Utility of dormant season pruning wood to predict nutrient status of grapevines

Grape growers utilize leaf blades or petioles collected during the growing season to monitor vine nutrition. However, an earlier indicator of vine nutrient status is desirable. The pruning wood derived from last season’s fruiting shoots (dormant stems) collected in winter may be a useful tissue to assess vine nutrition before the growing season. The utility of dormant stems to indicate grapevine nitrogen (N), phosphorus (P), and potassium (K) status was tested in Pinot noir grapevines (<i>Vitis vinifera</i> L.) from a microplot vineyard where varying levels of N, P, or K were provided over four years. Dormant stem nutrients were evaluated based on their response to varying nutrient supply and as predictors of vine nutrient status in the upcoming growing season. Concentrations of P and K in dormant stems reflected the amount of P and K supplied to vines, and effects grew larger over time. The concentrations of P and K in dormant stems also correlated well with next season P and K levels in leaf blades and petioles. Relationships between leaf blade and petiole tests and dormant stems were more consistent across three years for P than for K. Nitrogen concentrations in dormant stems did not consistently reflect N inputs and were correlated only weakly to leaf blade and petiole N tests during the growing season. These findings indicate that dormant stems can be useful for diagnosing P and K status of grapevines.