Farmyard Manure. 
47 
fresh (luno;, but it is rather less than has been found at Rothamsted 
in <>;()()d box-chmg'. 
But larmyard manure underjT^oes very considerable diminution 
by decomposition, and especially when carted out and formed 
into clamps. Hence the land would not receive so lara^e a quan- 
tity of matter as has been above estimated. The amount of 
organic matter diminishes very considerably, and in rotten dunjij^ 
the proportion of water is generally higher than above supposed. 
It also too frecjuently happens that both mineral matter and nitro- 
gen are allowed to go to waste by drainage or other mismanage- 
ment. Otherwise, as the organic matter diminishes, the amount 
both of mineral matter and of nitrogen should increase in propor- 
tion to a given weight of the manure. 
The composition and value of the manure is also very depend- 
ent npon the quality of the food consumed by the animals that 
help to produce it. Thus, if the same amount of dung had been 
produced from the same materials above mentioned, excludiiuj 
the 20 tons of oilcake, the yard of manure would have contained 
2185 lbs. less of nitrogen, equal to 2653 lbs., or considerably 
above a ton, less of ammonia ; and every ton of the dung Avould 
have contained nitrogen equal to only about 14^ lbs. instead of 
about \1\ lbs. of ammonia. In the one case the dung would be 
called poor, and in the other the farmer might congratulate him- 
self on having a yard of moderately good dung. Yet the whole 
weight of dry substance added by the oilcake to each ton of 
dung would only be about 11 lbs. ! a quantity which is so small 
that neither the man that loaded the cart nor the horse that drew 
the dung to the field would detect it. If 40 tons instead of 20 
tons of oilcake had been employed with the same amount of 
litter, only about another 11 lbs. of dry substance would be added 
to each ton of the manure, but the yard of manure would then be 
equal in quality to rich box-dung. In fact the consumption of 
400/. worth, or about 40 tons of cake, would only add about 10 
tons of dry substance to the manure heap, whilst the weight of 
Peruvian guano obtained for the same money would be about 
30 tons. 
It is quite immaterial to the growth of the crops whether the 
additional amount of nitrogen be purchased in the form of oil- 
cake and so supplied to the land in the farmyard manure, or 
whether it be purchased and applied in the form of artificial 
manure, provided only that the requisite mineral constituents are 
not wanting. It is also a matter of indifference to the crops 
whether the necessary mineral constituents are supplied in the 
form of the excrements of animals or of artificial manures. The 
question is entirely one of economy, depending chiefly on the 
relative prices of meat and corn and of cattle foods and artificial 
manures. 
