CHAPTER VI. 



GUANO. 



Composition compared with that of seeds ; small amount of potash in it ; its ac- 

 tion Guano and bone-earth, similarity of their active ingredients Guano 

 acts quicker than bone-earth, or a mixture of the latter and ammoniacal salts ; 

 reason of this Oxalic acid in Peruvian guano ; the phosphoric acid rendered 

 soluble by its means Peruvian guano, its efl'ect on the cultivation of corn- 

 Moist guano loses ammonia Moistening guano with water acidulated with 

 sulphuric acid ; effect Inactivity of guano in dry and very wet weather 

 Rapidity of its action as a manure, on what dependent Comparison of the 

 effect of farm-yard manure and guano ; effect produced by mixing the two 

 Guano on a field rich in ammonia Increased produce by guano, what it pre- 

 supposes Exhaustion of the soil by continuous use of guano Mixture of 

 guano with gypsum and with sulphuric acid The Saxon agricultural experi- 

 ments ; their results. 



PERUVIAN guano generally contains 33 to 34 per 

 cent, of incombustible, and 66 to 67 per cent, of 

 volatile and combustible ingredients (water and ammo- 

 nia). The latter consist principally of uric acid, oxalic 

 acid, a brown matter of uncertain composition, and 

 guanine. The uric acid amounts occasionally to as 

 much as 18 per cent., the oxalic acid generally to 8 or 

 10 per cent, of the weight of the guano. The relation 

 of uric acid to vegetation is not known, but it is hardly 

 likely that this substance can have a perceptible share 

 in the fertilising action of guano. To account for this 

 action, then, we have only the ammonia and the incom- 

 bustible constituents left to consider. An analysis of 

 two samples of guano, made by Dr. Mayer and Dr. 

 Zoeller, in iny own laboratory, showed 100 parts of 

 guano ash to contain : 



Potash 1-56 to 2'03 



Lime 34'00 " 37 '00 



Magnesia 2-56 " 2'00 



Phosphoric acid 41 '00 " 40'00 



