Electrical
conductivity is a measure of the nutrient solution’s concentration through its
ability to conduct electricity. Pure water does not conduct electricity, but
any water having solutes (elements) added to it has the capacity to conduct
electricity. The EC of a nutrient solution can significantly affect plant
growth. . Electrical conductivity (EC) is frequently used as a means of
determining elemental replenishment needs in closed recirculating nutrient
solution growing systems.
An EC measurement of the nutrient solution is
used to determine nutrient element top up levels. Note that the EC value
indicates the total strength of the solution but nothing about the balance of
nutrients within it, so, its use in the management of hydroponic solutions is
limited.
The raw water used for the hydroponic solution
may itself contain dissolved nutrients which will contribute to the strength of
the solution. A water quality test will ascertain which nutrients are present
and their concentrations, and should be taken into account when making up the
hydroponic solution
Units of
measurement
decisiemens per meter (dS/m)
millisiemens per centimeter (mS/cm)
microsiemens per centimeter (μS/cm)
(1 dS/m = 1 mS/cm = 1000 μS/cm = 1 mmho/cm)
(1 μS/cm = 0.001 dS/m)
EC (in dS/m) x 640 = TDS [in mg/L (ppm)]
(approximate measurement, depends on type of
salt)
cf.
(conductivity factor) of 10 = 1 dS/m
Electrical conductivity adjustment of the
nutrient solution is recommended when the plants are to be stressed, as water
uptake by the plant is reduced when the EC of the nutrient solution and/or
rooting
Medium is
increased. Change in the electrical conductivity (EC) of a solution surrounding
the root, or may alter the pH of the surrounding solution.
High EC in
the rooting medium can result in plant wilting on high atmospheric demand days
because insufficient water is being taken up through the plant roots to keep
the plant turgid.
The target
EC of a nutrient solution can vary according to the crop being grown, stage of
growth and climatic conditions. Most nutrient solution formulas have a fairly
low [<3.0 dS/m (mmhos/cm)] EC when initially made.
In hot,
low-humidity days, if the water loss is not replaced, the EC of the nutrient
solution will rise. The EC of the nutrient solution, and particularly
that of the solution in the medium, becomes critical when it exceeds 4.0 dS/m.
In an NFT
system most leafy greens such as Basil, Choy Sum, Tat Soi, and Coriander Pak
Choy grew best in the nutrient solution managed in an EC range of 1.5-2.5 dS/m.
0 comments:
Post a Comment