Systematic mischaracterization of the seasonal dynamics of N ₂ O emissions in soybean due to chamber placement

Abstract

Accurate quantification of soil nitrous oxide (N ₂ O) emissions depends on field measurements that adequately capture spatiotemporal variability. In annual row‐crop systems, N ₂ O emissions are expected to vary seasonally, but also spatially across the row to inter‐row gradient. However, most static chamber measurements place the chambers in the inter‐row, potentially overlooking differences in emissions between the row and inter‐row. We combined field experiments with a global literature review to evaluate whether current measurement strategies accurately represent the spatiotemporal variability of N ₂ O emissions in soybean [ Glycine max (L.) Merr.] systems. Field measurements revealed that spring N ₂ O emissions from the inter‐row were up to 2.2 times greater than those from the crop row. Conversely, maturity and postharvest emissions from within the crop row were 2.4 times greater than those from the inter‐row. However, our literature review found that 80% of published field experiments in soybeans (102/128 articles) did not include chambers over the crop row with rooted plants, indicating a systematic overestimation of early‐season N ₂ O emissions and systematic underestimation of late‐season N ₂ O emissions. In our experiments, spring overestimation offset the fall underestimation, resulting in similar cumulative annual emissions from both locations. However, this compensation may not occur universally, and inter‐row‐only measurements cannot be assumed to represent field‐scale N ₂ O emissions. Since field measurements provide the foundation for understanding and modeling soil N ₂ O emissions, improving chamber placement to better represent plant and soil processes is essential not only for accurate field‐scale estimates but also for developing more robust models, mitigation strategies, and reliable global N ₂ O inventories.