Corn, wheat, clover, and grass are the crops grown, of which the yields are as follows: Corn, from 40 to 60 bushels per acre; wheat, from 15 to 25 bushels per acre, and clover and grass, from 1-1/2 to 2-1/2 tons of hay per acre.
The Penn clay is the most highly prized soil of the Piedmont region of Loudoun and brings the highest prices.
The Penn stony loam consists of from 8 to 12 inches of a red or grayish heavy loam, somewhat silty, underlain by a heavier red loam. From 10 to 60 per cent of gray and brown fragments of Triassic sandstone, ranging from 1 to 6 inches in thickness, cover the surface of the soil. The color is in general the dark Indian-red of the other soils derived from Triassic sandstone, being particularly marked in the subsoil.
This type occurs in the southeastern part of Loudoun, on the Piedmont Plateau. It occupies three small areas whose total extent probably does not exceed two and one-half square miles. It is closely associated with the Penn loam and grades gradually into that type. The only great difference between the two is the presence of sandstone fragments in the Penn stony loam.
The topography varies from gently rolling to hilly and ridgy, with slopes that are sometimes rather steep. However, the surface is not so broken as to interfere with cultivation, and the slopes are usually gentle.
The type is well drained, the slopes allowing a rapid flow of water from the surface, while the soil water passes readily through the soil and subsoil. On the other hand, the texture is sufficiently heavy to prevent undue leaching and drought.
Little of the land is in cultivation, on account of its stony character, which makes cultivation difficult. Where unimproved it is covered with a heavy growth of chestnut, oak, and pine. The land is locally called "chestnut land." In a few small areas the larger stones have been removed and the land is cultivated, corn and wheat being the principal crops. The yield of corn ranges from 20 to 35 bushels and of wheat from 8 to 15 bushels per acre. Apples and small fruits and vegetables do well.
The soil of the Iredell clay loam consists of from 6 to 18 inches of light loam, usually brown or gray, although sometimes of a yellowish color, with an average depth of about twelve inches. The subsoil consists of a heavy yellow to yellowish-brown waxy clay. This clay is cold and sour, almost impervious to moisture and air, and protects the underlying rock from decay to a great extent. Often the clay grades into the rotten rock at from 24 to 36 inches. In the poorly drained areas a few iron concretions occur on the surface. Numerous rounded diabase bowlders, varying in size from a few inches to several feet in diameter, are also scattered over the surface of the soil. Occasional slopes of the type have had the soil covering entirely removed by erosion, and here, where the clay appears on the surface, the soil is very poor. In other places, where the soil covering is quite deep, as from 12 to 18 inches, the type is fairly productive, and its productiveness is generally proportional to the depth of the soil.