanding of drivers of CH4 and N2O production, we provide here insights on the potential climate change mitigation benefits of management and technological options (i.e., seeding, tillage, irrigation, residue management) pursued in the LAC region. Studies conducted in the LAC region show intermittent irrigation or alternate wetting and drying of rice fields to reduce CH4 emissions by 25–70% without increasing N2O emissions. Results on yield changes associated with intermittent irrigation remain inconclusive. Compared to conventional tillage, no-tillage and anticipated tillage (i.e., fall tillage) cause a 21% and 25% reduction in CH4 emissions, respectively. From existing literature, it was unambiguous that the mitigation potential of most management strategies pursued in the LAC region need to be quantified while acknowledging country-specific conditions. While breeding high yielding and low emitting rice varieties may represent the most promising and possibly sustainable approach for achieving GHG emission reductions without demanding major changes in on-farm management practices, this is rather idealistic. We contend that a more realistic approach for realizing low GHG emitting rice production systems is to focus on increasing rice yields, for obvious food security reasons, which, while not reducing absolute emissions, should translate to a reduction in GHG emission intensities. Moreover, there is need to explore creative ways of incentivizing the adoption of promising combinations of management and technological options.
Highlights
Rice production is increasing in Latin America and the Caribbean (LAC), as the crop is classified as both a staple and a cash crop in several countries [1,2,3]
The aim of this review is to explore the state of knowledge of greenhouse gases (GHGs) emissions and mitigation strategies for rice systems in Latin America and Caribbean (LAC)
Since research on GHG emissions from the rice sector in LAC is still limited to a few countries and management practices (Table 2), there is a need for more research to cover existing information gaps on the environmental impacts of other rice management practices conducted in the region
Summary
Rice production is increasing in Latin America and the Caribbean (LAC), as the crop is classified as both a staple and a cash crop in several countries [1,2,3]. Irrigated lowland rice production is a significant anthropogenic source of methane (CH4) and nitrous oxide (N2O), two important greenhouse gases (GHGs). Variations in the quantities of CH4 emitted from rice production systems depend on variations in the amounts of labile carbon from root exudates, sloughed root cells, mucilage and litter (the main sources of substrate for methanogenesis), soil oxygen dynamics, Sustainability 2018, 10, 671 soil characteristics such as iron oxides and nitrogen content and differences in rice aerenchyma structure [13,16,17,18]. It is important that increased rice outputs are not associated with increases in GHG emissions This is important if we consider that, under the 2015 Climate Agreement, several LAC countries have committed to reduce their economy-wide GHG emissions, including those from the agriculture sector [27]. Besides identifying pragmatic options for reducing GHG emissions from rice production systems, we aim to understand knowledge gaps in the GHG mitigation potential of rice systems in LAC and discuss possibilities for making rice production systems in LAC more sustainable
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