Abstract

Do you have any great-grandparents who lived through the Great Depression in the United States during the 1930's? If so, they might have stories to tell about terrible dust storms that blackened the skies, from the Midwest to the east coast. Severe drought was a factor in causing this "Dust Bowl" era, but decades of poor farming practices contributed to it, too. In this environmental science fair project, you'll learn about farming methods that help keep dirt from drying up into dust, and help keep topsoil where it belongs—on the farm.

Objective

To determine whether no-till or plow-based farming methods are best at retaining surface moisture and preventing surface runoff.

Introduction

Have you ever seen the extraordinary photographs of the "Dust Bowl" or the "Dirty Thirties"? Back in the 1930's, on the prairies of the United States and Canada, there were tremendous dust storms or "black blizzards" that turned day into night and reduced visibility to just a few feet. The storms were so enormous that at times they reached as far as the eastern coast of the United States, blackening the skies from Oklahoma, Texas, Colorado, and Kansas to Washington D.C. and New York City. In April 1935, the storms were so bad that many people thought the world was coming to an end.

The Dust Bowl was an environmental catastrophe caused by two events:

1. A severe drought brought on by cooler-than-normal tropical Pacific Ocean surface temperatures and warmer-than-normal tropical Atlantic Ocean surface temperatures.
2. Decades of poor farming practices, like deep plowing and failure to rotate crops.

The great prairies of North America used to be covered by grasses, which helped hold moisture in the topsoil and helped keep topsoil in place. As settlers moved into the area though, they began farming the grasslands, using deep-plowing methods which killed the grasses in the topsoil. When the drought struck in the 1930's, there were few grasses to help control its damage. The topsoil dried up and turned to dust, which rose up into great dirt clouds anytime there were winds. Much of the rich, fertile topsoil of the North American plains, over 100 million acres, was wasted when it was blown away into the Atlantic Ocean. Consequently millions of acres of farmland were lost, forcing hundreds of thousands of people to flee to other states to try and survive. Their difficult lives were written about in John Steinbeck's famous novel, The Grapes of Wrath, which won both the Pulitzer Prize and the Nobel Prize for Literature.

While the Dust Bowl was an ecological and human tragedy on an enormous scale, farming practices around the world today continue to contribute to the loss of topsoil and degradation of farmlands in less dramatic, but just as troubling ways. One such common practice is called "turning the soil." This conventional tillage or plowing of the soil before planting seeds does the following:

• Aerates the soil,
• Warms the soil,
• Buries leftover crops,
• Buries animal waste, and
• Buries weeds.

The downside of plowing, though, is that it makes it much easier for wind and water, both forces of erosion, to wash or blow away the topsoil, which compromises food production. It also increases runoff of soil, fertilizer, and pesticides into waterways, increasing water pollution.

An alternative to plowing is no-till farming, where the soil is disturbed as little as possible. The soil is not turned over, and farmers leave leftover crops in the field after a harvest to act as a mulch, similar to how the grasses on the prairies of North America were used to hold moisture and topsoil in place, before farmland replaced them. Seeds are planted with special machinery that can push them down through the mulch into the undisturbed soil below.

Some of the advantages of no-till farming are that it:

• Reduces wind and water erosion of the topsoil.
• Reduces moisture loss from evaporation.
• Reduces water pollution caused by surface runoff.
• Requires less energy to prepare the fields (reduces the number of passes over the field).
• Requires 50–80 percent less fuel to work the fields.
• Requires 30–50 percent less labor.
• Does not kill earthworms in the soil.
• Increases the diversity of plants and animals.
• Increases the amount of carbon dioxide the field can remove from the atmosphere.

The United States leads other nations in adopting no-till farming methods, with 41 percent of its crops grown (as of 2004) with minimal disruption of the soil (Scientific American, 2008). With all its advantages, you might wonder why no-till farming has been slow to develop in other countries. There are several reasons. No-till farming requires:

• Specialized seeders (machines to plant seeds in undisturbed soil), which are expensive; some cost more than $100,000!
• Greater use of expensive fertilizers for the first few years, since the thicker surface layer of organic matter covering the farmland from leftover crops keeps nutrients, like nitrogen, from freely moving about. Crop rotation can help reduce the need for these extra fertilizers.
• Greater use of expensive herbicides to control weeds and pests, although crop rotation and organic farming methods can help reduce this.
• Lower harvest for some crops, like corn that is grown at far northern latitudes, because the soil is not warmed through tillage, so seeds sprout later.
• In developing countries, farmers use leftover crops as fuel, or to feed animals.

In this environmental science fair project, you'll see if no-till methods retain moisture and prevent surface runoff better than plow-based preparation of the soil. You'll first create models of a plowed field and a field prepared by no-till methods to see how each retains moisture. Then you'll build a surface runoff channel and fill it with different types of prepared soil to see which one best withstands water erosion.

Terms and Concepts

• Deep plowing
• Crop rotation
• Degradation
• Tillage
• Plowing
• Aerate
• Erosion
• Runoff
• No-till
• Mulch
• Surface runoff

Questions

• What factors contributed to the Dust Bowl?
• What are the advantages and disadvantages of plow-based farming?
• What are the advantages and disadvantages of no-till farming?

Materials and Equipment

Note: Because this science fair project uses a lot of dirt and water, you will need to ask your parents for a good outdoor test area, one that can easily be washed down after you are done testing. You will also need to wear clothing that you don't mind getting dirty.

• Soil moisture meter; available at some hardware and garden stores, and from online sellers, like www.amazon.com.
• Plastic box, like a kitty litter tray, approximately 14x17x5 inches; available at pet stores
• Soil; can be potting soil, dirt from the ground, or a mix of the two (need approximately 2–3 large buckets full of soil)
• Liquid measuring cups, 4-cup size or larger, (2). The read-from-above types are easiest to use; available from your local home goods store.
• Mulch, such as straw, dead plant matter, or grass clippings (3–4 large handfuls)
• Hand trowel; available at garden or hardware stores
• Adjust-A-Spout^TM downspout extender or approximately 4–6 feet of a rain gutter; both available at hardware stores or online
• Dry measuring cup, 1-cup size
• Sturdy box or stool
• Permanent marker
• Clock
• Lab notebook

Experimental Procedure

Global Connections

Variations

Careers

If you like this project, you might enjoy exploring these related careers:

Related Links

• Science Fair Project Guide
• Other Ideas Like This
• Environmental Science Project Ideas
• Agricultural Technology Project Ideas
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