FARM CROPS 167 



must be used. Since soils differ greatly, it is impossible 

 to suggest a fertilizer adapted to all soils. The elements 

 usually lacking in wheat soils are nitrogen, phosphoric acid, 

 and potash. 



The land may be lacking in one or all of these plant 

 foods ; if this is so, a maximum crop cannot possibly be 

 raised. The section discussing manuring the soil will be 

 helpful to the wheat grower. 



It should be remembered always in buying fertilizers for 

 wheat that whenever wheat follows cowpeas or clover or 



FIG. 157. A BOUNTIFUL HARVEST 



other legumes there is no need of using nitrogen in the 

 fertilizer ; the tubercles on the pea roots will furnish that. 

 Hence only potash and phosphoric acid will have to be 

 purchased as plant food. 



The farmer is assisted always by a study of his crop and 

 by a knowledge of how it grows. If he find the straw 

 inferior and short, it means that the soil is deficient in 

 nitrogen ; but, on the other hand, if the straw be luxuriant 

 and the heads small and poorly filled, he may be sure that 

 his soil contains too little phosphoric acid and potash. 



