THE MANURE HEAP AND SEWAGE. I I 5 



quantities of the nitric bacteria which may be of direct value 

 to the soil. 



Of course this ripening need not take place while the manure 

 is still within the manure heap, for essentially the same 

 changes will occur if the fresh manure be thrown upon the 

 soil. The changes which then occur will be more or less 

 modified by the conditions, since there will be present less 

 water, a more complete separation of the liquid and solid 

 manure, and different relations to the supply of oxygen. It 

 seems, as the result of experiments, that the nitrogen loss 

 occurring when the manure is thus used fresh, is less than 

 when it ripens in the heap. Certainly the loss of nitrogen is 

 greater where large amounts of organic material are allowed 

 to ferment in a mass together, than when only small amounts 

 are present. The former condition is offered by the manure 

 heap, the latter by the manure scattered fresh upon the soil. 

 Indeed, some bacteriologists are inclined to believe that the 

 nitrogen loss from denitrification is really very small under 

 ordinary conditions where only a small amount of manure is 

 spread out and mixed with the soil, a conclusion which would, 

 of course, suggest the wisdom of using the manure fresh in- 

 stead of waiting for it to ripen in the heap. While this advice 

 may be sound it is of course impossible to follow it in climates 

 where the soil freezes in winter weather. But it is certain that 

 we must not apply too rigidly to the soil the conclusions 

 which have been reached from laboratory experiments under 

 the unusual condition of excessive organic material undergoing 

 decomposition. 



It must be borne in mind that in the ripening of manure it 

 is not desired that the nitrates should form too quickly. 

 Whether the denitrifying forces are active in soil or not they 

 certainly are active in the manure heap, and if nitrates form 

 early in the ripening these reducing bacteria will extract their 

 oxygen and cause their loss as ammonia or free nitrogen. The 



