Kratky Nutrient Solution

How to Mix Kratky Nutrient Solution

Mixing a Kratky solution takes a few minutes. Because nothing circulates or refreshes the water afterwards, it is worth doing carefully. Here is a method that works for jars, buckets and totes.

Measuring cylinder with volume markings

What you need

  • A clean bucket or jug for mixing
  • Your hydroponic nutrient and its label
  • Measuring spoons, a syringe or a small scale
  • An EC or TDS meter and a pH test kit or meter
  • pH down (and pH up, in case you overshoot)

Step by step

  1. Measure the water. Fill your mixing container with a known volume. Mixing one large batch and filling several containers from it gives every plant the same solution.
  2. Check the plain water. Note its EC and pH so you know your starting point.
  3. Measure the nutrient. Use the label rate for hydroponics, or for non-circulating systems if one is given (UF/IFAS). Shake liquid concentrates first.
  4. Add one part at a time. With a two-part nutrient, stir part A fully into the water before adding part B. Never pour the concentrates into each other.
  5. Check the strength. Stir, let the reading settle for a minute or two, then measure EC. If it is high, add water. If it is low, add a little more nutrient (Oklahoma State University Extension).
  6. Adjust pH last. Nutrients change pH, so check it only after the strength is right. Add pH down in small amounts, stir, wait several minutes and test again.
  7. Fill the containers. Fill to just touch the bottom of the net cup so the growing medium stays moist (Kratky, 2009). The level will fall from there as the plant drinks.

How much to mix

For leafy greens, UF/IFAS suggests planning on roughly 1 to 1.5 gallons of solution per plant from seed to harvest. Larger plants and longer crops need more. Sizing the container to hold the whole crop's supply means you will not need to top up.

Common mixing mistakes

  • Adding both parts of a two-part nutrient at once, or to a small amount of water
  • Guessing the dose instead of measuring
  • Adjusting pH before the strength is set
  • Mixing in a container that held soap, cleaners or garden chemicals

Sources

  1. Kratky, B.A. (2009). Three non-circulating hydroponic methods for growing lettuce. Acta Horticulturae 843: 65–72.
  2. University of Florida IFAS Extension. Set It and Forget It Hydroponics (HS1488).
  3. Dunn, B. and Singh, H. Oklahoma State University Extension. Electrical Conductivity and pH Guide for Hydroponics (HLA-6722).
All Kratky Nutrient Solution Guides

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