Cover Crop and Root Pruning Effects on the Rooting Pattern of SO4 Rootstock Grafted to Cabernet Sauvignon

Root biomass, root intercepts, and root length density of SO4 rootstock grafted to Cabernet Sauvignon and exposed to under-trellis cover cropping (CC) and with or without root pruning (RP or NRP, respectively) were evaluated over three years. The CC treatments included tall fescue (Festuca arundinacea Shreb.) varieties KY-31, with and without RP, Elite II without RP, and an 0.9 m wide, under-trellis herbicide strip with KY-31 fescue interrows, with and without RP. Around 70% of grapevine root biomass was observed at <= 60 cm soil depth, regardless of treatment or year. KY-31 fescue/NRP vines had the most (96%) root biomass at <= 60 cm soil depth in 2008. Rooting depth distributions were fitted to the model Y = (1 - beta(d)), where d is soil depth (cm), Y is the cumulative root fraction from the soil surface to depth d, and the unknown parameter beta is a measure of soil vertical root distribution used as a response variable to test for treatment differences. All root distributions across treatments and years, except KY-31 fescue/NRP in 2008, generated beta values greater than 0.970, similar to beta values from other root distribution studies. The modest treatment impact on root biomass and distribution suggests that these mature grapevines adapted to CC and annual RP in this environment, and partially explains the minimal impact on soil water content and vine water potential previously reported from this experiment.