336 



THE ROTHAMSTED EXPERIMENTS. 



Valuation 

 of unex- 

 hausted 

 manures. 



Percentages 

 of nitrogen 

 assimilated 

 and voided 

 by animals. 



Fattening 

 animals. 



Growing 

 animals. 



Cows. 



10 per cent from the amounts consumed in oilcakes and 

 leguminous seeds, which contain high percentages of nitro- 

 gen, and 15 per cent from the amounts in the foods which 

 contain lower percentages. These deductions were reckoned 

 to include the amounts of nitrogen actually stored up in the 

 increase of live-weight, and also some little loss if any, but 

 not to cover the larger losses that may take place in the 

 manure after it is voided by the animals. More recently, 

 however, we have estimated the amount actually stored up 

 in the animal, and have assumed the whole of the remainder 

 to be voided in the solid and liquid excretions. 



For details on the point, we must refer to our most recent 

 paper bearing upon the subject, entitled On the Valuation of 

 Unexhausted Manures. 1 The calculations relate to the use of 

 food for the production of fattening increase. It is assumed 

 that, on the average, such increase will contain 8 per cent of 

 nitrogenous substance, corresponding to 1.27 per cent of 

 nitrogen in the increase. According to the calculations it 

 results that, of the total nitrogen consumed in foods rich in 

 that substance, such as oilcakes and leguminous seeds, there 

 will generally be less than 5 per cent retained in the fatten- 

 ing increase in live- weight. In the case of the cereal grains, 

 on the other hand, which are much less rich in nitrogen, a 

 much larger proportion of the total amount consumed will 

 be retained in the increase — generally, perhaps, about 10 per 

 cent of it. Of the nitrogen in gramineous straws a still 

 higher proportion will probably be devoted to increase ; 

 whilst roots will, on the average, lose by feeding, perhaps, 

 only about 5 or 6 per cent of their nitrogen. 



Thus, when fattening increase only is produced, the pro- 

 portion of the nitrogen of the food which will be retained by 

 the animal, and so lost to the manure, is very small in the 

 case of the richer foods, but more in that of the poorer ones ; 

 though, even with them, it will seldom exceed 10 per cent, 

 except possibly in the case of straws. It may be assumed, 

 however, that when foods are consumed by store animals, 

 whose increase is largely growth, about twice as much of the 

 nitrogen of the food is retained, and so lost to the manure. 

 And when, as is more and more the case with early maturity, 

 the increase comprises a larger proportion of growth than in 

 mere fattening, the amount of the nitrogen of the food which 

 will be lost to the manure will be more than with fattening 

 only, but less than with merely store animals. When, how- 

 ever, food is consumed for the production of milk, a very 

 much greater proportion of its nitrogen will be lost to the 

 manure. 



1 Joum. Roy. Ag. Soc. Eng., vol. xxi., SS., Part II., 1885. 



