| Know your nutrients - I
Today there are many different plant nutrients available in the Hydroponics market. Their function is to provide the optimum mix of Potassium, Calcium, Nitrogen, Phosphorous and various other trace elements, in order to improve yields, sustain growth and allow the plant to achieve its potential. Concentrations and plant food components may vary with differing growing mediums. The plants requirements will vary to some extent as it develops.
The most important thing to remember about plant nutrition is that the NPK, (Nitrogen, Phosphorous, Potassium) Calcium and trace element ratios are correct. There can be a wide variation of ingredients in the various mixes for sale.
Since the plant will take whatever it requires from the elements available and leave the rest, the unused elements build up in the solution. If left unchecked results in a toxic build up of salts and a subsequent drop off in growth followed eventually by the death of your, well loved and nurtured, plants. This similar result will occur if the water is not replaced and the strength of the mixture increases. The concentration of elements within the solution will become dangerously high, if the plant transpires 50% of the water from the supply tank.
Electrical Conductivity (EC) meter is used to measure the concentration of nutrient’s salts in the feeding solution in parts per million as units of measurement. This means that in a 1000 PPM solution there are 1,000 units of dissolved salts to every 1,000,000 units of water. The meter measures the total nutrient salt concentration in solution. It cannot tell the difference between a good and a bad mix, only their relative strengths.
The EC meter works by measuring the speed at which electrons travel between probes immersed in a solution. In distilled water, the electrons cannot find any impurities to use as footholds to cross the water and so the meter returns a 0 reading in mMho or mS (these are units used to measure electrical conductivity). The meter reading rises, as food is added to the water, the concentration of impurities in the form of salts increases and the electrons can find more footholds, and so cross the water faster. One important thing to remember is that as in all things chemical temperature plays an important part. The lower the temperature, the slower the electrons move and the lower the EC reading and vice versa. This means that that in order to accurately assess your mixture’s EC you must record the PPM as mMho (mS) at a specific temperature.
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