Supplements for corn

I've been collecting duckweed from a neighbor's pond as a protein supplement when I eventually get chickens. I started thinking about other things it might be used for and dumped some over and around the corn seedlings.

Which led to other thoughts, and research that went far astray from the intended track. Of course.

I am thinking of corn now, and what I can do to supplement it without chemicals. Eggshell, of course, and the duckweed. I don't have access to fish or fish meal ($) so that's out. I thought of eggs, but apparently the only consideration when eggs are used as a fertilizer is the amount of calcium in the shell. The conclusion seems to be "Just use the shells," without considering what else is in the whole egg.

Nitrogen supplementation is relatively simple, it's the others that become a concern.

Any ideas? Just brainstorming at the moment. The items used need to be close by, non-chemical, and cost little or nothing.

Grind bones for bonemeal and make biochar from any wood trimmings.

I also use my plant trimmings as mulch.