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Show vents the puddling or " running together" of the surface soil under the impact of raindrops. Dead plant materials protect the soil from being detached by raindrops. As long as the soil is granulated water will soak in rapidly. However, water soon softens the binding material that holds the granules together, and then the granules and clods disintegrate. The impact of raindrops separates the fine particles, splashing them into the air. Then these particles accumulate on the soil XII. What Does Pill both boxes used in Activities X and XI with soil taken from the same place. Set them on a table and place the sticks under the end to make a slope. Place fruit jars below the spouts of the boxes as before. Using your finger or a pencil, make furrows across the soil in one box and up and down the soil in the other. Fill two sprinklers with water and slowly sprinkle the two boxes at the same time. Hold the sprinklers the same height above the soil and pour at the same rate. Compare the rate of flow into the two jars and note the difference in their contents. Another way to do this is to put mounds of soil in the middle of the boxes or in 2 large round surface and fill the spaces between larger particles and granules. The result is a " seal" over the surface that permits water to enter the soil very slowly, if at all. Water must then run off. If the land is sloping, it causes erosion during hard, beating rains. Mulches also reduce evaporation by shielding the soil from the wind and from the direct rays of the sun. In addition to mulches, high organic- matter content of the soil itself is needed. Contouring Do? low dishpans. With a pencil or your finger make furrows up and down one of the mounds and circles around the other mound. Sprinkle an equal amount of wTater on each mound and observe the water. Remember though, that such mounds probably have much steeper slopes than most cultivated land. You can do this in the yard if you have a sloping area where there is no grass or where the grass is badly worn by walking or playing. By doing this outdoors, you can use a larger area. Make two plots 3 feet wide and 5 feet long with 1 or 2 feet between them. With a regular garden hoe cut grooves 4 inches apart and about 2 inches deep across the slope 15 |