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Show store up water and let it go gradually. The result is that floods are less severe, water seeps to streams slowly and over a longer period of time, and water is stored in the soil for plants to use. Crops use lots of water. Vegetables use an average of 2 acre- feet, or 650,000 gallons an acre. Cotton takes 800,000 gallons an acre. An acre of alfalfa needs over a million gallons. To produce one ear of corn takes over a barrel of water. Organic matter helps soil store more water and thus helps prevent erosion and produce better crops. On land that must be cultivated and cannot be kept in grass all the time, farmers can keep the land covered as much of the time as possible by using crop rotations. By growing a cultivated crop like corn followed by a small grain crop and 1 or more years of grass- legume meadow, the land can be covered much of the time. Mulches can help in gardens. You will need two small boxes about 16 inches long, 12 inches wide, and 4 inches deep. ( These boxes can be used for several activities so they are worth making and keeping on hand.) Make them watertight by lining them with plastic material, tin, or tar paper. Many field tests have shown the improved water- holding capacity of well- managed soils that have enough organic matter to keep them crumbly and granulated. One deep soil in Texas that was high in organic matter held 25 percent or 1 inch more water in the 1- foot surface layer, after the free water had drained off, than the same depth and type of soil in another field where the soil was low in organic matter. This made a difference of 27,000 gallons of water per acre in the first foot of soil. At one end of each box cut a V- notch 1 to 1% inches deep and fit with a tin spout to draw runoff water into a container ( see drawing). You will also need 2 flower sprinklers, at least a quart in size ( half gallon is better); 2 half- gallon wide- mouth fruit jars; and 2 sticks of wood about 1 inch thick. Cut a piece of sod from a pasture, lawn, fence row, or the like, to fit one of the boxes. Trim the grass with scissors so that it is not more than an inch high. This makes it easier to handle. Fill the other box with soil from the same place- no grass, just soil, but don't try to pick a very poor soil. The idea is to have the same kind of soil in the boxes, one with grass, the other bare. Set the boxes on a table so that the spouts extend over the edge. Place the sticks under the other end to give them slope. Put the empty fruit jars on stools placed beneath the spouts. Fill the two sprinklers with water and pour the water on both boxes at the same time. Pour steadily and at the same rate for both boxes. Hold the sprinklers the same height from the boxes. About This is what happens when heavy rains fall on bare fields. X. How Does Crop Cover Affect Soil Loss? |