A field evaluation of the impact of temporary cover crops on soil properties and vegetation communities in southern Spain vineyards

Transition from bare soil to temporary cover crop-based soil management has been promoted for at least two decades in vineyards in southern Spain. However, there is limited field evaluation of its impact at commercial vineyard level. Our study evaluates the impact of these two soil managements in sixteen commercial vineyards in Southern Spain. Selected soil physical, chemical and biological properties were measured in a representative inter-row of each vineyard during 2015-2016. Overall, the temporary cover crop vineyard presented a significant improvement in soil organic carbon content and aggregate stability in comparison to the bare soil vineyards, 73 and 29% respectively, as well as presenting more diverse plant communities. Nevertheless, there was a large variability among vineyards that preclude the identification of other impacts and differences among the different kind of temporary cover crops followed by the winegrowers. A refined analysis concentrated in the eleven vineyards on more calcareous soils distinguishing among bare soil, spontaneous cover crop of low biomass production, spontaneous cover crop of high biomass production and barley cover crop of high biomass production was performed. It resulted in a larger improvement in soil properties in the vineyards having a spontaneous cover crop of high biomass production followed by the ones having a cover crop with barley. It also showed how the spontaneous cover crop of low biomass production presented a moderate or negligible improvement in soil properties as compared to the bare soil vineyards. In general terms, the best strategy seemed to be the vineyards with spontaneous cover crops that were able to achieve a high biomass production, above 0.91 t ha a per year, which also presented a high plant diversity. Our results indicate the need for a proper evaluation of the impact of cover crop-based management based on vineyard assessment of soil properties and their relation with driving variables, as in our case biomass production and composition of the cover crops.