Leaf-tissue Nutrient Dynamics in Mature Muscadine Cultivars Carlos and Noble in Georgia and North Carolina

Abstract

More than 3000 acres of commercial muscadine (Vitis rotundifolia) vineyards exist in the southeastern United States. The muscadine wine industry is generating an economic impact of $1 billion in North Carolina alone. Muscadines have been cultivated since the 1800s, but muscadine vineyard fertilizer programs, tissue sampling, and nutrient sufficiency ranges continue to be based on anecdotal knowledge. While seasonal changes in tissue nutrient concentration are well documented in bunch grape (Vitis vinifera), questions remain about the seasonal and cultivar-dependent dynamics of muscadine leaf tissue nutrient concentrations. The aim of this study was to assess temporal and cultivar-related differences in tissue nutrient concentration of mature commercially grown muscadines. Leaf tissue nutrient concentration of the muscadine cultivars Carlos and Noble were assessed in three vineyards (Piedmont North Carolina, north Georgia, and south Georgia) at bloom, véraison, and postharvest in 2018 and 2019. Our results show that nitrogen (N), phosphorus (P), and manganese (Mn) were generally above the recommended sufficiency ranges, with calcium increasing over the season—and N, P, and potassium decreasing over the season. ‘Carlos’ had significantly higher levels of N and P, compared with ‘Noble’, while ‘Noble’ showed higher Mn concentration than ‘Carlos’. With this evaluation, we demonstrate the need for a modification in muscadine tissue nutrient sufficiency ranges that are based on cultivar and vine growth stage.

Phenology Based Variability of Tissue Nutrient Content in Mature Muscadine Vines (Vitis rotundifolia cv. Carlos)

“…While the location of the sample (either primary shoot or opposite of a cluster) did not have an impact, the tissue type (petiole vs. full leaf) showed difference in content and variability between mobile and less mobile nutrients. This was reported previously in Vitis vinifera [5,10,29,33] and muscadines [26,32]. Generally, lower variability was observed when samples were taken as whole leaf samples.…”

“…Petiole P and K were mostly above the recommended sufficiency ranges [3], while full leaf P and K content were above or within the range with the progression of the season. Similar trends were found in a recent survey of muscadine tissue nutrient content across two states [26], suggesting a reevaluation and update of the recommended ranges for most nutrients. K was an exception in our study, as it showed lowest content during fruit set in full leaf samples.…”

“…In muscadines, however, there is a significant lack of standardization of tissue sampling methods and timing for the assessment of vineyard nutrition status [18][19][20][21][22]. Consequently, current recommendations of nutrient sufficiency ranges and tissue sampling time are based primarily on anecdotal knowledge [23][24][25][26], recommending whole leaf tissue sampling based on calendar month (June or early July), rather than on phenological stage of the vine [3,24]. Research to develop nutrient sufficiency ranges for muscadine production is mostly based on those of Jones and Mills from 1996 [3,27].…”