In winter, however, and in fallows loss takes place in the subsoil water.
It contains more roots, and as a rule, is darker in colour than the subsoil on account of the larger proportion of decaying vegetable matter present in it: it is also looser in texture than the subsoil.
And passing through Baker, Worth, Dooly, Dodge, Laurens, Johnson, Jefferson and Burke counties, has three distinct kinds of soil; a sand, forming what is known as the sand-hill region; red clay derived from silicious rock in the red hills; and grey, sandy soils with a subsoil of yellow loam.
On his farm Smith carried out his experiments in deep and thorough draining, and also invented a reaping machine, the subsoil plough and numerous other valuable appliances.
The effect of this industry, however, is to lay bare a subsoil of diluvial sand which offers little inducement for subsequent cultivation.
The work of earthworms in aiding in the production of the subsoil and in levelling the surface was first studied by C. Darwin, and has since been investigated by others.
With a wet, undrained subsoil and a large population of Indians and half-breeds living in crowded quarters, the death-rate has been notoriously high, though the completion of the Valley drainage works in 1900, supplemented by underground sewers in the better parts of the city, and by better sanitation, have recently improved matters.
In the British Isles wheat is, as a rule, sown in the autumn on a heavier soil, and has four or five months in which to distribute its roots, and so it gets possession of a wide range of soil and subsoil before barley is sown in the spring.
In this way as the water sinks down through the porous subsoil or into the subterranean drains oxygen enters and supplies an element which is needed, not only for the oxidation of organic matters in the earth, but also for the direct and indirect nutrition of the roots.
The subsoil not unfrequently contains materials which are deleterious to the growth of crops, and roots descending into it may absorb and convey these poisonous substances to other parts of the plant or be themselves damaged by contact with them.