FUNCTION OF THE PLANT-FOOD ELEMENTS 



55 



When a soil has an ample supply of the necessary elements in 

 soluble form or in a condition which may be easily converted into 

 soluble form when needed for the production of a large crop, that 

 soil is described as having sufficient ''available^' plant-food ele- 

 ments for a good yield. 



The fact that crop produc- 

 tion depends in a large measure 

 upon the availability of the 

 plant-food elements in the soil 

 makes it necessary that farmers 

 understand the conditions 

 whereby soils may give up these 

 elements in the amounts de- 

 manded by good crops. These 

 conditions and principles are 

 discussed in later chapters. 



Function of the Plant-food 

 Elements. — It is of interest to 

 note briefly the functions of the 

 elements required by crops. 



Carbon is used in the mak- 

 ing of carbohydrates, fats 

 and protein. 



Nitrogen is used in the 

 making of protein. 



Phosphorus is of much im- 

 portance in the '' filling out'^ 

 and development of the grain, 

 often hastening maturity. It is 

 also used in the making of 

 protein. Sufficient available 

 phosphorus causes young plants 

 to develop good, strong root 

 systems. 



Potassium is much needed 

 by plants to aid in starch and 

 protein formation. Such crops as corn, sugar beets, potatoes, 

 alfalfa and clover, therefore, require large amounts of this element. 



Calcium seems to be used largely in leaf and stalk development. 

 It is also regarded as a protective agent, in that it prevents harm-, 

 ful effects of acids formed within the cells. 



Fig. 23. — An argument in favor of a deep seed 



bed. The desirable type of sugar beet. 



(U. S. D. A.) 



