Yield, 

 ushels or Cwt. 



Returns & Cost. 

 Shillings . 



Vlineral Manures +200 lb. +400 lb. +600 lb. +800 lb. Amm. Salts. 



Fig. 5.— Relation between Cost of Production and Returns avith 

 varying (juantities of manure. 



[To face page 284. 



