Dissolved organic carbon (DOC), an organic carbon fraction with high activeness and mobility, migrated by runoff is a key part in carbon cycle. A rational straw mulching rate can be regulated to obtain maximum benefits while controlling runoff and sediment yield on sloping lands. However, little remains known about the optimal straw mulching rates required for effectively reducing the loss of DOC in runoff. Therefore, to overcome the existing limitations, this study investigated the effects of modified maize straw mulching rates on the loss of DOC during runoff, utilizing indoor rainfall simulation. Five mulching rates, including 0, 0.2, 0.4, 0.6, and 0.8 kg m−2 [control (CK) and treatments (T1, T2, T3, and T4), respectively], were tested in combination with three slope gradients (10°, 15°, and 20°) to evaluate how straw mulching rate influences runoff, sediment yield, and runoff‐related DOC loss under a heavy rainfall intensity of 90 mm h−1. Our results showed that various straw mulching rates did not significantly differ runoff rates; however, straw mulching significantly reduced sediment concentration and yield. Moreover, the reduction in sediment yield increased with an increase in mulching rate. Compared to the CK, T1 resulted in a 63% increase in DOC loss at a slope of 20°. Additionally, T2 caused an 8% and 7.2% increase in DOC loss at both 10° and 15° slopes. Conversely, T3 and T4 reduced DOC loss by 54.1%–80.8% and 51.1%–65.2%, respectively, across all slope gradients. These results suggested that mulching rates of 0.2–0.4 kg m−2 may potentially increase DOC loss in runoff on the sloping lands. Our results hold significant importance in optimizing the use of straw mulching for sustainable management practices in agricultural lands.

中文翻译：

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径流、沉积物产量和径流相关溶解有机碳损失对 Regosols 坡地可变秸秆覆盖速率的响应


溶解有机碳 （DOC） 是一种具有高活性和迁移率的有机碳馏分，通过径流迁移，是碳循环的关键部分。可以调节合理的秸秆覆盖率以获得最大收益，同时控制坡地上的径流和沉积物产量。然而，对于有效减少径流中 DOC 损失所需的最佳秸秆覆盖率，人们仍然知之甚少。因此，为了克服现有的局限性，本研究利用室内降雨模拟调查了改良玉米秸秆覆盖率对径流期间 DOC 损失的影响。测试了 5 种覆盖速率，包括 0、0.2、0.4、0.6 和 0.8 kg m-2 [对照 （CK） 和处理（分别为 T1、T2、T3 和 T4]），结合三个坡度梯度（10°、15° 和 20°），以评估秸秆覆盖速率如何影响径流、沉积物产量和径流相关的 DOC 损失在 90 mm h-1 的强降雨强度下。我们的结果表明，各种秸秆覆盖率没有显著差异;然而，秸秆覆盖显著降低了沉积物浓度和产量。此外，沉积物产量的减少随着覆盖速率的增加而增加。与 CK 相比，T1 导致 20° 斜率时 DOC 损失增加 63%。此外，T2 导致 10° 和 15° 坡度的 DOC 损失增加 8% 和 7.2%。相反，T3 和 T4 在所有坡度梯度上分别降低了 54.1%–80.8% 和 51.1%–65.2% 的 DOC 损失。这些结果表明，0.2-0.4 kg m-2 的覆盖率可能会增加坡地径流中的 DOC 损失。我们的结果对于优化秸秆覆盖物的使用以实现农业用地的可持续管理实践具有重要意义。