The same is generally true of the benchlands; the irrigator levels, slopes or terraces his land for irrigation with no thought of discrimination between soil and subsoil, and the cultural result as a rule justifies his apparent carelessness. It is only where from special causes a consolidated or hardpan subsoil is brought to the surface, that the land when leveled shows “spotted” crops. Such is the case in some of the “hog-wallow” areas of the San Joaquin valley of California, and in some cases where by long cultivation and plowing to the same depth, a compact soil-layer or plowsole has been formed, and the land is then leveled for the introduction of irrigation. In these cases a section of the soil mass will usually show a marked difference in color and texture. But, as a rule, in taking soil samples, no noticeable difference can be perceived between the first and the second, and oftentimes as far down as the third and fourth foot. The extraordinary root-penetration of trees, shrubs and taprooted herbs, whose fibrous feeding-roots are found deep in the subsoil and are sometimes wholly absent from the surface soil, fully corroborate the conclusion reached by the eye. The roots of grape vines have been found by the writer at the depth of twenty-two feet below the surface, in a gravelly clay loam varying but little the entire distance. In a similarly uniform and pervious material, the loess of Nebraska, Aughey[63] reports the roots of the native Shepherdia to have been found at the depth of fifty feet. [63] See Merrill, Rocks and Rock weathering.