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Pull a soil
analysis for any large landscaping project, it will help document
your failures on the bad sites. Nothing makes you look less
professional than to have all the plants on a site die and not
know what happened. If you know you have a 'ZINGER' it will allow
you to plan a battle plan to correct it or plant to it. A complete
analysis costs less than $100.00, no big deal on most
installations.
What is pH?
pH is a
measure of acidity in the soil (hydrogen ions). pH is logarithmic,
a pH of 6 is ten times more acidic than the neutral 7, a pH 7.8 is
about eight times more alkaline than a neutral pH of 7. The
confusing part is differences within the range, such as between 6
and 7.8. The numbers are multiples, so take the ten and times
eight, or pH of 6 has about 80 times as many hydrogen ions as pH
of 7.8. Conversely, pH 7.8 has 80 times more OH- than pH 6. H+ and
-OH make water (neutral), the balance of available units of each
is pH.
Make sure you have the appropriate plant material.
Plants are
adapted to certain ranges, some acidic (firs, huckleberries), some
alkaline (saltbush), if you plant an acid lover in an alkaline
area the the leaves will have brown or black margins on them,
before they drop off. The plants, generally, will lose their
leaves within a few weeks, decline and die. Plant an alkaline
lover in acidic soil they usually have yellow(chlorotic) leaves,
then burnt leaf margins, then rot off and die.
Things to look out for.
 Sodium
is an element that plants do not like much. Leaf burn starts
showing up at about 100 ppm (parts per million). 250 ppm kills a
lot of stuff, 500 ppm sodium only supports salt tolerant plants.
See coastal
salt marsh plants.
Boron, as
little as a few ppm will kill many plants.
Nitrogen,
Phosphorous, Potassium and most of the other stuff is not
important unless one of them is WAY off. The only low problem so
far was Potassium at 2 ppm ( should be at least in the 20's or
30's). A few bags of Potassium sulfate moved the numbers up to
planet earth. When the site has one of the way off values you got
problems that will not go away unless helped a little. Low numbers
can be brought up, high numbers have to be designed out with
plants.
The code
words are:
I planted a
few plants out, but they all died;
The last
contractor before killed all his plants here;
Our neighbor
has had a terrible time trying to plant his place; everything
died.
My favorite
two so far are: 'you might have a little trouble digging out
there, that's where they used to park the oil trucks'; and 'that
ground sure looks hard, that's about where the old stage line used
to run'.
If the area
has no bushes or trees and all that is there is grassy weeds, why?
It may be the soil or water. In California houses and subdivisions
are being put into areas that farmers couldn't farm because of
poor soils, high boron, high sodium or rock.
If the soil
report comes back with Boron higher than 1 ppm, pH higher than 8
or lower than 5, and Sodium greater than 200 ppm, you'll have to
do some planning to figure which plants can grow there. On many
sites whatever is native there may be all that can grow there.
Have a water analysis done also if a soil analysis comes back bad,
and then seek help.
 Options?
Site specific
planting can be cost effective if everything else dies.
If you have
one of these bald problem areas, have a complete report done
instead of a partial one. Sometimes there are problems that are
not supposed to be in the area. (Your garden is special because
the fill came from the nuclear power plant's holding pond.)
Look long and
hard at soils with hard pan, with serpentine, with salt spray,
with any white surface deposits(or any other color for that goes,
one site had a rainbow) or with a mining operation going on
nearby. It is amazing that people do not wonder about their soil
with a mercury, borax, lead, salt, gypsum, or other mineral
deposit on the site or next door.
If the site is
bald, ask about the history of the site, it can be important!
Native
plants have adapted to these soils and sites. Native plants have
both mechanical means (sheathing) and chemical means (greater
nutrition and depositing the chemical in the fungal parts and
sloughing them off) to help tolerate high soil toxicities.
How to kill the mycorrhizal fungus. BAD!
The
disturbance of the subdivision is enough to create instability in
the native community, never mind restoration of the mitigated
areas. One of the researchers in Australia tested backyards for
mycorrhizal presence, none. If the site is torn up, heavily
amended, and plants form all over the place planted together the
plant community is replaced with a ruderal (weed) community.
Hayman (1983)
reported that passing the soil through a 9.5 mm (about 4 inches)
sieve destroyed the soil mycorrhiza's hyphae and that the hyphae
was needed to reestablish grasslands, spores did not work. If you
till or otherwise work the soil below 12" you will kill most
of the mycorrhiza. (Protecting it, will save you time and your
customer's money.)
Do not amend
the soil. Get restrictive on what is planted if the soil analysis
comes back bad. Scraping off the alkaline domes to replace the top
soil, amending to counteract the 'bad' soil, does not work. 2
inches of soil sulfur on top of 300 feet of a lime dome will not
make the lime dome go away. Putting 12" of new soil on the
old, kills the old soil, the top soil also dies, and you create an
inversion layer at the interface. A triple whammy. If the soil
report is bad, work with the plants that are in the same soil,
same area, same plant community. Pick the best looking ones, have
them grown and design them into the landscaping. You will save
yourself lots of money.
If the site is
covered with rocks, why not make a rock garden? If the site is on
lime, why not make a lime-loving garden? (This is one soil/climate
where you should look at the plants in the Mediterranean region
that grow in the South European shrub basic community. You can get
some more variety.)
 If
there is no community there, match the community you're going to
create to the soil and climate. If you are given a subdivision
that has nothing but bare dirt that is very acid with poor
drainage along the coast, maybe you should look at making the
whole design work around this. Try an oak or pine forest around
the houses according to how much water you have, transitioning
from the dry areas through 'communities' to the wetlands around a
catch basin.
The healthier this soil and
its plant communities becomes, the more suppression there is of
the alien weeds and plant pathogens. "The greater the
complexity of the biological community, [including the
successional stages] the greater is its stability. At the very
least, cultural practices should be selected that do not
environmentally upset the suppressive communities of
microorganisms that help defend plants against pathogens."
(R.J.
Cook) Even
non-mycorrhizal plants benefit from this type planting often
becoming partially mycorrhizal.
Sites high in
metals will not support desert species, look to conifers and
chaparral species to help.
Sites with moderately high
salts support both desert and chaparral. As the salt level goes
higher you have to use specific species, predominantly VAM
desert/shadscale
types or dryland halophytes.
If the moisture is constant, certain non-mycorrhizal plants will
be in the salty
wet spots going to
VAM
in the dry spots.
One of the
normal procedures for developing a house site is to pile the top
soil in a pile until the house is done and then put it back. The
soil community die after about four-ten years when you do this. If
on the other hand, you plant it with the pioneer species, when you
move it back the soil community will often be viable.
If the stockpiled soil is
blended in with the remaining soil there will not be much soil
activity. Spread the stock piled soil back as it came, hopefully
only moving less than a 1 foot depth each time (a foot off and
then back on) and when the soil is dry. Never work wet soil! Keep
a native wildflower cover crop going on it as best as possible.
Control
the weeds, the
system sees weeds like a human body sees a staph infection.
Do not change
the soil levels if possible. Changing the level more than 1-2 feet
will greatly alter or kill the soil ecosystem. This is the primary
reason why oak trees die when you change the soil level.
Compacted
soils are not desirable. Rolling a roller over a site can
reduce/alter/destroy soil microflora. That is why there are wagon
tracks in the desert after a 150 years and many freeways can
support weedy species so well.
An interesting
note: the only soils that are primarily bacterial based are soils
where "modern" agriculture has occurred, sewage fields
and disturbed weedy sites. Native soils are fungal based. Native
systems and row crop type agricultural/weed systems are two
opposing ecosystems. Edith Allen showed that after 150 years alien
grasslands did not become native on their own.
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