The golf course superintendent has arguably the most difficult soil
management challenge in all of agriculture. After speaking recently to a group
Standard soil tests may not demonstrate nutrient mobility
as dramatically, since they show what nutrients are present on the soil colloids
but give no indication of their availability.
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of farmers on the issues of balancing soils, I was sitting at lunch with a few
who were complaining about soil compaction. As I was listening, I started to
chuckle to myself (or so I thought). One fine gentleman looked at me somewhat
disturbed by my grin, so I quickly explained to him that most of my work is with
golf course superintendents, who average 40,000 pairs of feet per year over
small areas of around 3,000 square feet - not to mention the physical pressures
of daily maintenance. They were concerned about running a plow over their
fields twice a year, which is a serious problem but nothing like what a
superintendent faces on a continual basis.
When a soil gets the kind of physical pressure that a golf course green
receives each and every year, there is simply no way to avoid damage to the soil
structure, even given proper mechanical aerification. Movement of air and water
is severely restricted. Consequently, microbes cannot function effectively.
The over-use of salt fertilizers can actually add to the physical damage of the
soil by creating an imbalance in the carbon-to-nitrogen relationship. This will
also affect the activity of beneficial bacteria, further restricting nutrient
mobility and ultimately leading to plant stress and potential disease pressures.
Perhaps the ultimate resolution for the golf course superintendent,
agronomically speaking, is to get rid of the golfers!!!
Nutrient mobility within the plant can be evaluated in a variety of ways,
including a LaMotte water-soluble soil test or a good tissue test. The LaMotte
test is a "weak Bray extraction", which uses an acidification process intended
to replicate the level of acidification that may be found in the soil. This is
just another tool - not an exact science by any means - but it can reveal some
interesting things. Standard soil tests may not demonstrate nutrient mobility
as dramatically, since they show what nutrients are present on the soil colloids
but give no indication of their availability. Tissue testing, on the other
hand, can reveal that even when the soil chemistry is in balance, nutrient
mobility may be inadequate to provide the plant all it requires for proper
growth. The level of nutrient mobility (as indicated by the LaMotte test) on any
given golf course will vary significantly from green to fairway. Nutrient
mobility on a green is usually significantly less than that of a fairway.
Biological indicators are also significantly reduced on greens when compared to
the fairway soils. This is clearly due to the intensified physical pressure
that a green receives compared to the same area in the fairways. No golf course
superintendent will find this surprising, but the level at which even a good
green is able to mobilize nutrients may be an eye opener.
While tissue testing can be of great value when trying to determine what is
actually being taken up by the plant, neither a LaMotte test (kits are available
from agronomic supply stores) or tissue tests should ever replace a good soil
testing program. It is imperative that you work both sides of the equation.
Managing the soil on the basis of a good soil testing program will help to
...it becomes an important management practice for the superintendent to take
care of both the soil and the plant as separate programs.
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balance the basic nutrients on the soil colloids. This will help to open the
soil physically, allowing for better infiltration of air and water, and in turn
provide a better environment for microbial activity.
All good soil management addresses the chemistry, physics and (most
importantly) the biology of the soil as one entity. Once this is done, managing
the leaf will help assure the plant gets what the soil cannot always provide.
Again, with the incredible physical pressures that a golf course suffers it
becomes an important management practice for the superintendent to take care of
both the soil and the plant as separate programs. Foliar feeding provides a
viable tool for the superintendent to help battle an incredibly difficult
agronomic environment.
Knowing that golf course soils, in the best of situations, are not mobilizing
all that the plant needs is an integral factor when developing a foliar feeding
program. The same foot traffic that affects nutrient mobility in the soil also
creates a tremendous stress on the leaf blade. Foliar feeding can not only
provide what the soil cannot, but it can also help to reduce the simple physical
stress that the grass blade suffers every time a golfer walks over it, or each
morning after mowing. The ideal foliar program provides a complete package of
NPK, calcium, magnesium, trace nutrients, carbohydrates and other bio-stimulants
Perhaps the most important aspect of a foliar program is the concept of
"small but frequent" applications.
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to help feed beneficial bacteria and the plant. The most important aspect here,
however, is these applications are made in a "small but frequent" manner.
"Spoon feeding" can be done in a number of ways. Many courses are installing
fertigation systems that can provide the mechanism to supply nutrients to the
entire course at one time. This can be a tremendous labor savings, and many of
the better systems offer the flexibility of multiple supply and mix tanks to
blend small batches of nutrients or bio-stimulants for better control. These
tools can be especially effective during a grow-in situation when it so
important to keep nutrient levels up since the plants and their root systems are
so young. However, these systems don't come without a price tag and not every
course can justify the expense. A simple spray tank can provide all that is
needed to work an effective foliar spray program. This method will apply the
nutrients exactly where you want them, while saving money by not spraying
unneeded areas. Flexibility is the key with a good foliar program; it provides
you control and the safety of using only small amounts of nutrients.
Perhaps the most important aspect of a foliar program is the concept of
"small but frequent" applications. A typical fertility program that feeds the
soil every month or two creates the "roller coaster" effect; high mobility in
the beginning of the cycle and lower mobility toward the end. This can even be
true with many slow release fertilizers. These kinds of 'peaks and valleys'
create stress on the plant at both the high end and at the low end. Managing
your fertility program in a more controlled fashion can help to reduce the plant
stress associated with this uneven level of nutrient mobility. Although not
always practical, the ideal situation would be to spray a nutrient mix every
week at very low rates. The idea is not to spray more, but to apply less on a
more frequent basis, so that you apply the same amount of nutrient as if you
were spraying twice monthly, or even monthly. This "small but frequent" rate
concept is very important on sand based greens where CEC's are low and nutrient
availability is limited, but even on a healthy soil green nutrient mobility is
not always strong enough to provide the plant what it needs.
The "soup mix" that you create for foliar application should include all that
the plant and the soil may need: NPK, calcium, magnesium, traces and
carbohydrates for the soil microbes. Available sources of nitrogen such as
ammonium sulphate or urea at very low rates (1/10, 1/16... of a pound of N) are
ideal. You should adjust these rates based on conditions with out affecting the
quantity of the rest of the mix. One of the advantages of a foliar program is
Do slow release liquid forms of nitrogen really fit into a program where you
become the source of slow release?
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that these "small but frequent" rates will allow you to use less nitrogen in the
long run, which is certainly beneficial agronomically. Do slow release liquid
forms of nitrogen really fit into a program where you become the source of slow
release? A good question that certainly has its own debate. Phosphorous and
potassium should be from clean sources such as phosphoric acid, potassium
hydroxide or sulphate. Calcium is as important a foliar feed as any nutrient
because it is used more in weight and volume than any other element. It is also
extremely immobile and, even in the healthiest of soils, does not move into the
plant well. For this reason, any golf course can benefit from foliar feeding
this important nutrient. The application rate of calcium should be increased
when the plant is under stress. Again, this shows the flexibility of a foliar
program. Although not needed at the same rate as calcium, magnesium should be a
small part of a good foliar program. Magnesium is critical for many
photosynthetic reactions.
A complete package of trace nutrients including boron, manganese, copper, and
zinc should be a part of any mix. Unfortunately, iron is often the largest
constituent of trace packages and will dictate the rate of other, perhaps more
important, nutrients. High levels of iron can actually restrict the mobility of
other nutrients including nitrogen. If iron is needed or wanted, it should be
used, but controlling its application rates will help prevent restricting
mobility of other nutrients.
Trace nutrients should be in the form of a good chelate such as
glucoheptonates or citrates. Although more expensive than sulfates or EDTA's,
these chelated materials are much less reactive and will mobilize more
effectively.
The other important addition to a proper foliar feeding program is a good
source of carbohydrate or bio-stimulant. In addition to reducing the physical
stress on the plant itself, they help to feed microbes which will in turn help
to more efficiently mobilize nutrients to the plant. In general terms, the best
The other important addition to a proper foliar feeding program is a good
source of carbohydrate or bio-stimulant.
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way to increase the over all mobility of nutrients in a soil is to "feed the
soil" and increase the beneficial bacteria activity. Sugars, humic acids, fish
and kelp meals are all good choices to help further round out your program.
Again, they should be applied in very "small but frequent" rates.
To get a really complete "soup mix" you will often have to do some of your
own mixing, which unfortunately may not always be practical. Premixed packages
can be a good start but may not contain everything needed for your situation.
Most of these packages are loaded with nitrogen and iron, the two nutrients that
should be used most sparingly and whose rates should be dictated by you, not by
a manufacturer. Remember: when preparing a mix, it's imperative that you
always do a bench test first. If problems occur, most likely it will happen in
the tank, and not as a phytotoxic reaction. When in doubt spray your mix in a
controlled area until you are comfortable with your blend. At low rates, with
agitation, you can get a chelated calcium (positively charged cation) and
phosphoric acid (a negatively charged anion) to tank mix with no problems.
Even when soils are properly managed and balanced with optimum nutrient
levels, external environmental factors often prevent turfgrass plants from
taking up what they need for proper growth and disease resistance. A good
foliar fertility program provides you with the ability to give the plant all
that it needs even when a soil cannot. Since the golf course superintendent is
faced with the most difficult agronomic environment in all of agriculture,
managing both sides of the plant are beneficial and cost effective. Testing and
managing the soil is critical and always the first place to start, but since we
know that nutrient mobility is limited in these high traffic soils a foliar
program is also very effective. The real key is that this approach is "small
but frequent," and you can increase or decrease application rates based on the
conditions and stress factors you face. This puts you back in the drivers seat
by giving you control and safety of application. There are as many foliar mixes
as there are golf courses and superintendents. The bottom line is, "Do what
works for you".
Joel Simmons is a former County Extension Agent and the owner of Earth Works
Natural Organic Products of Martins Creek, PA. He is currently teaching Soil
Fertility at the Rutgers Turf Management Program.
He can be reached at (800)732-TURF or eworks@soilfirst.com.
This article was first published in TurfNet Monthly, August 1998
