Inhibitory effect of high nitrate on N2O reduction is offset by long moist spells in heavily N loaded arable soils
2022
Senbayram, Mehmet | Wei, Zhijun | Wu, Di | Shan, Jun | Yan, Xiaoyuan | Well, Reinhard
Numerous interrelated factors (e.g., the labile C, soil NO₃⁻ concentration, and soil moisture content) are involved in controlling the microbial sources of N₂O and the product stoichiometry of denitrification; however, the interactions among different factors are still poorly understood. Here, a fully robotized continuous flow soil incubation system (allowing simultaneous measurements of N₂ and N₂O fluxes) was employed to investigate the interactive effects of a 51-day duration of moist spell, straw amendment, and the NO₃⁻ level on the rate and product stoichiometry (N₂O/(N₂O + N₂) ratio) of denitrification in heavily N loaded arable soils (i.e., paddy, vegetable, and orchard soils). The rewetting-induced N₂O emissions mainly originated from bacterial denitrification in all soil types, with a clear shift to fungal denitrification (plus contingent nitrification) over time. The vegetable and orchard soils showed a higher share of bacterial N₂O (62–70%) than that in the paddy soils (50–54%), which may be attributed to more labile-C driven bacterial activity induced by the greater manure and crop residue input therein. Interestingly, the inhibitory effect of high soil NO₃⁻ on N₂O reduction in these soils was offset by a 51-day-long moist spell, regardless of the amendment of straw. To our knowledge, our study is the first to show that the inhibitory effect of high residual NO₃⁻ on N₂O reduction is suppressed by a moist spell with a certain duration in heavily N loaded arable soils, suggesting that the water regime history should be considered when optimizing the N fertilizer application timing to mitigate soil N₂O emissions.
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