258 
THE GARDENING WORLD, 
March 26, 1904, 
Something about Plant Food. 
By J. J. Willis, Harpenden. 
(Continued from Vol. XX., p. 899.) 
The effect of soil conditions upon the growth and develop¬ 
ment of plants is well recognised. If >an attempt is made to 
grow a crop* on a soil not well adapted to it, the result is likely 
to be a failure, unless the skill of the gardener is able to 
modify the conditions of growth to meet, the requirements of 
the plants. Most, of the ordinary garden and greenhouse crops 
require abundant and readily available food for their maximum 
production and vigorous growth, but this food must not be in 
too strong a solution in the soil water, especially of concen¬ 
trated chemical manures ; and the water itself must be readily 
available, though the soil, as a. rule, must, not be so wet as to. 
exclude the air. It is more difficult to maintain these condi¬ 
tions 1 in light sandy soils than in soils containing more or less, 
clay. It is also more difficult to manage a sandy clay soil, 
poor in humus and fibrous matters, than one comparatively rich 
in rootffibre and humus. A light, clay soil with humus and 
fibre derived from decaying root® and plant residues., or stable 
manure, if the soil is properly drained, will not easily become 
too 1 wet or dry out too quickly. A great deal of .soluble plant- 
food 1 can be absorbed by such a soil witjjput danger to the roots 
of plants growing in it., and air is easily admitted to the roots. 
The mechanical condition of such a. soil, apart from these 
other factors., also favours a strong development of plant root. 
To Prevent Plant Starvation. 
In many ease® it requires very careful watching to prevent 
plant .starvation, and stunting in light sandy soils. These 
conditions, however, favour some crops, as those where sturdi¬ 
ness of habit is required with flower and seed formation, rather 
than luxuriance. 
Frequently it is most difficult to obtain seed from Carnations 
that have been too luxuriantly grown, and the same is true of 
many other plants. On the other hand, in very heavy soils 
there is danger from over-watering. There is also danger 
from bad drainage and lack of air, causing a weakened develop¬ 
ment of roots, and making them subject to root-rot and other 
diseases. 
Professor Sotauer, in his “ Physiology of Plants,” ha® de¬ 
scribed the ideal condition, of a soil for ordinary garden and 
greenhouse crops, as “ one in which it resembles a sponge, and 
in which it will retain the greatest amount of nutritive sub¬ 
stances and water without losing its capacity of absorbing air.” 
Speaking of forcing-house soil®, Bailey says,: “ They should 
not only be rich in available plant-food, but, they should be of' 
a mellow friable texture, so that water soaks through them 
uniformly, leaving them dryish and loose on top. A soil with 
much clay tends, to run together or to cement itself, especially 
if watered from a hose,, and the plants tend to make a .spind¬ 
ling and unwilling growth. On the ether hand, a, soil with 
very much manure or litter is so, loose a,s not to hold sufficient 
water to. keep the plant® in health; or if it does hold the re¬ 
quisite moisture, it tends to. produce a, robust and overwilling 
growth at the expense of the flower® and fruit. Yet, despite 
all this, the skill of the. gardener is. much more important than 
the character of the soil, for a, skilled man, will handle even 
hard clay soils in such a manner as, to give, good results. 
“ The chief single factor of manipulation in determining the 
productivity of a soil in, forcing-houses is the water.” 
Practical exp-erience of gardeners teaches us that a. plant- 
root can never have too much air, but, often, has. too little. 
“ It is not profitable,” says Professor A. F. Woods, “ however, 
to employ soils that require such close and constant attention, 
even when conditions are largely under control as they are 
under glass. It is the aim of economical production to select 
a soil, when possible, for a given crop that,, with a minimum 
of labour expended on the part, of the gardener, will produce 
the desired results, and this is true, in culture under glass as 
well as in the open garden.” 
Soil Foods Necessary to Plant Growth. 
Important as the mechanical condition of a soil may be 
in. its relation to growth of crops, the chemical condition is not 
less important. 
Every soil must have the essential elements of plantrfood 
in an available form, and of suitable strength. If there is too 
little of any one of these the plants growing in such soil will 
starve, and if there is too> great an excess of soluble salts, the 
roots will be injured. 
It is often a, difficult matter to determine by the behaviour 
of the plant what the trouble may be. Take, for example, the 
disease known as “ chlorosis.,” or the production of yellow 
foliage instead of the normal green leaves. The most common 
cause of this condition is the lack of available iron or potash, 
either in. their absence altogether from a soil or the failure 
of the root to dissolve and absorb such chemical compounds 
a.s may be present. Sometimes in the presence of an excess of 
lime (chalk) the root® are unable to, dissolve the iron and 
potash compounds and absorb them. The lack of nitrogen 
will also produce- yellowing of many crops, so will the lack of 
water or excess of water, lack of light or excess of light. 
Functions of Lime in the Soil. 
Lack of lime in plant development is first indicated by 
stunting and the production, of small yellowish leaves. The 
precise use of lime to, plants is imknown, but it cannot be re¬ 
placed in the food of plants which contain chlorophyll (leaf 
green.) by any other substance. It is especially abundant in 
the leaves of all greien plants, and the starch which such leaves 
develop is, in the absence of lime, with difficulty changed into 
sugar, possibly owing to the failure of the nucleus of the cell 
to manufacture diastase, the ferment necessary for transform¬ 
ing starch to. sugar in plant nutrition. Lime also, greatly con- 
tribute.® to- the, building up of the tissues in the form of organic 
matter. 
It, used to be thought that the main purpose of lime was to 
neutralise free acids developed in. the nutrition of the plant 
cell, and while it undoubtedly -seiwes this purpose to a large 
extent, it owes it® greatest importance to the fact that it is a 
necessary constituent of the foods entering directly into the 
composition of the chlorophyll or leaf-green bodies, and it 
cannot be replaced for this, purpose by any other plant food. 
In the soil lime also performs many important mechanical 
and chemical uses. One of the most, useful is the part which 
it plays in combining acids set free by decomposition or decay 
in soils. These are brought about through the action of roots 
and other organisms upon the soil particles, and further by 
chemical actions. If these free acid® were not neutralised they 
would act injuriously to the living root®. This is frequently 
seen in old rich garden soils which are black with excess of 
humus matter. 
The presence of lime also greatly favours nitrification in 
soil®. Heavy soils may be made more porous, by the use of' 
slaked lime, and fine sandy soil® may gain in firmness. The 
decomposition of humus in soils is hastened by lime, its 
nitrogen being liberated a® ammonia, gas which becomes avail¬ 
able toi the growing plants as nitrates after nitrification by 
micro-organism® within the soil. Lime ha® the power in cer¬ 
tain case® of releasing such potash in the soil as would other¬ 
wise be unavoidable. This, a® well as the enhanced root-hair 
production under the, influence of this ingredient, accounts for 
the greater absorption of potash by the growing plant® in. soils 
rich in. lime. Although for several reasons caustic lime is 
superior to carbonate of lime (chalk), and even in some cases 
cannot, be replaced by the latter, still there a,re instance® when 
finely pulverised chalk can be applied directly with great 
success, especially on sandy soils. 
(To be continued-') 
A Corner in Violets.— -The latest development of the trust 
system in America is reported to be a corner in Violets, which 
Mr. John D. Rockfeller grows at Dobbsferry. Florists are 
buying 30,000 daily, and the supply is not equal to the demand 
We hope that kind of gambling will not, reach this coiintry, 
