Purchased Food, and of its Residue as Manure. 
227 
It is evident, therefore, that the manuring-constituents of pur- 
chased food, which are recovered in the manure from farm-stock 
in this bulky and less available form, possess a much lower 
practical or market value than the estimated manure-value which 
different stock-foods are assumed to possess in Mr. Lawes's 
table. Mr. Lawes's estimate of the manure-value of different 
kinds of feeding-stuffs, however, are based on carefully ascer- 
tained facts, and, so far, have a permanent value, affording im- 
portant and useful data for comparative valuations. But in their 
application in practice, it appears to me, that we shall be nearer 
the mark if we deduct from 30 to 40 per cent, from the estimated 
money-value which is given in the table to the manure-con- 
stituents of a ton of the several articles of food, in order to 
arrive at the additional practical value in the land which is 
given to several (or a good many, say, 15 to 20) tons of farm- 
yard manure by the consumption of a ton of those several articles 
of food. Mr. Lawes is fully alive to the fact that it is not 
possible to recover in practice the full estimated manure-value 
of purchased food, for in his valuable paper on the " Valuation 
of Unexhausted INIanures," in Part I., Vol. XI. of this Journal, 
he says, at page 12, " If purchased food be consumed with a 
root-crop by the outgoing tenant, and he take no crop grown 
by the manure produced, he should be allowed compensation at 
the rate of 1 7s. for every 20s. of the original manure-value of the 
food if it have been consumed on the land, or 16s. if consumed 
in the yards." jNIr. Lawes thus makes a deduction of 20 per 
cent, from the calculated manure-value of purchased food ; 
whilst I am inclined to allow the largei deduction of from 30 
to 40 per cent, if the food be made into bulky farmyard-manure, 
the market-value of which, we have seen, is scarcely one-half 
that of its calculated money-value. On the other hand, if the 
food be consumed by sheep, with a root-crop, practically no loss 
in manuring elements is sustained when the urine and solid 
excrements of sheep are spread at once on the land, without 
being first put up into a dung-heap, like the excrements of cattle 
kept in yards or feeding-stalls ; no additional expense is incurred 
in carting, distributing, and ploughing-in the manure, and in 
that case Mr. Lawes's estimated manure-value of linseed and 
similar concentrated nitrogenous articles of food, with a deduc- 
ion of 20 per cent., I believe, gives a fair and correct estimate 
of the practical manure-value of oilcakes, and similarly con- 
stituted food. 
The composition of feeding materials certainly affects their 
nutritive and manurial properties ; at the same time the mere 
proximate analysis of an article of food does not give a suffi- 
cient insight into its real economical value. There is nothing, 
Q 2 
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