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Abstract U.S. rice paddies, critical for food security, are increasingly contributing to non‐CO2greenhouse gas (GHG) emissions like methane (CH4) and nitrous oxide (N2O). Yet, the full assessment of GHG balance, considering trade‐offs between soil organic carbon (SOC) change and non‐CO2GHG emissions, is lacking. Integrating an improved agroecosystem model with a meta‐analysis of multiple field studies, we found that U.S. rice paddies were the rapidly growing net GHG emission sources, increased 138% from 3.7 ± 1.2 Tg CO2eq yr−1in the 1960s to 8.9 ± 2.7 Tg CO2eq yr−1in the 2010s. CH4, as the primary contributor, accounted for 10.1 ± 2.3 Tg CO2eq yr−1in the 2010s, alongside a notable rise in N2O emissions by 0.21 ± 0.03 Tg CO2eq yr−1. SOC change could offset 14.0% (1.45 ± 0.46 Tg CO2eq yr−1) of the climate‐warming effects of soil non‐CO2GHG emissions in the 2010s. This escalation in net GHG emissions is linked to intensified land use, increased atmospheric CO2, higher synthetic nitrogen fertilizer and manure application, and climate change. However, no/reduced tillage and non‐continuous irrigation could reduce net soil GHG emissions by approximately 10% and non‐CO2GHG emissions by about 39%, respectively. Despite the rise in net GHG emissions, the cost of achieving higher rice yields has decreased over time, with an average of 0.84 ± 0.18 kg CO2eq ha−1emitted per kilogram of rice produced in the 2010s. The study suggests the potential for significant GHG emission reductions to achieve climate‐friendly rice production in the U.S. through optimizing the ratio of synthetic N to manure fertilizer, reducing tillage, and implementing intermittent irrigation.
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Multiyear methane and nitrous oxide emissions in different irrigation management under long‐term continuous rice rotation in Arkansas
Abstract Rice paddies are one of the major sources of anthropogenic methane (CH4) emissions. The alternate wetting and drying (AWD) irrigation management has been shown to reduce CH4emissions and total global warming potential (GWP) (CH4and nitrous oxide [N2O]). However, there is limited information about utilizing AWD management to reduce greenhouse gas (GHG) emissions from commercial‐scale continuous rice fields. This study was conducted for five consecutive growing seasons (2015–2019) on a pair of adjacent fields in a commercial farm in Arkansas under long‐term continuous rice rotation irrigated with either continuously flooded (CF) or AWD conditions. The cumulative CH4emissions in the growing season across the two fields and 5 years ranged from 41 to 123 kg CH4‐C ha−1for CF and 1 to 73 kg CH4‐C ha−1for AWD. On average, AWD reduced CH4emissions by 73% relative to CH4emissions in CF fields. Compared to N2O emissions, CH4emissions dominated the GWP with an average contribution of 91% in both irrigation treatments. There was no significant variation in grain yield (7.3–11.9 Mg ha−1) or growing season N2O emissions (−0.02 to 0.51 kg N2O‐N ha−1) between the irrigation treatments. The yield‐scaled GWP was 368 and 173 kg CO2eq. Mg−1season−1for CF and AWD, respectively, showing the feasibility of AWD on a commercial farm to reduce the total GHG emissions while sustaining grain yield. Seasonal variations of GHG emissions observed within fields showed total GHG emissions were predominantly influenced by weather (precipitation) and crop and irrigation management. The influence of air temperature and floodwater heights on GHG emissions had high degree of variability among years and fields. These findings demonstrate that the use of multiyear GHG emission datasets could better capture variability of GHG emissions associated with rice production and could improve field verification of GHG emission models and scaling factors for commercial rice farms.
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- Award ID(s):
- 1752083
- PAR ID:
- 10402900
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Environmental Quality
- Volume:
- 52
- Issue:
- 3
- ISSN:
- 0047-2425
- Page Range / eLocation ID:
- p. 558-572
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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