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Garden Soil and Why Soil is Important
The soil is the loose material of the earth’s crust, in which plants find a home for their roots and from which they are able to secure certain foods necessary for their growth.
Almost the entire land surface of the earth is covered with a layer of soil, which varies in thickness from a few inches to hundreds of feet, and in nature from fragments of rock on which weathering has scarcely begun, to muck soil, composed almost entirely of organic matter.
Some soils are rich in all the foods required by plants; some are rich in certain elements but deficient in others; some are low in practically all of the necessary foods; while some soils in arid regions contain excessive quantities of soluble salts.
This great variation makes clear the fact that what is called “soil” is by no means a definite thing, but may have almost any composition or structure.
The soil may be considered as the waste heap of nature, since almost everything eventually finds its way into the soil, where it is mixed and remixed with all sorts of substances to make a blanket-covering for the earth. Fragments of all kinds of minerals and rocks and the remains of all the plant and animals are brought together in the soil to make of it a home in which plants may thrive.
The soil is at the very foundation, not only of Agriculture, but of all human welfare.
The industries of our race would cease, and we would be left without food and clothing if the soil should fail to produce its bounties. Mines would close, railroads would cease to operate, factories would stop, in fact, every human activity would in time be discontinued if the soil should lose its producing power.
The growth of all cultivated plants is dependent on the soil, and the yield of crops is a direct reflection of its condition. Since livestock are maintained by crops, the livestock industry also depends for its existence on the productivity of the soil.
Soils are formed by the decomposition or wearing away of rocks under the influence of climatic conditions, glacial or volcanic action assisted by the presence of plant life. Variations of temperature have an important effect on the formation of soils, for rocks expand by heat and contract by cold; the heat of the sun by day causes the surfaces of the rocks to expand, and they contract again with the cool air at night; this causes them to crack, and particles crumble off, thereby giving rise to a constant addition to the soil. Vegetation contributes to the formation of the soil by depositing dead leaves and stems on the surface in the form of humus, to the presence of which is due the dark color of garden soils. Rivers grind down rocks and stones and carry particles to the valleys and plains, depositing them in the form of mud, which is known as alluvial soil; such deposits are generally rich in plant food.
Soil may be said to be composed of five substances, Sand, Clay, Lime, Vegetable Matter or Humus, and Stones. Generally speaking, soils are described under eight different terms, referring to their texture as:
1. Coarse sand
2. Medium sand
3. Fine sand
4. Sandy loam
6. Silt loam
7. Clay loam
Soil Water-holding Capacity
Of the properties of soils affected by texture, probably none is of greater practical importance than the water-holding capacity. This is more the case in Agriculture than Horticulture, but none the less plays a very important part in the growing of Fruit, Flowers and Vegetables. A clay soil may hold 45 per cent of water when a coarse sand would scarcely hold 15 per cent.
The term “texture,” as applied to soil refers to its stiffness, friability or looseness, as the case may be. For instance, clay is a “stiff” soil; sand is a “loose” soil. The happy medium between these two extremes is the ideal texture for a garden soil.
SAND. This is principally composed of quartz, flint or silica; it imparts a loose porous consistency to the soil, assists the air and water in finding their way through the land, and aids the roots of plants to penetrate in all directions. In potting composts sand is usually a necessary constituent. Sandy soils contain not less than 70 per cent. of quartz sand, and have little cohesion. Sandy soils are very porous and contain little nourishment for plants, but may be greatly improved by the addition of clay, farm-yard manure, etc.
CLAY. Two chemical bodies-Silica and Alumina in combination with water, compose clay, which is colder and retains more moisture than sand. Clay is often spoken of as a “heavy” soil. Sand is said to be a “light” soil. This means that clay is difficult, and sand easy to cultivate. An average sand weighs about 80 lbs. to the cubic foot, while clay weighs about 110 lbs. Clay soils are heavy and dense, retentive of water, cold and difficult to work, and require to be well drained in order to be properly cultivated. In periods of drought, plants on clayey soils are apt to suffer as the roots cannot penetrate into stiff clays, or obtain moisture from the subsoil. Though such soils may contain an abundance of mineral food for plants, it is often rendered unavailable by their stiff texture; this may be corrected by the addition of sand, lime or suitable manures, and by drainage.
LIME. Lime is an important soil-forming mineral which is but slightly soluble in pure water, although much more so in the presence of carbon dioxide. It is dissolved readily by acids. Limestone comes partly from the shells and frame work of marine and fresh water animals and partly through concretions of lime directly from water; hence much of it has been dissolved and precipitated many times. The old saying that “a limestone country is a rich country” has, on the whole, but few exceptions.
HUMUS OR VEGETABLE MOULD. Humus or Vegetable Mould is formed by decayed vegetable matter, such as leaves roots, stems, etc. Humus is the most important constituent of all soils for the gardener; it has a great influence on the capacity of soils for retaining moisture, renders their cultivation easier and encourages the activity of soil bacteria; soils that are deficient in Humus are liable to cake and quickly lose their heat in cool weather. Practically all plant residues eventually find their way into the soil, where they undergo changes of some kind. They may de ay entirely and form gas, which passes into the air, or they may undergo transformations which result in the formation of humus in the soil·; or they may remain preserved in almost their original form. The greater part of the organic matter that gets into the soil undergoes some process of humification, and as a result, it is of great benefit.
STONES. These are particles of the original rock from which the soil was formed; if not too numerous they serve a useful purpose in the soil, rendering it lighter in character, affording porosity and assisting in the retention of moisture; their gradual wasting away adds material to the soil.
COLD OR WARM SOILS. Clay Soils retain much more moisture than sandy soils, and this causes a great difference in regard to their temperature; the former are, therefore, sometimes spoken of as cold, and sandy soils as warm. As a certain amount -of warmth in the soil is necessary for plant life, this indicates the importance of draining low-drying, cold, clayey land.
The Power of Soil
The power of soils for drawing up water from the lower strata towards the surface is one of the greatest importance from the cultivator’s point of view. It is possessed in a greater or lesser degree by all soils being greater in proportion as their pores are finer Sand possesses this power to the least extent and clay to the greatest; thus a clayey soil is always wetter than a sandy soil placed under the same influences. When the surface soil is left undisturbed, and becomes hard, much of its moisture passes off by evaporation; a mulch or any dry covering that can be placed between the atmosphere and the damp soil will check this evaporation. Tillage also disturbs capillary action by forming a non-conducting surface, which acts as a mulch and retains the moisture in the soil within reach of the plants.
In order to get good results from your crops the type of soil and its treatment, as well as the varieties best suited to the various kinds of soil, must be considered, and the method of treating the soil at different seasons of the year so as to get the highest production, should be given careful attention.
Preparing The Soil For Planting
When the land has been properly laid out, the necessary draining done, and the paths made, the soil should be thoroughly prepared by trenching it to a depth of at least two feet. In trenching new ground, it is not advisable to bring the sub-soil to the st1rface, because shallow-rooted, and even rather deep-rooted plants do not always succeed well in it. When beginning to trench a piece of land, take out the su1 face soil one foot deep and two and a half to three feet wide, and cart or wheel it to the opposite end of the square or section. The sub-soil should then be dug as deeply as possible, and left rough. If the sub-soil is poor, a good dressing of wood ashes, half inch bones, or farmyard manure, spread on the top will keep it open and considerably improve its fertility. Another width should then be marked out, and the top soil to a depth of a foot turned over to take the place of that removed first, the sub-soil being treated as above and so on until the operation is completed. Care must be taken while the work is proceeding to preserve the general level of the ground.
In well-prepared soil the roots of plants ramify easily and deeply, and as the area of plant food is considerably increased, all kinds of plants will thrive, and be able to withstand dry weather during the hot summer months.
The summer or early autumn is the best time of the year for trenching new ground, and if the soil is left exposed to the influence of the sun and air for some weeks before planting, it becomes friable and benefits immensely.
Where it is desired to use bones and these are not available, bone dust or bone dust and superphosphate mixed will serve the purpose equally as well.