Science Beneath Our Feet – Julio Calero

Comment on A Practical Soil Health Index for Olive Grove Farmers

Regarding relevant publications wihtin the objectives and the scope of the LivingSoiLL project, Prof. Dr. Julio Calero highlights two articles that establish simple metrics (indices) to evaluate the effects of sustainable management on the health of olive grove soils, both from the point of view of analytical properties – following what is established in Annexes I and II of the Soil Monitoring Law – and from the point of view of field morphological properties. The aim is adding multiple soil properties in only one composed value that is easily understandable by the farmer, since can be interpreted in terms of percentage out of 100% (an index of 0% would be a “dead” soil, while a soil with 100% would be “optimal”, for the particular conditions of the site).

Focusing on the 2018 article (Calero et al., 2018), one of the main barriers to assessing soil health is the cost and difficulty of obtaining the soil data needed to quickly apply indices in the field. Furthermore, dynamic indicators such as biological ones (i.e., soil basal respiration) require highly specialized personnel for their determination and are not addressed by commercial soil analysis laboratories. The morphological properties of the soil (color, structure, consistency, etc.) are, on the contrary, determined through sensory descriptions, without requiring any specific instrumentation. Nevertheless, these descriptions must follow a standardized protocol to avoid subjectivity. For example, color is described by comparing the soil to a reference numerical color scale (the Munsell color charts), rather than by the user’s verbal description.

In this work, more than 150 soils were characterized by morphological and analytical (lab) properties, including no only olive grove soils but also another types of andalusian ecosystems as pastures, pine woods, oak holm forest, etc. First, a soil health index from morphological indicators was developed, the Field Soil Quality Index (FSQI). Second, this index was applied to a new set of soils (validation set), which did not include the experimental setting used for the FSQI development. Third, the performance of the FSQI was checked to differentiate between olive groves, which applied sustainable management (cover crops, organic amedment, etc.) and conventional ones, obtaining a significant difference between the average FSQI value in conventional (18%) and sustainable olive (46%) groves. Moreover, a high correlation was verified between the morphological properties of the FSQI and the analytical properties determined in the laboratory.

Beyond this, probably the most important advance of the FSQI was the ability to integrate it into a user-friendly and free web tool, accessible via smartphone, for any user. The tool includes a very simple form for filling in the morphological parameters (6 properties and 18 indicators) and an output form that displays the index value. The only requirement for farmers and users is a short and easy training (30 minuts) to righlty applied de standarised descriptions of morphological properties.

Finally, the web tool developed for the article has been migrated to the Andalusian Living Lab website, where the posibility to geographically reference the olive grove where the index is applied has been added. This tool, available in Spanish and English, can be used by anyone in here.

About Julio Calero

Prof. Dr. Julio Calero (on the right) graduated in Biology from the University of Jaén in 1999 and obtained his doctorate from the University of Granada in 2006. He has 20 years of research experience and an extensive career as a teacher, having held positions as Assistant Professor, Assistant Ph.D Professor, and full Professor since 2021.

As a researcher, he states that he is particularly interested in the sustainability of agricultural systems, especially the olive grove, not only from an environmental point of view, but also for the social and economic repercussions of the Sustainable Development Goals (SDGs) and the 2030 Agenda, the EU European Green Deal, the Common Agricultural Policy (CAP), and the Horizon Europe Soil Mission, around which much of his research aligns. As part of his teaching and research activities, he has supervised four doctoral theses and is currently supervising two more.

For several years, Prof. Calero has oriented his research towards the study of Soil Health in olive groves and has worked in decision support systems in the agro-environmental field, in close collaboration with members of the Department of Computer Science and AI of the University of Granada, where fuzzy data mining tools were applied to manage the imprecision and uncertainty associated with farmer knowledge and to merge it with expert knowledge. He has also been interested in the application of statistical learning techniques in the development of soil quality indices in crops, creating web tools for olive groves that have recorded more than 8,000 queries. He has examined the effects on ecosystem services (ES) and soil health of olive groves of nature-based solutions (NBS), such as organic agriculture, cover crops, and the use of olive mill pomace compost as fertilizer, modelling the effects of organic matter in the soil structure at the microscopic scale. In recent years, the focus has been the main degradation processes affecting ES in olive groves, such as soil erosion, the alteration of nutrient cycles, and the carbon footprint. In total, he has published 39 JCR articles, 24 of which are Q1.

Prof. Dr. Julio Calero has been Principal Investigator (PI) of three competitive projects and has participated in various research projects in the agricultural field. He highlights that the main part of his research has a marked multidisciplinary component, especially with researchers from the ICT field. He is currently involved in the SOIL DATASPACE project, whose objective is to deploy a federated data space allowing the creation of a public-private ecosystem to generate new business models based on soil data. He also has experience applying new technologies to the monitoring and tracking of soil quality parameters in olive groves through multiscale and multitemporal fusion of remote sensing and in-situ probes, within the SENSOLIVE project. In recent years, he has been strongly oriented towards the international research framework, contributing to three major projects related to soil health in olive groves — SUSTAINOLIVE, SOIL O-LIVE, and LivingSoiLL — which together represent a budget of more than 21 million euros and involve almost 100 public and private institutions from six of the largest olive-producing countries worldwide.

Reference: Ruiz-Cátedra, G., Calero, J., Domouso, P., García-Ruiz, R., 2025. Do management practices which enhance nature-based processes improve soil health in olive groves? Geoderma 457, 117276 // Calero, J., Aranda, V. Montejo-Ráez, A., Martín-García J.M., 2018. A new soil quality index based on morpho-pedological indicators as a sitespecific web service applied to olive groves in the Province of Jaen (South Spain). Computers and Electronics in Agriculture, 146, 66-76