The almond is a deep-rooting tree and draws heavily upon the
plant-nourishing elements of the soil. In ripening the large number of
seeds which it is required to do, the tree must draw upon a considerable
area of soil in order to supply the large amount of mineral matter that
is needed to develop and mature the seeds. Analyses of almonds, as
compared with other commonly grown fruits and nuts, made by Colby,[2]
show that the almond leads in the total quantity of mineral matters
withdrawn from the soil. Colby further states that “The stone fruits fall
much below the almond in total ash (mineral matter) excepting the olive,
the ash of which, however, is largely silica (nearly eight-tenths), an
ingredient so plentifully distributed in all soils that it is of no
pecuniary value.” Table I illustrates this statement.
These figures suggest the necessity of having a deep, rich, well-drained
soil for best results. For this reason and because of the deep-rooting
habit of the almond, the soil should be at least ten or twelve feet deep.
_Hardpan._—Compacted substrata in the soil, whether they be hard clay
layers or cemented layers of silicious, ferruginous or calcareous origin,
are objectionable. They not only prevent the roots from foraging to a
considerable depth as they normally tend to do, but they prevent proper
drainage and aeration of the soil. If such layers are comparatively
thin, that is, not more that two or three feet thick at the most, they
may be shattered with dynamite so as to allow the moisture, air and
roots to penetrate to the better soil below. Hardpan, therefore, should
be avoided where it is too thick to be broken up or where it is not
underlaid by desirable soil.