Abstract
Irrigation practices can greatly influence greenhouse gas (GHG) emissions because of their control on soil microbial activity and substrate supply. However, the effects of different irrigation management practices, such as flood irrigations versus reduced volume methods, including drip and sprinkler irrigation, on GHG emissions are still poorly understood. Therefore, this review was performed to investigate the effects of different irrigation management strategies on the emission of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) by synthesizing existing research that either directly or indirectly examined the effects of at least two irrigation rates on GHG emissions within a single field-based study. Out of thirty-two articles selected for review, reduced irrigation was found to be effective in lowering the rate of CH4 emissions, while flood irrigation had the highest CH4 emission. The rate of CO2 emission increased mostly under low irrigation, and the effect of irrigation strategies on N2O emissions were inconsistent, though a majority of studies reported low N2O emissions in continuously flooded field treatments. The global warming potential (GWP) demonstrated that reduced or water-saving irrigation strategies have the potential to decrease the effect of GHG emissions. In general, GWP was higher for the field that was continuously flooded. The major finding from this review is that optimizing irrigation may help to reduce CH4 emissions and net GWP. However, more field research assessing the effect of varying rates of irrigation on the emission of GHGs from the agricultural field is warranted.
Highlights
The global population is projected to rise to 9 billion by 2050 [1] and food production will have to double to meet food demands [2]
The impact of reduced irrigation on nitrous oxide (N2 O) emissions has been examined in many cropping systems globally, and though there are clear interactions between reduced or deficit irrigation on other management practices including fertilization and tillage, findings appear to be inconsistent
Under no-till management, they showed that the average N2 O emissions from a sprinkler-irrigated paddy field were 6.03 kg N2 O ha−1, 57% less than fields that were under continuous flood irrigation (14.24 kg N2 O ha−1 )
Summary
The global population is projected to rise to 9 billion by 2050 [1] and food production will have to double to meet food demands [2]. Intensification of agriculture, in particular through implementing various irrigation practices alongside improved high-yielding crops and application of fertilizers and pesticides, have already proven effective in increasing crop production through the green revolution [3]. Irrigation increases crop productivity, but its implementation often increases operational energy demand and potentially GHG emissions [5]. Though irrigation has been a solution to boosting crop production, it can alter soil biogeochemical characteristics and soil structure, which may adversely impact soil carbon sequestration potential [6,7]. A better understanding of the link between various forms of irrigation and the subsequent impact on GHG emissions is needed; this effort is timely given that as of 2012, over 275 million hectares of agricultural fields are irrigated globally and this area is projected to increase [3]
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