228 SOILS 



gen, for example, has its most important function in 

 developing stalks and leaves and stems rather than fruit 

 or seed. You observe readily this fact: Where large 

 applications of stable manure have been made, note the 

 heavy, rich growth ; and frequently you will find the yield 

 is decreased because of the abnormal growth of stalk and 

 stems due to an abundance of nitrogen in the soil. 



You get the same results when you plant a corn or 

 wheat or cotton crop after peas or clover or alfalfa or any 

 other legume that has added nitrogen to the soil. A prac- 

 tical observation is here : when you observe large devel- 



A CASE WHERE ALL THREE ELEMENTS ARE NEEDED 



opment of stalk and leaf at the expense of fruit, you may 

 know that nitrogen is not needed in the fertilizer; but 

 phosphorus and potassium, perhaps, ought to be supplied 

 that the plants may produce seed and fruit in proportion 

 to stalk and leaf. 



The offices of phosphorus and potassium. This sug- 

 gests the main office of phosphorus and of potassium. 

 Both are opposite to that of nitrogen ; and both are 

 directed toward increasing the grain or fruit of the plant. 

 When a large amount of some phosphorus-carrying fer- 

 tilizing material is applied to the soil, the growth of the 

 plants is not more pronounced, but the yield is increased, 

 and, at the same time, the crop matures earlier. On the 



