Response of Soil Detachment Capacity to Concentrated Hydrodynamic Parameters in Citrus Orchards

Abstract

[Objective] This study was aimed to explore the mathematical relationship between soil detachment capacity and concentrated water flow hydraulic characteristics parameters in the typical slope orange orchard in the Three Gorges Reservoir Area, and to provide theoretical basis and data support for predicting soil erosion in slope orange orchard. [Methods] Through concentrated flow erosion tests, the soil detachment amount of a clear plowed sample plot and three green manure (Trifolium repens L, Poa annua L, and Vicia sepium L) covered plots under gradient hydrodynamic conditions of different slopes (10°～30°) and flow rates (18~126 L/min) combinations was analyzed. The quantitative relationships between soil detachment capacity of citrus orchard plots and hydrodynamic parameters (water shear force, water power), flow pattern parameters (Reynolds number, Froude number) and resistance parameters (Darcy-Weisbach resistance coefficient, Manning’s coefficient) were explored, and corresponding mathematical models were established. [Results] There was a significant correlation between the soil detachment capacity of green manure coverage and clean cultivation of citrus orchard and various hydraulic parameters. The soil detachment capacity was positively correlated with hydrodynamic and flow regime parameters in a power function (R2 was 0.86~0.99, NSE was 0.88~0.98, p<0.01), and negatively correlated with water flow resistance parameters in a power function (R2 was 0.32~0.60, NSE was 0.39~0.64, p<0.05), indicating that the soil detachment capacity significantly increased with the increasing of hydrodynamic and flow regime parameters, while significantly decreased with the increasing of resistance parameters. [Conclusion] In the citrus orchard covered with green manure or cleared, the predictive effect of water flow shear force on soil detachment capacity was better than that of water flow power. The reynolds number was more effective in predicting soil detachment capacity than the froude number. The prediction effect of Darcy-Weisbach resistance coefficient was better than that of Manning’s coefficient. Overall, the prediction of soil detachment capacity capacity by water flow shear force had the best effect and the highest accuracy (R2 average value was 0.96, NSE average value was 0.96).

Keywords

• citrus orchard
• soil detachment capacity
• hydraulic parameters
• prediction models