MIXING FERTILIZERS ON THE FARM 93 



proportions of nitrogen, phosphoric acid and potash. But it must not be 

 supposed that these are in every case necessary or profitable. They have been 

 devised from the study of the manurial requirements of the various crops, as- 

 suming that the soil needs them all. But we will try to show how, by good 

 farming and a proper rotation of crops, we can avoid the constant application 

 of commercial fertilizers to every crop grown. The Experiment Stations 

 have devoted so much time and labor to the study of the manurial require- 

 ments of crops that farmers are apt to imagine that all they have to do is to 

 suit a fertilizer to the crop in order to make it. 



