16 FARMYARD MANURE. 



In putting this question we have to bear in mind that the loss 

 in valuable mineral matters, under proper management, practi- 

 cally speaking, can be avoided, since they are non-volatile, and, 

 therefore, must remain incorporated with the dung, if care be 

 taken to prevent their being washed away by heavy falls of rain. 

 We have likewise to bear in mind that, in an agricultural point 

 of view, the carbonaceous, non-nitrogenized manure constituents 

 do not possess a very high intrinsic value; and that we therefore 

 need not trouble ourselves about their diminution, if it can be 

 shown that it is accompanied with other beneficial changes. The 

 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 any appreciable loss in nitrogen ? 



Any one may ascertain that fermenting dung gives off am- 

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

 moistened reddened litmus-paper. The change of the red colour 

 into blue sufficiently shows that there is an escape of ammonia. 

 However, this experiment does not prove as much as is some- 

 times 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 practically 

 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 simul- 

 taneous 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 volatile 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 process 

 were not attended with the simultaneous formation within the 

 manure-heap of excellent fixers of ammonia. 



However, the mere analysis of farmyard manure cannot decide 

 the question which has just been raised, and I therefore at once 

 determined to make the analyses in conjunction with 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 has been given before. The manure was placed in a 

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



