Many people think soil is “just dirt.” However, you should know by now that it is not. Soil is the foundation for all the produce you see in the supermarket. In fact, it is indirectly connected to all the food you had for breakfast, lunch, and dinner. Soil not only affects our food supply, it is also the foundation for the diversity of habitats we share with plants and animals on this planet. It is important that we take care of the soil because however resilient it may appear to be, soil quality is greatly affected by its environment.

Soil Damage and Loss

Soil can be affected by many factors, such as the weathering and erosive effects of climate. Areas where weathering and erosion occur are sometimes caused by building and agricultural practices.

Certain forestry practices, such as clear cutting, are good examples of this. If all the trees growing in a certain area are suddenly harvested, the soil is then left exposed to all the weathering and erosion forces caused by climate. Without the cover of the trees, the sun evaporates the water the soil once stored. Tree roots that once held the soil in place can shrivel up and die leaving the soil vulnerable to erosion by wind and rain. Along with the loss of the nutrient-rich soil, wildlife can also be affected. The quick changes we impose on the environment will more than likely result in drastic consequences.

Forestry Practices

Forestry practices used today have improved. Some companies try to minimize the damage they cause to a habitat by using a variety of techniques depending on the landscape. For example, cut trees can be replaced with seedlings that, over time, will grow and keep the soil healthy. Another technique involves cutting only certain areas of trees within a forest to allow the land to recuperate faster from the damage caused by cutting. Untouched stands of trees are able to provide shelter for disturbed wildlife. Finally, a buffer zone of trees situated around rivers and streams is maintained. This helps prevents erosion of soil and sediment into streams and rivers, which can adversely affect aquatic life.

Farming Practices

Farmers must also consider the effects of their practices. In the past, very little consideration was given to how different crops required different amounts of nutrients from the soil. Farmers soon realized that after just a few planting seasons, extremely fertile soil was exhausted of its nutrients and not able to grow hearty plants.

Farmers today use techniques, like crop rotation, to help keep their soil fertile. For one season, farmers grow a crop, such as corn. After the corn is harvested, they can plant crops of a different family, such as sweet potatoes, or they may not plant anything to let the land lie fallow and rest. After these crops are harvested, farmers plant legumes, such as soy beans or alfalfa. Legumes are a type of plant that grow with the help of a special type of bacteria around their roots. These bacteria, called nitrogen-fixing bacteria, help to replenish the soil with much needed nitrogen.

Another soil conservation technique is the planting of crops specifically grown to provide soil cover. These are called cover crops and prevent erosion by wind and water by covering the soil and holding the soil together with their root systems. Some crops, such as legumes, can also increase soil quality and fertility.

Cover crops suppress the growth of weeds that would otherwise flourish on rich bare soil by taking up the available space and light. They can also control insect infestation by attracting beneficial insects like lady bugs or ground beetles. Insect diversity can prevent pest infestations by bringing populations into balance with a natural predator/prey relationship.

Farming for Energy Crops

Globally, soil holds twice as much carbon as the atmosphere because of all of the plant material that it contains. Many soils have room to store additional carbon, and getting more carbon into plants and soils is one way that humans might be able to remove some carbon dioxide (CO₂) from the atmosphere, which may help curb global climate change.

Farmers have traditionally tilled their lands to produce crops, but agitating the soil in this way can cause up to half of the carbon trapped in the soil to be released to the air. By converting some farmland to certain grasses or trees that only need to be re-planted every ten years or more, humans may be able to reduce carbon loss from soils while at the same time producing renewable fuels. The deep roots of these perennial energy crops could store more carbon in the soil. There would be other environmental benefits, too. Soils that contain more carbon are able to hold more water and nutrients for crops. Water in the surrounding streams would be cleaner since the stable plant roots would prevent sediments from washing into them on rainy days and since chemical fertilizers would no longer be needed. Less plowing of the land would mean cleaner, dust-free air.

Studying the combined advantages and limitations of growing switchgrass and other energy crops is another area of Dr. Virginia Dale’s research. While her work at Mount St. Helens involves looking at changes in an environment over time, her biofuels research involves the study of changes in the environment over space. She seeks to understand where and to what extent land should be converted to energy crops in order to maximize the benefits to our society.