CHAPTER XXXIX 

 SELECTION OF FARM CROPS 



412. Now that we have learned something of the gen- 

 eral principles of plant growth, we may more profitably 

 study the special requirements and uses of the most 

 important field, orchard and garden crops. We have 

 learned something about how plants grow. The Average 

 yields of staple crops in all countries is much below the 

 possible yields. Often only a fence separates a field 

 averaging only 20 bushels of corn to the acre from one 

 averaging 40 bushels. This average yield of corn in the 

 United States is less than 25 bushels per acre, yet most 

 farmers recognize that it is within their power to make 

 their yields exceed this average. 



413. The Four Essentials. We have learned that all 

 green plants require four important conditions for full 

 success; i.e., sun light, air, constant supply of water, and 

 certain mineral substances found in the soil. The control 

 of the last two constitute the foundation of cultivation 

 and is the first problem in successful crop raising. Culti- 

 vation includes more than simply plowing the soil. It 

 is making a favorable environment by any means. The 

 difference between the 20 and the 40 bushel crop can be 

 accounted for largely by the way these conditions are 

 controlled. 



414. The Second Most Important Problem of the 

 farmer is to learn to select seed from the better producing 

 plants, from which to grow succeeding crops. It is clear 

 that we would profit by a better seed, but it is often a 



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