In relation to permanent crops, these can be much more profitable and would suffer less erosion problems if combined with other crops, such as oilseeds or aromatic plants.
In the case of olive groves in particular, there are pilot experiments in which oilseeds for livestock, aromatic plants, medicinal plants, or even aloe vera are sown or planted between the tree lines. Interspersing the above-mentioned crops within the olive grove can be a good measure to halt depopulation in rural areas and facilitate the generational change, especially in hilly or sloping olive grove areas, where the abandonment of the land is usually higher.
Also, intercalating thyme, lavender or rosemary between the lines of the almond trees, or horticultural crops such as lettuce or broccoli between the fruit trees, can be a good example of diversification.
As for diversification in arable crops, the negative effects of rain-fed cereal monoculture could well be overcome with crop rotation and diversification by introducing fava beans, vetch, alfalfa, lentils or chickpeas, among many others (depending on the region).
Source: ABC de Sevilla and Fundación Global Nature