LECT. IV 



THE FOOD OF CROPS 



59 



(Fig. 12), the other ingredients being usually present 

 in the soil in the requisite quantities for supporting 

 crops. The only exception is lime, to the use of which 

 attention will be called presently. 



The result of both proper and inadequate feeding 

 is represented in the small photographic illustrations 

 of potatoes, a,s obtained in Professor Wagner's experi- 

 ments. The plant A (with its crop) is the result of 



FIG. 12. RESULTS OF FAULTY AND ADEQUATE MANURING. 



growing in poor soil, though containing some phos- 

 phoric acid and potash as applied in bone-meal and 

 kainit, but no nitrogen. B shows the result of sup- 

 plementing the potassic and phosphatic manures 

 with nitrogen applied as nitrate of soda, the addition 

 of this giving a three or four fold increase by, so to 

 say, bringing the other two into action. Not any 

 one of them alone would be satisfactory, but all must 

 be in combination. 



Natural or Farm-yard Manure. Under this 

 term is included the refuse from horse and cow stables, 



