EXERCISE 23 



SOIL WASTE THROUGH EROSION 



Statement. The greatest waste of soil fertility is the waste of the soil itself. It is the best portion 

 of the soil which is carried away by running water and by wind. 



Object. To ascertain the conditions under which soil erosion occurs and the most practicable 

 means of checking it. 



Materials. Gallon of loam; two 4-to-8-gallon vessels; one half-gallon vessel; one 2-gallon vessel; 

 two glass tumblers. 



Directions, i. As shown in Fig. 27, place a large vessel on a table and fill it with water to which 

 one-half gallon of loam has been added. At B place the half-gallon vessel, at C the 2-gallon vessel, 



and at D the other large vessel. Connect each by one- 

 fourth-inch rubber tubing as shown, letting the end of 

 the tubing extend one inch below the top edge of the 

 vessel in each case, except at A. Here the tube should 

 extend almost to the bottom of the vessel. 



Start the water running between A and B. As soon as 



B is full, start it between B and C, and likewise when C 



is filled, start it running between C and D. While all are 



running, stir the water in A continually. When most of 



the water has been transferred into the other vessels, note 



the comparative muddiness of the water in each. Examine 



at intervals of an hour and note which vessel of water 



becomes clear first. Note which contains the most sedi- 



Fig. 27. Method of illustrating effect of rate of flow ment after it becomes clear. A represents the soil, B the 



of water upon soil erosion swiftly-running surface stream, C the slower river, and D 



the lake or ocean. Which isr the more valuable, the sediment carried to D or that deposited at B ? 



2. Embed a tumbler in shallow, swiftly- 

 running, muddy water so that the top of 

 the tumbler is one-half inch above the bed 

 of the stream. In the same manner place 

 a tumbler in slowly-moving water. Leave 

 them a day and then remove and deter- 

 mine the amount of sediment in each and 

 whether it is sand, silt, or clay. 



3. Visit local areas of badly- washed soils 

 and plan ways to stop the erosion. Tell how 

 erosion might be prevented by terracing, 

 by planting crops such as pasture crops, by 

 properly-arranged dams, and by drainage. 



Questions. Which tumbler embedded in the stream contained the most sediment ? In which was 

 the sediment the coarser? Explain the reason. Apply this principle to checking surface erosion on 

 the fields. What is the source of the soil on bottom lands ? 



Fig. 28. A good example of the waste of the soil through 

 surface erosion 



References. Waters, H. J. Essentials of Agriculture, pp. 84-85. Ginn and Company. King, F. H. 

 The Soil, pp. 50-61. The Macmillan Company. Hilgard, E. W. Soils, pp. 218-219. The Macmillan Com- 

 pany. Mosier and Gtjstafson. Soil Physics and Management, pp. 358-375. J. B. Lippincott Company. 



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