CHEMISTRY OF SOILS AND MANURES 
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CHEMISTRY OF SOILS AND MANURES. 
By Dr. VOELCKEB., Professor of Chemistry in the Boyal Agricultural College, Cirencester. 
GENERAL COMPOSITION OF SOILS.-ORGANIC MATTER IN THE SOIL. 
W HEN we take a trip through any country, however limited its extent may be, we cannot help 
observing the great difference in the healthy condition of the crops in the fields w T e pass through. 
In one place we see a miserable crop, in another we admire the heavy golden ear, or the luxuriance of 
a green crop ; in one place rich pastures refresh our eyes by their bright green colour, and not far 
distant we feel compassion for the half-starved beasts, feeding on the scanty herbage. In the morning 
we may have passed perhaps the cottage of a farm labourer, and smiled at the simplicity of taste of its 
occupant, exhibited in the few common flowers in his window, which to him may afford as much 
luxury, as the choicest and rarest collection of flowers does to the nobleman; and in the evening we 
may be delighted with the variety and magnificence of trees, shrubs, flowers, and rich meadows adorn¬ 
ing the pleasure-grounds of the wealthy. At the same time we must have necessarily remarked the 
different appearance of the ground. White, blue, or red soils, porous, stiff, coarse, deep, or thin, hard 
or soft, smooth or rough soils may hate met our eyes in pursuance of our journey. These external 
characters are open to observation, and often very striking; the most superficial observers can have 
no difficulty of distinguishing a peaty from a chalky soil, or a stiff clay land from a light-coloured 
porous sandy soil. The external characters of soils are very numerous ; hence the great diversity of 
soils. Plants derive a great part of their food from the soil, and as different species of plants are pro¬ 
moted in their growth by certain substances, taken up in different proportions from the soils, and as 
the latter differ much in their chemical composition, as well as in physical properties, it is but natural 
to ascribe to the soil a great influence on vegetation. This will be admitted by every one, although it 
cannot be denied that situation, local influences, and, above all, climate, determine in a great measure, 
the existence of plants. 
However great the diversity of soils may be, they are all composed of a limited number of chemical 
substances. These substances, amounting to twelve or fourteen, are present in all fertile soils, and the 
preponderance of one of the constituent parts and the different proportions in which they are mixed, 
determine in a great measure the character of the soil. For instance, a soil rich in lime is called a 
calcareous soil; and excess of clay renders the soil stiff, whilst a preponderance of sand tends to 
produce an open, porous, light soil. But before we shall enter into details, let us first examine the 
chemical nature of the materials which we find in all cultivated soils. 
When we closely inspect the soil of a garden, or field, or pasture in this or any other country, it 
will be found to consist generally :—1. Of larger or smaller stones, sand or gravel. 2. Of a more friable, 
lighter mass, crumbling to powder when squeezed between the fingers, and rendering water muddy. 
3. Vegetable and animal remains (organic matter). 
The means by which the sand, gravel, and stones are separated from the finer portion, and all from the 
organic matter are very simple, and as they enable us to ascertain the nature of the stony fragments, 
the sand, and other materials, forming the component parts of the soils, we shall briefly describe them :— 
1. A portion of garden-earth, or soil from the field, is soaked in rain or distilled water, in an 
earthen-ware basin or Florence flask, agitating it occasionally in order to break any hard lumps of 
earth. Hard lumps of clay often take a long time before falling to powder ; it is better, therefore, to 
rub the soil with the pestle and mortar and a little water at first, adding more water afterwards. By 
allowing the whole to remain undisturbed for a few minutes, the sand, fragments of stones, larger 
remains of roots, &c., on account of their greater specific gravity, will settle to the bottom of the vessel 
almost immediately, whilst the finer impalpable powder will remain floating in the water, rendering it 
muddy. This muddy liquid is poured off in a tumbler or glass bottle, and the deposit washed repeatedly 
with new portions of water until the water ceases to become muddy. The sand, &c., thus freed from 
any adhering fine clay, is preserved for further examination. 
2. The muddy liquid poured off from the sand is allowed to remain at rest in the tumbler or glass 
bottle, until the fine mud has completely settled at the bottom of the vessel, and the water above it has 
become perfectly clear. The latter is then poured off, and the remaining fine mud dried. 
3. The clear water from 2 is evaporated to dryness in an earthen-ware, or better, porcelain basin. 
The residue, inconsiderable in amount, will be found to vary in quantity and composition, according to 
the nature of the soil. It is generally coloured brown by some soluble organic matter. 
4. The gravel and sand, the fine mud, and the residue of the watery liquid, into which we have 
separated the soil by this simple process, are mixed with organic matter; by washing, therefore, we 
can only separate the soluble organic matters from the insoluble, and the finer vegetable remains from 
