Your bat shit trick ought to work slick on the basil too.

The rule of thumb is that the leaves need nitrogen (N), the flowers phosphate (P), and the roots potash (K).

Too much nitrogen on plants that you want fruit or flowers from (squash, peppers, tomatoes, cannabis, etc.) and the plant will put out more foliage and less of what you want.

But plants you want greens from, including basil, can handle a lot of nitrogen with no problem. Bat guano has more than just N, of course, and even comes in different formulations for different crops.

I like to feed on top as a general rule, instead of so much at the bottom of the hole. Just scratch it in the top few inches surface and let the rain or watering take the nutrients to the roots. But, as you've discovered, it can work great in the hole too.

But my favorite way to feed is with manure tea, especially nitro loving crops. Nothing special is needed for this. Just a bucket and some water and manure. I'd usually fill a barrel in the middle of the garden with water and a couple of buckets of horse manure, and then water plants from dipping from it.......crude, but very effective.

Foliar applications of kelp is a great trick that pros i know use a lot. It isn't just about the NPK with kelp, it is full of micronutrients that really and obviously help. Plants pick up nutrients much faster and more effeciently when sprayed on the leaves. Be sure to do this in early morning or evening.....even with kelp.

great west coast organic grower supplies:
www.groworganic.com/item_F13...7_Oz.html

great east coast organic grower supplies:
www.7springsfarm.com/catalog...#LiquidF