Treatment Plan

Phosphorus deficiency is typically associated with low soil pH.  If soil pH is low, phosphorus availability can be increased with the addition of lime.  Petiole tests often indicate phosphorus deficiency in the absence of visible symptoms on American and hybrid cultivars.  Certain vinifera cultivars are more susceptible to phosphorus deficiency than others; Tony Wolfe, Virginia Tech, (Wine Grape Production Guide for Eastern North America) reports Merlot is more susceptible than other cultivars. Soil testing is used to measure soil pH and Cation Exchange Capacity (CEC) which are used to determine lime additions, and bloom or post-veraison petiole sampling are used to determine vineyard phosphorus status.