To Apply Boron. The window to apply foliar boron is the same as sidedress N - first square to first bloom. Otherwise, try hard to tank mix it. There are a number of good boron fertilizers available. Most liquid borons are derived from boric acid.
Boric acid is also now available as a granular material.
It mixes about the same as the Solubor DF and appears equally effective. There is at least one boron fertilizer currently available claiming better efficiency, therefore, a lower rate is needed. In the past similar claims have been made, but have been contradicted by research. For now, treat all boron materials as equally effective. Nitrogen, potassium and boron are the fertilizer elements on which to concentrate.