546 



The Storage of Farmyard Manure 



The cause of the loss. 



Summing up the work previously done we find that there are three 

 hypotheses in the field to account for the loss of nitrogen during the 

 bacterial decomposition of organic matter: 



1. A simple reduction, or denitrification, — nitrates being reduced 

 to gaseous nitrogen. 



2. A simple oxidation, the ammonia, or other nitrogen compound, 

 being oxidised direct to nitrogen. 



3. An alternate oxidation and reduction, nitrate being formed at 

 one time and reduced at another. 



The first hypothesis obviously requires anaerobic conditions : it is 

 excluded by the experiments described on pp. 528-530. 



The second hypothesis requires only aerobic conditions : this also is 

 ruled out by the experiment described on p. 539. But in view of its 

 importance it was still further tested, this time with the separate con- 

 stituents of the manure. Working with urine, with mixtures of urine 

 and straw, and urine and faeces, we obtained vigorous oxidation ; in 

 one case as much as 10 % of the nitrogen being changed into nitrate, 

 but the conversions were quantitative and there was no loss of nitrogen 

 during the process. 



The quantities used were as a matter of convenience much smaller 

 than in the previous experiments, otherwise the general arrangements 

 were the same. The following are typical of the results obtained with 

 urine : 



* In this experiment only 53 % of the ammonia formed was carried over and the 

 liquid was probably too alkaline for nitrification to occur. 



f In this experiment 82 % of the ammonia was carried over and the liquid was therefore 

 less alkaline : hence nitrification took place. 



A similar result was obtained with a mixture of urine and straw, 

 and of urine and faeces. In an experiment lasting for 34 days in a 



