68 SCIENTIFIC AGRICULTURE. 



or lime, because the potash contained in ashes, as 

 well as lime, sets free the ammonia. This ammonia, 

 in all ammoniacal fertilizers, is either free or in com- 

 bination with acids. Potash, soda, and lime have 

 a stronger affinity for these acids than the ammonia, 

 and hence they take its place. The ammonia being 

 a gas, passes off and diffuses itself in the air. It is 

 important to understand the chemical principles in- 

 volved in mixing fertilizers, as well as in their action 

 when applied to the soil. 



153. Stable or farm-yard manure is the most 

 common of fertilizers, and one which every farmer 

 and planter can have in great abundance without 

 much trouble or outlay of money. It only requires 

 the exercise of a little care in its preservation in or- 

 der to secure a large supply on every farm. Stable- 

 manure consists of the solid and liquid excrements 

 of animals which feed on some of our most valuable 

 crops, mixed with portions of these crops in a more 

 or less advanced stage of decomposition. It consti- 

 tutes a stimulating and nutritive fertilizer applicable 

 to all crops. 



154. The value of stable-manure depends to some 

 extent on the food of the animal ; the richer the food, 

 the better the manure. The liquid portion is espe- 

 cially rich in phosphates and compounds of nitrogen, 

 and should never be allowed to run to waste. When- 

 ever a manure-heap gives out a strong smell, some 

 of its valuable constituents are escaping. In such 

 cases, the smell of ammonia may not be perceptible, 



