EXERCISE 57 



CROP ROTATION 



Statement. Growing one kind of crop on the land year after year favors the accumulation of insects, 

 plant diseases, and weeds injurious to that crop. Also some crops, as corn, are classed as "exhaustive," 

 while other crops, as legumes and pasture grasses, to a limited extent, are considered to rest the land 

 upon which they are grown and are classed as " restoratives." By alternating exhaustive and restora- 

 tive crops the land is not so rapidly depleted as by growing exhaustive crops only. The labor load 



of the farm is better distributed 

 throughout the year by growing a 



variety of crops 

 one or two. 



instead of only 



Fig. 77. The effect of crop rotation on the yield of corn 



At the Missouri Experiment Station a test of the value of crop rotation has been in progress 

 for twenty-five years. The crib at the left shows the average amount of corn (20.3 bushels) 

 an acre produced when grown in corn continuously, and the crib on the right shows the amount 

 of corn (34 bushels) produced by an acre in a rotation of com, wheat, and clover. The 

 figures give an average production for twenty-five years 



Object. To study systems of 

 crop rotation as applied to the com- 

 munity and to plan systems of ro- 

 tation which will give a balanced 

 agriculture. 



Materials. A diagram of the 

 home farm, or one in the neighbor- 

 hood, showing the number of fields 

 and area of each ; a statement of 

 the nature and type of soil and the 

 kind of farming practiced. 



Directions, i. In planning a 

 rotation decide first which are the 

 main crops, and which secondary 

 or restorative crops will best fit in with the main crops and produce a well-balanced cropping system. 

 Study the most successful rotations of the neighborhood and apply one such to the farm for which you 

 are planning a rotation. Make a drawing, dividing the farm into as many units as there are crops in 

 the rotation chosen. For convenience each field should be numbered in laying out the system. Some 

 such form as that shown on the opposite page may be helpful. The first column contains four units, 

 the same as the number of crops in the rotation chosen. A unit may consist of any number of fields, 

 but all units should be as nearly the same size as possible. 



2. Plan two-, three-, four-, and five-year rotations respectively, using the crops grown in your com- 

 munity. Plan a desirable rotation for a general livestock farm, using corn, oats, and clover, and plan 

 a rotation system for a grain farm, using corn, wheat, oats, and clover, in which only the grain and the 

 seed of the clover are sold. Plan a rotation in which cotton, cowpeas, and corn are the principal crops. 

 Fill in the forms on the opposite page. Discuss each rotation planned and explain the reason for the 

 arrangement of crops. 



Questions. In planning a crop rotation show how excessive spring plowing may be avoided. 

 Explain how a crop rotation will help to control weeds. Explain how it will help to control diseases. 

 Name two plant diseases that are controlled by crop rotation. Name the important restorative crops 

 ■ of the United States. Which of these are adapted to the locality in which you live ? 



References. Waters, H. J. Essentials of Agriculture, pp. 86-87, l6 4> 287, 291, 310. Ginn and Company. 

 Hopkins, C. G. Soil Fertility and Permanent Agriculture, pp. 318, 362, 389. Ginn and Company. Burkett, 

 C. W. Soils, pp. 266-282. Orange Judd Company. Warren, G. F. Farm Management, pp. 402-416. The 

 Macmillan Company. 



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