Carbon-sink potential of continuous alfalfa agriculture lowered by short-term nitrous oxide emission events.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37024458.
- Also identified by DOI 10.1038/s41467-023-37391-2 and PMC identifier 10079834.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Alfalfa is the most widely grown forage crop worldwide and is thought to be a significant carbon sink due to high productivity, extensive root systems, and nitrogen-fixation. However, these conditions may increase nitrous oxide (N<sub>2</sub>O) emissions thus lowering the climate change mitigation potential. We used a suite of long-term automated instrumentation and satellite imagery to quantify patterns and drivers of greenhouse gas fluxes in a continuous alfalfa agroecosystem in California. We show that this continuous alfalfa system was a large N<sub>2</sub>O source (624 ± 28 mg N<sub>2</sub>O m<sup>2</sup> y<sup>-1</sup>), offsetting the ecosystem carbon (carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>)) sink by up to 14% annually. Short-term N<sub>2</sub>O emissions events (i.e., hot moments) accounted for ≤1% of measurements but up to 57% of annual emissions. Seasonal and daily trends in rainfall and irrigation were the primary drivers of hot moments of N<sub>2</sub>O emissions. Significant coherence between satellite-derived photosynthetic activity and N<sub>2</sub>O fluxes suggested plant activity was an important driver of background emissions. Combined data show annual N<sub>2</sub>O emissions can significantly lower the carbon-sink potential of continuous alfalfa agriculture.