To lime or not to lime

[nameless]

ha. the great lime debate. im still sorting this out myself and dont really have any valuable knowledge for the subject, just wanted to say thanks for weighing in on this everyone. tact good to see you around. im going to start cutting my lime back in my peat based water only mix and see if that changes things. too bad i mixed a double batch last time. let that be a lesson to all you soil amenders. if your mix isnt perfect for you, best not to mix up double batches right?

 

[mad librettist]

Why don't you start your own thread on this, instead of saying the same things over and over and over on this thread?

I was answering a question. It's more than just you and me on here, you know.

 

[grapeman]

I understand the dilemma to use DL in soil. I wouldn't. But using DL in a peat based mix is a no brainer and easier then shit.

 

[Scrappy4]

I understand the dilemma to use DL in soil. I wouldn't. But using DL in a peat based mix is a no brainer and easier then shit.

I agree, kind of. It seems to depend on if it is straight Unlimed peat or pro mix type peat that has some type and amount of lime added.

Then there is either peat or pro mix types that we typically mix with ewc of varying amounts, and Unknown qualities.

Add some type of amendments to the mix.

Add water of unknown quality, and soon it gets complicated.

I guess what I'm trying to convey is there is no one size fits all with lime.....scrappy

 

[apep]

Hi scrappy. Maybe this will help? Either way its a good read.

Water quality is a key factor affecting pH and
nutritional management in any container-grown crops,
including orchids. One challenge is that the water
quality in your operation can differ dramatically from
that of your neighbor, and certainly from greenhouses in
other locations both inside and outside the U.S. For
example, the range of water qualities used by
commercial greenhouses in the U.S. can be found in
Table 1. For those of you using rain water or reverse
osmosis purified water exclusively, the pH will range
from 4.0 to 5.5 (if measured correctly), the alkalinity
will be less than 10 ppm, and the concentration of other
ions will be very low to nonexistent.
Understanding a few technical details about
water quality will help you improve nutrient
management appropriate for your own greenhouse.
Always remember that the success or failure of any
fertilizer will always depend on the water quality
because it is the combination of the two that affect your
plants. In Part 2 of this series, we will discuss how
water quality affects pH and nutritional management of
the substrate.
pH and Alkalinity are two different aspects of
water quality
There is a great deal of confusion when it
comes to understanding the definition of water pH and
water alkalinity, and why they are important to the
health of your plants.
The term pH is a direct measurement of the
balance between acidic hydrogen ions (H+) and basic
hydroxide ions (OH-), and can be measured with a pH
meter. The pH of a solution can range between 0 (very
acidic) and 14 (very basic). At a pH of 7.0, the
concentrations of H+ and OH- are equal, and the
solution is said to be neutral. When the pH is above
7.0, the concentration of OH- is higher than H+, and the
solution is said to be basic or alkaline (not to be
confused with alkalinity). When the solution is below
7.0, the concentration of H+ is higher than OH-, and the
solution is said to be acidic.
Alkalinity is a measure of how much acid it
takes to lower the pH below a certain level, also called
acid-buffering capacity. Alkalinity is usually measured
with a test kit where dilute acid is added until a color
change occurs at a specific pH. Alkalinity is not a
specific ion, but rather includes the concentration of
several ions that affect acid-buffering capacity. Under
most conditions, the ions that have the greatest effect on
alkalinity are bicarbonates like calcium, magnesium, or
sodium bicarbonate and, to a lesser extent, carbonates
like calcium or sodium. Several other ions including
hydroxides, phosphates, ammonium, silicates, sulfides,
borates, and arsenate also can contribute to alkalinity,
but their concentration is usually so low that they can be
ignored.
In a water sample, the concentration of all of
the ions that makes up the alkalinity term are combined
Table 1. Average and median values for irrigation water pH, EC, and nutrient concentration used by
commercial greenhouses in the United States. Research by Bill Argo, John Biernbaum, and Darryl Warncke.
(For more information, See HortTechnology 7(1):49-51).
Units Average Median Range
pH 7.0 7.1 2.7 to 11.3
EC (mS/cm) 0.6 0.4 0.01 to 9.8
Alkalinity (ppm) 160 130 0 to 1120
Calcium (Ca) (ppm) 52 40 0 to 560
Magnesium (Mg) (ppm) 19 11 0 to 190
Sulfur (S) (ppm) 27 8 0 to 750
Sodium (Na) (ppm) 33 13 0 to 2500
Chloride (Cl) (ppm) 33 14 0 to 1480
Boron (B) (ppm) 0.2 0.02 0 to 11.7
Floride (F) (ppm) 0.1 <0.01 0 to 8.3
Ca:Mg Ratio 5.0 3.2 <0.1 to 150
SAR1 2.6 0.7 0 to 280
1 Sodium-adsorption ratio is a formula that compares the concentration of sodium to the combined concentration of calcium and magnesium.
Not for publication or reproduction without the authors consent. Pg. 2
and reported as equivalents of calcium carbonate
(CaCO3, which is the main component of lime).
Alkalinity can therefore be thought of as the “liming
content” of the water. The units used to report
alkalinity can be parts per million (ppm), mg/liter, or
millequivalents (meq.).
Water alkalinity has a big effect on substratepH.
When it comes to managing the pH of a
substrate, the alkalinity concentration has a much
greater effect than does water pH. Alkalinity (calcium
bicarbonate, magnesium bicarbonate, and sodium
bicarbonate) and limestone (calcium and magnesium
carbonate) react very similarly when added to a
substrate. And just like too much limestone, the use of
irrigation water containing high levels of alkalinity can
cause the pH of the substrate to increase above
acceptable levels for healthy plant growth.
For example, a limestone incorporation rate of
5 pounds per cubic yard will supply approximately 100
meq of limestone per 6 inch (15-cm) pot. Applying 16
fluid ounces (0.5 liters) of water containing 250 ppm
alkalinity to that 6 inch pot will supply about 2.5 meq of
lime. That does not sound like much until you consider
that after 10 irrigations you have effectively increased
the limestone incorporation rate by 25%. Even if you
are using a completely inert substrate, the liming effect
that high alkalinity water has will cause your substrate
pH to increase to unacceptable levels.
To compare the effect of water pH or alkalinity
on the ability to raise pH (or neutralize acid) in a
medium, 50 ppm alkalinity (which is a low alkalinity)
would be similar to having a water with pH 11 (i.e. an
extremely high pH). A water with a pH of 8.0 would
have the same effect on substrate pH as an alkalinity
concentration of only 0.05 ppm (i.e., almost nothing).
Don’t ignore water pH.
Water pH is still important for crop
management. Even though it has little impact on the
substrate, water-pH does affect the solubility of
fertilizers, and the efficacy of insecticides and
fungicides before you apply it to the crop. Generally,
the higher the water pH, the lower the solubility of these
materials.
Minimizing the effects of high alkalinity
The common problems associated with high
alkalinity result from its tendency to increase substratepH.
High substrate-pH can causes micronutrient
deficiency in container grown crops because
micronutrient solubility decrease as the substrate pH
increases.
In commercial greenhouses, the most common
method for minimizing the “liming effect” of high
alkalinity is to add a strong mineral acid (usually
sulfuric acid or phosphoric acid) directly to the
irrigation water. As the pH of the water decreases,
some of the alkalinity is neutralized. The ideal
alkalinity concentration will depend on the type of
fertilizer being used (to be covered in Part 3). All of the
alkalinity has been neutralized when the pH of the water
reaches 4.5. For more information on injecting strong
mineral acids into irrigation water, you can download
the “acid addition calculator” from Purdue University
and North Carolina State University at
www.ces.ncsu.edu/depts/hort/floriculture/software/alk.h
tml.
For small greenhouse operations and hobbyists,
strong mineral acids are very difficult and dangerous to
use. Difficult because these acids are highly
concentrated and therefore are difficult to add to a small
volume of water, and dangerous because small
greenhouses and hobbyists typically lack the specialize
equipment needed to safely add acid to water. Some
acids should never be considered, like anhydrous
hydrochloric acid or anhydrous acetic acid because they
not only are caustic, but are also fuming acids, which
make them extremely dangerous to handle. Nitric acid
is especially dangerous and should never be considered.
There are alternatives to adding mineral acids
for alkalinity control. The first is using a weaker,
organic acid, like citric acid. Citric acid is available in a
Units of measure for alkainity
The concentration of alkalinity (or any other plant
nutrient) can be expressed a number of different ways.
1) Parts per million (ppm or mg/liter). The term ppm is a
weight per weight ratio. One part per million is
equivalent to 1 unit of something dissolved in a
million units of something else. In the case of
anything dissolved in water, 1 ppm is equal to 1 mg
per 1,000,000 mg (or 1 Kg = 1 liter) of water. So, 1
ppm is equal to 1 mg/liter. A 1% solution (1 unit in
100 units) is equivalent to 10,000 ppm.
2) Milliequivalent (mEq./liter). The term mEq./liter is a
chemistry term that is not only dependent on a
materials concentration, but also on its molecular
weight and charge. In the case of alkalinity, 50 ppm
(or mg/liter) CaCO3 equals 1 meq/liter CaCO3.
Sometimes the concentration of bicarbonates is also
reported on a water test from a commercial laboratory.
In most cases, bicarbonate makes up most of the
alkalinity. The relationship is 61 ppm bicarbonate
equals 1 meq alkalinity.
3) Grains per gallon (gpg): An outdated term for
expressing concentration. 1 gpg = 17.1 ppm
Not for publication or reproduction without the authors consent. Pg. 3
pure granular form. A rate would be about 0.2 grams
per gallon to remove 50 ppm alkalinity. Pre-mixed
citric acid solutions (Seplex, GreenCare Fertilizer (815-
936-0096)) are also available for alkalinity control.
Other organic acids like vinegar and lemon juice will
also work, but because the concentration of acid in
these materials is variable, for example, the acetic acid
content in vinegar can range from 4% to 8% by weight,
that the results that you get will not be consistent.
Another option for alkalinity control is to use
acidic fertilizers (to be covered in greater depth in Part
3). Fertilizers high in ammoniacal nitrogen produce an
acidic reaction when added to the substrate, which can
be used to neutralize the affect of water alkalinity. For
example, 20-20-20 (69% NH4-N) has enough acidity to
be used with water containing around 200 ppm
alkalinity water without further acidification.
There are several drawbacks to using fertilizer
for alkalinity control. Fertilizers high in ammoniacal
nitrogen may cause excessive growth and are not
effective when the temperature of the substrate is less
than 60oF. In addition, you lose flexibility because you
can only choose commercial fertilizers based on
ammonium content. For example, high ammonium
fertilizers available to you may lack calcium or other
key nutrients.
Another option for alkalinity control is to
change water sources. There are a number of sources,
such as rain water or reverse osmosis purified water,
that contain little if any alkalinity. Drawbacks to using
alternative water sources include cost and storage
problems. Changing water sources will also change the
composition of the fertilizer solution applied to the
crop.
Low alkalinity Effects
Not everybody in the world has irrigation water
with high alkalinity. In the United States alone, there
are a large number of growers in states like AL, AR,
CA, CO, GA, HI, NC, NJ, NY, VA, and New England
states that have alkalinity levels below 40 ppm without
any acidification. Even in areas were high alkalinity is
considered the norm, some growers have switched to
low alkalinity sources such as reverse osmosis purified
water or rain water.
The primary problem associated with low
alkalinity water is a tendency for substrate-pH to drop
over time, which can cause micronutrient toxicity
problems. Usually, low pH problems are a result of
fertilizer selection. Fertilizers high in ammoniacal
nitrogen are acidic, and without any alkalinity in the
water to balance the reaction (resist lowering of pH),
acidic fertilizers will tend to drive the substrate-pH
down over time.
What about Hardness?
Hardness is a measure of a water’s ability to
form scale in pipes, produce suds from soap, or to leave
spots on leaves. Like alkalinity, the units used to report
hardness are calcium carbonate equivalents (CaCO3).
However, while alkalinity is a measure of all chemical
bases in the water (bicarbonates and carbonates),
hardness is really a measure of the combined
concentration of calcium and magnesium in the water
because it is insoluble salts of ions, like calcium
carbonate, that form scale. Another difference is that
while alkalinity is an important measure in pH and
nutritional management, hardness is not, because its
combined concentration tells you little about a waters
ability to supply nutrients to a plant.
A water softener is typically used to remove
hardness. What is occurring with hardness removal is
that the calcium and magnesium ions are being replaced
with an ion that doesn’t cause scale, like sodium or
potassium. However, with hardness removal, the
carbonates and bicarbonates still remain in the water but
they have been changed from calcium and magnesium
bicarbonate to sodium or potassium bicarbonate. Thus,
hardness removal has no effect on pH management. In
comparison, with alkalinity control, an acid is used to
neutralize the carbonates or bicarbonates, which will
affect pH management, but the calcium and magnesium
concentration remains unchanged.
What else is important in my water?
Electrical conductivity (EC, also know as
conductivity or soluble salts) is a term used to measure
the total concentration of salts in the water. The higher
the EC, the more salts that are dissolved in the water.
With irrigation water, EC is used to determine the
potential risk for salt buildup when water is applied to a
substrate. With fertilizer solutions, EC can be directly
correlated with the concentration of individual nutrients
(typically nitrogen) from a variety of fertilizer salts, or
with the total concentration of nutrients supplied by a
water-soluble fertilizer.
Electrical conductivity or EC units have
changed over the years. Twenty years ago, the units for
measuring EC were millimhos (mmhos) or micromhos
(μmhos). Currently, the units used to measure EC are
millisiemens/cm (mS/cm), microsiemens/cm (μS/cm),
or decisiemens/m (dS/m). The conversion for all these
units are 1000 μmhos = 1000 μS/cm=1 mmhos = 1
mS/cm = 1 dS/m.
A term closely related to EC is total dissolved
solids or TDS. A TDS meter measures the EC and then
converts the measurement into ppm by multiply by a
constant, usually 1 mS/cm = 1000 ppm salts. The
problem with TDS measurement is that the constant is
Not for publication or reproduction without the authors consent. Pg. 4
based on one salt (potassium chloride) and therefore
TDS measurements do a poor job estimating the actual
concentration of fertilizer salts under most situations. It
is important to remember that TDS measurements are
used to determine the acceptability of drinking water,
not fertilizer solutions. For these reasons, commercial
greenhouses use EC measurements almost exclusively
for fertility management
Another important consideration is the
concentration of individual plant nutrients. In general,
irrigation water is not a significant source of the
primary macronutrients nitrogen (N), phosphorus (P), or
potassium (K), which are the numbers that you see on a
bag or bottle of fertilizer. However, irrigation water can
contain high levels of the nutrients calcium (Ca),
magnesium (Mg), and sulfur (S). And just like
alkalinity, the concentration of nutrients contained in
the irrigation water can vary dramatically between
different locations (Table 1).
Since irrigation water can be an important
source of calcium, magnesium, or sulfur, water can
contribute a significant amount of the total
concentration of these nutrients being applied to a crop.
In other words, the water-soluble fertilizer that you
apply (like 30-10-10) is not the only nutrient source.
However, if you are using a very pure water source, like
RO or rain water, the only source of these nutrients may
be the fertilizer.
Waste ions
Some ions contained in irrigation water are
either not needed by the plant, or the plant requirement
is so low that only small amounts are required.
Examples of waste ions are sodium (Na) or chloride
(Cl). Generally their presence in irrigation water at
high concentrations increases the risk of salt build up in
the substrate. Even calcium, magnesium, or sulfur can
be considered a waste ion if their concentration is too
high or it is difficult to balance their concentration in
the nutrient solution with water-soluble fertilizer.
With most ions (including Na, Cl, Ca, Mg, or
S), excessive concentrations can be removed with
reverse osmosis purification. High salt concentrations
can also be managed by leaching at a heavier rate than
the commonly recommended 20% to remove any excess
salt build up. However, if you do use higher leaching
rates, then you may also have to increase the fertilizer
concentration because leaching washes out all salts
from the container including essential plant nutrients.
Boron (B) is a special example of a waste ion.
Even though it is an essential plant nutrient, the
presence of boron in irrigation water at high
concentrations can cause significant challenges.
Unfortunately, the difference between deficient,
adequate, and toxic levels of boron are very small. In
general, it is recommended that the maximum
concentration of boron in water used for plants be no
more than 1.0 ppm.
Unlike most other waste ions, boron can not be
effectively removed with reverse osmosis purification.
Instead, the only option for managing excessive boron
levels is to maintain a substrate pH above 6.0 and use
calcium-based fertilizer. The idea is that the high pH
and calcium will caused excess boron to precipitate out
of the soil solution, making it unavailable to the plant.
Another option for controlling high boron in the water
is to change water sources.
High concentrations of iron (Fe) in the
irrigation don’t usually effect plant nutrition or pH
management. However, iron can cause staining
problems on plant leaves and other surfaces, and the
presence of iron in the water can lead to the presence of
iron-bacteria growing in the pipes, which can clog mist
nozzles, or anything else with small openings. Water
treatments that oxidize the water, such as treatments
with ozone or potassium permanganate, can effectively
remove iron from the water.
Fluoride (F) and chlorine (Cl2) are commonly
added to municipal water at concentrations up to 4 ppm
and can cause problems growing crops. Generally, high
levels (above 1 ppm) of fluoride and chlorine can cause
damage to the foliage (especially at the tip) and the
flowers. These materials are easily removed from the
water source by using an activated charcoal filter.
Water testing is only a starting point
Obtaining a water test is an important first step
in determining if your fertility program will work, or if
you need to reevaluate. Most water sources (with the
exception of rain water) are susceptible to change. In
commercial greenhouses, it is recommended to do a
water analysis at least once a year, either to make sure
that the water source is not changing, or if it is
changing, to make adjustments in the nutrition program.
Equally important is understanding how your
fertilizer affects pH and nutrition by itself, and through
its interaction with your water. Next issue: fertilizer.
Not for publication or reproduction without the authors consent. Pg. 5
Where to get a water test?
Obtaining a water test is an important first step in determining if your fertility program will work, or if you need to
reevaluate. The type of testing should be to determine if the water is acceptable for plants, i.e. for greenhouses and nurseries,
not suitability for drinking water (there is a difference). The test should include, water pH, EC, and the concentration (in ppm
or mEq/liter) of alkalinity (and or bicarbonates), nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron,
manganese, zinc, copper, boron, sodium, chloride, and fluoride.
There are number of testing laboratories in the U.S. that work closely with commercial greenhouse and nurseries, and
so are familiar with many of the issue discussed in this article. A number of these laboratories also have international ties.
They are:
Name Location Web site or E-mail Phone Number
A & L Southern Laboratory Pompano Beach, FL Lgriff6250@aol.com 954-972-3255
J.R. Peters Laboratory Allentown, PA www.jrpeterslab.com 800-743-4769
Micro-Macro International Athens, GA www.mmilabs.com 706-548-4557
Quality Analytical Laboratories Panama City, FL www.qal.us 850-872-9535
Soil and Plant Laboratories, Inc. Orange, CA www.soilandplantlaboratory.com 714-282-8777
The cost of a water test will range from $25 to over $100 per sample. Remember that UPS and FedEx will ship
anywhere in the US, so it pays to shop around
Many state universities still operate testing laboratories, so you can also have your water tested through the state
extension service. Fees vary from state to state, and the time required to get the test back is usually longer than with
commercial laboratories.
Drinking water companies will also perform water testing, but they are testing for the suitability for drinking, and
whether or not you need some type of water treatment. If you want to grow plants, you need better, and more precise testing
than is supplied by these companies.

 

[mad librettist]

well that was fun, but I couldn't find the section that mentioned the buffering capacity of polysaccharide slime, or the effect of digestive acids used by fungi.

both are things you won't notice by testing runoff pH.

here's a little question: considering nitrifying bacteria don't produce nitrate below 7.0, what is the point of getting organic media pH so low? If your runoff is below 7, and your soil is still making plenty of nitrate, what does that tell you? Somewhere in your container is an area with a pH of 7.0 or higher.

Of course, if you really do have the whole media below 7, you need a source of nitrate. Like say, guano.

 

[Scrappy4]

Great post apep. Lots of information to digest. I'll have to save this......scrappy

 

[Clackamas Coot]

A simpleton's question........

A simpleton's question........

Let's say that Farmer Bob wants to test his soil and limit the testing to the pH paradigm.

And let's say that Farmer Bob gathers up a cubic foot of soil and takes it into "Testing Soils & Knitting Classes" there in Dog Turd, Oklahoma. And let's say that the lab takes this soil sample and puts it into a nursery pot and the testing process will be to water the soil in the pot and catch the (in)famous "run off" for analysis.

Does anyone actually think that Farmer Bob would pay for such a test? Seriously?

Wee!

CC

 

[mad librettist]

To lime or not to lime

Let's say that Farmer Bob wants to test his soil and limit the testing to the pH paradigm.

And let's say that Farmer Bob gathers up a cubic foot of soil and takes it into "Testing Soils & Knitting Classes" there in Dog Turd, Oklahoma. And let's say that the lab takes this soil sample and puts it into a nursery pot and the testing process will be to water the soil in the pot and catch the (in)famous "run off" for analysis.

Does anyone actually think that Farmer Bob would pay for such a test? Seriously?

Wee!

CC

very well said CC.