THE CROP 73 



deep down in the soil. When this crop is plowed 

 under it furnishes a food supply for the corn which 

 follows it. Now, if oats had been grown on this soil 

 year after year, their short roots would soon have 

 exhausted the food supply near the surface. This diffi- 

 culty has been avoided by the rotation of crops. Again, 

 crop rotation affords an opportunity for cultivation 

 which destroys weeds and increases the power of the 

 soil to produce the desired crop. 



Conditions Determine Kind of Rotation. The rota- 

 tion given in this chapter is only a "sample" rotation, 

 not an "ideal" one, and is introduced here only for the 

 purpose of illustration. The farmer should devise 

 rotations of his own, suited to the special needs of his 

 farm and to the market for his products. 



Free Bulletins, U. S. Dept. of Agriculture. 



No. 289. Practices in Crop Rotation. 



No. 320. Relation of Sugar Beets to General Farming. 



Experimental Study of Boot Systems. 



1. Pull or dig up full-grown stalks of oats, wheat, 

 rye, barley, corn, tobacco, clover, alfalfa and other 

 farm crops. Many of the roots will break off in the 

 ground, but those that remain will be sufficient for 

 comparison. Which of these penetrate the soil the 

 deepest? Classify them in the order of length. 



2. Bring in radishes, turnips, roots of oats, corn, 

 and other farm crops. Measure their length and count 

 the number of small roots on each of these plants. 



