BACTERIA AND ENZYMES IN AGRICULTURE 257 



are kept in the fields, manure is returned directly to the ground, 

 and gradually becomes broken down therein. It is when 

 manure is collected from stables and stalls that considerable 

 loss may occur, if care is not taken. Farmyard manure consists 

 of dung and urine, mixed with straw or other material used for 

 bedding, such as peat-moss Htter, etc. The dung will contain 

 the undigested portions of the animals' food, together with 

 a certain amount of waste material from the digestive organs. 

 The more valuable portion of the nitrogenous output of the 

 animal is in the urine. The main fermentations, therefore, 

 that wiU take place in stable manure are : — 



1. Ammoniacal fermentation of urine and of hippuric acid ; 



2. The breaking down of albumin derivatives ; 



3. The decomposition of carbohydrates and especially of 

 cellulose. 



AH of these have been referred to in previous chapters ; it 

 is only necessary here to indicate their practical bearing. 



It is clear, in the first place, that every care must be taken, 

 if the full value of the manure is to be obtained, that the urine 

 is not allowed to run to waste ; for this reason stables and yards 

 should be weU paved and the manure should be kept on an 

 impervious floor. Another less obvious cause of the loss of 

 nitrogen from manure, apart from the actual running to waste 

 of the Kquid portions, arises from the volatilisation of anmionia, 

 owing to the dissociation of the ammonium carbonate, 

 formed by ammoniacal fermentation. This loss is greatest 

 when the manure is fresh, as ammoniacal fermentation is 

 almost the first to set in ; later on acids are formed by the 

 decomposition of carbohydrates and cellulose, which tend to 

 fix the ammonia. One advantage of the use of peat-moss htter 

 is that it has the power of retaining ammonia. It has been 

 found, however, by the experiments of Deherain and others, 

 that if care is taken to pile the manure heap in such a way as 

 to exclude air, the COj evolved by various fermentations pre- 

 vents the dissociation of ammonium carbonate and consequent 



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