CHAPTER III. 



MANURES. 



Difference between natural vegetation and agriculture —Necessity for 

 manuring. Farmyard Manure. — Circumstances which influence 

 its character — Losses in preparation — Changes during fermenta- 

 tion — Its average composition — Slowness of its effect — Seaweed 

 — Guano — Fish Manure — Sulphate of Ammonium — Nitrate 

 of Sodium — Soot, Dried Bloody Powdered Horn, and Woollen 

 Refuse — Meat Guano — Bones — Oilcakes — Phosphatic Slag and 

 Ground Phosphates — Superphosphate — Gypsum — Lime, Chalk, 

 and Marl — Potassium Salts— Common Salt. Belative Value of 

 Manures. — Results of comparative experiments — Price per unit. 

 Application of Manures. — Importance of thorough distribution- 

 Best time for application. Beturn for Manure Applied. — Increase 

 from nitrogenous manures — Effect of residues of previous 

 manuring. 



In the natural vegetation of a forest or prairie the 

 soil suffers no diminution of plant food. The elements 

 taken from the soil are returned to it on the decay of 

 the plants which the soil has nourished, or on the 

 death of the animals which have fed on these plants. 

 Under these circumstances the surface soil becomes 

 rich in carbon and nitrogen, the quantity contributed 

 by the atmosphere at first exceeding, and then balanc- 

 ing, all losses. The surface soil also becomes rich in 

 the ash constituents of plants, these being collected 

 from the subsoil by the roots, and left at the surface 

 on the decay of the plant. A virgin soil thus generally 

 contains an abundance of plant food at the surface, 

 and will produce large crops without manure. 



As soon as land is brought under the plough the 



