The dissolved solids in water can cause problems in your garden. Pure water is often not available for hydroponic growers. Usual salt imbalances can be kept in check with a PH correction program. But there’s a limit.
Already existing salts and other solids can combine with elements in the nutrient solution and create havoc in your garden. Water containing more than 50 parts per million (ppm) of calcium and magnesium can create serious problems. Other common elements that may be present in hard water include various carbonates, sulphur, sodium, iron and boron.
You must make a thorough scientific analysis of the water you will be using and if the results are not very good install a reverse osmosis filter system, de-ionisation system or use pure water without any added minerals.
It is critical that the nutrient solution not exceed the plant's tolerance for dissolved salts. That tolerance can vary for every crop. Unless you know the specific tolerance of a given crop, it is best to use a nutrient between 800 and 1,200 ppm. When in doubt, remember – Less is More.
Not all salts give equal ‘conductivity’ and may be misread as ‘weak’ or ‘strong’ though they may not be so. Be aware that a nutrient may be stronger than what it appears to be. Always pay attention to manufacturer’s recommendations for mixing nutrients and measure the resultant ppm (though the actual ppm may vary due to nature of the salt).
Weather has an impact on the intake of nutrients and transpiration of water by plants. In hot, dry regions the ppm may rise and the opposite holds true in cool, humid environments. At the same time, a fast growing crop can take in a huge quantity of nutrients. In such case, if your reservoir is small, you’d better change the solution frequently to avoid slow, spindly growth and plants that look sick. Some plants that are light feeders will intake nutrients slowly.
Different types of plants have differing nutrient needs. All plants may need similar nutrients. But the ratios in which they are required can differ greatly for various plants. The growth stage of the plant impacts its nutrient requirement greatly. During rapid vegetative growth and structure building, a plant needs a lot more nitrogen. But when it is flowering or developing fruits, requirements of phosphorous and magnesium may peak. That’s what gives hydroponic growers an edge over soil growers –ability to manipulate nutrient concentrations for enhanced growth.
Nutrient formulations that have the same NPK combination throughout the plant’s growth cycle do not do justice to your plant’s needs. Some nutrient formulas may be developed for a particular plant only eg: tomato, orchid, etc. It is best to use a multi-stage nutrient that allows you to adjust the total ppm and NPK ratios according to the requirement of the plant to gain full advantage and maximum profits from your hydroponic garden.