Open Collections

Abstract

Cover crops (CCs) provide many services to the agroecosystem. The efficacy of CCs varies by species composition and site-specific conditions. This study compared CC mixtures in two growth zones: the under-vine areas and alleyways, at two irrigated organic vineyards in the Okanagan Valley, British Columbia, Canada. The vineyards varied in climate and soil texture. Mixtures were compared with respect to weed suppression, biomass production, and N and C input potential. The effects of CCs on vineyard productivity, and fruit quality were assessed. Three alleyway and three under-vine CC mixtures were sown in May 2021 and reseeded in 2022. Alleyway treatments included mixtures composed of a grass and legume species; one mixture included tillage radish. Under-vine treatments included two legume monocultures, and one mixture composed of a grass with a legume. Large variation was observed between sites and years due to soil texture, environmental conditions, and disease/pest pressure. Overall, CC biomass production was positively associated with both weed suppression and CC aboveground N content. Alleyway mixtures containing perennial clover species, especially when paired with tillage radish, produced larger CC biomass, had greater CC N contents and superior weed suppression than the CC mixtures containing a cool-season annual legume. Under-vine CCs performed differently between sites. At Site 1, the perennial clover monoculture outperformed other treatments. At Site 2 in 2022, the grass and legume mixture was the most productive CC. The phenology of CC species, driven by genetic makeup, played a large role in both establishment and stand persistence under regional conditions. Perennial grasses and legumes, which were able to recover after mowing and resist traffic, demonstrated superior weed suppression, especially when paired with a companion crop such as tillage radish. No differences among CC mixtures were observed in grape yield, or fruit quality, indicating that CCs exerted minimal competitive pressure on vines. This study indicates that perennial legumes, when paired with a perennial grass, are well suited for use as CCs in irrigated Okanagan vineyards. Further research is needed to clarify how these cover crop mixtures interact with vineyard irrigation regimes, and how they compare to grower standard practices.