You’ve heard that soil is the root of all life. And physically, soil does hold all the roots and provide a substrate to support roots for plants and trees, but what else does it do? Isn’t it just an inert substrate beneath our feet, and the stuff we put in flower pots, meant to provide structure for our plants?
Soil is life
Of course, soil provides a substrate for our trees, crops, and most of the plants growing on earth. But healthy soil is anything but inert, it’s just that humans cannot see most of the activity going on in soil. According to the Soil Science Society of America, there are more living organisms in one tablespoon of soil than there are people on the earth! For many years, these organisms were just part of a ‘black box’ in the soil – no one really knew what they did. But over time, researchers isolated these organisms and learned of their role in breaking down plant litter, converting nutrients into forms that plants can use, and in building humus. Humus, or organic matter, doesn’t just provide food for plants and organisms, but also has many sites on its varied surface area to absorb carbon. In fact, the earth’s soil resource contains more carbon than our atmosphere and terrestrial vegetation combined!
Soil is the world’s water filter
Through physical, chemical, and biological processing of water as it trickles through it, soil is the best water filter on earth. Have you ever held two magnets together? You’ve likely experienced that one set of magnet ends (positive/negative) attract; while when similar charged ends are placed together they repulse each other. A similar attraction helps soil clean water. Most soils (especially heavy clay soils) have a negative charge. Many water contaminants have a positive charge. As contaminated water infiltrates through soil, the contaminants are attracted to the soil particles, namely clay, and are trapped in the soil, where they are transformed by soil organisms into inert ingredients. The clean, pure H20 water molecules then move down through the soil profile into the water table.
Plants need food, just like all organisms. Food for plants means 19 essential elements. These elements are mostly positively charged ions. Think of the magnets again: the negative charges on soil link up with the positively-charged ions such as calcium, ammonium, and potassium elements essential for plant growth and reproduction. Nitrate (an inexpensive common fertilizer) is negatively charged, and if there are few positive sites on the surface areas of a soil, it will flow through soil and NOT be plant-available, and can then pollute groundwater. However, organic matter (or humus) has many surface area sites that are negatively charged as well as positively charged, to hold on to positive and negatively charged plant foods (as well as nitrate) better so that it doesn’t flow away with water flowing through soil. This is why farmers want to improve soil organic matter (SOM). Soil organic matter is created by and has more diverse populations of soil bacteria, fungi, protozoa, and nematodes. With recent oil spills, scientists have found that certain strains of bacteria that live in soil can transform petroleum into less toxic things like carbon dioxide and water. Try our Water Filtering and Soils lesson and see for yourself how two different soils differ in their ability filter impurities in water!
Soil is a carbon sink
Farmers know the importance of soil carbon and SOM. Only the oceans have a greater capacity to absorb carbon from the air, but we as farmers, foresters, and ag professionals are more capable of managing soil to improve carbon sequestration using tools such as crop rotation, conservation tillage, and cover crops. Researching are finding new ways increase carbon absorption by soils from the atmosphere, no matter how it got there. Managing soils as a ‘carbon sink’ means less carbon dioxide in the atmosphere to hold in the sun’s heat in our atmosphere. The Natural Resource Conservation Service (NRCS) was formed after the Dust Bowl of the 1930s to prevent future soil loss events. They still provide resources to introduce new techniques to keep soil covered and build organic matter so that the tragedy of the Dust Bowl is avoided in the future.
AITC’s Earth as an Apple and Soil Conservation lesson reviews the causes and the effects of the Dust Bowl, and our YouTube Playlist has videos that discusses this extremely hard time in American history. This lesson demonstrates how precious soil is, and practical tools that humans can use to improve soil conservation and the lessons of the Dust Bowl.
The Dust Bowl instigated the formation of the Natural Resource Conservation Service, still educating about healthy soils today.