40 THE BOOK OF CORN 



an abundance of water. Further, the plants seem to 

 be more easily affected by insect and fungous pests and 

 quickly succumb to any unfavorable circumstance. 



When potash or phosphorus is lacking In the soil, 

 the ears do not fully develop or mature. In soils 

 which have a large amount of nitrogen and too little 

 potash or phosphorus, the stalks become abnormally 

 large while the ears are small and usually poorly filled. 

 By correcting the proportions of nitrogen, potash and 

 phosphorus, through manuring and other treatment of 

 the soil, an otherwise unproductive section may be 

 made to yield maximum crops of corn. 



METHODS OF OBTAINING NITROGEN 



The cheapest and best method of obtaining nitro- 

 gen is by means of leguminous crops. Of such plants 

 common red clover, cowpeas, soy beans and alfalfa are 

 most generally used in all sections of the United 

 States. These crops add large supplies of nitrogen to 

 the soil and provide great yields per acre of valuable 

 food for animals. They not only are a source of the 

 supply of plant food for the soil, but have a valuable 

 mechanical effect on the soil. Their extensive and 

 deep root systems bring plant food from the subsoil 

 to the surface soil, where it may be used by future 

 crops. They loosen and break up the hard subsoil so 

 that the roots of the corn plants can penetrate this 

 portion of the soil and secure plant food. The roots 

 of the leguminous crops remaining in the soil decay 

 and add to the humus. 



Clover has been grown in this country as a part 

 of the crop rotation for many years, but not until the 

 last fifteen years has it come into general use as a soil 

 fertilizer. There are several varieties, adapted to dif- 

 ferent conditions of soil and climate, and for various 

 uses. Of these varieties the mammoth red, the medium 



