“…However, estimates about soil exchangeable K are not always related to yield parameters or to grape yield in producing vineyards, since vines' root system exploits a larger soil volume than the herein sampled soil volume (Tramontini et al, 2013; CQFS-RS / SC, 2016) and has internal nutrient reserves, including K (Pradubsuk & Davenport, 2010). Therefore, estimates of nutrient concentrations, such as estimates of K content in leaves, (assessed at full bloom or at berries-color-change time) can be closely related to vineyards' yield parameters, as well as to grape must oenological parameters such as (TST), pH, total titratable acidity (ATT), malic acid, among other parameters (Ciotta et al, 2016;Messiga et al, 2016) that can influence the quality of the wine (Walker & Blackmore, 2012). It is likely estimating K critical level in leaves (collected at full bloom) to assess oenological quality parameters in grape must, since these parameters can also apply to other wine types.…”