496 The Storage of Farmyard Manure 



great importance in crop production when reckoned over an acre of land, 

 is, nevertheless, very small on the few grams of soil used in a laboratory 

 experiment lasting only for a few weeks. 



The difficulties arising out of the smallness of the amount to be 

 measured led us to seek out a parallel case where the absolute quantities 

 are larger, and where, therefore, there is greater hope of getting precise 

 information. The manure heap affords such a case: it is the seat of 

 biochemical decompositions which in several important respects resemble 

 those in the soil : in particular it undergoes loss of nitrogen, but the 

 amount is far greater than that suffered by soil, and the loss proceeds 

 much more rapidly. The elucidation of the causes of loss of nitrogen 

 from a manure heap appeared by no means a hopeless task, and would, 

 if successful, afford a useful guiding hypothesis for starting an investi- 

 gation on the loss of nitrogen from soil. 



As the work progressed, however, the technical importance of the 

 problem led us to widen the scope of the investigation, and to make it 

 deal with the changes in the manure heap independently of their 

 bearing on the changes within the soil. 



When a manure heap is put up fermentation rapidly sets in accom- 

 panied by a considerable rise in temperature. All the organic con- 

 stituents of the heap appear to alter : we have devoted most attention 

 to the nitrogen compounds, and this course is justified by the field 

 experiments, but the non-nitrogenous constituents also change to 

 an equal, and sometimes to a greater extent. As a rvde the loss of 

 nitrogen proceeds fari fassu with that of the other constituents, so 

 that the percentage shows no great change or only a small falling off: 

 under certain circumstances, however, it proceeds more slowly, leading 

 to an actual increase in percentage amount, though of course a decrease 

 in absolute quantity. 



The loss of nitrogen seems to fall on all the nitrogen compounds 

 excepting perhaps the amides. The ammonia invariably falls off in 

 amount : in no case have we observed an increase. The amides usually 

 remain constant, sometimes they fall but they do not increase. The 

 more complex nitrogen compounds, — obtained by difference, — usually 

 fall, but in some cases they remain constant. But there is nothing to 

 show what reactions have taken place, or how the losses have occurred. 



In laboratory work on bacterial decomposition of protein there is 

 always an accumulation of ammonia, so also there is in the decomposi- 

 tions taking place during sewage purification. In these cases the 

 reaction appears simply to be the ordinary hydrolysis of protein to 



