The depth down to which the last should be taken will depend on circumstances. It is always necessary to know what constitutes the foundation of a soil, down to the depth of three feet at least, since the question of drainage, resistance to drought, root-penetration, etc., will depend essentially upon the nature of the substratum. In the arid region, where roots frequently penetrate to depths of ten or twelve feet or even more, it is frequently necessary to at least probe the land to that depth or deeper. The specimens should be taken in other respects precisely like that of the surface soil, each to represent the average of not more than twelve inches. Those of the materials lying below the third foot from the surface may sometimes be taken at some ditch or other easily accessible point, and if possible should not be broken up like the other specimens.
If there is hardpan or heavy clay present, an unbroken lump of it should be sent, for much depends on its character.
Seventh.—When in the case of cultivated lands, it is desired to ascertain the cause of differences in the behavior or success of a crop on different portions of the same field or soil area, do not send only the soil which bears unsatisfactory growth, but also the one bearing normal, good growth, for comparison. In all such cases, try to ascertain by your own observations whether or not the fault is simply in the subsoil or substrata; in which case a sample of surface soil sent for examination would be of little use. In such examinations the soil probe will be of great service, and save much digging or boring.
Eighth.—Specimens of alkali or salty soils should preferably be taken towards the end of the dry season, when the surface layers will contain the largest amount of salts. A special sample of the first six inches should in that case be taken separately by means of a post-hole auger, and then, in a different spot close by, a hole four feet deep should be bored, and the earth from the entire four-foot column intimately mixed before the usual quart sample is taken. Samples of the plants growing on the land should in all cases be included in the package, as they indicate very closely the agricultural character of the land.
All samples taken while the land is wet should be air-dried before sending; in the case of alkali soils this is absolutely essential.
Ninth.—All peculiarities of the soil and subsoil, their behavior under tillage and cultivation in various crops, in wet and dry seasons, their location, position, “lay,” every circumstance, in fact, that can throw any light on their agricultural qualities or peculiarities, should be carefully noted, and the notes sent by mail. Without such notes, specimens cannot ordinarily be considered as justifying the amount of labor involved in their examination. Any fault found with the behavior of the land in cultivation or crop-bearing should be specially mentioned and described. The conditions governing crop-production are so complex that even with the fullest information and the most careful work, cases are found in which as yet the best experts will be at fault.
APPENDIX B.
SUMMARY DIRECTIONS FOR SOIL—
EXAMINATION IN THE FIELD OR ON THE FARM.
While the general principles upon which the cultural value and adaptations of lands should be judged, have been given in the text of this volume, it seems advisable to summarize their practical application to land examination here, for convenient reference.
The directions given in [Appendix A] for the sampling of soils having been carried out, the samples so taken may be subjected to farther examination by any intelligent farmer to good purpose, and often with great saving of time and expense.