Humus is not just soil, it is a community of living things. Organic matter is a breeding ground for many types of microbes, including bacteria and fungi which break down plant material, and for other microorganisms that help plants roots absorb necessary nutrients.
I agree with your analysis, but I disagree that cagers refers to an entire class of persons, all motor vehicle drivers. To me, and maybe I am not using the right definition, a cager is an @sshole motor vehicle driver.
overcomer - someone who overcomes and establishes ascendancy and control by force or persuasion. Synonyms: subduer, surmounter. controller, defeat, get the better of, overcome, restrainer, subduer, surmounter.