Decision Support Guide for the Implementation of Cover Crops in Olive Groves.

According to the European Environment Agency, Southern Europe is one of the regions facing the most serious soil degradation issues, mainly due to adverse edapho-climatic conditions and unsustainable agricultural practices ^[1]. In Spain, the National Soil Erosion Inventory reports an average agricultural soil loss of 30 t ha^-1 yr^{-1 [2]}, with the highest soil erosion rates observed in woody crops with bare soil management ^[2]. The intensification of tillage and the use of herbicides to control herbaceous vegetation has yielded agronomic benefits for olive groves in the short term. However, in the long term, it generates both negative agronomic impacts and environmental imbalances.

After years of research and collaboration with olive growers, the benefits of ground cover are increasingly recognized and accepted. This trend is increasingly supported by the Common Agricultural Policy 2023-2027 and the well-known P6 and P7 eco-schemes ^[3]. However, at farm scale, successfully establishing ground cover requires tailoring technical and economic management to the specific soil, climate, and olive grove conditions, as well as machinery, personnel, and economic constraints. In fact, there is a mismatch between environmental needs and policy regulations, and the required technical advice at farm scale. This is particularly relevant because, depending on local condition, the implementation of cover crops in woody crops in Mediterranean conditions can be costly and decrease crop yield ^[4].

This communication presents a decision support guide for cover crops implementation in olive groves, providing a series of basic principles, decision rules and management examples, with costs estimations, from surveying 39 olive growers across different regions of Spain. The guide is divided into four sections: I. Basic Concepts. This section briefly explains a set of elementary principles concerning the effects of ground covers, seeding rate determination, etc. II. Management Criteria. This section aims to identify appropriate strategies for specific initial conditions in olive groves, depending on the goals and constraints. III. Illustrated Examples. This section presents particular examples from olive groves that can be adapted to other groves. IV. Costs. This complex topic addresses the peculiarities of management and access to variable public funding. It explains how the costs have been calculated for the examples. The guide also includes a cost calculator which aims to be a practical tool designed to support olive growers in adopting more sustainable and economically viable practices. It allows for customized cost estimation of management and potential seeding with fertilization, by entering specific data from the agricultural operations ^[5].

Acknowledgements: Operational group BIOLIVAR; H2020 TUdi (GA 101000224) and ECOMED (PR.AVA23.INV202301.035) projects.

References:

[1] The European environment — state and outlook 2020: knowledge for transition to a sustainable Europe.

[2] Estrategia Nacional de Lucha Contra la Desertificación.
https://www.miteco.gob.es/content/dam/miteco/es/biodiversidad/temas/desertificacion-restauracion/estrategia_nacional_lucha_desertificacion_web_2022_tcm30-542085.pdf

[3] Regulation of eco-schemes in Spain: Real Decreto 147/2023, de 28 de febrero.
https://www.boe.es/eli/es/rd/2023/02/28/147/con

[4] Profitability of erosion control with cover crops in European vineyards under consideration of environmental costs.
https://digital.csic.es/handle/10261/215919

[5] Link to download the calculator:
https://digital.csic.es/handle/10261/364793