THE MANURE HEAP AND SEWAGE. 113 



terials which have been recommended for the preservation of 

 the nitrogen of the manure the most common are gypsum, 

 kainit, superphosphates, marl and sodium bisulphate. Each of 

 these has appeared to be of some utility in this respect and 

 each one has been recommended. The disadvantages which 

 also accrue and the expense involved make it doubtful 

 whether the use of any one of them can be unhesitatingly 

 advised. 



Of less doubtful value are suggestions arising in regard to 

 the treatment of the manure. The loss of nitrogen appears to 

 be greater in manure when there is a perfectly free access of 

 air than when it is compactly massed. Hence it seems wise 

 to keep the manure in compact heaps. As already noticed 

 the denitrifying processes require some carbonaceous material 

 as a source of energy to the bacteria, and this material may be 

 furnished by straw. Hence it has been concluded that the 

 mixing of the manure with straw in the form of bedding in- 

 creases nitrogen loss by denitrification. Moreover, since the 

 manure of horses always contains a considerable amount of 

 such undecomposed straw, its presence in the manure heap 

 tends to increase nitrogen loss, and the wisdom of keeping the 

 manure of the horse and cows separate is clearly indicated. 

 The use of sawdust for bedding as a substitute for straw is an 

 aid in decreasing nitrogen loss. The separation of the liquid 

 from the solid manure is recommended by those who have 

 studied into the matter. The former decomposes very rapidly, 

 and its presence in the manure heap is believed to hasten the 

 denitrifying processes and to cause a large nitrogen loss which 

 would be partly prevented if the two kinds of manure were 

 kept separate. 



All of these plans for preserving manure from loss are evi- 

 dently based upon bacteriological phenomena. Each one is 

 directed, consciously or unconsciously, either to checking the 

 growth of bacteria in the manure or to holding in solution the 

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