Soil and Water Research - In Press
Multi-objective optimization and synergistic mechanisms of expansive soil improvement using organic fertilizer, slow-release fertilizer, and rice strawOriginal Paper
Yonggang Huang, Hongri Zhang, Xinzhong Wang, Yuexing Wu, Xianliang Tan, Kang Xiong
This study systematically investigated the synergistic improvement of expansive soil using organic fertilizer (OF), slow-release fertilizer (SRF), and rice straw (RS) through Box-Behnken design (BBD) and response surface methodology (RSM). Key findings include: The quadratic models demonstrated high statistical significance (root density: R² = 0.765, F = 25.84; shear strength: R² = 0.885, F = 18.65; swelling rate: R² = 0.20, F = 15.23; all P < 0.001) with low prediction errors (root content: ± 0.08 mg/cm³; shear strength: ± 0.58 kPa; swelling rate: ± 0.38%); The combination of 12.30% OF + 0.7 kg/m³ SRF + 0.4% RS achieved 58% improvement in shear strength, 32% improvement in root content, 42.7% reduction in swelling rate; OF exhibited negative linear effects on root density (β = –0.18, P = 0.002) with > 10% dosage reducing root growth by 9.0%; SRF showed positive linear impacts on shear strength (β = +0.25, p=0.001) and root density (β=+0.12, p=0.023); RS enhanced shear strength below 0.5% (β=+0.08, P = 0.042) but impaired root density due to pore clogging (β = –0.15, P = 0.008). The optimized formulation, validated by triplicate center-point tests (coefficient of variation ≤ 2.1%), is recommended for slope stabilization while limiting OF to ≤ 10% to prevent performance degradation. This data-driven approach provides actionable insights for balancing agricultural waste utilization and geotechnical performance in expansive soil improvement.
Rainfall pattern impact on runoff and sediment of the sloping cropland in Northeast ChinaOriginal Paper
Xu Fan, Wei Hu, Zhongzheng Ren, Yuan Chen, Qingsong Shen, Xingyi Zhang
Rainfall is a major contributor to water erosion of sloping cropland in Northeast China. Identifying how rainfall and slope gradient (S) influence runoff depth (RD) and sediment yield (SY) is crucial for preventing water erosion. Field measurements from runoff plots were collected from 2023 to 2024, and K-means clustering was applied to clarify the rainfall patterns. Response of RD and SY to the rainfall pattern and S were analysed. Key factors impacting RD and SY were explored. The results showed that three rainfall patterns were identified for 34 erosive rainfall events: A (41.2%, medium duration, medium rainfall intensity, and medium rainfall amount (RA)). B (50.0%, short duration, high rainfall intensity, and low RA) and C (5.4%, long duration, low rainfall intensity, high RA). Furthermore, the cumulative RD and SY increased with S for the same rainfall pattern. The cumulative RD and SY responded similarly to rainfall patterns for the same S. The contribution of the rainfall pattern to the cumulative RD and SY decreased in the order of C, A, and B. In addition, rainfall duration (D) and maximum 30 min rainfall intensity was the key factors affecting RD and SY for rainfall pattern A, respectively. Rainfall erosivity (R) was the key factor affecting RD and SY for rainfall pattern B and C. R and RD was dominant factor influencing the RD and SY for all rainfall events, respectively.