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Organic Lawn
Care
by Paul Sachs
The philosophy of growing turf (or anything else)
organically is simply that a healthy soil grows healthy plants.
When you feed the life in the soil, those growing populations of
microorganisms begin to accomplish many jobs that now consume
great amounts of your time, money, and energy. For example,
microorganisms serve to help: fertilize, by fixing nitrogen from
the air, mineralizing soil organic nutrient, generating carbon
dioxide (the plant’s most needed nutrient), and dissolving mineral
nutrient from rock; de-thatch, by decomposing thatch and other
organic matter into valuable nutrients and humus, which in turn
increase the water and nutrient holding capacity of the soil;
aerate the soil; and control many insect and disease problems by
competition and predation. These are only five examples, derived
from a far greater list. It is widely accepted by researchers that
many of the benefits we get from soil life have yet to be
discovered.
Organic fertilizers contain raw materials meant to
stimulate and feed the life in the soil. The apparent low N-P-K
analysis has relatively little meaning when you are feeding the
soil because those numbers refer to plant nutrients not soil
nutrients. Synthetic fertilizer ingredients contain very little
that feed the life in the soil. The benefits of feeding the soil
cannot be quantified or qualified on any fertilizer label.
Fertilization
It’s a good idea to take some soil samples from
your lawn and send them to a lab for analysis. If any one
essential soil nutrient is deficient, you may not get the desired
response from your fertilizer. Take several samples with a clean
tool from the top 5-6 inches of the yard, remove any undecomposed
residues, and mix all the samples together in a clean container.
Send about a cup of the mixture to your local soil lab (contact
the extension service if your not sure where the lab is). The lab
analysis should tell you if you’ll need to apply one or more
nutrients to balance your soil’s base fertility. Ask the lab if
they can test for organic matter, which is an important component
of a healthy soil system. Quality turf growing on soils with less
than 3 percent organic matter may be very difficult to maintain.
You may want to consider applications of compost if your soil
organic matter is low. If you do apply compost, the best time is
in the early spring before the grass wakes up and in the late fall
after the grass has gone to bed for the winter. Don’t apply more
than a ½ inch layer per application and make sure the compost is
mature (little or no odor and/or heat).
If the base fertility of a soil is balanced,
organic fertilization should consist of only 2-3 applications per
year, depending on the length of your growing season and the
condition of the soil. Generally, a natural fertilizer with an
approximate ratio of 3-1-2 (nitrogen (N), phosphate (P), and
potash (K)) is appropriate for turf. Strict adherence to that
ratio is not critical, so anything close, such as 5-3-4, 7-3-4, or
5-2-4 will be fine. If, however, a test indicates that the soil
has optimum or above optimum levels of P and K, then 1 lb. of N
per 1000 ft2 from a natural organic source is all that needs to be
applied. The best times of the year to apply fertilizer are early
spring, late spring or early summer, and fall. (If you are
applying fertilizer during a hot dry period, it’s a good idea to
water it in.) Usually an application of 1 lb. of N per 1000 ft2 is
just right. To calculate how much fertilizer you’ll need to apply
exactly 1 lb. of N, divide 1 by the first number in the analysis
and then multiply by 100. For example, if you are using a 5-3-4,
divide 1 by 5 (=0.2) and then multiply by 100 (=20). Spreading 20
lbs. of a 5-3-4 fertilizer per 1000 ft2 will apply 1lb. of N.
Mowing
Mowing practices are as important as soil care in
an organic turf program. Proper mowing is the single most
effective way of controlling weeds without herbicides. Mower
blades must be sharpened on a regular basis (every 7-8 hrs of
mowing time). Dull blades tear and stress the plant inhibiting its
natural resistances and aggressive growth. The plant spends more
energy recovering from being mowed and less on competing with
weeds, insects and disease. Lawns should always be mowed high (3-4
inches) and often, never removing more than one third of the total
height. Taller plants can photosynthesize energy more easily,
shade out low growing weeds such as crabgrass, and develop deeper
and more extensive root systems. Clippings should not be bagged.
Recycled lawn clippings can add close to 2 pounds of nitrogen per
1000 ft.2 per year and significant amounts of organic matter.
Areas where large quantities of clippings threaten to smother the
turf should either be chopped finely with a mower or gathered for
compost and reapplied to the lawn when decomposed.
Watering
In most cases, leaving the responsibility of
irrigation to mother nature is better than entrusting it to an
automatic system, especially one activated by a timing device. Too
much or too little water can stress turf plants and lower their
resistance to other problems, such as insect or disease attacks.
Overwatering reduces the amount of oxygen in the soil, causing
stress to roots and to microorganisms. Anaerobic soil conditions
can also cause denitrification. Too little water can be even
worse, causing severe stress to plants and soil organisms. Recent
research suggests that low volume, high frequency irrigation is
best for mitigating stress to turf; other experts disagree, opting
for deep and infrequent watering. The trick is to avoid the
extremes. Soils rich in organic matter can buffer turf from those
extremes by absorbing more water during wet periods, building
greater reserves for periods of drought.
Weed Control
A weed is a misplaced plant. Millions of dollars
worth of so-called weeds are sold each year as ground covers,
perennials, herbs and wild flowers. However, most homeowners don’t
appreciate having them in their lawns. Weeds are effectively
controlled in an organic program in some of the following ways:
Turf plants grown in healthy soil are very aggressive and can
crowd out or smother most weeds when fed and mowed properly. Some
university studies indicate that good mowing practices (mentioned
above) can control certain weeds as well or better than
herbicides. A diverse mixture of turf grasses is also important. A
monoculture of only one or two species of turf plants in a lawn is
not natural and does not compete as well against weeds. If
conditions arise that one or two cultivars cannot tolerate, weeds
will then begin to dominate the area. Once weeds gain the upper
hand, they become much more difficult to control. A genetically
diverse turf is more able to survive, thrive and compete against
weeds under any conditions. Where weeds are already well
entrenched, corn gluten, a natural organic preemergent herbicide,
can be used. Corn gluten breaks down into allelochemicals that
inhibit root development on the germinating seeds of crabgrass,
dandelion and many other common lawn weeds.
New Installations
Choice of seed is very important when renovating or
installing a lawn. A genetically diverse seed blend will grow well
in almost any conditions. Deep-rooted varieties are needed to
locate water and nutrients easily. Blends that are endophytically
enhanced (endophytically enhanced grasses contain natural
endophyte fungi living symbiotically with the cells of the plant
found to be insecticidal to foliar feeding insects) will repel
foliar feeding insects. A soil test is always recommended before a
new seeding or renovation of an old lawn that hasn’t been tested
in the past 3 years. Soil amendments such as lime, greensand, rock
phosphate or compost may be needed, depending upon the outcome of
the soil test. Under normal conditions, apply ½ pound of N and ½
to 1 pound of P and K per 1000ft.2 using a low nitrogen, natural
starter fertilizer (we use a 2-3-3) and lightly work it into the
surface of the soil before seeding. The fall is the best time of
year to install new lawns from seed because there is less
competition from weeds and more reliable rain.
Aeration and De-Thatching
With organic turf care practices, aeration and
de-thatching can quickly become obsolete and unnecessary
activities. The populations of microbes, earthworms, and other
beneficial organisms that thrive in a healthy soil will decompose
thatch and clippings faster than they can be produced. That
digested organic matter plus the recycled bodies of the bacteria
themselves create humus which expands and contracts within the
soil by the varying levels of moisture content, creating air and
water passages, relaxing soil compaction and improving the crumb
structure of the soil. Earthworms that thrive on organic matter
dig deep and extensive tunnels that air and water can travel
through.
Disease Control
Many of these bacteria whose populations explode in
healthy soil also compete antagonistically with pathogenic fungi.
Studies noted in the Cornell University Turfgrass Times warn that
soils with low organic matter content managed with high levels of
pesticides are much more susceptible to devastating turf diseases.
Organically maintained turf rarely if ever has problems with plant
pathogens. When problems do arise, it is usually an indication
that bacteria levels in the soil have dropped. This can be
remedied by an application of compost and liquid seaweed extract.
Insect Problems
Plants that are grown in healthy soil are less
susceptible to insect attack just by virtue of natural selection.
Insects that cull out weaker plants are doing the plant species a
favor by allowing only the strongest and healthiest to reproduce.
However, when a whole lawn is planted in unhealthy and infertile
soil, disaster can strike. A balanced soil ecosystem also contains
many predator and parasitic organisms that can help with pest
insect control. Other controls—such as good cultural practices and
endophytically enhanced seed—will help tip the scale in the turf’s
favor. Grubs can be controlled in many circumstances by using
beneficial nematodes. When applied to thoroughly moist soil
beneficial nematodes can infect and kill most species of lawn
grubs. Lawns with severe grub damage should be renovated with tall
fescue, which has proven to be resistant to grub damage.
A Final Note
Organic turf care is not a great mystery. It is a
different system that requires observation and common sense. In an
organic program, the soil life ends up doing most of the work.
Source: Vermont
Public Interest Research Group |
