Salinity & Salinity Meters

Plants need water for growth and healthy development. If plants are deprived of the required amounts of water, over a period they will whither and die. Unlike plants grown in soil, plants grown hydroponically in grow rooms and indoor greenhouses, are completely dependent on supplied water to meet their nutritional needs. It is therefore important that growers gain a basic understanding of certain vital aspects concerning water supply and plant nutrition.

Water is an excellent solvent and whether it is drawn from a tap, a lake, river or other natural sources, contains dissolved impurities along with mineral salts. The salts commonly found in water include common salt (sodium chloride), calcium chloride and carbonates. Plant growth is not adversely affected as long as salinity levels (levels of dissolved salts) are not excessive, but beyond certain threshold limits it can cause extensive tissue damage.

Chemicals used in standard hydroponic nutrient solutions contain only minor quantities of common salt (sodium chloride) which does not normally constitute a problem. Usually, it is the amount of dissolved salts in the water used for making nutrient solutions and the water added to replace the water transpired by plants that can be potentially damaging to plant tissue. Unless this water is purified to remove the salts it can lead to high concentration in the nutrient solution which can cause damage. The dissolved salts are present as anions and cations, which are negatively and positively charged atoms or groups of atoms. These always exist in pairs as so that the net electric charge is zero. Salinity can be defined as the total amount of soluble salts in the nutrient solution, which is a measure of its conductivity. It can also be defined specifically with reference to the level of sodium chloride in the solution.

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