88 
I'llE TROPICAL 
AGRICULTURIST. [Aug. 1, I8&9. 
THE FEETILITY OP SOILS. 
The factors upon which the fertility of the soil 
depend are many. The amount of plant-food and its 
defireo of solubility' the ineohaniciJ texture or tilth, 
and the climate, v/hich includes teinperatiii e, amount 
of rainfall, &a., are the chief of the.-ie. 
Soils 10 ba fertile must co'itiiin the elements of 
plant-food in such forme that they can be readily used 
for the nutrition of vegetation. At the same time, its 
condition must not be too loose, else a firm hold will 
not be afforded to the roots of plants, and there will 
be too much drainage and evaporation ; nor must it be 
too heavy and plastic, for then air and y^ater could not 
freely permeate it, nor the roots extend themselves 
beyond a very limited area Generally spealcing, 
light, loose soils are not as rich in plant-food as those 
in which clay pred'iLi) iiiates ; yet, on account of the'r 
excellent condition of tilth, and the ease with which 
they are worked, they t-.re spec ally adapted for most 
horticultural purposes, and having a sufficiency of 
manure, they often yield in favourable seasons heavier 
crops than the, stronger soils would do. Stiff heavy 
clays, though rich in inorganic food, potash, and phos- 
phoric acid, are often poor in nitrogen, while their 
mechanical condition is such as to prevent through 
atiration and the penetration of the roots. It is these 
Boils especially that are benefited by drainage. By 
a system of drainage the wator which saturates the 
siivfacf -soil carried off, air allowed to permeate, the 
whole is rendered more friable and easily worked, and 
much plant-food is converted into assimilable foinis. 
Where sand largely preponderates, the soil is not 
ret''ntivo of moisture and fertilising material, espe- 
cially if the subsoil be light, and though easily worked 
it is not so desirable in very dry seasons as on a 
heavier soil. A proper proportion of sand and clay 
therefore, for many reasons, makes the best soil. 
With the clay and sand, varying amounts of peaty 
matter, or humus derived from the decomposition 
of vegetable matter, may be mixed. In horticulture 
leaf-mould is largely used. Calcareous matter, chalk, 
lime, and bone-meal, are usually associated, and a 
light proportion of these exerts a beneficial influence 
upon the tilth of the soil, as well as upon the solubi- 
lity of the plant-food. By the slow decomposition 
of the clay, the vegetable matter, and the lime, 
valuable plant-nutrients, are liberated in a soluble 
form, and therefore the function of these soil consti- 
tuents is, not only mechanical but chemical. 
The most important ignorganic constituents of a 
soil are potash and phosphoric acid. These, together 
with nitrogen, are known as the essential elements of 
plant-food. 
To understand the question of soil-fertility, the 
gardener should become familiar with these matters, 
should know what these elements will do for crops 
and plants, and when and how to apply them. 
Nitrogen. — This element, like potash, lime, and 
phosphoric acid, is an essential constituent of all 
plants. In its free state it is a permanent gas, and 
13 one of the most widely distributed elements, com- 
prising about fouv-fiths of the earth's atmosphere. 
This vast supply of nitrogen is, however, of no direct 
v^ilue to plants, since they ai'e unable to use it, except 
when combined with the elements oxygen or hydrogen, 
.forming nitric acid and ammonia, that may be taken 
up through the ro its of plants. Leguminous plants, 
like Peas, Bsans Lupins, (fee, and possibly Orchids, 
are indirectly able to build up their nitrogenous ingre- 
dients from the free nitrogen of the air, through the 
activities of raisroscopic plants (known as bacteria) 
intimately associated with tbem ; other plants may, 
possibly, under favourable conditions to some extent 
have the same faculty. 
Nitrogen is present in the soil iu simple combinations 
as nitrates or ammonia salts, or as more complex 
organic compounds, forming the dark coloured humus 
especially abundant in peat, leaf-mould, and forest 
soils. The total quantity of nitrogen in ordinary 
soils varies between (VI and 0 2 per cent. ; occasionally 
the nitrogen content wiU approach one per cent., as in 
the case of rich pasture soils. Pent soils will often 
coataia ovor two per cent, of nitrogen ; this ia how- 
ever ; largely in a combination that will not directly 
sustain plant life, but has to undergo a weathering 
process before the plant can make use of it 
Nitrogenous mi^.nures help to strengthen plants in 
their earlier growth, favour leaf development, and 
give a deep green healthy colour to the foliage ; applied 
i:i excessive qnantiues they induce rank growth at the 
expense of the development of the fruit. 
Phospboiic acid is present in soils in combination 
with a number of other chemical substances, which 
exert a very beneficial influence on the growth of 
plants. Phosphoric acid is found in soils partly iu a 
form that plants can readily dissolve and make use of 
in the building of their structure, partly in an insolu- 
ble form which under the infinence of water carbonic 
acid and air, or the mineral components of the soil 
are gradually changed into available plant food. There 
is only a small quantity of phosphoric acid in ordinary 
soil-, viz., less than 0-2 per cent., and often only 0-05 
per cent. ; but as the content is not decreased in any 
way except by the growing of crops, the s«il \^ill oniy 
become deficient in this constituent in case of con- 
tinuous cropping without manuring, 
Phosphoric acid is of special importance iu the 
early Ufe of plants ; it stimulates the assimilation of 
mineral substances in the plant, and favours the 
development of its root system. There is an intimate 
relation between the nitrogenous principles and the 
phosphoric acid in plant", and we find that, generally 
speaking, a high nitrogen content is accompanied 
by a high percentage of phosphoric acid. The 
phosphoric acid of plants is usually concentrated in 
their maturing organs, the flower and seed. 
Potash is found in Nature in conbination with 
acids like sulphuric, carbonic, and silicic acid. 
Potash is generally distributed iu small quantities 
in most soils, except light sandy soils, which are 
apt to be deficient in this fertilising element it is 
found in ordinary soils in somewhat larger quantities 
than phosphoric acid, namely, from one to three- 
tenths of one per cent., and occasionally as much 
as one per cent, in case of soils orginating from 
granite, basaltic, and other rocks rich in potash, 
Like phosphoric acid, potash may be present in the 
soil in a non-availaljle form, especially as double 
silicates, that are but slowly decomposed through 
the action of water, air, and other constituents of the 
soil. 
Potash is found in the largest quantities in foliage 
plants, in leguminous plants, in Vines, and in Potatos. 
It is of the greatest value to plants, in facilitating 
the flow of sap, and the diffusion of starch from cell 
to cell. It gives increased strength to the cell structure 
of plants and has in general a benifioial influence on 
the flavour and texture of fruits and Potatos. 
Lime_ is present in most fertile soils in sufficient 
quantities to allow of the production of large crops, 
but occasionally there will be too little of it to reach 
this end, in which case the addition of some lime 
compound to the soil, will produce very beneficial 
results. It is considered that a lime content of one- 
half of one per cent, an ample supply in light soils, 
while heavy soils may need 2 per cent, or more. 
The good effects from the addition of lime to 
soils do not come only from the increase of an ingre- 
dient essential to plant growth, but the mechanical 
condition of the soil, its texture, water and heat- 
retaining capacity, are improved. This same is true 
in perhaps all cases when fertilisers are applied to 
soils, a fact which is generally overlooked by horti- 
culturists. — Gardener's Chronicle. 
^ 
THE IIAMIE SYNDICATE. 
The Eamie Syndicate, Hythe End Mill, Staines, 
sends us the following : — You will perhaps not be 
indisposed to give your readers the news of our 
experments having proved most successful. When 
w6 started we were confronted with the following 
difficulties : 1st, supply ; 2nd, , decortication ; 3rdi 
preparation ; 4th, spinning, and lastly demand or 
market. I will deal with these seriatim later. Va* 
