A new incubation system to simultaneously measure N$_2$ as well as N$_2$O and CO$_2$ 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 N$_2$, N$_2$O and CO$_2$. 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 N$_2$ and N$_2$O fluxes, we used $^{15}$N-enriched fertilizer and a $^{15}$N mass balance approach. The system inherent leakage rate was about 55 µg N m$^{− 2}$h$^{− 1}$ for N$_2$, while N$_2$O leakage rates were below the detection limit (< 1 µg N m$^{-2}$ h$^{-1}$). In our experiment, we found higher cumulative gaseous N$_2$ + N$_2$O 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 $^{15}$N mass balance approach, were found to be 1.7 ± 0.5 g N m$^{-2}$ f 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. ... mehrSoil respiration rates were also higher in sown mesocosms, with cumulative soil and aboveground biomass CO$_2$ respiration reaching 4.8 ± 0.1 and 4.0 ± 0.1 g C m$^{-2}$ f 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.