How to Use Meters for Nutrient Level Hydroponics
One of the big advantages of hydroponic gardening is the level of control you have over your plants' environment. You'll never worry about frost warnings or drought. However, you will need to monitor the health of two important things: total dissolved solids, as measured by conductivity, and pH. The conductivity of your nutrient solution tells you how many dissolved solids (the actual nutrients) are present in your water. Acidity level, or pH, affects how much of the dissolved nutrients are actually available to the plants. Does this Spark an idea?
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Things You'll Need
- pH meter
- Electrode storage or buffer solution
- pH strips or liquid test kit to verify the meter's calibration
- Phosphoric acid (to lower pH)
- Potassium hydroxide (to raise pH)
- TDS (total dissolved solids--also called conductivity) meter
- TDS calibration solution
- Concentrated nutrient or fertilizer solution
Instructions
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Measure The pH of Your Nutrient Solution
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1
Purchase a reliable pH meter. Three types are available: pH paper, liquid pH test kits and digital pH meters. pH paper is the least expensive, but is also the hardest to read accurately. Liquid test kits are easier to read but are more difficult to use than pH paper or a digital meter. Digital pH meters are the most accurate, if properly calibrated. The best solution is to use a digital pH meter and keep a liquid pH test kit handy to double-check if you suspect your digital meter needs calibration. As of late 2009, a basic digital pH meter costs around $20.
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2
If you haven't done so recently, calibrate your digital pH meter according to the manufacturer's instructions.
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3
Dip the electrode of the pH meter in the nutrient solution and record the result shown on the digital display. Check this result against the ideal pH for the plants you are growing. Most plants need a slightly acidic environment with a pH between 6.0 and 6.5.
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Adjust the pH levels as necessary. If the pH is too low (too acidic), add a very small amount of base to the solution. If the pH is too high (too basic), add a very small amount of acid to the solution, mix well and retest.
Measure The TDS of Your Nutrient Solution
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5
Purchase a conductivity or TDS (total dissolved solids) meter. As of late 2009, a basic TDS meter costs around $25.
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Calibrate your TDS meter according to the manufacturer's instructions.
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Dip the TDS meter probe in your nutrient solution and record the results. The optimal TDS reading for most plants is between 1,000 and 2,000 parts per million (ppm). Many plants have nutrient requirements above or below this level, so it's a good idea to familiarize yourself with the requirements of the specific crop you are growing.
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If your nutrient levels are too low, add a small amount of concentrated nutrient solution or soluble fertilizer and retest.
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Tips & Warnings
While the pH and TDS levels mentioned here are averages that will work for most plants, knowing the exact requirements of the plants you will be growing will allow you to maximize your yield and the quality of your produce.
Buy the best meter you can afford. Cheaper meters will tend to lose their calibration more frequently than better ones.
Combination meters that test pH, TDS and water temperature are a good alternative to separate meters if storage space and time are at a premium. They are significantly more expensive than basic pH and TDS meters.
Double-check the calibration of your pH meter periodically using a liquid pH test kit or pH papers. This will let you know if your pH meter needs to be recalibrated.
