Composition and Nutritive Valm of Straw. 
383 
the presence of certain organic and mineral constituents — is, 
1 conceive, very insig-nificant. Its chief merits are as an 
absorbent of the most vakiabh; portions of the excrements of 
animals, and as the best fixer of the ammonia which is always 
•jenerated when excrementitious matters in contact with porous 
materials and a sufficient quantity of moisture enter into active 
fermentation. The action of straw in fixings ammonia may be 
thus explained. During the fermentation of dung the woody 
fibre of straw is converted by degrees into ulmic, humic, and 
similar organic acids, which impart to liquid manure or to the 
drainings of dungheaps a more or less dark brown colour. The 
gradual resolution of the nitrogenised part of the excrements into 
ammoniacal compounds proceeds simultaneously with the forma- 
tion of organic acids belonging to the humic acid series. All 
the acids of that series possess great affinity for ammonia, in 
virtue of which they unite with the ammonia of the volatile car- 
bonate of ammonia, Avhich, without the addition of a proper 
(juantity of litter, would evaporate from a heap of fermenting 
excrements. Straw thus furnishes the raw material for the pro- 
duction of a number of organic acids, which, by laying hold of 
ammonia, preserve that most valuable constituent in our manure. 
The indirect fertilising value which attaches to this important 
property of straw, in v irtue of which rotten straw prevents the 
loss of ammonia in dungheaps, in my opinion, is far greater than 
its intrinsic manuring value, which is dependent upon the various 
small proportions of nitrogen, potash, phosphoric acid, silica, 
and other constituents which it contains. These constituents 
can, I believe, be supplied in various artificial manures and 
refuse matei'ials, more economically than in straw. But I do not 
see clearly how the most valuable portion of the dung is to be 
preserved without straw, and how the comfort of cattle is to be 
secured without a sufficient quantity of litter, or what economical 
and available substitute can be found for straw applied as litter, 
I am therefoi'e inclined to attach much more value to straw than 
most theoretical men, and yet can go a long way with those 
farmers who broadly and somewhat vaguely state that it is not 
manure but only litter. 
As straw contains only from 14 to 17 per cent, of moisture, 
there is in it about as much solid matter as in meal and other 
kinds of dry food, although it is considered to be worth only 
from 20s. to 30a\ per ton. 
The bulk of straw, however, includes a large proportion of 
woody fibre, which, if digestible at all, is only partially assimi- 
lated in the system. Still, assuming that not more than one-third 
of the weight of straw is digested by cattle and probably less by 
horses and sheep, and granting that the assimilable part is not 
