Nitrogen stoichiometry promotes post-waterlogging soil function recovery through enzymatic bio-indicators and microbiome-associated processes

Abstract

Transient waterlogging fundamentally disrupts soil nitrogen (N) cycling, yet the dominant constraint on post-drainage recovery remains debated: persistent hypoxia or stoichiometric nutrient imbalance. We compared two recovery strategies following a 4-day field waterlogging event: chemical nitrogen rescue (4dFN) and passive physical aeration (4dFO₂). Waterlogging induced pronounced anaerobic conditions, evidenced by elevated dehydrogenase activity and disrupted ammonium-to-nitrogen (NH₄/NO₃) ratios. Passive re-aeration was inferior to N-supplementation in terms of restoring soil–plant functioning when nitrate pools were depleted. Linear mixed-effects models accounting for spatial block heterogeneity revealed that short-term changes in soil organic matter and total N reflected shifts in analytically defined, labile pools rather than net losses of stabilized soil stocks. High-throughput 16S rRNA sequencing indicated a pronounced microbial legacy effect during the recovery phase, where bacterial diversity at 2 weeks post-drainage was strongly associated with final N uptake. Random forest, Principal Component Analysis, and correlation network further showed that recovery trajectories were consistent with inorganic nitrogen balance and enzyme-mediated soil quality dynamics. Collectively, these results suggest that under these experimental conditions, post-waterlogging recovery is more closely associated with nitrogen stoichiometric imbalance than residual hypoxia. Effective remediation therefore requires restoring bioavailable N to re-couple soil biochemical processes and plant uptake, rather than relying on drainage alone.