Reduction of soil detachment and potassium leaching after treatments with rice‐husk‐derived nanosilica in paddy soils

Abstract

Soil erosion and nutrient leaching due to overland flow are among the major threats to the sustainability of rice paddy systems, particularly where rainfall is intense. The objectives of this study were to evaluate the effectiveness of rice‐husk‐derived nanosilica for reducing soil detachment capacity (D _c ) and potassium (K) leaching and to test the accuracy of key hydraulic variables in predicting D _c . Laboratory flume experiments were performed on paddy soil samples treated with four nanosilica rates (0%, 1%, 2%, 3% and 4% w/w, referred to as NS0, NS1, NS2, NS3 and NS4, respectively) and untreated under multiple flow discharges and low slope (<1%). Soil detachment capacity and K leaching were measured, and D _c was modelled based on key hydraulic parameters (shear stress, τ, and stream power, Ω). Nanosilica application significantly reduced mean D _c soil across all flow conditions on average by 15%–50% compared to untreated soil, depending on discharge and dose. The largest decrease (over 45%) occurred at doses over 2% nanosilica, beyond which improvements showed a plateau. Potassium leaching losses were also significantly reduced by 55% (NS2) to 60% (NS4) compared to the control. Moreover, critical shear stress and stream power both increased, while soil erodibility coefficients decreased with nanosilica addition. Non‐linear regression models based on shear stress and stream power showed strong prediction accuracy of D _c ( R ²  = 0.86–0.96). This confirms that these key hydraulic predictors reliably estimate D _c and capture amendment effects. Overall, the combined reduction in particle detachment and K loss demonstrates that rice‐husk‐derived nanosilica can simultaneously improve erosion resistance and nutrient conservation; modelling results indicate a threshold‐type response. Beneficial effects of nanosilica amendments are observed at the highest doses, suggesting that moderate application rates may be sufficient. These findings support the use of waste‐derived nanosilica as a circular‐economy soil amendment for improving the physical and functional resistance of rice paddy soils.