Well first, humus content. Humus content is the amount of organic matter, or humus, in the soil. And it's pretty easy to judge on a sort of a simple homeowner level. If you pick up the soil that's fairly dry and you crush it and it stays together like that, there is a decent amount of humus. Yes, nice and brown, too.
Soils can be all different colors and be equally fertile and good.
But this just happens to be dark-looking soil to begin with. Now, you mentioned drainage. If I grab it and it stays together, that's fine. If there's puddles on the soil surface you know you have a problem with a very clay soil, and the answer to that is to add sand or some other type of aggregate material. You've got some manure and compost for us here.