Second.—As a rule, and whenever possible, take specimens from spots that have not been cultivated, nor are otherwise likely to have been changed from their original condition of “virgin soils”—e.g., not from ground frequently trodden over, such as roadsides, cattle-paths, or small pastures, squirrel holes, stumps, or even the foot of trees, or spots that have been washed by rains or streams, so as to have experienced a notable change, and not be a fair representative of their kind.
Third.—Observe and record carefully the normal vegetation, trees, herbs, grass, etc., of the average virgin land; avoid spots showing unusual growth, whether in kind or in quality, as such are likely to have received some animal manure, or other outside addition.
Fourth.—Always take specimens from more than one spot judged to be a fair representative of the soil intended to be examined, as an additional guarantee of a fair average, and mix thoroughly the earth taken from the same depths.
Fifth.—After selecting a proper spot, pull up the plants growing on it, and sweep off the surface with a broom or brush to remove half-decayed vegetable matter not forming part of the soil as yet. Dig or bore a vertical hole, like a post-hole, and note at what depth a change of tint occurs. In the humid region, or in humid lowlands of the arid, this will usually happen at from six to nine inches from the surface, and a sample taken to that depth will constitute the “soil.”
In California and the arid region generally, very commonly no change of tint occurs within the first foot, sometimes not for several feet; hence, especially in sandy lands, the “soil” sample will usually be taken to that depth, so as to represent the average of the first foot from the surface down.
Samples taken merely from the surface, or from the bottom of a hole, have no definite meaning, and will not be examined or reported upon.
Place the “soil” sample upon a cloth (jute bagging should not be used for the purpose, as its fibres, dust, etc., become intermixed with the soil) or paper, break it up, mix thoroughly, and put at least a quart of it in a sack or package properly labeled, for examination.
This specimen will, ordinarily, constitute the “soil.” Should the change of color occur at a less depth than six inches, the fact should be noted, but the specimen taken to that depth nevertheless, since it is the least to which rational culture can be supposed to reach.
In the same way take a sample of each foot separately to a depth of at least three feet; preferably four or five, especially in the case of alkali soils, or suspected hardpan.
Sixth.—Whatever lies beneath the line of change, or below the minimum depth of six inches, will constitute the “subsoil.” But should the change of color occur at a greater depth than twelve inches, the “soil” specimen should nevertheless be taken to the depth of twelve inches only, which is the limit of ordinary tillage; then another specimen from that depth down to the line of change, and then the “subsoil” specimens beneath that line.