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WHY
ARE TESTS SO IMPORTANT?
Modern growing
practices include scientific evaluations of soil, water, fertilizers, diseases,
etc. While some tests are best performed by a laboratory, others can be easily
conducted on location, saving time and money. Three tests in particular, EC, pH,
and ALKALINITY, can reveal valuable information about water quality, soil
salinity, and fertilizer concentration. MyronL
Company’s portable
AGRI-METERS™
provide you with a simple, fast, and accurate means of testing these parameters.
WHAT IS
ELECTRICAL CONDUCTIVITY (EC)?
EC is the
measurement of a solution’s ability to conduct an electrical current. For
horticultural applications, the unit of measure is often expressed as millimhos.
Absolutely pure water is actually a poor electrical conductor. It is the
substances (or electrolytes) dissolved in the water which determine how
conductive the solution will be.
Therefore, EC can be an excellent indicator of:
1.
Water quality
2. Soil salinity
3. Fertilizer concentration
EC AND WATER
QUALITY
The quality of
irrigation water is one of the most critical factors influencing your growing
operation. It is important to have a complete water analysis performed on a
regular basis. Environmental conditions such as drought, changing seasons, heavy
rainfall, etc., can cause the concentrations of dissolved salts in your water to
vary significantly. These dissolved salts (i.e. calcium, sodium, etc.) can
directly affect your plants’ health and, over time, render even the best soil
useless.
You can monitor
your overall water quality by testing its electrical conductivity with a MyronL
AGRI-METER™. The higher the EC, the more salts are dissolved in your water. By
comparing your EC with previous readings, you can tell if any dramatic changes
have occurred. Nutrient deficiencies are possible when water is too pure (low
EC) or if the relative concentrations of some nutrients are unbalanced (i.e.
calcium/magnesium). On the other hand, nutrient toxicities or osmotic
interferences can also be traced to water quality. Water EC of even one millimho
or below can cause problems. High EC readings of more than two millimhos can
suggest serious problems, and special cultural procedures may be required.
EC AND SOIL
SALINITY
“Water, water,
everywhere, but not a drop to drink” is an old saying that applies to your
plants when the soil salinity becomes too high. Salts from irrigation water and
fertilizers tend to accumulate in your soil or growing media. High soil salinity
disrupts the normal osmotic balance in plant roots. In severe cases a plant will
become dehydrated even when the soil is wet. Symptoms of high soil salinity
include: leaf chlorosis and necrosis, leaf drop, root death, nutrient deficiency
symptoms, and wilting. All too often these symptoms are not recognized as being
caused by soluble salts in the growing media. Sampling your soil and testing the
EC of an extract can reveal important information about a soil’s suitability and
your crop’s health.
Samples should be representative of different depths and locations.
An easy-to-perform extract method is available with the MyronL
Soil Test Kit. A 2:1 or 5:1 water-to-soil ratio is made using the
small vials provided. Soil test labs often use a method that calls
for testing the EC of an extract from a thicker slurry. Therefore,
you may see higher soil EC readings from a lab. It is important to
standardize your sampling, extract, and testing methods. This will
keep the difference between lab and field testing to a predictable
factor.
EC AND
FERTILIZER CONCENTRATION
You know how
important fertilizer is to your plants, but do you know how accurate your
fertilizer dosage is? Relying on traditional proportional methods is risky to
plants and can waste expensive fertilizer. Improperly mixed fertilizer or a
malfunctioning injector can lead to less than optimal results or even a
disastrous loss of crops. Many fertilizer companies now recommend using a simple
EC test to verify correct fertilizer concentrations. Many growers check their
fertilizer injectors on a weekly basis, or they use a continuous EC monitor.
Fertilizer
companies and suppliers often can provide a chart relating EC to parts per
million concentrations of their various fertilizers. If one is not available for
the fertilizer you use, carefully make some stock solutions at commonly used
strengths and test their EC. This will give you a data base for future
reference.
To
test the EC of fertilizer solutions:
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Test and
record the EC of the water to be mixed with the fertilizer.
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Test the
conductivity of the fertilizer and water mixture.
-
Subtract
the water conductivity determined in #1 above.
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The
resulting figure is an accurate indication of how much fertilizer is
present (a higher conductivity means more fertilizer).
Important note:
Interpretation of results differs from formula to formula and even among
manufacturers of the same formula. Obtain the proper EC charts from the
fertilizer company.
Myron L Company
manufactures both portable and inline instrumentation to make your fertilizer
monitoring easy. Myron L
AGRI-METERS™, AG-5 and AG6/PH, TH1, waterproof
TECHPRO
II™
models TP1, TPH1 and TH1, and waterproof
ULTRAMETER
II™ models 4P
and 6P are handheld instruments which make fertilizer testing as simple as
filling a cup and pushing a button.
The Myron L 750
Series
II™ EC
Monitor/controllers can be used to continuously monitor your fertilizer
concentration. Their “alarm” relay circuit acts as a safeguard in a fertilizer
injection system or even as the main controller for your injector. A 0-10 VDC
output for chart recorders or PLC (SCADA) input is standard on all
monitor/controller models.
IMPORTANCE OF
pH
pH, the measure of
acidity or basicity, should be included in any soil or water test. It is well
documented that growing media pH is critical to successful plant growth. This is
especially true for new soilless mixes and hydroponics. pH affects the roots’
ability to absorb many plant nutrients. Examples include iron and manganese,
which are insoluble at high pHs and toxic at low pHs. pH also directly affects
the health of necessary micro-organisms in soil.
The
effectiveness of pesticides and growth regulators can be severely
limited by spray water pH that is either too low or too high.
ALKALINITY
It is important to
note that testing the pH of irrigation water reveals only part of the story.
Testing water alkalinity (bicarbonates and carbonates) is much more important
than generally recognized. Alkalinity dictates how much influence the water’s pH
will have on your soil and nutrient availability. In addition, alkalinity has a
very great effect on the ease or difficulty of reducing the pH of water.
For
additional information, please refer to Myron L data sheets, or
Contact us by phone, fax, or email sales@myronl.com.
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