The pH of the soil should be close to neutral, meaning that the ideal pH level should be between 5. 5 and 7. 5 in order for the walnut tree to grow healthy and strong. However, within the neutral levels, your best bet would most likely be a pH of seven, or as close to that number as possible.
Google the following: James A Duke 1983 Handbook of Energy Crops; Robert D Williams Black Walnut; and JLPeroys Walnut Blight.... pH 4.6-8.2 add a comment