Page 317 - Moving the Earth_ The Workbook of Excavation

LANDSCAPING AND AGRICULTURAL GRADING

LANDSCAPING AND AGRICULTURAL GRADING 7.11

Seed scattered on the ground surface in very early spring may be worked underground by
freezing and thawing so that no effort is required to cover. Seed lying on the surface will sprout
and take root successfully during a long wet spell, but hot sun may kill it, or birds eat it. Raking
after seeding reduces these dangers.
The grass will come up faster and better if the ground is rolled lightly after seeding. This may
be done with a muscle-powered lawn roller, a hand tamper, a power lawn mower of the roller type,
or the smallest size of steel wheel gasoline roller.
Erosion. A sloping lawn is vulnerable to severe damage from flowing water from the time the
topsoil is spread until the grass has made a good root growth. The probability of such damage
should be figured into cost estimates by both the owner and the contractor.
Danger of erosion can be reduced by mixing straw or lawn clippings into the surface. This
necessitates a heavy addition of nitrogen fertilizer, and makes it harder to cover the seed.
If a seeded surface is sprayed with asphalt emulsion, it will be held against ordinary erosion,
without preventing growth of the seedlings.
It is sometimes possible to divert drainage into other areas. One section may be fixed up and
seeded first, and water routed through the part which is only rough-graded. After grass is firmly
established, drainage may be shifted to go over it, so the rough area can be smoothed and planted.

Sod. Drainageways and steep slopes can be protected with sod. This is cut out of existing lawns
or mowed fields by means of hand tools or an engine-driven sod cutter, laid on freshly loosened
and smoothed topsoil, and tamped into firm contact. It is sometimes fastened in place by driving
pegs or thin stakes, or by pegging chickenwire firmly over the whole area.
Sod may be cut in strips 12 or 15 inches wide and 6 to 10 feet long or in squares or rectangles
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of any convenient size. A depth of 1 ⁄ 2 inches usually suffices to get practically all the roots.
It is essential that newly placed sod be thoroughly watered and tamped to establish its contact
with the ground. It should be watered as necessary until it shows that it can take care of itself.

TREE PROTECTION AND REMOVAL

Trees are liable to destruction or damage from various causes during construction work. Trunks
or branches may be broken or scraped by accidental contact with machines; roots may be dug
away by ditching or lowering of grade, lessening the tree’s ability to obtain food and water and
rendering it more vulnerable to uprooting by wind; its trunk may die because of dirt piled around
it; or its roots may be drowned or suffocated by placing of fill.
In general, the larger and more valuable trees are less subject to fatal damage from collisions,
although the scars they do get heal more slowly; but they are much more likely to die from root
cutting or suffocating than younger and more adaptable specimens.

Bark Damage. Trees can be partly or wholly protected from collisions by wrapping with burlap
or other cloth, and tying thin wood strips around the trunks and any particularly exposed branches.
If used for anchors in pulling out machinery, trunks must have very heavy padding and thick wood
pieces between the bark and the chain; and the chain loop should be fastened with a grab hook, bolt,
or knot that will not slide. The choker effect obtained from round hooks or rings can readily crush
bark and wood all around a tree so that it will be fatally injured.
If a tree is girdled by removing even a narrow ring of bark around the whole trunk, it will prob-
ably die. However, if the sapwood is not injured and the damage is kept shaded so that the wood
will not dry out, young and vigorous trees may repair the cut by growing several inches of callus
and new bark across the injury from top and bottom.
If the gap is wide, a skillful worker may be able to graft strips of bark across the injury. If cir-
culation is established through these, they will serve to keep the tree alive and they will widen out
so that the damage may heal over entirely.
Scars on trunks or branches should be promptly covered temporarily or left bare for self healing.