Is it a commercial size vineyard?All I know is that fertilizing and spraying my vineyard with all modern chemicals gives me 5 times more yield.
I tried a very conservative approach in the last 3 years and it clearly failed.
I could potentially have done better, if I had introduced chicken tractors. That could have fertilized the soil enough to get back to respectable yields.
But there is no escaping powdery mildew without chemicals.
Chemical fertilizer will always give a short term benefit of increased growth at the expense of long term soil health. I'm not to familiar with how to grow crops where the soil is kept exposed in between plants in a regenerative way. I've been more focused on forage. Have you tried fertilizing with compost/manure?