Heavy rains early in April, May, and June contributed to several problems for vineyards in Oklahoma. Although we spent most of our days fighting black rot, it may be time to turn our attention to replacing nutrients leached out of the soil.
UC Davis provided a presentation by Andrew Teubes, a viticultural consultant from South Africa, on the nutrient requirements for grapevines. The presentation specifies the most important nutrients, the recommended levels, and timing of foliar and granule applications. See the Powerpoint presentation here (PPT).
Soil tests and petiole are the best ways to determine if you have deficiencies in the soil or grapevines. Samples of can be submitted through the Cleveland County Extension office on Robinson.