1. The stratum of soil lying immediately under the surface soil.
1799. J. Robertson, Agric. Perth, 287. On light land, with a gravelly subsoil, thirty or thirty-five bolls are accounted a sufficient dose.
1850. Ansted, Elem. Geol., Min., etc. § 1018. In most cases the subsoil is immediately, and the soil intermediately, derived from the decomposition of the subjacent rock.
1879. Jefferies, Wild Life in S. Co., 44. The chalky subsoil coming there nearer to the surface.
1890. Hardwicke’s Science Gossip, XXVI. 208. Barley with very short roots obtains its food from the surface-soil and does not affect the sub-soil, whence clover with very long roots draws its supply.
b. transf. and fig.
1839. Carlyle, Chartism, iii. 123. This crude subsoil is the first subsoil of all true husbandry.
1852. M. Pattison, in Westm. Gaz. (1906), 15 Feb., 2/1. It would be the beginning of a system by which the University would strike its roots freely into the subsoil of society.
1871. Browning, Pr. Hohenstiel-Schwangau, 98. The subsoil of me, mould Whence spring my moods.
2. attrib. and Comb. (also SUBSOIL PLOUGH).
1831. Jas. Smith, Thorough Draining (1843), 23. For the purpose of breaking the subsoil furrow.
1840. Buel, Farmer’s Comp., 103. Subsoil draining, or the drainage of waters that rise through the subsoil, or pass off at its outcroppings.
1851. H. Stephens, Bk. Farm (ed. 2), II. 663/2. The subsoil-trencher of the Marquis of Tweeddale.
1860. O. W. Holmes, Prof. Breakf.-t., vi. Doctors assiduous,… undertakers solemn, but happy; then the great subsoil cultivator, who plants but never looks for fruit in his garden.
1879. Cassell’s Techn. Educ., II. 171/2. Subsoil-trench plough.
1884. W. P. Trowbridge, in Harper’s Mag., April, 761/2. This subsoil water … is scarcely less foul than sewage itself.
b. fig. with adj. force = penetrating deep down.
1882. W. Cory, Lett. & Jrnls. (1897), 485. German is used by subsoil research men.
1894. Advance (Chicago), 13 April. Deep sub-soil repentance makes strong, healthy Christians who will stand wash and wear.
