212 Farmyard Manure. 



only other constituents which can come into consideration are 

 the nitrogenized matters. The question may therefore be thus 

 simplified : Is the fermentation of farmyard-manure necessarily 

 attended with an_y appreciable loss in nitrogen ? 



Any one may ascertain that fermenting dung gives off am- 

 monia, by holding over a dungheap, in active fermentation, 

 a moistened reddened litmus-paper. The change of the I'ed 

 colour into blue sufficiently shows that there is an escape of 

 ammonia. However, this experiment does not prove as much 

 as is sometimes believed ; for inasmuch as the most minute 

 traces of ammonia produce this change of colour, the escape of 

 this volatile fertilizing matter may be so small that it is practi- 

 cally altogether insignificant. The comparison of fresh with 

 rotten dung, we have seen already-, does not decide whether or 

 not fresh farmyard manure sustains a loss in nitrogen in becoming 

 changed into rotten manure. Apparently there is a gain in 

 nitrogen, for we have seen that rotten dung contains more nitrogen 

 than fresh. This gain in nitrogen, however, is explained by the 

 simultaneous disappearance of, relatively, a much larger quantity 

 of carbonaceous organic matter. Still the accumulation of nitrogen 

 in rotten dung is important, and hardly to be expected ; for, 

 since a considerable portion of the nitrogenized organic matters 

 is changed into A'olatile ammonia during fermentation, a loss, 

 instead of a gain, in nitrogen naturally might be expected. A 

 much greater loss in nitrogen than is actually experienced would, 

 indeed, take place during the fermentation of dung, if this pro- 

 cess were not attended with the simultaneous formation within 

 the manure-heap of excellent fixers of ammonia. 



Alreadj- at the beginning of my experiments I was thoroughly 

 convinced that the mere analysis of farmyard manure would not 

 decide the question which has just been raised, and therefore at 

 once determined to make the analyses in conjunction witli direct 

 weighings of dung in various stages of decomposition. To this . 

 end I weighed out carefully two cartloads-full of the same well- 

 mixed sample of fresh farmyard manure, the full analysis of 

 which is given in the preceding pages. The manure Avas placed 

 in a heap set against a stone wall, but otherwise exposed to the 

 influence of the weather. The entire crude loss which this 

 experimental heap sustained in the course of time was ascer- 

 tained by periodical weighings on the weighbridge. Simul- 

 taneously with these weighings the manure was submitted to 

 analysis, and thus I was enabled not only to determine from time 

 to time the loss in weight which the experimental heap sus- 

 tained in keeping, but also to ascertain which constituents were 

 affected by this loss, and in which relative proportions. I shall 



