How strongly do management practices and scales influence soil erosion rates in olive orchards? Empirical evidence from Alentejo (Portugal)

The use of vegetation suppression, such as herbicide application and mechanical plowing in olive orchards can exacerbate soil erosion. Maintaining understory vegetation can mitigate erosion and enhance soil fertility. Although prior research has assessed the soil management impact on erosion, knowledge gaps persist regarding dominant erosion processes across spatial scales and management effects on soil microenvironments (tree canopy, wheel ruts, vegetation strips). This study systematically evaluates how soil management (herbicides, plowing, no intervention) and spatial scales (microplots, hillslope plots) affect erosion dynamics, soil properties and their interactions with rainfall, ground cover, and orchard characteristics in Alentejo, Portugal. Over two years, seven orchards with varying management practices were monitored for erosion rates, ground cover, and soil properties. Soil management strongly influenced erosion, with herbicides inducing the highest hillslope-scale erosion (average 11.3 t ha−1 yr−1) and plowing dominating microplot erosion, while untreated plots exhibited minimal erosion (up to 99 % lower than the herbicide treatments). Wheel rut areas increased hillslope erosion through runoff concentration and bare soil, while vegetation strips suppressed it completely. Tree canopy areas varied: plowing mobilized new sediments, whereas untreated/herbicide microplots showed no erosion due to vegetation cover or stone‑lag armoring. Hillslope erosion stemmed from cumulative runoff, while microplots were influenced by soil properties like roughness or bulk density. Our findings highlight the need to consider scale effects in erosion modelling and policy. Future research should explore longer-term trends, expand underlying conditions (e.g. soil types, climatic zones or management practices), and refine soil erosion models to support sustainable soil conservation.