CHAPTER XV 



CROP ROTATION AND ITS RELATION TO SOIL FERTILITY 



Crop Rotation Defined. — Crop rotation is a system of growing 

 different kinds of crops in recurring succession on the same land. 

 For example, on a certain field a farmer grows clover one year, 

 corn the second, oats the third, clover the fourth, corn the fifth, 

 oats the sixth, etc. This is a three-year rotation, since each crop 

 recurs every third year. Another farmer may grow these same 

 crops in a rotation as follows: clover followed by corn, then another 

 crop of corn, which in turn is followed by grain seeded to clover. 

 This is a four-year rotation since it requires four years for the 

 complete succession of these crops to recur. 



Some systems of cropping are designated as fixed rotations, and 

 others as definite rotations. 



A fixed rotation is a system of cropping in which the different 

 crops recur at regular intervals, and which occupies a fixed number 

 of years. Clover followed by potatoes, then rye seeded to clover, 

 is a good example of a fixed three-year rotation practiced by some 

 potato growers on sandy soils. Some fixed rotations may occupy 

 four years, others five and sbc years or more. 



A definite rotation may be defined as a system of cropping in 

 which the different crops continually recm* in a definite order, 

 but is not fixed as to the number of years it occupies. Many 

 farmers, for example, grow alfalfa, corn and grain on the same land 

 in the order named, in anything from a five-year to a ten-year 

 rotation — alfalfa three to six years^ corn one to tv/o years, and 

 grain one to two years. Another common, definite rotation is, 

 hay (clover) followed by pasture, then corn, then grain seeded to 

 clover and grass. In such a rotation the land may be pastured one 

 to three years. 



Very often in a rotation some one crop is grown two or more 

 years in succession; as, tobacco (three years), followed by wheat 

 (one year), clover (one year), tobacco (three years), etc. 



Nearly all farmers practice crop rotation in some form or other. 

 Comparatively few adhere to fixed rotations, since they prefer 

 to follow a cropping system that is more or less flexible so thab a 

 shift^ can be made when prices or seasonal variations should make 



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