Alternate and complete inter-row spontaneous vegetation covers versus tillage in a Graciano vineyard in Rioja Alavesa

Abstract

More than 40% of the Rioja Alavesa vineyards have an average slope higher than 10%, making them susceptible to erosion. Furthermore, it is foreseeable that rainfall will be less evenly distributed and that intense precipitation will occur more frequently because of climate change. Considering that most of the vineyard soils in Rioja Alavesa are managed by tillage, the objective of this study was to evaluate the impact that different soil management practices have on the vegetative growth and yield of the vineyard and the quality of the grapes and wine. To this end, a trial was conducted with a randomised block design and three replicates in a vineyard of the Graciano variety with a slope of between 10-20% during the years 2020, 2021, 2022, 2023 and 2024. Three treatments were compared: tillage (T), spontaneous vegetation cover (SC) and a combination of both with cover in alternate rows (AR). Growth was clearly reduced in the SC treatment, but the AR treatment had the same pruning weight as tillage in the last two years. Yield was also higher in the tillage treatment, with differences of 20-40% compared to cover treatments. However, these differences were smaller in the alternate row cover treatment, and in the last year the yield was even equal to that of tillage. In terms of quality, a higher malic acid content was observed in the grapes in the tillage treatment in 2020 and 2022. In addition, lower K content was detected in wine from the cover crop treatment. In general, there were no differences in probable alcohol content, or these were inconsistent. There were also no differences in pH, total tartaric acidity, and easily assimilable N in must, nor in colour intensity, total polyphenol index, anthocyanins, and tannins in wine. Spontaneous ground cover significantly reduces vegetative growth and production compared to vineyards managed by tillage. However, the treatment in alternate rows o tend to balance out over the years and is close to the tillage treatment in terms of production and yield. The most notable differences in quality relate to an increase in malic acidity in tillage and an increase in potassium in must. The alternate row cover treatment represents a viable alternative to traditional tillage management and would significantly reduce the problem of erosion.

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Acknowledments

This work has been funded by several projects: MONTCLIMA: Climate and natural hazards in the SUDOE mountains, co-funded by the European Regional Development Fund (ERDF) through the Interreg SUDOE programme; extension of the RiskAqua Soil project (EAPA_272/2016) co-financed by the European Regional Development Fund (ERDF) through the INTERREG Atlantic Arc programme; VITISAD2 project (EFA116/10) of the INTERREG POCTEFA 2021-2027 programme. We would also like to thank the Maisulan winery (Eva and Luis) for their hospitality, willingness and participation in all the work.