Revegetation of vineyard terrace embankments: A matter of seed mixture and seeding technique.

Maintaining traditional agricultural management to preserve agrobiodiversity remains one of the major challenges for biodiversity conservation in Europe. In Germany, viticulture on steep slopes has shaped cultural landscapes of high conservational value but has declined strongly in recent decades due to insufficient profitability. One promising approach to keep management economically viable is modern vineyard terracing. Here, vineyard rows run parallel to the hillside, thus facilitating management and lowering production costs. At the same time, terrace embankments offer large non-cropped areas between the vines that could make a significant contribution to biodiversity. However, to fully exploit that potential sustainable revegetation of terrace embankments is mandatory but barely studied. For three consecutive years, we evaluated the effects of different seed mixtures (hay threshing, regional and commercial mixture), seeding techniques (manual vs. hydro-seeding), and the effect of nurse plants, hay mulch, and fertilizer on the establishment and maintenance of vegetation on three terraced vineyards in the Upper Middle Rhine Valley, Germany. The regional mixture best met the demands of biodiversity conservation by providing high herb and flower cover. Hay threshing and the regional mixture provided sufficient vegetation cover to reduce the risk of erosion, whereas the commercial mixture performed poorly in terms of vegetation cover and plant diversity. For hydro-seeding, target species richness was higher and bare ground cover was significantly reduced compared to manual seeding. Nurse plants, hay mulch, and fertilizer application only marginally improved plant establishment. Together these results emphasize that hydro-seeding with regional seeds is the best approach for revegetation of vineyard terrace embankments by combining high biodiversity and sufficient vegetation cover to reduce erosion risks at the best cost-benefit ratio for winegrowers. Vineyard terracing contributes to maintaining economically viable viticulture on steep slopes and may concurrently act as a conservation tool for biodiversity in vineyard landscapes.