The stakes are high. Olive cultivation is deeply embedded in the economies, landscapes and food systems of Mediterranean countries, yet orchards are increasingly exposed to drought, heatwaves, intense rainfall and shifts in the timing of seasonal water. Traditional groves, especially rainfed systems, depend on a limited reservoir of soil moisture. At the same time, intense storms can send water racing downslope, carrying away fertile soil before it can infiltrate. This creates a difficult balancing act: farmers need management practices that keep rainfall in the root zone, limit erosion and runoff, and preserve oil production without increasing competition for water between trees and vegetation growing beneath them.

To investigate that trade-off, Ignacio J. Lorite of the Andalusian Institute for Agricultural Research and Training and colleagues developed AdaptaOlive-WABOL, an olive-crop simulation model designed to connect soil processes with tree productivity. The model estimates the orchard water balance—the movement of rainfall into runoff, evaporation, transpiration, soil storage and drainage—and uses those calculations to project olive oil yield under contrasting climates and management systems. In practical terms, the model represents the orchard as a dynamic water budget. Rainfall adds water, while runoff removes water from the field before it reaches the soil; evaporation and plant transpiration return water to the atmosphere; and the remaining moisture becomes available to olive roots, subject to soil water-holding capacity and the timing of demand.

The researchers used an ensemble of climate projections from the Inter-Sectoral Impact Model Intercomparison Project, or ISIMIP, to explore how strategies might behave across different climatic conditions. The analysis included a relatively wet regime receiving about 600 millimetres of annual precipitation and a drier regime receiving about 400 millimetres. The study compared traditional tillage with alternatives that included cover crops and other forms of ground management. A cover crop can protect soil from raindrop impact, slow the movement of water across sloping land and improve the physical structure of the soil. But it is also a living competitor: before it is terminated, its roots and leaves draw water from the same soil reservoir that sustains the olive trees.

That competition explains why the same intervention produced opposite hydrological outcomes. Under the wetter conditions, a cover crop dominated by red brome, Bromus rubens, reduced runoff by approximately 28 per cent compared with traditional tillage. When rainfall is relatively abundant, vegetation can function as a protective layer. Its stems and residues interrupt overland flow, while roots and organic matter can promote infiltration, allowing more water to enter the soil rather than escaping from the orchard surface. Under the drier conditions, however, the cover crop increased runoff by about 5 per cent compared with tillage. The model indicates that this result is consistent with a cover crop consuming soil moisture and potentially leaving the ground less able to absorb later rainfall, particularly when the soil is already water-limited.

The yield cost of the cover crop was more consistent than its effect on runoff. Olive oil production declined by roughly 4 per cent under the wetter climate and by about 14 per cent under the drier one. The disparity is important because a small hydrological benefit may not compensate for a large production loss in a rainfed orchard. In a water-limited system, every litre taken up by temporary vegetation is a litre unavailable to the olive trees unless it is returned to the soil at the right time. The timing of cover-crop termination therefore matters as much as the decision to plant one. The study’s broader management framework includes termination by herbicide, livestock grazing, tillage or brush cutting, as well as inert ground cover and no-tillage approaches, each of which changes how much living vegetation, residue and exposed soil remain through the season.

The researchers do not present the results as a rejection of cover crops. Rather, they show why recommendations based on a single average climate can be misleading. A practice that protects soil during a year of substantial rainfall may be poorly suited to an orchard facing a sequence of dry winters and hotter spring conditions. The same region can contain steep and flat fields, shallow and deep soils, and orchards with very different water-holding capacities. Rainfall can also vary sharply from year to year, with long dry intervals punctuated by storms intense enough to overwhelm the soil surface. By linking climate projections with soil-management variables, AdaptaOlive-WABOL offers a way to examine these interactions quantitatively instead of assuming that an adaptation measure will behave consistently everywhere.

The model also captures a central problem in agricultural adaptation: improving one environmental service can impose a cost elsewhere. Reducing runoff can conserve soil and limit the export of nutrients and sediment, but increasing ground vegetation may reduce the water available for fruit development and oil accumulation. Tillage can leave soil more exposed to erosion, yet in some dry settings it may reduce competition from weeds or cover crops and preserve moisture for trees. No-tillage, residues and inert covers may offer different compromises, but their success will depend on surface conditions, rainfall intensity, soil texture and orchard design. The study therefore points toward management that is spatially and temporally targeted—using protective cover when runoff risk is high, while avoiding excessive water consumption during the most critical periods of olive growth.

Because the study is based on simulation rather than a single long-term field experiment, its results are best understood as evidence for testing strategies, not as a universal prescription. Simulation models simplify complex orchards, and their reliability depends on the quality of the climate inputs, soil parameters, crop responses and management assumptions. The researchers made the model available for evaluating water balance and yield under diverse climatic conditions, while the simulation outputs can be requested from the corresponding author. Even with those qualifications, the sharp contrast between the 28 per cent reduction in runoff under wetter conditions and the 5 per cent increase under drier conditions delivers a powerful message for a region confronting climate uncertainty. Mediterranean olive farming may become more resilient not through one ideal soil practice, but through flexible decisions that match ground cover and water use to local rainfall regimes, soil storage and the coming season’s risks.