Soils and Soil Erosion

Steve Norberg, Malheur Co. Extension and Erik Feibert,OSU Experiment Station

When a field is irrigated, water moves through the fields. That water moves soil off of the field. When the water runs off the bottom of the field, the soil in the water is lost.

The erosion station demonstrated irrigation induced erosion and methods of reducing
irrigation induced erosion. There were 4 small trays with soil (left to right):
Tray 1: Soil with turf growing in it
Tray 2: Soil with straw mulch
Tray 3: Soil with polyacrylamide (PAM)
Tray 4: Bare untreated soil.

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Farmable soil represents very little of the earth's surface.

An apple was used to illustrate the importance of managing our soil properly. By cutting the apple in half, the peel represents the crust or top layer of the earth's surface. Cutting one of the halves into two, the quarter apple represented that only about 25% of the earth's surface consist of land suitable for plant growth. Peeling the quarter section of the apple to represent all the ground where plants grow, only a small percentage of the land has farmable soil. Placing the parts back together demonstrated just how small the peeling off the quarter section of the apple is in comparison to the whole apple. This exercise allows us to visualize just how little farmable soil there is in relation to the rest of the earth's surface.

Soil differs greatly in texture, color, and water holding capacity. These features are important because they affect plant productivity.

Soil types were discussed. Sand, silt, and clay differ in particle size, water holding capacity and water infiltration rates.

Students performed a simple test. Soil was placed into a jar with water and a little detergent and sealed with a lid. After shaking the mixture, we allow the soil to settle. After 5 minutes all the sand should settle to the very bottom of the jar, after 30 minutes the silt should make the next layer, and after 24 hours clay will have settled out, forming the top layer. Organic matter will float to the top of the water. The students did not have 24 hours or even 30 minutes to see the test through to the end, but the groups were able to get the main idea and were encouraged to perform this experiment at home or at school where they would have the time needed to see the complete results.

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