THE POTENTIAL PLANT FOOD 



This table shows the total quantities of three plant-food 

 ingredients secured by plants from the soil during each 

 cycle period. Since 10 of these periods are included in 

 the entire period of 50 years, there are removed 3,026 

 pounds of nitrogen, 861 pounds of phosphorus, and 2,425 

 pounds of potassium : in the aggregate a large quantity. 

 The next questions arising now are : Can the soil sup- 

 port this draft on it? Does the soil hold in store enough 

 plant food to fill these demands? 



To answer these two questions, we will consult the 

 soil itself. For the purpose, we will call for evidence 

 25 soils that produce on an average the yields suggested 

 in this study 50 bushels of corn, 25 bushels of wheat, 

 and 4 l / 2 tons of clover and timothy (in three years). We 

 will get these soils from different sections of the country : 

 from the South, North, East and West, from the cotton 

 belt, the hay belt, and the corn belt, from the arid lands, 

 the semi-arid and the humid regions ; in short, we will 

 take typical lands of the country. 



The quantities of plant-food ingredients nitrogen, 

 phosphorus and potassium found in the fine particles 

 of each acre in the surface foot are as follows : Nitrogen, 



