AUXILIARY AND EXCEPTIONAL MANURES. 83 



one of the most important offices, the decomposition of 

 organic matter in tlie soil, and convert that into plant 

 food seems improbable, because the ability of lime to do 

 this depends in a great measure upon its avidity for car- 

 bonic acid, while limestone being already a carbonate, 

 has no need of more. That limestone can not produce 

 all the effects of lime is shown by the well-known fact 

 that soils underlaid by limestone, and naturally contain- 

 ing a large proportion of finely divided carbonate of lime, 

 are as much benefited by the use of quick-lime as are soils 

 deficient in limestone. 



CHAPTER VIII. 



AUXILIARY AND EXCEPTIONAL MANURES. 



Guano : Statistics. — Prices.— Valuation. — Application. — Bones : Bone- 

 dust. — Bone-ash. — Superphosphate.— Ground phosphate. — Nitro- 

 genous Manures : Nitrate of soda.— Sulphate of ammonia. — Alka- 

 line Manures: Potash. — Kainit. — Gypsum. — Common salt. — Ashes. 

 — Other Manl-res: Soot. — Rape-dust.— Fish refuse.— Blood. — Sea- 

 weed. — Sewa.c^e. — Liquid manure. — Application of Manures: 

 Top-dressing. — Value, of manures from foods. 



Guano. — The constituents of value in guano are (1) 

 ammonia and ammonia-forming compounds ; (2) soluble 

 and insoluble phosphates ; and (3) alkaline salts. The 

 approximate value of any sample can be arrived at by 

 multiplying the commercial values of these materials by 

 the percentage found of each ingredient. The values of 

 ammonia, phosphoric acid, and potash, vary according to 

 the source which supplies them. 



Analyses ought always to be made before purchasing; 

 and if there be reason to doubt the guarantee of the man- 

 ufacturer, a private analysis can be made afterwards. 



