Curriculum

EXAMINING WHAT GOES ON BELOW THE GROUND

Soil

As you walk through the park or across your yard, look down! What are you walking on? It may look like ordinary grass or dirt, but underneath the ground we walk on is the realm of soil—a part of the earth teeming with organisms that work together to create a fertile place for plants to grow. Home to abundant communities of worms, beetles, and mites, crisscrossed by roots big and small, the realm of soil is where our gardening adventure begins.

Soil is created by the continuous process of erosion, during which the actions of wind, water, ice, and waves break down rocks and minerals into a finer material that serves as the core substance of our soil. Added to this rocky material is organic matter, which originates from the decomposition of animals and plants. Organisms living in the soil, such as earthworms, fungus, and bacteria, feed on this organic matter to help further decay and recycle important nutrients. What results may not look like anything special, but it is more valuable to life on earth than even the prettiest diamond or gold.

Although we often think of soil as brown dirt, soil quality varies widely in character. For example, humus is a dark coffee-colored fertile soil found in the topsoil layer. It is rich in organic matter and high in moisture, making it ideal for planting. Sandy soil, on the other hand, is lighter brown in color. While it drains easily and warms up quickly, it does not hold moisture well, is low in nutrients, and is susceptible to water and wind erosion. The five factors influencing a soil’s “character” are parent material, topography, time, climate, and the diversity of organisms present. It is these soil characteristics that ultimately determine the productivity and diversity of plant species growing in your garden.

Most plants begin their lives in soil, and this soil will continue to support them as they grow. Plants need soil to anchor their roots firmly in the earth so that they don’t blow away in the wind. In addition, the microbiological activity within the soil provides the nutrients and water growing plants need to survive.

Beginning with the very first agricultural societies, gardeners learned how to improve soil quality to ensure optimal plant growth. The most common efforts revolve around adding minerals to nutrient-poor soil and breaking up the earth to allow for aeration. One of the most effective and popular methods of improving soil’s nutrient content is by adding compost. Compost is created by controlling and optimizing the conditions under which biological decomposition occurs. Made of organic matter that has been expertly decomposed, compost is especially rich in nutrients and moisture.

Although the process of creating compost may seem like a science, it is easy to do at home! Composting consists of taking organic waste from your garden or kitchen, placing it in conditions conducive for decomposition, and then watching and waiting as the waste turns into a precious nutrient-rich soil amendment. The basic recipe for compost involves a mix of carbon-rich “brown” material, such as dried leaves, hay, wood shavings, and even paper, plus nitrogen-rich “green” material, such as grass clippings, fruit and vegetable scraps, eggshells, and coffee grounds, plus oxygen (achieved through turning and aerating the compost pile) and water. It is often recommended that compost be created with a ratio of 20 to 30 parts carbon to 1 part nitrogen, so start saving those browns! As the compost recipe comes together, microorganisms will get to work, too, heating up the pile and breaking down the organic material.

With a little research, you can find the perfect compost setup for your individual situation. Need an outdoor compost bin system? Build your own! Have a small indoor space in which to compost? Try vermicomposting! Check out the Organic Gardening Beginner’s Guide to Compost for more details on concocting the perfect compost pile.

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