19-21.] 



Artificial Farmyarj> Mani re. 



409 



results in an increased production of soluble nitrogen, which, 

 owing to the normally overloaded condition of the litter, is 

 liable to relatively greater loss than where such feeding stulfs 

 are not used. 



We have attempted to test the accuracy of this view by, 

 computing the amount of nitrogen that ought under ordinary 

 conditions to be recovered in the form of manure from any 

 given system of feeding. For this purpose we have taken: — 



(a) the total amount of nitrogen contained in the straw used as litter ; 

 this is apparently not in a form liable to loss ; 



(b) the amount of indigestible or faecal nitrogen as calculated from the 



digestion co-efficients of the foods consumed ; 



(c) the amount of nitrogen which the quantity of litter employed should 

 be theoretically capable of retaining^ i.e., 0*72 lb. of nitrogen per 

 100 lb. of straw ; and, 



(d) the amount of nitrogen present as ammonia at the end of the experi- 

 ment; this quantity is extremely variable and is determined by the 

 actual conditions, aeration, exposure, and the length of the period 

 during which the manure is stored. 



The application of this method to the actual results obtained 

 in a number of feeding experiments show^s that a fairly close 

 approximation may be obtained. 



Two instances may be given, the first relating to Professor 

 T. B. Wood's experiment at Cambridge,* and the second to that 

 of Professor Hendrickt on the feeding of bullocks on roots and 

 straw. The following table gives an extract of Professor Wood's 

 data relating to the amount of total and digestible nitrogen 

 suppHed to the respective sets of animals, and the net amount 

 excreted after deduction of the calculated nitrogen due to the 

 live-weight increase of the animals. As the animals w^ere not 

 fed with straw but were able to pick over that supplied :is litt.-»*, 

 it has been assumed that one-quarter of the whole would be 

 consumed, and due allowance has been made for this. In the 

 two instances, therefore, after making this deduction. 41.15 

 and 83.85 lb. of nitrogen were supplied to the animals, whilst 

 only 30.9 and 46.70 lb. w^ere recovered in the manure. The 

 totals obtained by calculating the indigestible or fircal nitrogen, 

 together with that contained in the litter and the amount which 

 this litter is theoretically capable of fixing, closely approach 

 those obtained by actual analysis of the mannro. being 33.6 as 



• Jour. Aiiric. ScL, 1007-08. Vol. IT, d. 207. 

 t North Scot. Coll. Agric, 191R. Bull. Xo. 22. 



