_Preparation of soil_ is for the purpose of securing a favorable start
for the young crop; its effects are lost after the first few years.
Most land that is to be devoted to forest planting does not admit of
as careful preparation as for agricultural crops, nor is it necessary
where the climate is hot too severe and the soil not too compact to
prevent the young crop from establishing itself. Thousands of acres in
Germany are planted annually without any soil preparation, yearling
pine seedlings being set with a dibble in the unprepared ground. This
absence of preparation is even necessary in sandy soils, like that
encountered in the sand-hills of Nebraska, which may, if disturbed,
be blown out and shifted. In other cases a partial removal of a too
rank undergrowth or soil cover and a shallow scarifying or hoeing is
resorted to, or else furrows are thrown up and the trees set out in
them.
In land that has been tilled, deep plowing (10 to 12 inches) and
thorough pulverizing give the best chances for the young crop to
start. For special conditions, very dry or very moist situations,
special methods are required. The best methods for planting in the
semiarid regions of the far West have not yet been developed. Thorough
cultivation, as for agricultural crops, with subsequent culture, is
successful, but expensive. A plan which might be tried would consist in
breaking the raw prairie in June and turning over a shallow sod, sowing
a crop of oats or alfalfa, harvesting it with a high stubble, then
opening furrows for planting and leaving the ground between furrows
undisturbed, so as to secure the largest amount of drainage into the
furrows and a mulch between the rows.
_The time for planting_ depends on climatic and soil conditions and
the convenience of the planter. Spring planting is preferable except
in southern latitudes, especially in the West, where the winters are
severe and the fall apt to be dry, the soil therefore not in favorable
condition for planting.
The time for fall planting is after the leaves have fallen; for spring
planting, before or just when life begins anew. In order to be ready in
time for spring planting, it is a good practice to take up the plants
in the fall and "heel them in" over winter (covering them, closely
packed, in a dry trench of soil). Conifers can be planted later in
spring and earlier in fall than broad-leaved trees.
_The density_ of the trees is a matter in which most planters fail. The
advantages of close planting lie in the quicker shading of the soil,
hence the better preservation of its moisture and improved growth and
form development of the crop. These advantages must be balanced against
the increased cost of close planting. The closer the planting, the
sooner will the plantation be self-sustaining and the surer the success.
If planted in squares, or, better still, in quincunx order (the trees
in every other row alternating at equal distances), which is most
desirable on account of the more systematic work possible and the more
complete cover which it makes, the distance should not be more than 4
feet, unless for special reasons and conditions, while 2 feet apart is
not too close, and still closer planting is done by nature with the
best success.
The following numbers of trees per acre are required when planting at
distances as indicated:
1½ by 1½ feet 19,360 | 2 by 4 feet 6,445
1½ by 2 feet 14,520 | 3 by 3 feet 4,840
2 by 2 foot 10,890 | 3 by 4 feet 3,630
2 by 3 feet 7,260 | 4 by 4 feet 2,722
To decrease expense, the bulk of the plantation may be made of the
cheapest kinds of trees that may serve as soil cover and secondary or
nurse crop, the main crop of from 300 to 600 trees to consist of better
kinds, and with better planting material, mainly of light-needing
species. These should be evenly disposed through the plantation, each
closely surrounded by the nurse crop. It is, of course, understood that
not all trees grow up; a constant change in numbers by the death (or
else timely removal) of the overshaded takes place, so that the final
crop shows at 100 years a close cover, with hardly 300 trees to the
acre.
_After-culture_ is not entirely avoidable, especially under unfavorable
climatic conditions, and if the planting was not close enough. Shallow
cultivation between the rows is needed to prevent weed growth and to
keep the soil open, until it is shaded by the young trees, which may
take a year with close planting and two or three years with rows 4 by 4
feet apart, the time varying also with the species.
It is rare that a plantation succeeds in all its parts; gaps or fail
places occur, as a rule, and must be filled in by additional planting
as soon as possible, if of larger extent than can be closed up in a few
years by the neighboring growth.
When the soil is protected by a complete leaf canopy, the forest crop
may be considered as established, and the after-treatment will consist
of judicious thinning.