A Beginners Guide to Hydroponic Nutrients
Nutrient management is the crux of a healthy hydroponic system.
Great nutrient management occurs when growers are:
1) Aware of all necessary plant nutrients and where they come from
2) Supplying adequate nutrients in correct ratios to plants
3) Monitoring and measuring how much of each plant nutrient is available in their system at any given time
4) Making economic and work-flow conscious decisions about how to source and supply nutrients.
Most plants (and all of the crop plants that you’re likely to grow) rely on 16 nutrients to grow and reproduce. Of these, three are available through water uptake and gas exchange (the air): Carbon through CO2, hydrogen, and oxygen.
Why Are Nutrient Levels Important?
The remaining thirteen nutrients are the mineral nutrients delivered to plants through nutrient solutions (dissolved fertilizer).
The overall nutrient level in a solution is measured in EC, or electrical conductivity. The units used to measure EC are ppm (parts per million) or mS/cm (millisiemens per centimeter), although ppm is used more commonly for measuring total dissolved solids. That’s a different measurement for a different blog post. Hydroponics really need to understand the second unit, mS/cm. This is often just expressed as the “EC level”. (For example, “The EC of the solution is 1.8,” with no unit.)
Ideal mS/cm is typically between 1.2 and 3.3. There’s a broad range of acceptable EC levels, and each crop has an ideal range.
The Importance of pH
Supplying the correct ratio of nutrients in adequate levels is only half of the nutrient management picture; the other task for farm managers is to keep those nutrients available to plants, and the main factor influencing that availability is pH.
Nutrients are soluble at different pH values. Check out an absorption chart (there’s one in the article version of this video) to learn more.
Adjusting pH to your ideal range can be done with pH Down or pH Up, which are acids or bases (respectively). Never add both at once!
Liquid or Dry Fertilizer?
There are two main forms of fertilizer: dry and liquid.
Dry fertilizer is mostly used in commercial settings because there’s a lot less to ship (you’re not shipping water), making it more cost-effective. You can also tailor dry fertilizer better to your needs because it comes in separate parts.
Liquid fertilizer is simple to use and great for home and hobby systems. It’s easier to manage since you can just add a certain amount of one liquid to your system water, but it’s more expensive to ship. (Most people on a small scale only buy a little at a time though, so shipping is less important.)
Mixing and Measuring
The best way to mix a solution is to follow the manufacturer’s instructions.
If you’re not using an auto-doser, you’ll still mix it the same way, but you’ll add it to your system bit by bit in equal ratios and test it until it’s at the right level. You’ll get better and better at this over time.
There is a multitude of handheld measuring devices and testers. My favorite suppliers are Blue Lab, Hanna Instruments, and AutoGrow. I’ve used each of these and are currently using AutoGrow’s NutriTest, a handheld meter that measures both EC and pH with the same device. There are a variety of options out there.
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I hope you found this to be a useful general article on all points of plant nutrition! The fertilizers below are all well-liked in the industry and will serve you well.
Please be sure to comment and share your questions or what fertilizers you find to be best!