What is Soil
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To kick off my new series the Science of Sustainability I have decided to start with a topic that is near and dear to me.
Soil is not dirt, I just want to make that clear right from the the start. Dirt is what happens when soil is no longer doing what it is suppose to do. Soil can be defined as a mixture of minerals, organic matter, water and air that together form a matrix that supports life. Without a decent soil, building a truly sustainable life for yourself is impossible. If you can't grow food, support livestock and otherwise sustainable use the soil you will have nothing that can provide you the basics of what you need. To truly understand soil you have to understand its components and how they work together to create this life giving substance.
Soil is made up of three different sizes of materials. You have sand, silt and clay with sand being the largest and clay being the smallest. The different combinations and proportions of these materials are what make up the soil texture. Soil texture along with soil structure determines how well your soil drains water, soaks up rain, stands up to erosion, and deals with compression forces etc. The minerals in a soil are derived from the parent material that lies beneath all soils. That parent material can be limestone, sandstone, granite, volcanic ash, pretty much anything that can be eroded into smaller and smaller particles.
The organic matter in a soil is a combination of both living and dead material. It is everything from the smallest microbe to the largest tree roots that are in the soil. Organic matter plays a critical part in having a healthy, sustainable soil. It provides the food and fuel for microorganisms, so that they can enrich the soil and make nutrients available for the next generation of plants. Organic matter also plays a critical role in maintaining water levels in the soil. It acts like a giant sponge that soaks in water and releases it slowly as plants need it.
Air and Water
Though most people wouldn't consider water and air to be critical parts of soil they are. If you have adequate pore space which is what holds the air and water then that signifies that you have a healthy, well aggregated soil that allows for good root penetration and water infiltration. Plus the roots of plant need both air and water to sustain life in the plant. Like most things in life everything in moderation is best.
Soil and the Sustainable Life
Without healthy well managed soils the future of life and human civilization on this planet is in doubt. With well managed soils we can continue to thrive and grow as a species. But it takes more than just good intentions, we have to know what to do in order to better manage our lands.