TM 5-803-13/AFM 126-8
(2) The final grading of a site will determine its
agronomists or USDA Soil Conservation Service district
potential for surface drainage. In extreme cases, such as
representatives.
sites with heavy clay soils, implementation of subsurface
(5) Legumes and ground covers. These plants,
drainage may be necessary to remove excess water. When
often of ornamental value, can be used where turf
natural drainage is poor enough to warrant subsurface
establishment or maintenance is difficult and where little
drain lines, alternatives to turf should be sought so that
or no foot traffic exists. Properly established and
costs and maintenance problems can be minimized. TM
maintained ground covers will require less maintenance
5-820-4/AFM 88-5, Chap 4 contains guidance for
than turf-grass; however, initial maintenance (during the
drainage in areas other than airfields.
first one to three years) will be high. Many legumes and
b. Soil modification. The incorporation of amend-
ground covers can be recommended as turfgrass
ments in an existing soil can improve soil texture and
alternatives; however, availability and climatic adaptation
structure so that a high-quality turf can be established.
will determine final selection.
Soil modification is especially appropriate in semi-
(6) Wildflower mixes. The seeds of mixed species
improved and improved areas where the existing soil has
of wildflowers may be substituted for all or part of the
a high clay or sand content. Soil amendments should be
grass seed in a seed mixture. Wildflower plantings are
worked into the soil to a depth of 8 to 12 inches. In many
appropriate for large flat areas or slopes in areas with
cases, an adequate vegetative cover can be established
little or no foot traffic. These plantings are limited to
without amending the existing soil. Where soil texture is
semi-improved and unimproved areas. Care should be
expected to present a management problem, a mechanical
taken to select self-sustaining species which are locally
analysis of the existing soil should be obtained and
hardy and thrive without regular care or irrigation. Spe-
prospective sources of available soil amendments
determined.
cies should not be selected which produce large numbers
(1) Sand. The incorporation of large sand particles
of wind-borne seeds that may spread to other areas of the
into clay soils will enhance aeration and water percola-
installation.
tion, as well as reduce the tendency for compaction. It is
(7) Artificial turf. The use of artificial turf is
necessary to incorporate at least 2 inches of coarse sand
generally not recommended due to cost and maintenance
into the upper 6 to 8 inches of the existing soil to create
requirements.
adequate pore space. Use of ungraded sand with a high
(8) Porous surfaces. Porous surfaces of crushed
percentage of fine particles may intensify the problem
rock or gravel aggregate may be used in areas where
rather than alleviate it.
grasses cannot survive due to drought or poor soil con-
(2) Organic amendments. The addition of organic
ditions. In areas where irrigation is impractical, rainfall is
matter improves soil structure and aeration and promotes
low or soils are unproductive, a 1 to 2 inch blanket of
nutrient and water retention. Sandy soils especially
gravel or crushed rock may be used. Crushed rock should
benefit from the addition of organic matter. The amount
be coarse enough to allow drainage.
of organic material added to a soil may vary; however,
recommended amounts for 1,000 square feet of soil are 3
4-5. Site Preparation.
to 4 cubic yards of well-rotted compost, 2 to 3 cubic
a. Clearing and grading. The extent of clearing and
yards of rotten manure or 3 bales of peat moss. Other
grading in an area where turf is to be established will be
materials which may be used are rotted sawdust or
governed by site use, land slope, climatic conditions and
ground bark. Nitrogen deficiencies can occur if organic
planting method. Clearing and grading should be
materials are not decomposed when they are added to
soil.
minimized to avoid unnecessary dust and erosion. Prior
(3) Topsoil. Topsoil is a select or mixed soil mate-
to grading, reusable topsoil should be removed and
rial applied to a soil surface prior to seeding or planting
stockpiled.
turf. Grading and provisions for surface drainage should
(1) All turf areas should be graded to have slopes
be completed prior to the addition of topsoil.
not steeper than 3:1; 4:1 slopes are optimum. If slopes
Replacement of existing topsoil is generally unnecessary
are too steep, mowing with standard equipment can be
except where there are disproportionate amounts of sand,
hazardous. Athletic areas should be graded with a 1.5 to
silt or clay. In such eases, a gradual transition of soil
3 percent slope toward the sidelines, and lawn areas with
material is necessary in order to provide good internal
a 1.5 percent slope away from buildings. In areas with
drainage.
pavement, turf grades should be established 1 inch below
c. Nutrient additives. Soil fertility can be adjusted by
pavement grades. Abrupt or irregular grading makes
the addition of nutrients as determined necessary through
maintenance more difficult and should be avoided.
soil testing.
Swales should be preserved or installed during grading to
(1) Gypsum. Gypsum is used to improve soils
receive and convey surface drainage. Vegetation should
which have a high percentage of soluble salts. Where pH
be preserved in swales where erosion potential is high.
4-4
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