CHAPTER III. 



MANURES, 



Difference between natural vegetation and agriculture — necessity for 

 manuring. Farmyard Manure. — Circumstances which influence its 

 character ; its average composition ;" slowness of its effect — Seaweed 

 similar to farmyard manure — Guano — Sulphate of Ammonium — Nitrate 

 of Sodium — Soot, Dried Blood, and Woollen Refuse — Bones — Ground 

 Phosphates — Sujjerphosjjhatc — Gypsum — Lime, ChalJc, and Marl — 

 Potassium Salts — Common Salt — Ap)plitation of Manure — Importance 

 of thorougli distribution — Best time for aj)plication — The return 

 made by the crop. 



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 

 exceeding 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 con- 

 tains an abundance of plant food, and will produce large 

 crops without manure. 



In human agriculture, on the other hand, both vege- 

 table and animal produce are consumed off the land 



