WHY TESTS ARE 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
Three tests in particular, CONDUCTIVITY, pH, and ALKALINITY, can
reveal valuable information about water quality, soil salinity, and
fertilizer concentration. Myron L® Company's portable AGRI-METERS provide
you with a simple, fast, and accurate means of testing these parameters.
WHAT IS CONDUCTIVITY?
Conductivity 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 salts) dissolved in the
water which determine how
conductive the solution will be.
Therefore, conductivity can be an
excellent indicator of:
1. Water quality 2. Soil salinity 3. Fertilizer concentration
CONDUCTIVITY 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 Myron L® AGRI-METER. The higher the conductivity, the
more salts are dissolved in your water. By comparing your conductivity
with previous readings, you can tell if any dramatic changes have
occurred. Nutrient deficiencies are possible when water is too pure (low
conductivity) 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 conductivities of even one millimho or below can cause problems.
High conductivity readings of more than two millimhos can suggest serious
problems, and special cultural procedures may be required.
CONDUCTIVITY 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 conductivity 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 Myron L® 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 which calls for testing the
conductivity of an extract from a thicker slurry. Therefore, you may see
higher soil conductivity 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.
CONDUCTIVITY AND FERTILIZER
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 conductivity test to verify correct fertilizer
concentrations. Many growers check
their fertilizer injectors on a weekly basis, or they use a continuous
conductivity monitor. Fertilizer
companies and suppliers often can provide a chart relating conductivity 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
conductivity. This will give
you a data base for future reference.
To test the conductivity of fertilizer solutions:
1.Test and record the conductivity of the water to be mixed with the
2.Test the conductivity of the fertilizer and water mixture.
3.Subtract the water conductivity determined in #1 above.
4.The resulting figure is an accurate indication of how much fertilizer is
(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 conductivity charts from the fertilizer
Myron L® Company manufactures both portable and in-line instrumentation to
make your fertilizer monitoring easy. Myron L® AGRI-METERS, AG-5 and
AG6/pH, TechPro™ models pH1, AR1, ARH1 and waterproof ULTRAMETER™ models
3P, 4P and 6P are hand-held instruments which make fertilizer testing as
simple as filling a cup and pushing a button. The new Myron L® 750 Series
II Conductivity 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 soil less 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
which is either too low or too high.
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.
AG-5, AG6/pH, 4P, 6P, AR1, ARH1
AG6/pH, 3P, 6P, pH1, ARH1
Soil Test Kit
757II or 758II
722II or 723II
(requires soil test kit):
AG6/pH, 4P, 6P, pH1, ARH1
AG6/pH, 3P, 6P, pH1, ARH1
AG6/pH, 4P, 6P, AR1, ARH1
AG6/pH, 4P, 6P, AR1, ARH1
AG6/pH, 4P, 6P , AR1, ARH1
Water (for cut flowers, etc.):
EP, 4P, 6P
532T1, 532T2, 4P, 6P, AR1, ARH1
757II or 758I