Saturated Media Extract (SME) Measurements
Growth media used in most greenhouse operations is high in organic material and
processed materials and low in mineral soil. These materials are easier to handle, are
well aerated and have good moisture-holding properties but have limited ability to retain
nutrients. Therefore, tests developed for field soils do not always yield meaningful
results. Saturated Media Extract (SME) analysis has been shown to eliminate these
problems. The samples should not be fired, sieved, or pulverized as this will affect the
growth medium properties and alter the results. Traditionally, the soil solution from the
saturated medium is extracted by a vacuum pump. However, the Field Scout Soil &
Water EC Meter allows the saturated sample to be tested directly.
Procedure
•
Moisten the media sample with distilled water to reach a consistent “saturated”
moisture level. When saturated, the media should glisten and slide from the
mixing spatula with little or no free water.
•
Wait 15 minutes and add more water if needed. The sample should have the
consistency of a paste with slightly more water than if the media was in a pot and
fully irrigated.
•
Press On/Off button to power up the meter.
•
Insert the probe tip into the media and read the results.
Liquid Measurement/Other Functions
Water (Liquid) Measurements
The Field Scout Soil & Water EC Meter can also measure the EC of liquids. Simply dip
the electrode tip into the solution and wait for the reading to stabilize (a stable reading
occurs when the readout has not changed for 3 seconds).
Converting Meter Readings to PPM
To convert ms/cm to Parts per Million (PPM) simply take the meter reading and multiply
it by 640. Example 2.75 mc/cm X 640 = 1760 ppm
Sensor/Tip Replacement
If the probe cannot be calibrated, or if it does not hold the calibration for a
reasonable amount of time, the probe or tip must be replaced.
An “Temperature out
of Range” message on the LCD
may indicate a failed probe or
simply that the probe has come
unplugged from the meter.
I. Removing a direct-insert probe
The 8” probe do not have a
replaceable tip. The re-placement
procedure is outlined below.
1. Remove the black nut from
the strain-relief where the
cable feeds into the meter.
2. Remove the white nut on the
cable end of the meter.
