278 
ON THE CULTURE OF THE CEREALS. 
addition of native phosphate of lime or bone earth. An addition of twenty-five pounds of the 
former (phosphate of lime,) to every ton, will be rather more than sufficient to equalize the 
differences between them. This mineral can now be obtained, and its use will mark an era 
in the husbandry of any district where it is employed. It may be used as the basis of all 
composts : it will equalize the value of the different compounds, and diminish the expense of 
high cultivation. 
But there is an element which must be taken into account, when we undertake to estimate 
the comparative value of manures ; it is the food from which they are derived. This element 
has been referred to. For example, if the cow has been fed upon timothy, or the common 
mixed dried grasses, the amount of silica in the excrements will be five times as much as if 
they were fed upon clover. This must follow from the composition of these plants ; the former 
being very rich in silica, while the common red clover is poor. See volume second, where 
the composition of each is given. So if fed upon grain, leaves or any cereal or substance rich 
in phosphates, the composition will vary still more. It is, therefore, by approximation only 
that we can arrive at the value of fertilizers; and what increases the difficulty is their mixed 
condition as it regards their source, and as it regards also the food of the animals from which 
they are immediately derived. 
An early supply of these essential elements of grain is important. The leaves and stalk 
may be said to ripen first, and it is not until their ripening that the plant proceeds to the fulfil¬ 
ment of a higher duty—the production of seeds, for the continuance of the species, or the 
production of the grain for the sustenance of man. When this is done, the forces of the plant 
are directed, or should be, to this end, and it would seem that when the period has arrived, or 
time has come for this, if the leaves are yet immature, the forces of the plant are divided be¬ 
tween the growth and perfection of foliage and the production of fruit. 
An acre of corn will require an amount of one thousand pounds of inorganic matter to be 
added to it, where the acre has been reduced by cultivation below the ordinary standard of 
fertility, or where only twenty-five bushels of corn could be expected upon that area. This is 
rather more than twice the amount which a good crop would remove from the acre in its stalks, 
leaves, husks, cobs and kernels. It is always necessary to add twice the amount which a crop 
is known to remove. This is a good rule in any case, in the older sections of the country, 
where fertilizers are depended upon from year to year; of course in the new lands, where the 
original fertility is unimpaired, this rule will not apply. The determination of the amount of 
inorganic matter may be obtained by consulting the analyses of the fertilizers from the different 
kingdoms. Thus in dry peat there is 5 - 8 per cent of white and pure ash, or inorganic matter. 
The excrements of the horse contain from 8 to 9 per cent, nearly 3 per cent of which is silica 
in a soluble state, and which, on this account meets very well the wants of maize. I am thus 
particular in stating these facts for the purpose of directing the attention of farmers to the im¬ 
portance of knowing how much they are taking yearly from the fields, and also how much they 
should return to them. 
