Better Landscaping Today Newsletter
Volume 3, Issue 9 September
2000
CASE HISTORY AT PERSHING
SQUARE
PAM TECHNOLOGY HELPS TO
RESTORE DISTURBED SOILS:
The
disturbance of soils causes an alteration of the profiles and of the proper ties.
These properties often have been developed over centuries. Weathering of the
parent minerals forms the smaller sized particles of silt and clay. Over time,
rain leaches the soluble salts from the upper profile and the salts accumulate
in the deeper profile. The presence of plants undergoing photosynthesis
increases the content of organic matter of the upper profile. With microbial
activities and other organisms, soil structure is developed as the organic
matter is transformed into mucilaginous materials that imparts physical soil
structure by cementing the silts and clays together. Soil crumbs which are
formed from the primary particles hold moisture and nutrients while the space
between the crumbs allows for air exchange and water penetration, Other holes
are formed by earthworms and by decaying roots.
The
disturbance of soils generally results in the loss of the natural properties
due to compaction, inversion of profiles(horizon A- zone of soluble salt
depletion and horizon B- zone of salt accumulation) and infertility. Compaction
during grading or because of vehicular traffic prevents water movement through
the soil, resulting in salinity increase and prevents sufficient aeration.
Erosion is also increased. On the other hand, when water penetrates soil, there
is no erosion. Erosion occurs when water carries sediments down slope. Fugitive
dust also becomes a problem without the cementing of soil into aggregates.
The
redevelopment of good soil properties is not accomplished with the installation
of topsoil. Topsoil will probably have the desired chemical properties, but
will not have the desired physical properties until it develops them through
means.
The
historical technique for land restoration of disturbed soils has been the
incorporation of large amounts of waste organic matter. Organic matter is
unable to effectively condition until it is metabolized and converted into
mucilaginous materials. The initial results of improvement can be slow.
Frequently, the organic matter contains excessive soluble salt, often enough to
cause injury to sensitive plants, Newer polymeric conditioners (water-soluble,
anionic polyacrylamide) (WS-PAM) have shown great value in safely and
effectively conditioning soil. These materials have been extensively evaluated
by numerous groups, including universities and federal agencies. The United
States Department of Agriculture and the American Society Agronomy sponsored a
symposium on them in November 1993. Over a hundred scientific articles have
been written on them (for a review, see Soil Conditioner and Amendment
Technologies, Vol 1, 1995).
WS-PAM
is a mucilaginous cement designed to function like humic acids and other
natural cements. It promotes excellent soil structure. However; only low
amounts are required, and the longevity is one to two decades, 1ong enough for
natural means to become effective. Unlike waste products, WS-PAM is low in
salinity, low in heavy metals and other potential growth inhibitors, It works
immediately in increasing good drainage and enhancing good aeration if applied
to non-compacted soil, according to directions. Compacted soils require tillage
first. WS-PAM prevents non-compacted soils from becoming compacted or crusted
if caused by settling due to water with the loss of crumbs.
In
addition to use for proper improvement in the physical properties, chemical
analyses of soil are needed to make recommendations for correction of
undesirable elements. Those present may include: sodium in drilling muds or
from salt contamination; and heavy metals which may be present, as well as for
fertility requirements.
The
Case History of Pershing Square, City of Los Angeles
Pershing
Square is an over-structure park covering a city block in downtown Los Angeles.
Over $14 million was spent on the park to revitalize it in 1992/1993. Part of
the money was provided by the adjoining commercial property owners with 50-year
property bonds. The project managers wanted to keep the expenses low but
realized that the park must last throughout the life of the bonds.
In
lieu of using synthetic soils based on organic matter with a short life cycle,
real earth was used for the planters which averaged five feet in depth, Growth
problems were observed in the summer of 1993, immediately after planting. The
trees did not grow. They started wilting, defoliating and scorching. Analysis
of the site soil indicated high concentrations of boron, sodium and chloride.
The soil aeration was insufficient for root growth. Two proposals were offered,
one by each consultant. One firm proposed to replace the entire soil with a
mixture of fir bark and sand. This would have cost over $1 million to implement
The second proposal was to properly amend the soil on site to provide
sufficient aeration and porosity to leach the salinity and boron from the soil.
Comparative growth studies with amended site soil using agricultural gypsum and
Complete Green Soil Drain/P.A.M. soil conditioner showed that the soil could be
reclaimed.
Late
in 1993, soil of the entire park was amended with Soil Drain/P.A.M. Improvement
of the plantings which were reused was quickly noticed. The camphor trees
started to root immediately. Within two weeks they had rooted two inches and
had new bud growth. The citrus developed new growth. The sod developed healthy,
white roots one week after planting. The cost factor for the P.A.M.? $10
thousand worth of material was used. Over the seven years since it was
replanted, the plants have thrived.
Partial reprint from Soil Conditioner and
Amendment Technologies, Vol. 2,
1997.
For more information, contact Complete Green
Company, 365 Coral Circle, El
Segundo, CA 90245, (310)640-6815,
(800)473-3699, fax (310)640-6863,
www.wallace-Labs.com/cgreen/