What is kakawate as fertilizer?

Kakawate [Gliricidia sepium] isn't a fertilizer. Instead, it's an ornamental tree that functions as a natural fertilizer. Specifically, it shares membership with beans and peas in the Fabaceae family. That family is known for its contributions to soil fertility. It does so by nitrogen-fixation, which makes present but inaccessible nitrogen available in the soluble form that plant roots and soil food web critters need for intake.

Nitrogen is one of the three main components in the fertilizer that you buy from the store or that you make through composting.