"For many of us soils are a black box. We put things into the box and we get things out of the box, but we don’t have a very good idea of what happens inside the box. We put seed, fertilizer, and water into the soil and out from the soil comes the crops we are growing. But what exactly happens inside that black box we call soil?"
Farmers and scientists have been studying that question for hundreds of years and continue to study it today. They have learned that many complex physical, biological, and chemical processes are carried out in soil. Lets open up that black box just a little and learn something about the biological processes that occur in soil.
Because most of the life forms in soil are extremely small, “microbiology” is an appropriate term to describe the study of those life forms. Those who study soil biology quickly learn that soil life consists of intricate and complex interactions and cycles among the various living organisms in the soil. The activities and interactions of soil organisms largely determine the capacity of a soil to function in an agricultural, or any other, system. Knowing something about soil biological systems will help us to better understand how soil management impacts soil biology and the capacity of soil to function in agricultural production systems.
Before going any further, lets review the five basic functions that soils used for crop production need to be able to carry out.
• Soil must firmly anchor plant roots. It must be strong enough to hold crops and even large trees erect. Yet soil must be permeable enough to allow tiny root hairs to penetrate it.
• Soil must retain rain that falls on it in order to continuously supply water to growing plants. Yet it must also allow excess water to drain. The soil must drain because it must also supply air, more specifically oxygen, to crop roots. Too much water means too little air and the crops suffocate.
• Soil must supply nutrients for plant growth. To do so it must be able to store nutrients and then release them to the roots of growing crops.
• But soil must not release those nutrients to draining water.
Soil is a truly remarkable material to be able to perform each of these tasks – tasks that sometimes seem to be in conflict with each other.
