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For normal plant growth hydroponics nutrient solutions are in the range 0.5
to 4.5 mS/cm2. Wilting, leaf scorch, bolting and other abnormalities will be
experienced when conductivity levels are outside their prefered range.
Because most of the materials in water used in hydroponics are
salts the mineral content of a nutrient solution is sometimes
referred to as the Total Dissolved Solids ( TDS) in the nutrient
solution. The convention in hydroponics is to use either E.C.
as the units to measure the strength of a nutrient solution. See
Know your meter
Plants tend to fall into three groups requiring a high, medium
and low conductivity.
Leafy greens, lettuce, beans and most herbs require a low conductivity .7 to 1.5 ms/cm in winter and 1.5 to 1.8 in summer.
Cucumbers, melons, many ornamentals and some cabbage-relatedcrops like medium conductivity 1.6-1.8 mS/cm in summer and 1.8-2.2 mS/cm in winter.
Tomatoes, peppers and eggplants prefer a stronger cF 2.5 - 3.6 mS/cm in summer and 3.6 to 5.0 mS/cm in winter.
For more detailed information on optimum conductivity levels for different plants read Hydroponic Gardening by Steven Carruthers pages 12 & 13 ( ISBN 0 85091 557 0 )
Prepared by Trevor Croll,
42 Pearse Street, Keperra, Queensland Australia, 4054.
Phone 61 7 3855 1115