BD#501 should be been used after using BD#500.
Horn silica (501) stimulates photosynthesis and the ripening process, regulates leaf growth, enhances flavor and storage quality.
How to use BD #501 Stir vigorously for one hour in sufficient water to meet your application requirements. Apply immediately to foliage. Apply periodically during the growing season. One unit is enough for one acre when stirred properly. Tip: Spray in early morning before the heat of the day.
501 should be used before flowers are open and after they are closed, not while flowers are open. Additionally, 501 should mostly be used after 500 horn manure.
For additional information, visit: JPI Preparation Articles ; Instruction Handouts
Additional Article: Brief Instructions: 500, 501, 508