|S JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Guano. 



The next manure on the list is guano ; many horticulturists 

 believe in guano who will use no other artificial manure ; and 

 the attraction of the name has kept this article, until recently, 

 at a high price compared with other fertilisers of the same 

 efficiency. Multitudes of inferior manures — many of them 

 almost worthless — have been sold under the magic name of 

 guano, of which I quote two instances that have recently come 

 to hand. 



Peruvian guano when pure is certainly one of the most 

 important of the nitrogenous manures. Average samples contain 

 from 5 to 8 per cent, of nitrogen, and from 20 to 35 per cent, of 

 phosphate of lime. It is estimated that 1J ton of nitrogenous 

 guano is equal to about 33 tons of average farmyard manure, 

 the nitrogen of the guano being much more active than that 

 contained in the dung. 



In Table V. the "good" guano No. 1 contains in each 

 one ton 357 lbs. of nitrogen, 213 lbs. of phosphoric acid, 182 lbs. 

 of potash, and 198 lbs. of lime. As the greater part of the 

 nitrogen in guano readily becomes soluble, it follows that if the 

 deposit has been exposed for a long time to the weather, much 

 of this constituent will have been washed away, and the residue 

 will be chiefly insoluble, and consist to a considerable extent of 

 phosphate of lime. Thus sample No. 2 gives an example of this 

 kind, and is seen to contain in each ton, only 15G lbs. of nitrogen, 

 less by 201 lbs. than sample 1 ; but 314 lbs. of phosphoric acid, 

 being an increase in that constituent of 101 lbs. over sample No. 1. 

 The potash shows a decrease of 108 lbs. in each ton, while the 

 lime, the least valuable ingredient, shows an increase of 84 lbs. in 

 each ton. 



Now this very striking difference in the composition of guano 

 not only applies to samples obtained from different sources, but 

 even to those from different parts of the same cargo; therefore 

 prudent buyers may naturally look to sellers for some guarantee 

 a to the quality of their purchases, and should never purchase 

 without it. 



Specimens of glaring adulteration are shown by the two 

 tamplefl quoted. Thus No. 1, which had been adulterated with 

 •'ypsuin (sulphate of lime), contained in each one ton only 4 lbs. 



