114 
THE GARDENING WORLD. 
February 7, 1903. 
Something about Plant Food. 
By Mr. J. J. Willis, Harpbnden. 
Plants, in/ order to live and thrive, require certain elements 
of food, fourteen in number, some of which are supplied by the 
air and some are found in the soil. 
To understand the subject aright, some consideration is 
necessary of the composition of soils- and plants and the 
elements of the former that are essential to the growth of 
the latter. The science of chemistry is our main dependence 
for this study. 
A fertile soil is one which bears a luxuriant, natural vegetal 
tion, or produces good crops of cultivated plants. Failing to 
do either, the soil may be regarded as deficient in one or more 
of the fourteen elements, necessary to the growth of plants, or 
as having some of those elements in a form that cannot be 
taken up by plants. The soil may then be said to be lacking 
in fertility, and any substance which, being added to the soil, 
enables it. to produce a better vegetation or an increased crop 
may be called a manure. In fact, any substance that will 
furnish this plant food, anything that will cause the gardens to 
produce what climate or season is capable of producing, is 
manure. A gardener may increase his crops by artificial heat,, 
or by an increased supply of water, but these are not plant food. 
The effect in this case is due to improved climatic conditions. 
It, has nothing to do with the question of manure. 
The proper definition of manure is anything containing one 
or more of the fourteen elements of plant food which, if the 
soil needed it, would, if supplied in sufficient quantity and in 
an available form, produce according to soil, season, climate, 
and variety, a maximum crop. 
Such substances may be divided into two general classes—■ 
direct manures, and indirect manures. Direct manures con¬ 
tain substances which, added to the soil, are at once available 
as food for plants. Indirect manures may be material of which 
the land is not destitute, and winch is not in itself plant food, 
but which acts on the matter already in the soil, and changes 
some of it from the insoluble to the soluble form. 
Light and Air.—In the absence of light and air plants cannot, 
thrive, for, while air supplies, the greater portion of plant 
nourishment, light serves to convert such nutriment within 
the plant into vegetable substance. Since, however, light and 
air are abundantly provided by Nature, it will not be necessary 
here to dwell at any length upon their horticultural functions. 
It is, however, important to- point out, that roots, as well as 
stems and leaves of plants, require air. Water-logged, badly- 
drained soils, whether in pots or in the open garden, and heavy 
plastic clays exclude air, and consequently have a low standard 
of fertility. Farmyard and stable manure, vegetable refuse, 
peat moss-, and all organic manures do excellent service for such 
soils by rendering them more porous and permeable to air. 
Respecting the value of light, it will only be essential to 
point out that the full effect of plant food is not obtained when 
crops are too thickly sown, or plants are allowed to become 
too dense with branches and foliage. 
Warmth and Moisture.—With these elements, also-, the con¬ 
trol of the gardener is only indirect, although lie has, by means 
of. frames and glass-houses, greater resources than has the 
farmer. It is well to remember that judicious culture, or til¬ 
lage, as it is called, may vastly increase and also- regulate a 
soil’s warmth, a condition so necessary, especially in seed ger¬ 
mination and during the earlier stages of plant-growth, as well 
as to affect beneficially its capacity for holding moisture. 
Between 80 per cent, and 90 per cent, of a growing plant con¬ 
sists of water. All of this, and much more which is transpired 
through the leaves during the life of the plant, is drawn by 
the roots from the soil. 
Humus.—The presence of organic matter, which is sometimes 
described as humus, is beneficial in controlling a, right degree 
of soil moisture during seasons of drought, and by the decom¬ 
position and fermentation of the humus the soil temperature 
becomes raised. This property is very important in a garden 
where many of the plants cultivated have to lie grown rapidly 
in older to be at their best, and also to raise plants " out of 
season." This fact teaches us that even with a full supply of 
the fertility elements in a soil, climate and season exert an 
enormous influence upon its productive powers. 
Nitrogen.—Humus matter has been called the soil’s store¬ 
house of nitrogen. The element nitrogen is the only one of 
the combustible class of plant' foods that is not supplied by 
Nature in abundance, in an available form. 
It may be pointed out that the nitrogen in humus is not 
directly assimilable by plants, but is rendered so by nitrifica¬ 
tion, a chemical process resulting from the activity of certain 
microscopic organisms within the soil, which live upon and 
decompose the organic matter there present. In the course of 
the decomposition of the organic matter ammonia gas js given 
off This is eagerly grasped by the micro-organisms and con¬ 
verted into nitrates, in which form it becomes the most active 
of plant foods, and, unless.a growing plant is on the spot to 
make use of this soluble nitrate, it is very liable to be washed 
away by the rains into the lower depths of the soil. And in 
pot culture too copious artificial waterings may result in soil 
exhaustion by the washing away of the soluble nitrates. 
Recent research has shown that soil fertility is very largely 
dependent upon the presence of these micro-organisms. Also, 
that warmth, moisture and air are primarily necessary for the 
development and reproduction of these microscopic creatures ; 
in other words, these are the necessary conditions for the nitri¬ 
fication of the humus. Accordingly, this process is more active 
in the warm spring and summer months than in the autumn 
and winter. Also, more active in garden frames, green¬ 
houses and conservatories than in the open garden. In fact, 
the soil beneath our feet is not a dead mass, but material, full 
of life and activity; it may be described as a laboratory, in 
which many wonderful chemical changes are continually going 
on in order to turn the insoluble plant food into such an avail¬ 
able form that it can be taken up by crops. 
(To be continued.) 
Big Vine at Bearhill. 
On my visit to Brechin the other day I made a call at 
Bearhill Gardens, Brechin, the residence of Robert Duke, Esq. 
Although Bearhill is now about the centre of the city, there 
are really some good things, more particularly in Coniferae, 
including Abies nobilis, A. nordmaimiana, and a most hand¬ 
some Wellingtonia gigantea. About 2 ft. from the ground it 
is 15 in. in diameter and about 80 ft. high, and beautiful. The 
most notable to me was the wonderful Bearhill Vine, known 
to be 135 years old, in perfect health. Fifteen years ago- Mr. 
Duke had the house enlarged. 
At one time the house was only. 8 ft, wide and about 15 ft. 
long, and the V ine planted outside. In the new vinery, arranged 
over it, they have kept the stem inside and made the vinery 
20 ft, long, 12 ft, wide, and the back wall 18 ft.diigh. Seven¬ 
teen rods in all start from the main stem, which is 2 ft. long 
and 12 in. in diameter. It is really a noble old Vine. In 1897 
they cut off more than 585 bunches, averaging all over 1 lb. 
per bunch ; every year about the same number till last year, 
when there were only 460, but extra fine in colour and quality. 
Mr. Duke is naturally veiy proud of his noble Vine; and 
his enthusiastic gardener, Mr. W. Tosh, now has had charge 
of it for over twenty-seven years. Mr. Tosh told me he had 
never used 2 cwt. of artificial manure, but the roots are all 
over the kitchen garden. The garden has a beautiful granite 
subsoil—no inducement for the roots going down. I hope 
this noble old Vine will last for many years yet to come. 
J. M. 
READERS AND ADVERTISERS are requested 
to note that the address of THE GARDENING 
WORLD is now 37 and 38, Shoe Lane, London, E.C. 
