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Show Slope is a very important land feature. It often determines whether a piece of land should be used for grass, trees, or cultivated crops. The size of particles moved \> y water ranges from the smallest clay particles, carried in suspension, to large stones and boulders that slide or roll along on steeply sloping stream beds. Water flows slowly over a gentle slope and rapidly over a steep one. Since the slope of a field itself cannot be changed, a farmer needs to do what he can to slow the movement of water down his slopes. Growing grass or trees, or using conservation measures like contour farming and strip- cropping will help. Or he may shorten the length of slope by building terraces and diversions. But reducing the speed of the water is essential. Increasing the velocity of a stream increases its cutting or eroding power. The greatly magnified power of swift currents as compared with mat of slow ones explains the work of streams at flood stage on steep slopes. OH- eo, 809 Serious erosion on unprotected soil in foreground compared with grassed lawn that prevents soil loss. Dig another hole in the fence row at the edge of the field or just across the fence in a pasture that has not been plowed. Try to dig the second hole at about the same point on the slope and as close to the first one as possible. Study the soil layers as you did with the first sample. Lay the two samples side by side and compare them. Compare the depth of the topsoil layer and the structure of the soil. 2. Find a field where there is a fence built across the slope. Compare the height of the land at the fence row with that in the field down the slope. To do this attach a string to a stake driven in the ground above the fence row. From a spot down the slope ( see drawing), pull the string parallel XV. Measure Am< You can measure how much soil has been eroded away in several ways. You may want to try one of the following in your neighborhood: 1. Find a cultivated field where the slope has at least a 5- foot fall in 100 feet of horizontal distance. Try to find a field that has been in cultivation for some time. You can check this information about the farm with the owner or the neighbors. Dig a small hole deep enough to get below the topsoil layer. Then cut off a slice an inch or more thick along the vertical side of the hole. Lay this slice on the ground and study it. Note the depth of the topsoil layer. Study the structure- how the particles are held together. Are they tight and does the soil hold together in large lumps ( clods) ? Or is it crumbly Tike cake? Amount of Soil Loss 19 |