Vineyard floor management intensity impacts soil health indicators and biodiversity across South Australian viticultural landscapes

Introduction

Vineyard floors in warm, dry landscapes including those in South Australia, have traditionally been managed using intensive practices such as tillage and herbicides to control weeds and vegetation, thereby limiting competition with grapevines for water and nutrients in order to not compromise yields (Celette et al., 2009). However, due to increasing awareness about the detrimental environmental impacts associated with chemical herbicides, tillage, and resulting bare earth on soil health and biodiversity (Winter et al., 2018; Guzmán et al., 2019), many recent investigations have been made as to the potential of increasing vineyard floor ground cover through the use of sown or spontaneous vegetation in addition to reducing the frequency and intensity of tillage and herbicides (Garcia et al., 2018).

Although there has been a noticeable shift in vineyard floor management towards more extensive and ecological practices in the last two decades, there are differences in the rates of adoption between winegrowing regions and between the mid-row and under-vine row areas in vineyards (Payen et al., 2022). While it has been demonstrated that in some vineyard sites, competition with grapevines for water and nutrients limiting grapevine yield is one of the main factors restraining the use of complete vineyard floor vegetation cover (Karl et al., 2016), this yield discrepancy is not always significant (Giese et al., 2014). Recent investigations of complete vineyard floor coverage systems have been predominantly focused in cool, wet winegrowing regions such as those in the Eastern United States, where many studies have indicated improved provisioning of ecosystem services in addition to more ideal vine balance as a result of these strategies (Vanden Heuvel and Centinari, 2021).

Thus, we propose to investigate how complete vineyard floor coverage is used by commercial vineyards in drier viticultural regions, such as those of Australia, and specifically, we aim to assess how these systems comparatively affect biodiversity and soil health indicators. Findings from another viticultural landscape study in a drier climate in Spain indicated that vineyards with cover crops compared to bare soil had higher soil organic carbon and greater plant biomass; however, this study focused solely on vineyard mid-row areas (Guzmán et al., 2019). Furthermore, a landscape study demonstrated that high mid-row management intensity at vineyards across Austria, France, Spain and Romania reduced plant species richness (Hall et al., 2020). Therefore, it is yet to be determined how plant biodiversity and soil health indicators compare at South Australian vineyard sites across a landscape with different floor management intensities, and in both the mid-row and under-vine row areas. In order to address these questions, a comprehensive investigation at the landscape level of varying intensity levels of vineyard floor management practices used in the Barossa and McLaren Vale regions was conducted to explore the effects on various environmental indicators of biodiversity and soil health.