MANURES. — THEIR SOURCES AND PREPARATION. 45 



as a manure. By burning, it loses its adhesiveness, which 

 in its natural state prevented air from permeating it, and 

 water from passing off. Its saline constituents, and those 

 also of the roots of the plants it contains, are set free, 

 while it is rendered permeable to the air and freely admits 

 the advancing roots of plants. The burnt particles ab- 

 sorb ammonia from the air, and hold it in their pores until 

 washed out by showers into the soil to act as nourishment 

 for the crops. It may be prepared in connection with 

 charcoal, as hereafter shown. There is some loss of or- 

 ganizable matter which is more than made up by chemical 

 changes produced. 



Organic Manures, beginning with those of vegetable 

 origin. The very best is cotton seed cake, where it can be 

 obtained. Properly prepared, it is scarcely inferior in 

 strength to guano itself. It may be applied with advan- 

 tage to any crop. 



Charcoal renders the soil light and friable, gives it a 

 dark color, and additional warmth for early crops. The 

 bed whereon charcoal has been burnt is always marked 

 by a most vigorous growth of plants when it becomes 

 sufficiently mixed with earth. It contains also small quan- 

 tities of salts of potash and other fertilizing salts. 



It absorbs both carbonic acid and ammonia from the 

 air, and yields them to the roots of plants. It is most 

 marked in its effects on plants which require abundant 

 nitrogen. As it is^ indestructible, its beneficial effects last 

 as long as it remains in the soil, supplying the rootlets of 

 plants with carbonic acid, which is renewed as fast as ab- 

 stracted. Its good effects begin to be seen when the dust 

 is applied at the rate of forty bushels per acre. Charcoal 

 is invaluable for destroying the odor of decaying animal 

 matter, retaining all the gases in its own substance ready 

 to yield them up for the use of plants. Hence, the best 

 application of this substance is not directly to the soil, but 



