204 BOARD OF AGRICULTURE, 



It is found that a manure containing more phosphate and less 

 ammonia is safer, and better to use, and cheaper to buy ; and 

 this experience, coupled with the fact that we have in fish guano, 

 or porgy chum, so largely produced along our coast line, abun- 

 dant supplies of a manure nearly identical in character and results, 

 with Peruvian guano, — has caused an almost total abandonment 

 of its use in this section. It is true that our fish guano is of less 

 uniform quality and less concentrated, but its cheapness makes 

 amends for the difference. 



It is much to be regretted that so large a proportion of the fish 

 refuse is not better cured, so as to retain the manurial efficacy 

 which it has while fresh. Within the last ten years, however, 

 there has been a vast improvement in this respect, and yet there 

 is need of a great deal more. When well dried immediately upon 

 coming from the press, fish guano may be deemed to be one-half 

 as valuable as Peruvian guano. 



I come now to the consideration of Supeb-Phosphates, of which 

 probably a larger amount is used in New England than of any 

 other concentrated manure. 



What is commercially known as a "Super-phosphate," is a, concen- 

 trated comiwst manure, containing a considerable proportion of solu- 

 ble phosphoric acid, together with a portion more or less insoluble, 

 and usually a quantity of nitrogenous matter or of ammoniacal salts. 

 It ought to contain as large a proportion of phosphoric acid in a 

 condition available to plants, as it can be made to contain and yet 

 be sold at a- price admitting its profitable use in agriculture. It is 

 not expected to be a chemically pure soluble phosphate, for this 

 would place its cost far beyond the possibility of economical use. 

 Go to a chemist and inquire the price of potash. You can find it 

 good enough for surgical use for about one dollar per pound, but 

 for chemically pure the charge will be much higher. It is clear 

 that no one will buy at such prices to put on land, or to make 

 soap with, when he can obtain the same quantity in commercial 

 potash, mingled with some impurities, but good enough for the use 

 required, for a dime or two. 



So too, if he asks the price of the purest phosphoric acid in the 

 market, he will find it about three dollars per pound, but he can 

 buy the same quantity in several pounds of a good superphosphate 

 for a quarter of one dollar, and possibly for rather less. 



To be commercially pure, a superphosphate should be made ivifh 

 skill, fy^om good materials, and tuith no additions made to cheapen its 

 cost, thereby reducing its quality. 



