Carbon (C) and nitrogen (N) coupling regulated by intensified microbial activity and turnover in the rhizosphere hotspots are essential for balancing C-N budgets, sustaining agroecosystem productivity and mitigating global climate changes. However, it remains unclear whether and how the (different) spatial distribution of root-derived C from rhizosphere to non-rhizosphere will regulate N transport and transformation. To address this, a rhizobox (100 × 80 × 80 cm) experiment was conducted on soils from the same site using ¹³C-CO₂ (for 2 weeks) and ¹⁵ N-urea labelling for two cultivation systems, upland wheat and paddy rice. The paddy system showed larger proportion (43.5 versus 10.1%) of root-derived ¹³C retained into bulk soil, wider spatial transportation of both C and N (> 40 mm versus < 6.7 mm), higher proportion of plant-N uptake from soil pool (86.4 versus 62.3%), and higher loss of N derived from fertilizer pool (29.7 versus 13.2%), compared to the upland system. We identified that in paddy rice, larger amounts of N can be horizontally transported from bulk soil to the rhizosphere; the effects of root-derived C on N transformation mediated by soil microorganisms are more profound; higher plant uptake of soil-N as well as higher loss of fertilizer-N than those of upland wheat. Our results suggest that the transport and transformation of N are under the regulation of the spatial distribution of root-derived C and the associated microbial activities. This paves a new path towards proper management for weighing nutrient availability against fertilization reduction and balancing productivity with sustainability.

碳 (C) 和氮 (N) 耦合受根际热点微生物活动和周转强化的调节，对于平衡 CN 预算、维持农业生态系统生产力和缓解全球气候变化至关重要。然而，尚不清楚根源碳从根际到非根际的（不同）空间分布是否以及如何调节氮的运输和转化。为了解决这个问题，在同一地点的土壤上进行了根瘤箱 (100 × 80 × 80 cm) 实验，使用¹³ C-CO ₂（持续 2 周）和¹⁵  N-尿素标记两种栽培系统，陆地小麦和水稻. 水稻系统显示出更大比例（43.5 比 10.1%）的根源¹³C 保留在大块土壤中，C 和 N 的空间运输更广泛（> 40 毫米对 < 6.7 毫米），植物从土壤库中吸收氮的比例更高（86.4 对 62.3%），以及来自肥料库的氮流失更多（29.7 对 13.2%），与高地系统相比。我们发现，在水稻中，大量的 N 可以从大块土壤水平运输到根际；根源碳对土壤微生物介导的氮转化的影响更为深远；与陆地小麦相比，植物对土壤-N 的吸收更高，对肥料-N 的损失也更高。我们的结果表明，N 的运输和转化受根源 C 的空间分布和相关微生物活动的调节。