Folks are always wanting to do the impossible. "Impossible"
area consists of trying to change the alkaline soils in this
acidic or even neutral. Novices always try to change or modify
local soil pH in an effort to grow their favorite gardenia or
The results are always the same -- failure.
The alkalinity problem can be treated or temporarily altered.
The temporary alteration involves elimination of the culprit
problem - the soil. If extremely acid-loving plants such as
gardenias are to be grown, an artificial growing media should
Standard potting soil is not acid enough and will not maintain
condition over a long period of time with the alkalinity bombardment
water and soil leachings. To insure an acid-enduring growing
mix two-thirds sphagnum peat and one-third WASHED sand (not
since it contains lime and weed seed). Excavate a suitable (large
enough to contain the root system of the mature-size plant which
planting) size hole, and fill with the sphagnum-peat-sand mix.
INCORPORATE ANY OF THE NATIVE SOIL WITH THE MIX! This may sound
a lot of trouble but it prevents a lot of ugliness later. Many
growers follow a similar plan of action to insure vigorous plant
And, if you don't make this "modification BEFORE you plant,
expect to correct the problems later!
Of course, the choice of peat moss may make the difference
success or failure. One has to be careful of the kind of peat
or she uses to alter the soil horror with which we must contend.
There are three major types of peat moss in the trade. They
moss-peat (peat moss), reed-sedge peat, and peat humus. Peat
organic remains of plants accumulating in swamp areas where
decay has been retarded by immersion in water. It may require
to over 500 years to produce a layer of peat a foot thick. The
depends on the type of plant and its environment. Moss-peat
moss) is formed chiefly from the sphagnum type mosses. Nearly
imported from Canada or Europe is derived from sphagnum moss.
very acidic with a pH of 3.6 to 4.2. The color is tan to brown.
peat is light weight, porous, high in moisture-holding capacity
in nitrogen (0.6 to 1.4 percent). It is an excellent soil conditioner
but will require some lime when used to grow anything other
acid-loving plants in containerized or container-like (such
excavated hole) situations.
This is what we need in South central Texas --- something
that is inherently acid and will release acid gradually as it
decomposes. Because sphagnum peat moss is so extremely acid,
be neutralized by the constant bombardment of alkalinity which
experienced in local soils. The pH of most landscapes ranges
to 8.2. Organic material (leaves, grass clippings, tree trimmings)
produced locally, grown in alkaline soil, will produce a more
alkaline decomposed product. So to "fight off" the
alkalinity, an organic material produced in an area which has
MUST be used.
So why is pH so important? When the pH of a soil is too
high (alkaline) or too low (acidic), most of the minor fertilizer
elements (iron, manganese, molybdenum) become unavailable for
uptake. Plants must have the minor elements, especially iron,
Iron deficiency in plants is a problem common to many landscapes
our very alkaline soil. For further information about lawn
Iron is essential for the formation of chlorophyll (the green
pigment in plants). Therefore, when iron is unavailable to the
iron deficiency (sometimes referred to as iron chlorosis) results.
Prolonged iron deficiency can result in decreased shoot and
because of a lack of chlorophyll to maintain photosynthesis.
deficiencies do not usually result from a lack of iron but rather
because the iron is tied up or "fixed" in insoluble
compounds. Iron is
most commonly deficient in alkaline soils although excessive
phosphate, manganese, zinc and copper can produce iron deficiency.
Waterlogged soils can also reduce the availability of iron.
Identification of the problem is not difficult. Look for two
1) Progressive yellowing of the newest leaves occurring first.
lower, older leaves turn yellow first, then the problem is something
other than iron deficiency.
2) Leaves with darker green veins and the tissues between
veins turning yellowish green. When iron deficiency is severe
entire leaf may become white and finally brown.
Iron chlorosis is most prevalent on members of the grass family
(such as St. Augustine even though some varieties such as Floratam
more resistant), certain fruit trees (citrus and peaches), many
vegetables (particularly beans), many flowers and ornamentals,
shade trees. Plants that thrive in acid soil, such as azaleas
gardenias, can likewise be severely affected. Since iron deficiency
often the result of alkaline soil reactions, acidifying soils
appear to be a practical solution. Calcareous soils, however,
large reserves of calcium to buffer attempts to lower the pH,
particularly if the soil is fine textured.
To prevent a plant's suffering the fate of "iron poor
the following techniques:
1) Totally avoid the perpetual problems with yellowing foliage
plants by planting only Extension recommended, tried-and-proven
types. Lists of recommended ornamentals are available at:
2) Add iron. The best approach to correct the yellowing
condition of existing plants is to use either chelated iron
sulfate (Copperas) as both a soil treatment and as a foliar
Spray applications of sulfates and chelates often are more effective
give quicker results than soil applications. However, the effect
normally not be as long-lasting and repeat applications may
necessary. Be certain to keep any iron products off walks, driveways,
brick or masonry surfaces, since they will cause staining. MALCOLM
BECK OF GARDENVILLE ADDS: "Fresh iron stains on a sidewalk
can easily be cleaned up with oxalic acid. Gardenville sells
it or it
can be purchased at some True Value stores. It is normally used
bleach wood. It will not hurt plants and works really good on
iron stains." Soil applications of iron sulfate to green
that is yellow and suffering from iron chlorosis MUST be made
uniformly and concisely to avoid foliage burn and stripping.
a drop-type spreader, be sure to overlap wheel paths on passes
the area being treated, walk at a rapid, steady rate (to avoid
of the free-flowing, granular iron sulfate). Water the iron
sulfate-treated area after the application has been made.
The good news is that there is now a granulated, i.e., doesn't
pour through the spreader as Copperas does, product which contains
same percent iron as Copperas and has the nitrogen fertilizer
provide a quick green-up. It is sold as Ironate (NOT Ironite
not been effective in my tests! and is said to contain arsenate
is a mined product.)
Iron chelates are expensive and some commercially formulated
types don't perform well in alkaline soils. Malcolm Beck and
discovered a way for homeowners to make their own iron chelate.
chelate is an piece of organic material with the iron molecule
attached. As the organic material decomposes, the iron molecule
released into the soil for use by the plants. So, basically,
chelate is a slow-release iron source. If you can imagine how
and completely iron products will stain walks, driveways, brick
masonry surfaces, you can readily see how those iron molecules
quickly attach to an organic product (carrier) such as leaves,
clippings, mulch, lawn dressings, etc. From this notion years
began to recommend that gardeners make their own iron chelate
This can be simply done by spreading iron sulfate, in the form
Copperas or the new improved version with nitrogen named Ironate,
and into organic mulches. This should be done in layers and
organic material is added. How much to add? Add it until the
each layer of the organic material is darkened -- it would be
to add too much since the soil deactivates the iron molecule
If you need a measurement, mix one cup of iron sulfate (copperas
Ironate) to each bushel of mulch applied.
A COMMENT FROM MALCOLM BECK: "The best product I have
grow plants and keep them green is Green Sand. I introduced
to this area and it contains from 10 to 20 percent iron. It
naturally occurring mineral found in Texas. The Green Sand should
applied to a garden area at the rate of two pounds per 100 square
and to lawn areas at the rate of 15 pounds per 1000 square feet.
will not burn so additional amounts can be added to severely
Gardenville is selling SAWS compost mixed with Greensand and
sold as Sports Turf Plus."
If you have the concept of how to cure yellowing, chlorotic
lawns by the addition of iron and nitrogen, how would you like
certain fungus diseases as well? Dr. Phil Colbaugh and
Research-Extension colleagues at the Texas A&M Research
Center at Dallas
have discovered that using a top-dressing or lawn dressing with
peat moss (Michigan Peat or Peat Compost) results in control
on St. Augustine grass on Dallas area home lawns. In comparison
studies, peat moss topdressing reduced symptoms of TAKE-ALL
for longer periods than cow manure compost and is thus considered
more effective disease control product.
In recent years we have discovered that underground organs of
grasses are commonly attacked by ectotrophic fungi that cause
destructive patch diseases. Ectotrophic fungi grow over living
grass roots and underground stems as runner hyphae (dark fungal
threads). There are several ectotrophic fungi that cause turf
diseases and their appearance is similar on the different turf
hosts they attack. For convenience, all of these fungi are referred
as ETRIF (ectotrophic root infecting fungi) to simplify their
and associations with the similar turf diseases they cause.
Take-all root rot (TARR) of St Augustine grass has emerged
major problem on landscapes in Texas as well as other states
Gulf Coast including Florida. The disease is caused by Gaeumannomyces
graminis var. graminis, which belongs to the ETRIF pathogen
brown-black mycelial growth of the fungus (Fig.1) colonizes
stolons and shoots but it is primarily a root destroying pathogen.
Damaging effects of this disease on St. Augustine grass were
observed and described in Texas by Dr. Joseph Krausz (plant
at Texas A&M University) and in Florida by Dr. Monica Elliott
(University of Florida). In a 1999 survey of St. Augustine grass
in north Dallas, we observed yellow patch symptoms (Fig. 3)
disease on 61% of 70 lawns during the month of September. If
disease progresses it kills the stolons and produces patches
grass during summer ranging from 3-10 ft in diameter. Because
widespread nature of this disease, our research investigations
develop a practical control measure for landscapes with St.
DESCRIPTION OF FIELD SYMPTOMS
Symptoms of take-all root rot disease (TARR) typically appear
St Augustine grass as diseased patches of turf during late spring
throughout the summer months. Pathogen activity causes a severe
that completely destroys tap roots which anchor St. Augustine
stolons to the ground. Visual symptoms of the disease on lawns
initially small yellow patches of turf with leaf blades that
chlorotic while the healthy leaves remain a typical green color
3). The yellow patches are thought to be associated with the
of a toxin by the ETRIF fungus when the turf is growing under
conditions. Yellows symptoms of the disease can persist on lawns
throughout the summer growing season. Dark brown or black mycelial
threads of this fungus (Fig. 1) are distinctive and produce
black dots (hyphopodia) that anchor the fungus to the plant.
affected plants become shortened, discolored, and often have
colored lesions that are visible upon inspection with a hand
Eventually the roots become completely rotted and shriveled
to form a
non-functional root system (Fig 2). In the final stages of decline,
diseased stolons gradually succumb to hot summer temperatures
winter weather and produce large patches of dead grass that
recover from injury.
Affected patches of turf can at first be quite small ranging
1-2 feet in diameter; however, they also appear as larger areas
range from 5-10 feet in diameter. Diseased areas are not always
but often appear as roughly circular patterns in the lawn. In
TARR survey on North Dallas lawns, we observed a higher number
take-all symptoms in heavily shaded areas compared to areas
direct sunlight or partial shade for most of the day (Fig. 5).
disease should not be confused with white grub damage which
appear at the same time of the year. The best clue is to look
yellow or chlorotic leaf extensions (fig. 3) on St. Augustine
that has not received mowing for several days. Symptoms of TARR
also include the appearance of brown shriveled roots that are
the fungus as opposed to white grub damage where the roots are
removed by insect feeding.
SEARCH FOR A PRACTICAL DISEASE CONTROL ON DALLAS HOMELAWNS
We used two approaches to control the TARR disease in field
investigations on area lawns during the past three years.
One approach utilized conventional fungicide sprays with
Terraguard or Bayleton, Heritage, and Banner Maxx using 2.9L
per 10 m2. A second approach utilized topdressing lawn care
including (1) manure compost and (2) sphagnum peat moss. Manure
can enrich the microbial number and diversity for variable lengths
time and low pH products like peat moss had been shown to suppress
Gaeumannomyces fungus in previous research. While some of the
based topdressing regimens demonstrated improved turf grass
effects on disease control were only partial and limited in
Research field plots with the fungicides Terraguard (4 - 8 oz)
Bayleton (2 oz) treatments gave good results for controlling
take-all root rot symptoms. Success with fungicide treatments
on a lawns maintained under shaded conditions compared to lawns
A second approach with topdressings used low pH topdressing
sphagnum peat moss. This topdressing approach has consistently
demonstrated TARR disease suppression in field studies during
two years. Our field comparisons of manure compost vs. peat
topdressings indicate the peat moss to be a more effective long-term
approach for reducing symptoms of the TARR disease. Some of
research literature on the fungus causing TAP indicates its
low pH. This might explain how the peat moss (pH = 4.4) controls
fungus on exposed stolons and roots where the disease is active.
There is no indication of varietal resistance to take-all root
since the disease has been noted on all of the commercial St.
grass varieties. The use of fungicide applications is also limited
only a few fungicides that are approved for use on this disease.
Although there is good evidence that fungicides are capable
controlling the disease, environmental conditions and vigor
of the turf
may pose some limitations on the effectiveness of fungicide
At this time we have no explanation as to why we observed a
uniformity in fungicide effectiveness on different lawns.
The use of organic topdressing to control turf grass disease
relatively new approach to controlling turf grass diseases.
the complexity of microbial antagonism, fertility values of
materials, different types of diseases and susceptibility of
to pH, most of this type of research is directed by trial and
experimentation. We do have good evidence that the acid peat
topdressings result in control of TARR on St. Augustine grass
area home lawns. In comparison studies, peat moss topdressing
symptoms of TARR for longer periods than cow manure compost
and is thus
considered the more effective disease control product. Additional
research will address the best time to apply peat moss topdressing
products as well as possible effects on other turf grass pathogens