Modelling the event-based hydrological response of olive groves on steep slopes and clayey soils under mulching and tillage management using the SCS-CN, Horton and USLE-family models

The SCS-CN, Horton and USLE-family models are used worldwide, but few examples are available for olive groves on steep and clayey soils under mulching of pruning residues. We evaluate the accuracy in predicting runoff and soil loss of a steep (20%) and clayey olive grove subject to three soil conservation practices: mechanical tillage (MT), mulching with pruning residues (NTR) and standard protection (SP), measured at plot scale in Southern Italy during 30 months under natural rainfall. The models were calibrated by adjusting the Curve Numbers (for the SCS-CN model) and the C-factors (MUSLE and USLE-M); the Horton model was not calibrated. The model performance was assessed by qualitative and quantitative procedures. In all practices, the SCS-CN was more accurate for runoff predictions (mean difference of 7% compared with corresponding observations) compared with the Horton (mean difference of 30%). For soil erosion, the MUSLE showed better performance in soils subject to MT or total protection (differences lower than 10%), while the USLE-M was more reliable to simulate soil loss in mulched plots (differences of 8%). A set of Curve Numbers (95 for MT, 70 for SP and 85 for NTR) and C-factors (0.4 for MT, 0.2 for SP and 0.1 for NTR) are proposed for applications in steep slope and clayey soil olive orchards using the SCS-CN and USLE proposed models, respectively. Validation exercises in other environmental experimental conditions would enhance the export these models for runoff and erosion control in agricultural soils treated with mulching.