Calcium has always taken a back seat to the "big boys"
of soil fertility. The industry buzz is usually nitrogen and
new forms are frequently being released to the market. Recently
potassium has taken on the role of "favored son." Referred
to as a secondary nutrient behind nitrogen, phosphorous and potassium,
calcium is finally starting to take its place in the ranks of
vogue nutrients.
It is true that NPK is used in greater percentages than calcium,
but calcium is used more by weight and volume than any other nutrient.
Practically speaking, calcium is rarely considered as a nutrient
at all! Instead the focus on calcium has been more as a soil
buffer to help adjust pH. Calcium is of macro importance to both
the plant and the soil in many more ways than simply moving the
pH scale. It plays a major role in the physiology of the plant,
strengthening its physical structure and helping in protection
from disease attack. In the soil, the importance of calcium is
many fold, including the reduction of soil compaction and helping
to provide a better environment for the proliferation of beneficial
bacteria. Some research even suggests that calcium plays a role
in weed populations. The list goes on and yes, it can have
a role in the pH of the soil!
THE PLANT
Imagine the room that you're sitting in is a plant cell of your
favorite turf species. The walls that surround you are made of
calcium pectase. The more calcium that is available to that cell
Calcium plays a major role in the construction of numerous
hormone and enzyme systems that can help protect the plant from
insect and disease attack...
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the stronger those walls become. If calcium is limited the walls
are as weak as balsa wood. As more calcium becomes available,
those walls take on the strength of cinder blocks. The stronger
the cell,
the stronger the plant, and the quicker its recovery
from the enormous pressures that it's faced with on the golf course.
This works for both leaves and roots. The stronger the root
cells are the more aggressive the roots will be moving through
the soil. Proper levels of calcium within the plant strengthens
the whole plant and allows for efficient use of sunlight, carbon
dioxide, water, nitrogen and mineral nutrients.
Calcium also plays a major role in the construction of numerous
hormone and enzyme systems that can help protect the plant from
insect and disease attack. It has been reported that as a pathogen
probes its way into a cell it injects an enzyme to help break
that cell down. There is research that suggests that as this
occurs proper levels of calcium within the cell can actually slow
this attack down or stop it all together. The levels of calcium
within the cell are going to be dictated, to a large extent, by
the management of calcium within the soil.
THE SOIL
Calcium plays many roles in the soil, but it is the relationship
with other nutrients such as magnesium, potassium and sodium that
are most significant. To associate calcium only as a buffer of
pH in the soil is an injustice. In fact pH can be driven by numerous
minerals such as magnesium, potassium, sodium or even aluminum.
Often times calcium is applied to the soil to lower pH.
It is important to understand that an imbalance of calcium will
lead to tight, hardpan soils which will restrict the flow of air
and water through the soil profile. This will not only affect
the plant roots, but perhaps even more important, will slow down
the growth of beneficial micro-organisms.
The soil is an extremely dynamic environment consisting of numerous
chemical, biological and physical reactions. It is on all three
levels that we must manage the soil. We can change the physical
structure of a soil by properly managing the chemistry, thus providing
a stronger biological environment. It is this biology that is
so important to the success of managing any crop, turf being no
exception. For the first time in recent memory soil biology has
risen to the forefront of our industry. Pathologists are introducing
soil inoculants as biological controls for pests, advocates of
IPM are starting to look closer at soil management as an integral
part of their success and we are all beginning to understand the
need for soil carbohydrates. If we are going to make any improvement
in the health of the plant, proper soil management is imperative,
and this all starts by managing calcium levels in the soil.
MANAGING CALCIUM IN THE SOIL
Dr. William Albrecht, the former head of the soils department
The beauty of base saturation methodology is that is deals
with the relationship among the cations, not the actual poiunds
per acre of any one nutrient.
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at the University of Missouri, established the protocol for balancing
the basic cations on the soil colloid over 50 years ago. Today
that research is the backbone behind a growing interest in sustainable
soil management. Many of the predominate soil testing laboratories,
including Brookside Labs, a company that Dr. Albrecht helped to
form, uses this methodology today. His research focuses on the
soil tests' base saturation readings, where calcium plays the
largest role.
Base saturation measures the relationship between the cations
on the soil colloid. These nutrients are expressed in percentages
and will always add up to 100%. The beauty of base saturation
methodology is the fact that it deals with the relationship among
the cations, not the actual pounds per acre of any one nutrient.
On a soil with a high holding capacity, or CEC, the pounds per
acre of a nutrient is naturally going to be much higher than on
a similar soil with a lower CEC. If we manage soils to specific
levels of a nutrient, the relationship between the cations will
vary significantly depending on this holding capacity.
When evaluating the base saturation percentages of a soil the
ideal targets are:
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68% calcium
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12% magnesium
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5% potassium
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2% sodium
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3% trace nutrients
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10% hydrogen
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With an ideal range of calcium in the high 60 percentile it becomes
very clear to see why calcium is so important. Using these percentages
as a standard, the manipulation of these nutrients becomes manageable.
If one nutrient is high it can be exchanged off the soil colloid
by applying one of the other nutrients. For example, if magnesium
is excessive in a soil, 20% or higher, another nutrient becomes
weaker. The relationship is always 100% so it becomes a game
of "give and take." Very often the nutrient given up
will be calcium. The addition of calcium will drive out the excessive
magnesium allowing calcium to saturate the colloid. This manipulation
will work with any nutrient that is out of balance.
One of the great fallacies of conventional soil management is
that we too often manage exclusively to soil pH. The acidity
of a soil is dictated by the percentage of hydrogen on the soil
colloid. On the above example, base saturation of hydrogen is
10%. On this test, with 10% hydrogen the pH will always be 6.3.
As the percentage of hydrogen increases the pH drops and as it
increases it rises. If we effectively manipulate the relationship
of the base saturation, we can always manage the soil to 10% hydrogen
and end up with a pH in the range where we have the greatest potential
nutrient mobility (6.0 - 6.5).
When imbalances among the cations exist the soil becomes very
tight and air and water can not penetrate. When this occurs roots
are not the only thing that suffers, but beneficial bacteria suffers
as well. Since the relationship between calcium to magnesium
makes up 80% of the soil colloid it is this relationship that
is most important. As calcium drops below 60% and magnesium creeps
above 20%, the soil becomes very tight. These are looked at as
heavy, unmanageable soils, and excessive mechanical aeration appears
Soils that once went to battle with a GA60 aerator now see
that machine walk across the fairways with ease!
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to be the only help. Unfortunately, this does not address the
real problem and until the Ca:Mg ratio is addressed that soil
will remain tight.
We have seen soils all over the country "open up" through
the use of appropriate liming materials and the balance of base
saturation. Soils that once went to battle with a GA60 aerator
now see that machine walk across the fairways with great ease!
Because air and water movement improves so does biological activity.
This helps to suppress disease problems, reduces isolated dry
spots and allows for the reduction of nitrogen usage. Earth worms
that were once not present are now actually becoming a management
problem, one that is agronomically the best "problem"
to have.
TYPES OF CALCIUM
There are a number of good ways to supply calcium to a soil but
when calcium levels are below 60% base saturation, limestone is
the most appropriate. Not all limestone is created equally!
There are two basic forms of lime, high calcium lime, or calcitic
lime, and high magnesium lime or dolomitic lime. Depending on
the source, calcium levels can vary from around 30% to 45%, but
the real difference is that percentage of magnesium. High calcium
lime will have a magnesium oxide reading of about 5% while dolomitic
lime will read closer to 20%. This difference in magnesium is
significant since it will drive pH up faster than calcium and
will quickly create a tight soil. In soils with excessive magnesium
levels dolomitic lime would not be appropriate, and in fact can
create even worse imbalances in the soil. In this situation high
calcium lime will actually allow for the exchange of magnesium
for calcium and can often actually lower soil pH by better balancing
the base saturation, and allowing for better hydrogen saturation.
In many situations both high calcium and dolomitic lime would
be called for to best balance this critical Ca:Mg ratio. The
specifics of these recommendations are often best left to a qualified
consultant, but in general terms, if the soil shows a high percentage
of magnesium and calcium levels are below 60%, high calcium lime
is the lime of choice.
Gypsum is calcium sulphate and is typically around 23% calcium
and 18% sulfur. It has this magical reputation of reducing soil
compaction, which it will do in many situations, but is often
misused. Gypsum is not very effective in a soil that shows less
than 60% base saturation calcium. A soil with a significant calcium
deficiency often needs large quantities of calcium to saturate
the soil colloid. If this is applied as gypsum, too much sulfur
is being applied and problems can occur. It is important to use
the appropriate type of lime on calcium poor soils. Once the
calcium base saturation is above 60% gypsum becomes the calcium
of choice. Here it will help to knock excessive magnesium (or
any other excess) off the soil colloid through a reaction with
sulfur and the exchange with calcium. Since it is sulfur rich
it will typically not raise the pH.
Calcium is an extremely immobile nutrient. This is supported
by the water soluble LaMotte soil tests and tissue testing. Even
in the calcium rich soil with strong biological activity calcium
does not mobilize well. In heavily managed soils with high compaction,
such as a golf course green, calcium mobility is very weak. If
it is appropriate to use gypsum, mobility can be improved slightly
but in order to get the calcium to the plant, foliar applications
are best applied. Foliar calcium is perhaps the greatest vogue
in the industry today, and it's about time! It is imperative
we balance the calcium in the soil so we can provide the environment
that microbial populations need to proliferate, but it is also
very important we provide the plant cell with calcium. Since
the large majority of golf course soils do not provide enough
Since the large majority of golf course soils do not
provide enough mobile calcium, foliar feeds are important.
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mobile calcium, foliar feeds are important. This is very true
on all the greens and tees but often can be justified in the fairways
as well.
There are no great secrets with calcium. The two most popular
forms of foliar calcium are calcium nitrate (8% Ca) and calcium
chloride (12% Ca). There are many forms of chelated calcium
products available and they do provide an added value by stabilizing
the calcium, and making it more available to the plant. The chelates
are more expensive but can be worth the cost. Another way to
make calcium available is to use ammonium sulphate. This will
actually knock calcium off the soil colloid, putting it into solution
and making it more available. This is how it can lower the soil
pH, which is getting a lot of attention for disease suppression.
Is it possible that this available calcium may play a role in
this disease suppression?
THE CONCLUSION
Calcium perhaps plays more roles in the overall health of both
the plant and the soil than another nutrient. If well balanced
on the soil colloid it will help to physically open up the soil
for better air and water movement. This in turn provides the
needed environment for beneficial bacteria creating checks and
balances for pathogens. Within the cell it provides turgidity
and is needed for numerous physiological reactions. It helps
in root and leaf development and makes phosphorous and micro-nutrients
more available. If well balanced the proper levels of calcium
are going to help reduce the need for nitrogen by making nitrification
more efficient. As Dr. Albrecht explains it in his volumes of
research, if we get the calcium right in the soil most of our
work is done.
Joel Simmons is a former County Extension Agent and the owner
of Earth Works Natural Organic Products. He is currently teaching
Soil Fertility at the Rutgers Turf Management Program. Joel can
be reached at 800 732-TURF or at eworks@soilfirst.com.
This article was first published in TurfNet Monthly, December 1997
