106 THE PEOPLE'S FARM AND STOCK CYCLOPEDIA. 



When manure undergoes fermentation, a considerable portion 

 of the carbon unites with oxygen from the air, and escapes in 

 the form of gas. The heat which this occasions drives off part 

 of the water, and, if the process is properly managed, the total 

 weight of the heap may be reduced one-half without any appre- 

 ciable loss of nitrogen, phosphoric acid, or potash, and the 

 manure that is left will "be worth twice as much per ton. 

 This will not be because the fermentation has added any thing 

 to the heap, but because it has reduced the total quantity in 

 the heap without reducing its total value. It is evident that, 

 if a farmer had a heap of manure weighing twenty tons, and 

 worth forty dollars, if it could be reduced to ten tons and still 

 be worth forty dollars, the smaller pile would be worth twice 

 as much per ton as the larger one had been. 



Another advantage gained by fermentation, and thus reducing 

 the bulk, is that the cost of hauling and spreading is reduced. 

 Farmers who buy manure in town and haul to their farms will 

 often find the expense of hauling fresh manure is greater than 

 its value, while a pile of old and thoroughly rotted manure may 

 be a profitable purchase. 



Fermenting manure also improves it by rendering the plant 

 food it contains more soluble. In fresh manure nearly all the 

 nitrogen is in combinations which are not available to the plant, 

 and it only becomes available as the manure undergoes decom- 

 position, either in the manure heap or in the soil; and, as this 

 process is much more rapid in the manure heap than in the soil, 

 there is an advantage in having the manure thoroughly fer- 

 mented in the heap. 



In these calculations we have supposed that the carbonaceous 

 matter in the manure was of no value in the soil. It is of no 

 value as plant food, but it has a value when the soil is deficient 

 in humus, as by its decomposition it is converted into that sub- 

 stance, which is so essential to a fertile soil. At the same time 

 the humus in the soil can usually be increased more cheaply by 

 plowing under green crops than by hauling out manure. There- 

 fore, the great object in manure should be to secure the largest 

 proportion of plant food ; but the carbonaceous matter it con- 



