230 FARMYARD MANURE [chap. 



arise, and we find as a matter of practice that, despite 

 the utmost care that can be taken in making dung, there 

 will always be a loss of nitrogen due to the volatilisation 

 of the ammonia derived from the fermentation of the 

 urea. This loss, furthermore, falls upon the most 

 valuable of the nitrogen compounds, i.e. upon those 

 which are soluble in water and readily available as food 

 for plants. A large number of experiments have been 

 made in which the amount of nitrogen supplied to the 

 animals was carefully determined and compared with 

 the amount which was afterwards found in the dung 

 that had been made, and under the most favourable 

 conditions of practice the loss amounted to about 1 5 per 

 cent, during the making of the manure. The best 

 conditions are found to be attained by keeping the 

 straw and manure tightly trodden down beneath the 

 feet of the animals, and in a fairly moist condition so as 

 to exclude the action of air. If the straw was allowed 

 to remain in the yard or box in a loose, open condition, 

 or if the litter was cleared from under the animals and 

 simply thrown into a heap day by day, then the losses 

 of ammonia were very much increased, and often rose to 

 half of the nitrogen that had been given in the food. 

 All disturbances of the manure should be avoided, 

 because they result in very active fermentation, with a 

 corresponding increase in the evaporation of ammonia. 

 For example, when fresh strawy manure is repeatedly 

 turned, it is well known that the temperature of the 

 whole mass rises to 70° or 80° through the fermentation 

 that sets in, and quantities of ammonia are given off 

 during the turning, as m_ay be detected by the smell. 

 The heat that is generated by the active bacterial 

 fermentation is utilised by gardeners in the preparation 

 of a hotbed, and it is well known that only fresh strawy 

 manure, which contains plenty of easily fermentable 



