Soil bacteria, the Axarquía avocado's ally against drought

The study, published in the npj Biofilms and Microbiomes online journal by Nature.com, concludes that soils managed for long periods under ecological systems are particularly enriched in bacterial populations of the genus Bacillus. These microorganisms are able to survive in extreme conditions and help plants to better withstand water stress.

The research was carried out by comparing two avocado plantations located in the Axarquía. One of them had been under organic management for more than 20 years, while the other followed a conventional system, based on chemical fertilisation and intensive agricultural management.

The scientists analysed the rhizosphere, i.e. the soil attached to the roots of the plants, to study how the microbial communities varied depending on the cultivation system used. The first author of the study, Blanca Ruiz Muñoz, explains that the study detected "important differences" in the physicochemical properties of both soils, with a greater presence of Bacillus bacteria on the organic plantation.

According to the researchers, these microorganisms act as invisible allies of the plants. Not only do they favour their growth, but they also improve their physiological state when the crop faces water shortage conditions, a factor which is particularly relevant in the Axarquía.

In a second phase of the study, the team isolated Bacillus bacteria from organic soils and evaluated their behaviour under controlled laboratory conditions. The results showed that some of these bacteria significantly improved the response of plants under water stress and favoured their development even in water-scarce scenarios.

The finding is of particular importance for the Malaga countryside and, in particular, for the Axarquía, where avocado cultivation has experienced rapid growth in recent decades, but which has also been greatly affected by drought, the lack of water resources and the debate on the sustainability of subtropical crops.

The study also opens the door to the development of bioinoculants, products made from microorganisms beneficial to soil and plants, which could help reduce the use of chemical fertilisers and other plant protection products. The researchers point to an agriculture in which not only more resilient plants are selected, but also soils with microbial communities that are better able to cope with climate change.

Professor José A. Gutiérrez Barranquero explained that "it is not only about growing plants, but also about managing and training soil microorganisms to move towards another form of agriculture". Víctor Carrión, Francisco Cazorla and Kevin M. Bretscher, researcher at the University of Leiden, also participated in the study.

The main conclusion of the study is that the way crops are cultivated today may condition the ability of crops to withstand future droughts. In a context of higher temperatures, more erratic rainfall and reduced water availability, soil is no longer just a physical support but a living ecosystem whose microbial biodiversity can be decisive in ensuring agricultural production.