The hydrodynamic mechanism of rainfall runoff from loess slopes treated with incorporated straw

Abstract

The hydrodynamic parameters of rainfall runoff are important for those studying hillslope water flow, which in turn affects soil erosion, chemical pollutant migration, and diffusion. Straw incorporation into the cultivated soil layer may affect soil properties, resulting in different hydrodynamic behaviours of hillslope runoff. The objective of this study was to evaluate the influences of straw incorporation, rainfall intensity, and slope gradient on hydraulic parameters, such as the Reynolds number (Re), Froude number (Fr), Darcy‐Weisbach friction factor (f), and hydrodynamic dispersion coefficient (DH). Laboratory experiments were conducted under four straw incorporation rates (SRs: 0, 2, 4, and 8 t ha−1), three rainfall intensities (RIs: 80, 120, and 160 mm hr−1), and three slope gradients (SGs: 10, 15, and 20°) to examine the hydrodynamic characteristics. The results show that the increase in SR significantly reduces the DH. Compared with bare soil slope (0.020 m2 s−1), the mean DH decreased by half (0.011 m2 s−1) at an SR of 2 t ha−1 and approximately three‐quarters (0.005 m2 s−1) at an SR of 8 t ha−1. Both Re and Fr decreased with a rise in the SR; however, the slope roughness increased, which caused a significant increase in frictional force compared to results observed for the bare soil. A rise in RI and SG increased the driving force on the farmland slope. The Re and Fr decreased with RI and SR, while f increased with RI and SG. Therefore, this study elucidates that the incorporation of straw in the soil can alter the hydrodynamic parameters, thus influencing water flow velocity and soil erosion.

Effect of straw incorporation on controlling runoff and soil erosion in cropland with different land degradation degrees

“…How to effectively use those straw, burning, mulching, or incorporating, is a substantial issue related to economic development and environmental protection (Chen, Zhang, et al, 2023; Li et al, 2018). Judging from the results of the current study, straw incorporation can be widely applied to improve soil functions of degraded croplands (Li et al, 2020; Liu et al, 2021; Xing et al, 2023). Overall, great attention should be paid to management strategies to enhance straw decomposition rate, i.e., applying organic fertilizer, nitrogen fertilizer, and adding microbial inoculum when straw is incorporated, for improving soil hydrological properties and promoting soil erosion resistance in degraded cropland of Chinese black soil region.…”

“…How to effectively use those straw, burning, mulching, or incorporating, is a substantial issue related to economic development and environmental protection (Chen, Zhang, et al, 2023;Li et al, 2018). Judging from the results of the current study, straw incorporation can be widely applied to improve soil functions of degraded croplands Liu et al, 2021;Xing et al, 2023).…”

“…The mechanism of straw return for reducing runoff and erosion varies according to the approach. Among them, straw cover can effectively protect topsoil from direct raindrop splash, avoiding the increase in surface runoff and sediment yield (Liu et al, 2021), resulting from the reduced infiltration rate in response to the damage of soil structure (Rahma et al, 2019; Wang et al, 2021) and raindrop induced soil detachment (Hu et al, 2016; Keesstra et al, 2019; Omidvar et al, 2019; Serio et al, 2019). The incorporated straw within soil layer not only modifies soil structure and enlarges soil porosity, increases rainfall infiltration, and delays the time of runoff generation, but also its decomposition promotes the stability of soil aggregate, reduces soil erodibility, and sediment yield (Bombino et al, 2021; Ma et al, 2022; Yang et al, 2021).…”

“…Overall, straw return has great potential to reduce runoff and soil erosion. Compared to traditional tillage, the runoff reduction rate (RR) and soil erosion reduction rate (ER) of different straw approaches range from 3.1% to 95.1% and from 30.7% to 99.7% (Keesstra et al, 2019; Liu et al, 2021; Liu, Yang, et al, 2020; Ma et al, 2022; Wang et al, 2021).…”

Effects of straw mixed mulch length and coverage on infiltration, soil and water loss of Loess Plateau slopes

“…The exposed straw‐covered part reduced splash erosion due to rainfall and relatively constrained the loose sediment source formed by splash erosion (Sahu et al, 2019; Satoru et al, 2015). Moreover, the Reynolds and Froude numbers on a mixed straw‐covered slope are small, the Darcy–Weisbach drag coefficient value is high, the energy of water flow is reduced, and the slope stripping ability is relatively lower (Liu et al, 2021). The incorporation of straw further increases soil adhesion and the agglomeration stability, thus increasing the soil resistance to runoff erosion (Sahu et al, 2019).…”