20 MAINE AGRICULTURAL EXPERIMENT STATION. 



Bulletin No. 33. 



FERTILIZER INSPECTION, 1897. 

 The bulletin gave the text of the law regulating the sale of 

 commercial fertilizers, the manufacturer's guarantees and the 

 analyses of manufacturer's samples, but as these figures are of 

 only passing value they are omitted here. 



Bulletin No. 34. 



BOX EXPERIMENTS WITH PHOSPHORIC ACID 

 FROM DIFFERENT SOURCES. 



L. H. Merrill. 



Probably nine-tenths of all the commercial fertilizers used in 

 Maine are purchased in the form of "complete" or "mixed fer- 

 tilizers" — that is, they contain in varying proportions nitrogen, 

 potash and phosphoric acid. While the majority of these goods 

 are honestly made up, yet like many of the so-called condi- 

 mental foods, they are designed to cover all probable contin- 

 gencies and are hence often wastefully applied. It is evident 

 that where but one or two of the constituents named are lacking 

 in a soil, it is not business-like to apply and pay for three. A 

 little intelligent experimenting on the part of the farmer will 

 often determine what is lacking. The next care is to supply 

 this want in the most economical manner. 



The use of materials containing nitrogen, phosphoric acid or 

 potash singly is fast growing and is to be encouraged. In the 

 choice of these materials two things are to be considered: the 

 availability, or the readiness with which they can be used by 

 crops, and the cost. It is the object of this bulletin to consider 

 some of the sources of phosphoric acid, with special reference 

 to the matter of availability. 



Nearly all of the phosphoric acid used for fertilizing purposes 

 is in combination with lime as phosphate of lime. Three forms 

 are in common use, viz. : 



