One of the most important courses you take in horticulture school is Soil Science, a two-parter that focuses on physical properties and then on chemistry. To a horticulturist, everything starts with soil (don’t ever call it “dirt”). The first step in any job is to determine what the soil is like, what it’s composed of, what you can do to improve or harm it, and what plants will grow best in it.
The role of insects, worms, and other soil organisms is extremely important in forming and sustaining healthy soil: they break down organic matter, aerate the soil, mix things up, and perform countless other tasks. (That’s a major reason why it’s a really, really bad idea to apply pesticides to your lawn.) An interesting article about termites in yesterday’s Science Times illuminates the many roles of these social insects in improving soil and, indeed, in creating entire ecosystems in desert areas. It also gives a good overview of the many factors that go into soil structure and composition.