I am aware of the theory of balanced plant sap pH at 6.4, and have heard several consultants speak of it. I believe Carey Reams was the first to really promote this idea. I chased it for 5 years and never saw any results nor the ability to arrive at 6.4 pH for most crops. Once I started using plant sap testing like at NCC, they tell you the ideal range for each crop and I have seen that ideal change from crop to crop. And it is fairly wide across up to a whole pH point in some circumstances. For example grape leaves ideally would be around 4.5 ideally and I’ve seen them range from 3.5 to 5.0 pH. I generally think it’s more important to look at the balance of all the nutrients and understand what they accomplish than to chase a 6.4 pH. I could be very wrong and I am open to correct but this is my current belief.