20 



Farmyard Manure. 



[april, 



does the loss fall upon the active compounds of nitrogen, but part 

 of them is also converted into much more slowly acting bodies. 

 For example, in the last quoted experiment there were 43 ■ 83 lb. 

 of digestible nitrogen fed, of which the animal only retained 

 3-07; the remainder, 40*76 lb., was excreted as urea, but 

 only 28-6 lb. of ammoniacal and amide nitrogen were found in 

 the dung, so that besides the loss of 7-38 lb. another 4-78 lb. 

 had been transformed into proteins and other insoluble com- 

 pounds. 



It will be seen that in all cases the losses fall most heavily 

 on the rich dung made by animals receiving concentrated 

 foods ; they also fall almost entirely on the most valuable part 

 of the manure— the urea and ammonia compounds arising from 

 the digestible portions of the food. It is also clear that these 

 losses are avoided when the food is consumed upon the land, 

 as by sheep folded on the arable, milch cows grazing, or beasts 

 fattened with cake upon the summer grass. 



Of course, in all these considerations no account has been 

 taken of such preventible losses as those which too often occur 

 because of the escape of the liquid portions of the manure through 

 a leaky yard or into the drains or by the washing of rain 

 through the dung heap. Such losses are very great and fall 

 on the most valuable substances in the manure, the soluble 

 ammonia and potash compounds which occur in the liquid 

 portion. 



In order to minimise these losses of nitrogen a number of 

 substances have been suggested which when strewn about the 

 cattle stalls and mixed with the fresh dung would either combine 

 with the ammonia and prevent its volatilisation, or by reducing 

 the bacterial actions, would hinder its formation. These 

 preservatives fall into two classes : those designed merely to 

 fix the ammonia, and the true antiseptics which will check the 

 production of either ammonia or free nitrogen gas. 



Of the first class of substances the oldest proposal was 

 to use gypsum, which would react with the ammonium 

 carbonate and form the non-volatile ammonium sulphate. 

 The drawback to the use of gypsum lies in the large quantities 

 that are required ; owing to the reversible nature of the 

 change and the insolubility of the gypsum, a great excess 

 of gypsum would be necessary in practice— about \ cwt. of 



