98 HATCH EXPERIMENT STATION. [Jan. 



From the great variations in the results of analyses of 

 the above special crop fertilizers (see* Table B) it will be 

 readily observed that it will be unsafe to be guided by 

 trade names wholly when selecting fertilizers for the grow- 

 ing of special crops. 



Local conditions as to the character of the soil and sub- 

 soil, the previous management of the soil and the system 

 of crop rotation employed should all enter into considera- 

 tion when selecting a fertilizer. A study of the soil should 

 be made, to find in what direction the plant food has be- 

 come depleted ; and when these facts have become estab- 

 lished, then supply the wants of the soil in the most suitable 

 and economical manner. When the character of a soil is 

 not known and its wants are not manifested, it is advisable 

 to use a fertilizer more nearly corresponding to what a 

 chemical analysis of the crop shows is required for its 

 proper development. 



An example is here inserted for the purpose of illustrat- 

 ing how the chemical composition of a crop may serve as a 

 guide in the compounding of a commercial fertilizer, also 

 to serve as an object lesson of how to intelligently use the 

 compilation of analyses which is a part of the annual report 

 of the chemical department for this year. We will take 

 the average composition of cranberries, as this appears first 

 in our table of compilation of fruits, etc. : — 



Average Analysis of Cranberries. 



Parts per Thousand. 



Phosphoric acid, . 30 



Potassium oxide, 1.00 



Nitrogen, .80 



The relative proportion of phosphoric acid, potassium 

 oxide and nitrogen present, according to this analysis, is : — 



Phosjmoric acid, 1.00 



Potassium oxide, 3.33 



Nitrogen, 2.66 



In other words, for every pound of phosphoric acid re- 

 moved from the soil by a crop of cranberries, there are 3.33 

 pounds of potassium oxide and 2.66 pounds of nitrogen re- 



