We have to define the limits for each size group. Macro organisms are considered to be larger than 2 mm in diameter greater than the thickness of a looney. Meso organisms are between 2 mm and 0.2 mm in diameter. Micro organisms are less than 0.2 mm and we normally need a magnifying glass or microscope to observe them. When you study soil organisms try to understand not only the individual organisms but also the complex interactions and processes that make them part of the soil ecosystem.
Many soil organisms are beneficial but others are devastating to crops and animals.
Beneficial organisms take part in many physical and chemical reactions that improve soil structure , break down organic matter and cycle nutrients. Others, however such as the tiny nematode, a worm,less than 0.1 mm long can cost farmers billions of dollars, every year, in lost production. In their search for food and nest building, these animals dig and burrow, bringing tons of subsoil to the surface. A valuable tilling service if it isn't your lawn or golf fairway. The most important members of our soil macroflora group are the living plants or more importantly below-ground portion or the roots.