Many options for reducing nitrogen (N) losses from agriculture rely on changing the surface pathways of N runoff in one way or another, but the runoff N mechanism by agricultural interventions such as biochar, grass, and cross-ridge is not well understood. Herein, 12 artificial simulated rainstorms by three biochars (0%, 3%, and 6%), two planting modes (conventional flat planting, cross-ridge), and two underlying surfaces (bare, grass) were designed to investigate the surface pathways of N loss and possible tradeoffs in loessial sloping lands under 60 mm·h⁻¹ rainfall intensity. Results indicate that: (i) 3% and 6% biochar application can aggravate soil erosion on bare slope, but planting grass on 0% or 3% biochar bare slope has good reduction effects on sediment and N loss, while 6% belongs to excessive biochar on grassed slopes. (ii) Grass planting may decrease the loss fractions of particulate nitrogen (PN) more obviously than bare slope because it decreases the kinetic energy of raindrops, slows the rate of water flow, and improves the shear strength of soils with deep penetrating roots. Configuring cross-ridge with 0% or 3% biochar on grassed slope can reduce PN fraction obviously but the interception of cross-ridge on bare slope is limited and easy to fail. (iii) The hydrological pathways transporting various N fractions vary greatly owing to the interaction of biochar, grass, and cross-ridge. Runoff N from 10°, 15°, and 20° bare slope materializes mainly in particulate fractions (65.58%, 50.15%, and 60.46%), while from grassed slope it occurs mainly in dissolved fractions (54.01%, 59.50%, and 66.48%). These findings may help provide new insights needed to enhance soil health and maintain agroecosystem sustainability through decreasing N losses via sloping farmland management in loess hilly and gully regions.

减少农业中氮 (N) 损失的许多选择依赖于以一种或另一种方式改变氮径流的地表路径，但生物炭、草和跨岭等农业干预措施的径流氮机制尚不清楚。在此，设计了三种生物炭（0%、3%和6%）、两种种植方式（常规平植、横垄种植）和两种下垫面（裸露、草地）进行的12次人工模拟暴雨，以研究地表路径60 mm·h ^-1以下黄土坡地的 N 损失和可能的权衡降雨强度。结果表明：(i) 3%和6%的生物炭施用会加剧裸坡土壤侵蚀，而在0%或3%的生物炭裸坡植草对泥沙和氮流失有很好的减少作用，而6%属于过量biochar 在草坡上。(ii) 植草可以比裸坡更明显地降低颗粒氮（PN）的损失率，因为它降低了雨滴的动能，减慢了水流速度，并提高了深根穿透土壤的剪切强度。在草坡上配置0%或3%生物质炭横垄能明显降低PN分数，但对裸坡横垄截留有限且容易失效。(iii) 由于生物炭、草和横岭的相互作用，运输各种 N 组分的水文途径差异很大。来自 10°、15° 和 20° 裸坡的径流 N 主要以微粒部分（65.58%、50.15% 和 60.46%）的形式出现，而来自草坡的径流 N 主要以溶解部分（54.01%、59.50% 和 66.48）的形式出现%）。这些发现可能有助于提供新的见解，通过在黄土丘陵和沟壑地区进行倾斜农田管理来减少氮损失，从而增强土壤健康和维持农业生态系统的可持续性。