Weathering, Erosion, and Soil
Soil is essential in providing the basic needs of humans and many other organisms. Yet only a small portion of Earth’s surface has productive soil. A single centimeter of soil can take hundreds
of years to form, but it can be eroded away in the blink of an eye. Human activities can dramatically increase rates of erosion. Because life on Earth is so dependent on soil, its care and protection
is in everyone’s best interest.
Soil Erosion
Scientific studies estimate that soil loss occurred at an annual rate of 9 billion metric tons before humans existed. Since the appearance of humans, however, annual rates of soil loss have more than
doubled to roughly 24 billion metric tons. Overgrazing, poor farming techniques, poorly planned development, and misuse of land have contributed to the accelerated rate. In addition, wind and water erode
soil through natural processes. The best way to prevent this type of erosion is by planting vegetation, which serves as a protective cover that keeps soil from being carried away by wind or water. In
addition, farmers now routinely practice sound agricultural techniques that reduce soil erosion.
LINK UP: Find out more information about soil erosion.
Strip-Cropping
Strip-cropping can be thought of as a sort of tag-team approach to farming. It involves planting alternate rows of crops. One crop typically has a good network of roots, while the other crop does
not. Alfalfa, for example, has an extensive root system that traps water and holds soil in place. Corn, on the other hand, has swallow roots that allow soil to be easily eroded. In strip-cropping, alfalfa
and corn are often planted in alternative rows—two crops are harvested and rates of soil erosion are reduced.
Contour Farming
When you think of a farm, do you picture acres of flat land stretching toward the horizon? Flat land is characteristic of the Great Plains area, which is known for its fertile farms. However, the
land in many agricultural regions is not completely flat. When this land is plowed, runoff carries soil downslope. Contour farming helps reduce this type of soil loss by plowing and planting crops along
the natural contour of the land. Instead of planting crops up and down hillsides, farmers who use contour farming sow rows of plants around the natural twists and turns of hills. Water then flows downslope
and is absorbed by the plants.
Terracing
In some areas, the only land available for crop production is too steep for even contour farming. In these cases, a special technique called terracing can be used to help reduce water erosion. Terracing
involves building steps of earth material along a slope. The steps are planted with crops that are harvested each season. Permanent vegetation with dense root structure is also planted between the steps.
This vegetation holds the soil on the slope in place and traps water that flows downhill.
No-Till Farming
Farmers who use the no-till method do all the planting, fertilizing, and pest control at one time. Fields then remain undisturbed until harvest. There is no tilling of the soil. After harvesting,
all portions of the plants that are not used, such as stalks and leaves, are left on the field instead of being plowed under. The decaying material returns nutrients to the soil to help maintain fertility.
No-till farming is one of the most efficient methods of soil conservation because the left-over crop material protects soil from erosion by wind and water. In addition, the crop material provides food
for wildlife, such as deer, wild turkeys, and migrating geese.
Activity
Use a map and reference materials to select a farming region in an area of your choice. You may choose your own county or state, if applicable. Decide which method of reducing soil erosion is most
appropriate for your region. Write a brief paragraph explaining your choice.
