Year: 1879

Plants get part OF their food from the air,
through their leaves and other green parts,
the rest from the soil through their roots.
This was proven by vast amount of la
borious and accurate experimenting, car
ried on for the most part in the European
experiment stations for the purpose OF dis
covering the laws of plant nutrition and
growth.


Wat,r.-Plants have the power of absorb
ing water through their leaves, but the
bulk of their supply comes, and must come,
from the atmosphere to the soil and thence
to the plant through the roots.


Organic Matter.-Carbon, OXYGEN, and by
drogen. The carbon of plants is taken
from the atmosphere. The leaves absorb
carbonic acid, and with the aid of light
wrest its carbon and oxygen asunder, set
ting oxygen free, and thus purifying the
air, while they retain the carbon. Carbon
unltes with hydrogen, oxygen, and nitro.
gen, to make up the various tissues OF the
plant, the root, stem, leaf and seed, the
wood and bark, the gluten, starch, sugar,
and so on. The atmosphere supplies car
bon far in excess of the demands of plants.
The best experiments indicate that the
carbon is all, or nearly all, obtained from
the air. The source of the oxygen and



very probable that the water absorbed
through the roots is the main, if not the
entire, source OF supply.


NtrogSn.-Our cultivated plants get the
bulk of their nitrogen from thesoil, through
their roots. Many years of labor of the
best investigators, and many thousands Of
dollars, have been devoted to the study of
the nitrogen of plant food. The theory
that plants avail themselves of the free
nitrogen OF the air, of which there are
thousands of tons over every farm, must be
egIrded as wrong. The theory that plants
in general and the lHrge-leaved" plants
in particular, as clover, turnips, corn, etc,
obtain a good deal of combined nitrogen
ammonia and nitrate4) from the air by
their leaves, is hardly tenable. The gain
of nitrogen from this source, seems to be
very small indeed. The most of the nitro
gen of our crops is got from the soil through
the roots The soil gathers some nitrogen
compounds from the air, however, and it is
extremely probable that it asslmilates free
nitrogen, and thus, in two ways, stores
up atmospheric nitrogen for plant food
The nitrates in the soil, formed mostly
from the decay Of vegetable and animal
matter, are the chief natural sources of the
nitrogen of plant-food. Ammonia, which,





debris and from manures, ss we'll as from
the air, is also used by plants. Other COM
pounds OF nitrogen, no one yet knows
what or how many, can also be assimilated
by plants.


Mineral Matter, or ASh.-The mineral in
gradients of plants are derived exclusively
from the soil. OF these, potash, lime mag
nesia, iron. and sulphuric acid, must be
furnished to all agricultural plants through
their roots and by the soil, in order to
their growth. If the available soil supply
of any one of these is deficient, the whole
crop must suffer. As regards soda, silica,
and chlorine, the experimental evidence is
not so decisive. small quantity OF
chlorine has been proven necessary for the
perfection of some plants. Soda is needed
in very minute quantities, il at all, by crops.
little OF silica is probably necessary to the
perfect blossoming and ripening of grain.


To sum up in few words Air and
water together yield the material out of
which fully ninety to ninety eight per cent.
of crops is built up. The soil has to give
for their nourishment only the two to
eight per cent. of mineral matters which
remain as ashes when they are burned,
and the one.half to two per cent. of nitro
gen which they also contain. ."-Americal
AgricultTist.