AN IMPORTANT CONTROLLABLE FACTOR 189 



FIG. 125. Sixty-nine and one-half bushels of oats per acre. Unfertilized. (See Fig. 126.) 

 Bundles represent growth on one square rod. (Wisconsin Station.) 





FIG. 126. Eighty-seven bushels per acre when fertilized with three hundred pounds of 

 acid phosphate per acre. (Wisconsin Station.) 



important a subject, it will be discussed in a chapter by itself. 

 In this chapter special consideration will be given nitrogen, phos- 

 phorus, and potassium. 



