Fig. 33.—Kentucky Maize, grown
in region of Summer Rains.
(Photography by A. M. Peter.)
Fig. 34.—California Maize,
Grown Without Rain or Irrigation.
Such examinations are most quickly made by means of a probe consisting of a pointed, square steel rod five or six feet long, provided at one end with a loop for the insertion of a cross-handle like that of a carpenter’s auger. The handle being grasped with both hands, the probe is forced into the soil with a slight reciprocating motion, by the weight of the operator; who soon learns how to interpret the varying kinds of resistance, and on withdrawing the probe carefully will generally be able to determine if bottom water has been reached. Should this easy method of examination not convey all the needful information, the post-hole auger may be resorted to; and it is desirable that extra (three-foot) rods or gaspipe joints be provided for the purpose of lengthening the probe or auger, when necessary, to nine or twelve feet. It will rarely be necessary to go to the trouble of digging a pit for such examinations; but even this is to be recommended rather than “buying a cat in a bag” in the guise of an unexplored subsoil.
Faulty Substrata.—A number of examples of “faulty lands,” i. e., such as are underlaid by faulty substrata, are given in the annexed diagram [Fig. 35]; the examples being taken from California localities because of their having been most thoroughly investigated. Similar cases, as well as others not here illustrated, of course occur more or less all over the world.
No. 1 shows a case which, though at first sight an aggravated one of a rocky substratum, is in reality that of some of the best fruit lands in the State. The limited surface-soil is very rich, and is directly derived (as a “sedentary” soil) from the underlying bedrock slate. But this it will be noted stands on edge, and the roots of trees and vines wedge their way along the cleavage planes of the slate to considerable depth, deriving from them both nourishment and moisture. Under similar conditions the California laurel, usually found on the banks of streams, grows on the summits of rocky ridges in the Coast Ranges.
The case of No. 2 is quite otherwise. Here the shale lies horizontally, and though much softer than the slate of the first column, obstinately resists the penetration of roots; so that the land, though fairly provided with plant-food, is almost wholly useless for cultivation. It is naturally covered with low, stunted shrubs or chaparral; only here and there, where a cleft has been caused by earthquakes or subsidence, a large pine tree indicates that nourishment and moisture exists within the refractory clay stratum, and suggests blasting as a means of rendering the land fit for trees at least.
FAULTY LANDS. CALIFORNIA
Fig. 35.—Faulty Lands, California.