Mix the Nutrient Solution

Lesson 6 of 14

In a Kratky container the plant lives on one batch of solution from transplant to harvest. Mixing it carefully at the start is the single most important step in the course.

Sweet basil seedling in a Kratky net cup

Use a hydroponic nutrient

Plants in water get every nutrient from the solution, including calcium, magnesium and micronutrients that soil would normally supply. Use a product labelled for hydroponics, and follow its rate for non-circulating systems if it gives one (UF/IFAS).

  • One-part nutrients have everything in one bottle or bag. Simplest for a first jar.
  • Two-part nutrients keep calcium separate so it does not react in the bottle. They are no harder to use, as long as each part goes into the water separately.

How to mix

  1. Measure a known amount of water into a clean bucket or jug.
  2. Measure the nutrient at the label rate. Shake liquid concentrates first.
  3. Stir the first part fully into the water before adding the second. Never mix concentrates together.
  4. If you have an EC meter, check the strength now (see below).
  5. Check and adjust pH last. That is Lesson 7.

How strong

Strength is measured as EC (electrical conductivity). For hydroponic lettuce, Oklahoma State University Extension lists an EC of 1.2–1.8 mS/cm, and for basil 1.0–1.6. UF/IFAS suggests about 1.25 mS/cm (roughly 800 ppm on a 500-scale meter) for Kratky greens. If you do not have a meter, follow the label exactly rather than guessing.

How much to make

UF/IFAS suggests planning on about 1 to 1.5 gallons of solution per lettuce plant from transplant to harvest. A quart jar holds far less than that, which is why jar-grown lettuce is usually picked young, or topped up once (Lesson 10). A gallon container lets one lettuce plant finish on a single fill.

Your task for this lesson

Read your nutrient label and work out the amount for your container. Mix the solution on the day you transplant, not days ahead.

Sources

  1. University of Florida IFAS Extension. Set It and Forget It Hydroponics (HS1488).
  2. Dunn, B. and Singh, H. Oklahoma State University Extension. Electrical Conductivity and pH Guide for Hydroponics (HLA-6722).

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