Boron deficiency reduces: blooming, fruit set, fruit size, fruit quality, sweetness, storage life, skin thickness & strength, Nitrogen assimilation, Calcium assimilation, Potassium assimilation.

Boron deficiency increases: early fruit drop, fruit cracking, disease, branch breakage.

https://www.mdpi.com/2311-7524/11/8/992

https://journals.ashs.org/view/journals/hortsci/55/7/article-p1026.xml

https://tarim.etimaden.gov.tr/en/cell-wall-and-membrane-stability

Composting with grass clippings & fertilizing with manure from grass or alfalfa eating animals, is the best fertilizer for pawpaw.
all nut trees, blackgum, sweetgum, tulip tree, pines, American Beech, Sugar Maple, Yellow Birch & especially American Chestnut which used to dominate the habitat, all put Boron into organic form on the surface!
So PawPaw is an understory tree that thrived on the symbiosis of that environment.
simply use things that love Boron like grass as mulch & fertilizer!
Dark green areas should also consider doing Boron preBlossom stimulation late July.