April 11, 1P03. 
THE GARDENING WORLD . 
315 
How Nature Imparts Fertility to Soil, 
By J. J. Willis, Harpenden, Herts. 
In continuing our subject of plant food (see page 269), we 
may usefully ask, How does Nature impart fertility to soil? 
From a few very common and abundant substances like air, 
water, nitrogen and earthy matters, Nature forms an endless 
variety of plants and animals, with a soil in every respect 
adapted to the peculiar wants of each species. 
The natural requirements of plants and annuals are, in the 
main, uniform ; indeed, judging by their cellular structure and 
early growth, the vital germ in a seed and in an egg appear 
to have no other difference than the obvious fact that one is 
endowed with the life of its parent plant, and the other with 
the life of its animal parents; so that, as development pro¬ 
ceeds, from one may emerge a flowering plant or a fruit tree, 
and from the other a. reptile or a bird. 
WATER. 
If we inquire, what substance most promotes the develop¬ 
ment of all organised beings in the world, “ water ” will be 
found entitled to that distinction. Water covers three-fourths 
of the surface of the globe as ocean, partly in a solid condition, 
as at the extreme north, partly fluid, as in all warm coun¬ 
tries ; it flows through the land in all directions in the form 
of rivers ; it ascends into 1 the air as vapour, forms clouds there, 
and falls again to' the earth as rain, snow, hail, and dew. 
This continuous circulation of water, produced by heat, is the 
essential agent which penetrates the dormant earth like an 
awakening breath, filling it with life and prosperity. 
To clearly understand the enormous, quantities of water 
represented by a. few inches of rain, it is necessary to' remem¬ 
ber that 1 in. depth of rain over a.n acre of land represents 
22,622 gallons of water, or about 101 tons per acre. 
One ft. in depth of snow, when melted, will yield 1 in. in 
depth of water. 
AIR AND WATER. 
It has long been known, that air and water contribute a 
much larger proportion of the dry substance of plants than do 
the soils in which they grow. 
A fertile soil, therefore, is one which yields up liberally to 
the growing plant nitrogen and the mineral substances, whilst 
the carbon, hydrogen and oxygen, of which the greater propor¬ 
tion of the diy substance of a plant is made up, is mainly 
t derived from air and water. 
Thus Dame Nature showers over our gardens in rain-water 
and other aqueous deposits minute proportions of ammonia 
and nitric acid, and these are precisely those which science has 
introduced so successfully in our artificial manures. First, 
ammonia, in guano and in sulphate of ammonia, etc. ; secondly, 
(nitric acid in nitrate of soda, and nitrate of potash (saltpetre), 
etc. 
When the gardener is applying these materials so exten¬ 
sively and so profitably, lie is merely enlarging a supply of 
fertiliser- which, - from the time of creation, has been falling 
upon our soils, treading in Nature’s long-hidden footsteps, 
which is ever grateful for being thus aided. 
3XYGEN. 
The oxygen of the air is the constituent which, in combina- 
ion with water, sustains those processes occurring in the soil 
vhich the gardener understands under the name of ripening 
,nd mellowing in the soil. The roots, of plants must receive 
onstant fresh supplies of oxygen to keep them healthy and 
uake them grow vigorously. Hence the extremely favourable 
ssult of hand-hoeing growing crops, which increases the access 
nd circulation of air. Young growing plants absorb an 
mount of oxygen about equal to their volume in from twenty- 
iur to thirty-six hours. And many greenhouse plants send 
p to the surface numerous root formations for the special 
urpose of securing fresh air or oxygen. 
LIGHT AND HEAT. 
Light and heat are produced from the rays of the sun ; they 
are the vital breath which awakens the earth from its winter 
sleep. The mysterious sympathy between the light, and 
warmth of the' sun and the vegetable kingdom is made mani¬ 
fest to our eyes in the bending of plants towards the light. 
In order to become plant, food, the carbonic acid of the air 
is first absorbed, largely by the leaves; and then utilisation 
depends upon the green colouring matter of the leaves, which 
is called chlorophyll, and upon sunlight. The chlorophyll 
absorbs some of the heat-rays of sunlight, and, by means of 
the energy thus provided, the carbon unites in some unknown 
way with the elements of water, ultimately forming starch. 
The longer plants are exposed to the influence of light the 
more carbonic acid they take up from the air, and the more 
rapidly proceeds the vegetation. This explains the surprising 
Cypripedium Venus Oakwood var. (Seep. 316.) 
rapidity of vegetable growth in high northern latitudes, and 
also the enhanced growth of plants under the influence of 
electric light. In some experiments in a greenhouse with in¬ 
candescent gaslight it was found that Lettuce plants grown 
in artificial light were taller, heavier, grew faster, and matured 
quicker than plants grown front the same lot of seed under 
normal conditions. In one experiment. 400 plants exposed 
to the stimulating influences- of the artificial light for forty- 
six nights weighed 68) lb. ; whilst a similar lot grown under 
normal conditions weighed 49) lb., an increase in favour of 
the incandescent light of 38f per cent. 
Radishes were grown between the rows- of Lettuce, as is 
commonly practised when growing for market. The artificial 
light notably increased the development of the tops of the 
Radishes and slightly increased the size of the roots. Spinach 
plants, subject to the influence of the light, grew faster and 
completed their growth in less time than plants grown 
normally. 
