At Selvanuova we value wild legume plants because they contribute to nitrogen fixation, thus naturally increasing the availability of this nutrient for our olive trees.
Nitrogen is the key nutrient for plant growth, therefore deeply influencing production in most crops, including olive trees.
However, the industrial production of nitrogen fertilisers used in conventional farming entails a high consumption of energy, which leads to air pollution and to the release of greenhouse gases.
Moreover, nitrogen compounds used in conventional agriculture (nitrates and ammonium) move very easily in the soil, and therefore, they are leached into watercourses and groundwater.
In contrast, fertilisers allowed in organic farming release nitrogen compounds very slowly, thus reducing the risk of water pollution.
At Selvanuova, besides adding organic manure, most of the nitrogen needed by the olive trees is fixed to the soil by wild plants belonging to the legume family.
The green cover of wildflowers growing under our olive trees include many legume plants, that have a symbiotic relationship with bacteria living on their roots and that are able to get nitrogen from the air and convert it into nitrates, which are used by plants. However, unlike chemically produced fertilisers, nitrogen fixed by legume plants, through their symbiotic bacteria, becomes available in the soil bit by bit, just in time to satisfy the needs of the plants, and therefore there is no risk of excess of nitrogen in the soil and consequential leaching into groundwater.
In this perspective, our extra virgin olive oil is the result of an intricate network of plants and other living organisms, among which our beloved olive trees are just one component.
The commonest legume plants in our olive groves belong to the Medicago genus and are strictly related to alfalfa. They belong to a group of very similar species (Medicago polymorpha, M. murex, M. orbicularis) which cannot be exactly identified unless we see the pod (which is not available in this season).
Another common species is the milkvetch (Astragalus hamosus).
Much scarcer is the vetch (Vicia sativa), which is also grown as a fodder crop.
Off topic: a plant that does not belong to the legume family, the grape hyacinth (Muscari neglectum), which anyway deserved a picture because of its beautiful blue flower.