874 EXPERIMENT 8TATI0N RECORD. 



which inauure, especially that of horses, contains in large numbers, and 

 was observed, not only in the fresh solid excrement, but also in the 

 partially decomposed manure. 



(0) When 100 gm. of solid horse excrement was mixed with 1 liter of 

 water and 3 gm. of nitrate of soda and kept at an average room tem- 

 perature, the nitric nitrogen was completely converted into free nitrogen 

 in from 8 to 14 days. 



(7) When a solution of nitrate was mixed with a humus soil, elemen- 

 tary nitrogen was very slowly set free. The same was observed when 

 straw acted ujion solutions of nitrate. The denitrifying action of the 

 soil and straw was much greater when the two were mixed than when 

 each was used alone. The denitrifying action of the solid excrement 

 was decidedly increased by the addition of straw. 



(8) Theoretically a well-balanced manure should contain equal amounts 

 of nitrogen in the form of urine and in that of solid excrement and lit- 

 ter, but in practice manure contains as a rule 25 to 35 and even as low 

 as 10 parts of nitrogen in urine to 100 parts in solid excrement and 

 litter. This may be explained by the facts {a) that often in practice 

 the liquid manure is drawn away from the solid manure and stored 

 separately, and (ft) a part of the nitrogen of the urine is lost in the 

 form of ammonia or of free nitrogen. 



(9) The objects of preservation of manure should be to check or pre- 

 vent the formation of ammonia and its volatilization from the solid and 

 liquid manure and the setting free of nitrogen by the action of bacteria. 

 The formation of ammonia in a mixture of solid excrement and litter is 

 so slow that it may be left out of consideration in practice, except in 

 so far as it may aflect the decomposition processes and products of the 

 urine. 



(10) When solid excrement and straw are spread in layers 2i to 3 ft. 

 thick they undergo very little alteration in the course of a year if the 

 mass is packed down so as to exclude the air as perfectly as possible. 

 If, however, the mixture is loosely spread out and frequently stirred so 

 that the air has free access, it undergoes decomposition by which heat 

 is generated and organic matter is converted into humus, with a loss of 

 as much as 50 per cent of the organic matter originally present. The 

 usual preservatives, gypsum, superphosphate gypsum, and kainit, as 

 well as burnt lime, used in amounts ordinarily recommended have 

 no appreciable influence on the process of humification. During this 

 process of humification the denitrifying power of the manure is largely 

 reduced, but it is never entirely destroyed by this process. The effect- 

 iveness of well-rotted manure as compared with fresh manure is prob- 

 ably due to this reduction of the denitrifying power of the manure. 

 The use of the usual amounts of preservatives has no appreciable effect 

 on the denitrifying power of the manure. It was observed that on long 

 storage and complete humification, gypsum, superphosphate- gypsum, 

 and kainit exerted a preservative efl'ect upon the denitrifying action 

 of the manure, while lime produced an opi)osite effect. 



