CROPS AND SOIL IMPROVEMENT 



decrease, the only plant-foods with which we are 

 concerned are nitrogen, phosphoric acid, and 

 potash. 



The materials were stored in all agricultural 

 land, and much of the supply is in inert forms. 

 They help to make what we call the natural 

 strength of the land. The rotting of organic 

 matter, tillage, and many other agencies bring 

 about some availability. The removal of crops, 

 leaching, etc., reduce the supply. The right use 

 of commercial fertilizers involves the addition of 

 some plant-food when the available supply in a 

 particular soil is inadequate. 



Prejudice against Commercial Fertilizers. 

 The owner of land that was made very fertile by 

 nature, and that has not been cropped long enough 

 to reduce the supply of available fertility to the 

 danger-point, rarely fails to entertain a prejudice 

 against commercial fertilizers. It is the rule that 

 he refuses to consider their use until the decrease 

 in crop yields becomes so serious that necessity 

 drives. If his land is not contributing its fair 

 share of grain, vegetables, etc., to the markets, 

 but has all its products converted into meat or 

 milk, the supply of available plant-food may re- 

 main sufficient for so long a time that the matter 



[160] 



