48 



BOARD OF AGRICULTURE. [Pub. Doc. 



lowing proportions : nitrogen, 5 parts, phosphoric acid, 2 

 parts, and potash, 8 parts. Twenty-six different brands of 

 so-called potato fertilizers sold in Maine had the following 

 composition : — 



Nitrogen 

 (per Cent). 



Available 



Phosphoric Acid 



(per Cent). 



Potash 

 (per Cent). 



12 brands, . 

 6 brands, 

 8 brands, . 



1.5-2.5 



2-2.5 



2.5-3.5 



8-9 

 6-9 



5.5-8 



2-3.25 



4-6 



7-10 



The first twelve brands mentioned cannot properly be 

 called potato or special fertilizers as their composition is 

 practically the same as all general purpose goods. The 

 formulas of the last eight approximate more nearly to the 

 popular idea of what a potato manure should be, but even 

 these carry much more phosphoric acid in proportion to the 

 nitrogen and potash they contain than is found in the plants 

 or in farmyard manure. It is possible that in using com- 

 mercial fertilizers more phosphoric acid is applied than is 

 needed in many cases, yet there is not much evidence at 

 hand in the form of accurate experimental data to prove this 

 assertion. An analysis of the ash of the potato shows it to 

 be exceedingly rich in potash, and the fact has led many to 

 believe that a potato manure should contain a large amount 

 of this element, but when we consider the small amount of 

 ash a potato contains, we find the amount removed by an 

 ordinary crop (58 pounds) is not greater than is taken up 

 by many other form crops. Two tons of mixed hay would 

 take away 63 pounds, while two tons of red clover would 

 remove 88 pounds of potash. 



In preparing a field for any crop it is more essential to 

 consider the special needs of the soil, to render it fertile, 

 than the special needs of the crop to be grown upon it. 

 While it is true that some plants take up more of some one 

 element than others, the difference is insignificant when 

 compared with the difference in soils. The soils of New 



