Here the prevailing soils are grey and sandy with a subsoil of loam, but they are less fertile than those of the Lime Sink or Cotton Belts.
As the drainage by cuniculi removed the moisture in the subsoil, so the drainage of the lakes by emissaria, outlet channels at a low level, prevented the permeable strata below the tufa from becoming impregnated with moisture which they would otherwise have derived from the lakes of the Alban Hills.
Deep, and in a large portion of the state there is a subsoil of yellow clay.
Except on extremely heavy soils or on shallow soils with a subsoil which it is unwise to bring upon the surface, the modern tendency is in favour of the digging plough.
It is suitable for stiffish soils where the subsoil is fairly open, but is less successful in sand.
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 was composed principally of clay and sand, and the railway had to be carried over the moss on the level, requiring cutting, and embanking for upwards of 4 m.
Put comprehensively, it involves the control of the subsoil and surface waters by drainage, the regulation of rivers and floods, suitable agriculture, the clearing of forests or jungles, which tend to increase the rainfall and keep the ground swampy.
It is deeper and more fertile, however, in the basins of the Great Miami and Little Miami rivers, where there is a liberal mixture of decomposed limestone and where extensive areas with a clay subsoil are covered with alluvial deposits.
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.
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.
In winter, however, and in fallows loss takes place in the subsoil water.
Their growth makes no new addition of mineral food-constituents to the land, but they bring useful substances from the subsoil nearer to the surface, and after the decay of the buried vegetation these become available to succeeding crops of wheat or other plants.
Moreover, where deep-rooting plants are grown the subsoil is aerated and rendered more open and suitable for the development of future crops.
In the Piedmont Plateau and Appalachian Mountains Regions the surface soil is generally sandy, but in considerable areas the subsoil is a red clay derived largely from the decomposition of hornblende.
The soft limestone underlying this region is covered, in the uplands, with grey, sandy soils, which have a subsoil of loam; in the lowlands the surface soils are loams, the subsoils clays.
The surface soil is clay in which are embedded fragments of siliceous sandstone, used for millstones and constructional purposes; the subsoil is limestone.
At least, and the deeper the better so as to bring up the subsoil - whether it be clay, sand, gravel, marl, &c. - Jor exposure to the weather and thus convert it from a sterile mass into a living soil teeming with bacteria.
The nature of the subsoil is of scarcely less importance than that of the surface soil.
An uneven subsoil, especially if retentive, is most undesirable, as water is apt to collect in the hollows, and thus affect the upper soil.
When the subsoil is too compact to be pervious to water, effectual drainage must be resorted to; when it is very loose, so that it drains away the fertile ingredients of the soil as well as those which are artificially supplied, the compactness of the stratum should be increased by the addition of clay, marl or loam.
Amongst causes of variation in the quantity of water needed will be its quality and temperature and rate of flow, the climate, the season, the soil, the subsoil, the artificial drainage, the slope, the aspect and the crop. In actual practice the amount of water varies from 300 gallons per acre in the hour to no less than 28,000 gallons.
Land is not in a satisfactory condition with respect to drainage unless the rain that falls upon it can sink down to the minimum depth required for the healthy development of the roots of crops and thence find vent either through a naturally porous subsoil or by artificial channels.
On this account deeper tillage than usual, which allows of easier penetration of roots, or the carrying out of operations which bring the subsoil to the surface, must always be carefully considered.
Carolina on a loose porous sand, which must be at least a foot deep, and contains usually about 8% of clay; this sand is underlaid by a clay subsoil, and, as Mr Milton Whitney points out in Tobacco Soils (U.S.A. Dept.
The dark drift, composed chiefly of clay, sand, gravel, boulders and lime, is both the soil and subsoil of the greater part (about 66%) of the state, being especially predominant in the N.
Mexico was formerly one of the worst drained large cities of the New World, its subsoil being permanently saturated and its artificial drainage being through open ditches into the San Lazaro Canal which nominally discharged into Lake Texcoco.
As a group they are cosmopolitan, their northern limit approaching that of the permanently frozen subsoil, while in the southern hemisphere the southern point of Patagonia forms the farthest limit.
Many gardeners are still afraid to disturb an unsuitable subsoil, but experienced growers have proved that by bringing it up to the surface and placing plenty of manure in the bottoms of the various trenches, the very best results are attained in the course of a season or so.
A pit of this character may be sunk into the ground deeper than is indicated in the figure if the subsoil is dry and gravelly, but in the case of a damp subsoil it should rather be more elevated, as the soil could easily be sloped up to meet the retaining wall.
In the second case all roots that have struck downwards into a cold uncongenial subsoil must be pruned off if they cannot be turned in a lateral direction, and all the lateral ones that have become coarse and fibreless must also be shortened back by means of a clean cut with a sharp knife, while a compost of rich loamy soil with a little bone-meal, and leaf-mould or old manure, should be filled into the trenches from which the old sterile soil has been taken.
These fine-grained materials are at first mixed with broken and more or less weathered rock fragments and coarser mineral particles in the soil and subsoil, but by the action of wind and rain they are swept away and deposited in distant situations.
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.
In this case, as in that of a level plane of uniformly porous sand, the vertical section of the figure is tangential to the vertical well and to the natural level of the subsoil water.
Even the beds of sluggish rivers flowing over porous strata generally become so impermeable that excavations made in their neighbourhood, though freely collecting the subsoil water, receive no FIG.
Speaking generally, the Ozark region is characterized by reddish clays, mixed with gravels and stones, and cultivable in inverse proportion to the amount of these elements; northern Missouri by a generally black clay loam over a clay subsoil, with practically no admixture of stones; the southern prairies, above referred to, share the characteristics of those north of the Missouri.
The effect of this industry, however, is to lay bare a subsoil of diluvial sand which offers little inducement for subsequent cultivation.
The soil is almost a pure sandy gravel with a subsoil of varied nature, but principally altos, gravel, clay or sand.
There seems reason to believe that it refers to the time when the site, or a portion of it, formed an island, as sea-sand is the subsoil even of the oldest quarters.
It thrives most in a light loam with a dry subsoil; rich and, in particular, wet soils are unsuitable, conducing to the formation of too much wood.
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.
Limit approaches that of the permanently frozen subsoil, going into the arctic circle in Scandinavia, elsewhere sinking to about 54° N.; in the S.