Modelling phenological development of Mediterranean cover crop species as a tool for designing better management strategies in Southern Spain

A key management strategy for erosion control  for woody crops grown under Mediterranean climatic conditions is temporary crops, which grow during fall and winter and are terminated in early Spring, to minimize the risk for water competition with the main crop (Gómez et al; 2014; Winter et al., 2018). Although most farmers opt for a cover crop of adventitious vegetation present in their farms, there are situations when seeding a cover crop is necessary. For instance, on degraded soils, or  to enhance biodiversity. There is research by different teams for identifying and characterizing new specifies to be used as cover crops for woody crops (e.g. Gómez et al., 2020). Among the traits used for identifying the most suitable species or varieties are: emergence in early fall, early maturity in late winter or early Spring, rusticity, low height,  … 

The core question to be addressed by farmers and technicians when implementing this technique is to identify the proper termination date for the cover crop. This date needs to be set before depleting the soil water content beyond risking a yield decrease (Gómez et al., 2014) while, simultaneously, allowing seed maturity of the cover crop (to allow self-seeding and making this technique economically viable). Given the large variability in edapho-climatic and agronomic conditions in the Mediterranean region, this seed maturity date will vary significantly among areas, even within a relatively short distance (Gómez et al., 2020), more than the date of onset of the risk of water competition. As a result, farms in different areas will need to use, not only different termination dates, but also different strategies to manage the cover crop. For instance, leaving narrow strips un-terminated to produce seed if the cover crop termination needs to be done before seed maturity. 

This communication presents the results of a study evaluating the phenology of different varieties of Brachypodium and its modelling using a simple phenological model based on growing degree days following that of Gómez et al. (2020). Using climate records and this model, this communication will also present the results of an analysis of different cover crop management strategies based on the regional climatic differences in Andalusia. 

References
1- Gómez, J.A., et al.,  2014. Modeling to Evaluate and Manage Climate Change Effects on Water Use in Mediterranean Olive Orchards with Respect to Cover Crops and Tillage Management. Practical Applications of Agricultural System Models to Optimize the Use of Limited Water. Advances in Agricultural Systems Modeling, 5: 237-265
2- Gómez, J.A., Soriano, M.A. 2020. Evaluation of the suitability of three autochthonous herbaceous species as cover crops under Mediterranean conditions through the calibration and validation of a temperature-based phenology model. Agriculture, Ecosystems and Environment, 291, art. no. 106788.  
3- Winter, S., et al.,  2018. Effects of vegetation management intensity on biodiversity and ecosystem services in vineyards: A meta-analysis. Journal of Applied Ecology 55: 2484-2495. 

Acknowledgements: Financial support from grant TED2021-131496B-C22 (BRACHYCOVER) funded by MICIU/AEI/ 10.13039/501100011033 and by the “European Union NextGenerationEU/PRTR”; and from the European Union’s Horizon 2020 project TUdi (GA 101000224) .