Q. Could you add boron into a compost pile to try to solubilize it and then spray it?
A. The problem is that boron in a pure concentrated form is a biocide, so if you add boron to a compost pile, it will suppress biological activity if you put on large enough amounts to translate effectively in the field. You have a mismatch in the concentration. If you put on a high-enough concentration of the compost to do a good job delivering it to the plant, you’d have a negative effect on the compost. So, I’m not a fan from that perspective.
Now, would combining boron with a humic acid before adding it to the compost pile reduce the biocidal effect? Possibly. I would expect it to buffer it to a degree, but I don’t know for sure. It’d be worth experimenting with.
From John Kempf’s Eco-Ag U presentation at the 2025 Acres U.S.A. conference. Recordings of the conference are available at conference.acresusa.com.recordings-2025.
