206 WALL'S MANUAL 



exists in the air, by the action of the oxygen of the 

 air, becomes nitric acid. These are facts. Ammonia 

 in the air, in contact with porons vegetable matter in 

 a decaying condition, becomes aqua-fortis, or nitric 

 acid. Moist decaying substances induce the nitrogen 

 of the air, inclosed in their pores to become first 

 ammonia, then nitric acid. There is a constant 

 formation of nitric acid in the decomposition of 

 vegetable matter. What becomes of the nitric 

 acid? It forms nitrates, a class of salts of great 

 value in the soil. All these changes are worthy 

 of study j the ultimate results are the formation 

 of water and carbonic acid ; the intermediate pro- 

 ducts are ammoina nitrates and soluble salts in the 

 soil, essential to the growth of plants. 



Hence the necessity of the presence of humus or 

 mold in the soil. No practical farmer ever had other 

 opinion than this, that decaying vegetable matter in 

 soil (matter in active state of decay), is essential to 

 good crops. It may be assumed that science has now 

 shown the specific grounds for this universal belief. 

 It is perfectly useless for a farmer to spend time 

 and money in putting lime, potash and other salts on 

 his land, when there is no vegetable matter in the 

 soil. This fact well understood will save thousands 

 of dollars every year. 



CHAPTEE Y. 



THE MUTUAL ACTION OF THE ORGANIC AND INORGANIC 

 ELEMENTS OF THE SOIL. 



We will now take up and study the mutual action 

 of the organic and inorganic matter in thesoil. How 



