Soil is primarily made up of minerals, air, water, and organic material. Approximately 45 percent, overall, is made up of particulate minerals in the form of sand, silt, and clay. Sand is the largest of these particles, followed by silt and clay, respectively. The proportions of these mineral particles help to determine some of the physical properties of soil and allow us to separate soil into different categories based on their texture. But soil is not merely a conglomeration of minerals. An additional 25 percent of soil is made up by water and another 25 percent by air. That leaves only 5 percent for organic material. Some of that material is dead and decaying matter of previously living organisms or parts of organisms, such as decaying leaves or grass and the occasional decomposing body or pile of excrement. Yet, some of that material is still actively living.
Their contribution is small but yet very mighty. Macroorganism, such as earthworms and arthropods, are also found in the soil but we also have microorganism, such as bacteria, fungi, and actinomycetes, that all call the soil their home. Each play a part in the overall ecosystem that is the soil. Some aide in the fixation of nitrogen for plants; others help to protect plants by outcompeting potential plant pathogens; and still others form symbiotic relationship based on mutually beneficial interactions between plant roots and microbes. More detailed and in-depth information in regards to species specific benefits can be found in both the teacher and student guides which is located on the Resource Document CD provided with the LaMotte Microbe Hunter Kit.