Rates of application will vary with soil type and initial pH. The buffer pH indicates the rate of lime to apply. In established plantings, petiole analysis in grapes is the best method of determining nutrient needs. The nutrient levels in these plant tissues most accurately reflect the uptake of nutrients by the crop. Soil analysis is used in conjunction with petiole analysis to determine the nutrient status of the soil and to monitor soil acidity. A combination of both analyses best evaluates fertilizer and lime needs.
Nutrient uptake is affected by many vineyard conditions.
Consequently, each year the nutrient levels will vary slightly depending upon the season. In order to obtain optimum growth and fruit quality, adequate levels of all nutrients must be present in the petioles and the relative amounts must be balanced. Even with optimum levels of nitrogen and potassium, poor growth can be attributed to low levels of magnesium, boron, zinc or other micronutrients. These will be reflected in the leaf analysis. For petiole analysis to be most effective, sample the same vines each year.