Gypsum is useful out West for loosening up soils that are tight due to high sodium content, but that's not usually a problem here. Instead, our soils are tight due to high clay content or compaction. Still, grass usually grows pretty well on Indiana soils. We have a hummingbird vine called Campsis radicans. We've had it for three years already, and it has never bloomed, although the vine is hardy and healthy.
Excess nitrogen encourages foliar growth at the expense of flowers.
Trumpet creeper blooms profusely along country roads where it receives no care at all, so it shouldn't require fertilizer. Regular fertilizing of the surrounding lawn can also boost nitrogen to high levels. If your vines are growing in a shady location, move them or prune overhanging branches so they receive more sunlight. At least a half day of sunshine will promote blooming. Finally, pruning it back to several buds in the spring may promote flowering.