Properly Using Slow-Release, Sulfur-Coated
On Your Lawn
Spring has sprung in this part of Texas-or
so many people believe! Tomato and pepper plants have been
planted, fruit trees are in full bloom and folks are anxious
to re-sod lawns and fertilize everything that's living.
From now until April 1- NEVER de?thatch your St. Augustine
lawn. Instead, trim it back to 1/2 to 1/3 its current height.
(This could be called scalping but that term is more hostile
than trimming.) Do not collect the dead clippings. Let them
remain as a source of organic material and, eventually, recycled
fertilizer. Our landfills don't need any more grass-filled
plastic bags occupying much needed and diminishing space.
(Hybrid Bermuda turfs can be de-thatched if needed.)
On April 1-after you have probably mowed your
grass twice (although you may have mowed the lawn weeds numerous
times!), apply a slow-release fertilizer, such as 19-5-9,
20-7-7, 21-7-14, 25-3-5 or 22-3-3, 20-5-10, and 15-5-10. Why
use a slow-release or sulfur?coated fertilizer instead of
just regular fertilizer? Slow-release or sulfur-coated fertilizer
is controlled-release fertilizer made possible by coating
nitrogen and other plant nutrients with molten sulfur in varying
thicknesses to allow turf feeding for 10 weeks. Regular, fast-release
fertilizer doesn't last much longer than 30 days.
Nutrients of slow-release fertilizer become
available when the coating degrades to expose them or when
nutrients diffuse through small pores in the coating. If all
sulfur-coated fertilizer particles were identical, the release
of nutrients would occur at the same time for each particle.
Fortunately, coatings are not the same on all particles.
Particles with thin or imperfect spots in the
coating, which are covered by the sealant, have quick to moderate
release rates. The longest delay in release comes from the
thicker-coated particles with no imperfections. Thus, it is
the variability in the particles that provides the sustained
release of nutrients from slow-release or sulfur-coated fertilizer.
The exact feeding duration of slow-release
or sulfur-coated fertilizer depends on the dissolution rate
of the product. The 7-day dissolution rate is a laboratory
measurement of the percentage of nutrients that go into solution
when a sulfur-coated fertilizer sample is placed in 100 degree
F. water for 7 days. It is used to indicate the relative rate
of nutrient release. As the coating thickness increases, the
dissolution rate decreases. Basically, 1/2 of the nutrients
in slow-release or sulfur?coated fertilizer release is in
the first month, and the remaining 50 percent is released
over the next 6 weeks.
As temperature increases, the release rate
increases. Release rate is not greatly affected by soil water,
soil pH or microbial activity. Slow-release or sulfur?coated
fertilizer lasts longer, so fewer applications are needed
to maintain uniform quality turf. Use of slow-release or sulfur-coated
fertilizer reduces the risk of fertilizer burn and decreases
the loss of nitrogen through leaching and volatilization (changes
to gas). Fewer applications and decreased nutrient loss means
greater product efficiency, which more than justifies the
higher cost of slow?release fertilizer. The sulfur of slow?release
or sulfur?coated fertilizer remains after it is oxidized to
the sulfate form. The oxidization from sulfur-coated fertilizers
falls between the fairly rapid oxidization of powdered sulfur
and the slow oxidization of granular sulfur.
So why should you use slow-release or sulfur-coated
fertilizer on your lawn? It has the following advantages:
1) It makes more nitrogen available as a nutrient
to the plant.
2) It resists leaching or washing through the
soil into the water supply.
3) It decreases the risk of fertilizer burn
associated with heavy
applications of conventional fertilizers.
4) It minimizes surge growth and reduces excessive clipping
when mowing. This, in turn, eliminates the necessity of bagging
clippings if mowing occurs every 5 to 7 days.
5) It releases independently of microbial and
6) It offers controlled-release feeding for
7) It provides sulfur as a plant nutrient.
8) It stimulates a more drought tolerant grass
which only requires one
thorough watering once a week.
9) It reduces the occurrence of brown patch fungus. Excessive
amounts of fast-release fertilizer stimulate lush grass growth
predisposes turf to brown patch fungus.
On or around July 15-if the greenness of the
lawn is fading and the area is not in the grip of a severe
drought, make a second application of slow-release or sulfur-coated
fertilizer. Since the first application was made on April
1, and because the fertilizer only lasts 10 weeks, your turf
will be out of nutrients by then. The July 15 fertilization
will last for another 10 weeks or until the first of October.
This will be the ideal time to apply the winterizer fertilizer
ratio of 3-1-2 (15-5-10, 18-6-12) or 4-1-2 (20-5-10, 16-4-8).
Slow?release or sulfur?coated fertilizer SHOULD NOT be used
for fall feeding because grass needs immediate availability
and uptake of nutrient elements so that the winterization
can occur. Besides, the grass will be dormant in less than
the 10 weeks that the slow-release fertilizer types would
be coming available.
So, there is your lawn maintenance outline
which will insure beautiful green grass with a minimum amount
of effort and resources.