A new incubation system to simultaneously measure N₂ as well as N₂O and CO₂ fluxes from plant-soil mesocosms

This study presents a novel plant-soil mesocosm system designed for cultivating plants over periods ranging from days to weeks while continuously measuring fluxes of N₂, N₂O and CO₂. For proof of concept, we conducted a 33-day incubation experiment using six soil mesocosms, with three containing germinated wheat plants and three left plant-free. To validate the magnitude of N₂ and N₂O fluxes, we used ¹⁵N-enriched fertilizer and a ¹⁵N mass balance approach. The system inherent leakage rate was about 55 µg N m^− 2 h^− 1 for N₂, while N₂O leakage rates were below the detection limit (< 1 µg N m^− 2 h^− 1). In our experiment, we found higher cumulative gaseous N₂ + N₂O losses in sown soil (0.34 ± 0.02 g N m^− 2) as compared to bare soil (0.23 ± 0.01 g N m^− 2). N₂ fluxes accounted for approximately 94–96% of total gaseous N losses in both planted and unplanted mesocosms. N losses, as determined by the ¹⁵N mass balance approach, were found to be 1.7 ± 0.5 g N m^− 2 for the sown soil and 1.7 ± 0.6 g N m^− 2 for the bare soil, indicating an inconsistency between the two assessment methods. Soil respiration rates were also higher in sown mesocosms, with cumulative soil and aboveground biomass CO₂ respiration reaching 4.8 ± 0.1 and 4.0 ± 0.1 g C m^− 2 over the 33-day incubation period, in sown and bare soil, respectively. Overall, this study measured the effect of wheat growth on soil denitrification, highlighting the sensitivity and utility of this advanced incubation system for such studies.