Transient soil nitrogen transformation but persistent root morphological impairment associated with reduced apparent post-anthesis nitrogen accumulation and grain yield in winter wheat under anthesis waterlogging conditions

Context Waterlogging during anthesis limits winter wheat production in the Yangtze River Basin of China. Although waterlogging is known to alter soil nitrogen cycling and crop productivity, the temporal relationship between recovery of soil nitrogen availability and recovery of plant traits associated with grain yield remains poorly understood. This study tested whether anthesis waterlogging creates a temporal mismatch between soil nitrogen recovery and recovery of measured plant traits. Methods A two‑year field experiment was conducted on the Jianghan Plain using two winter wheat cultivars (Xiangmai 55 and Zhengmai 9023). Waterlogging was imposed for seven days at approximately 50% anthesis. Soil inorganic nitrogen dynamics, root morphological traits, flag-leaf SPAD and LAI, nitrogen accumulation and partitioning, and yield components were monitored during grain filling. Results Waterlogging caused rapid changes in soil inorganic nitrogen, decreasing NO₃⁻‑N by 40.8–48.9% while increasing NH₄⁺‑N by 95.0–147.6% after seven days. Soil nitrate recovered to control levels within approximately seven days after drainage. However, root morphology remained impaired: at 28 days post‑anthesis, total root length, root surface area, and root volume were reduced by up to 41.3%, 39.9% and 44.0%, respectively. These changes were accompanied by reductions in leaf chlorophyll content, leaf area index and apparent post-anthesis nitrogen accumulation. The amount of nitrogen remobilized from vegetative organs did not consistently increase, whereas the contribution of pre‑anthesis nitrogen to grain nitrogen increased by 12.4–18.8% and the contribution of post-anthesis nitrogen decreased. Grain yield decreased by 25.24–37.93% in Xiangmai 55 and 34.81–43.33% in Zhengmai 9023, and was primarily associated with reductions in 1000‑grain weight and grain number per spike. Multivariate analysis showed that grain yield was associated with canopy traits, root morphological traits and apparent post-anthesis nitrogen accumulation. Conclusions Anthesis waterlogging induced a transient shift in soil inorganic nitrogen composition, whereas root morphological traits and apparent post-anthesis nitrogen accumulation remained affected after drainage. The temporal mismatch between soil nitrogen recovery and recovery of measured plant traits was a prominent feature of the response. Differences between cultivars were associated with their recovery of canopy, nitrogen accumulation and yield traits, indicating that traits supporting recovery after waterlogging deserve further evaluation for wheat improvement.