Short answer: yes, but tomatoes are much more demanding than lettuce. They need a stronger solution, a far larger container and regular topping up over several months.
Why tomatoes are harder
The Kratky method was developed with lettuce, a fast crop that finishes before its solution runs out (Kratky, 2009). Tomatoes grow for months, become large plants and use a great deal of water, especially once they set fruit. UC Master Gardeners note that fruiting crops such as tomatoes usually need the solution replenished over time.
Solution strength and pH
Oklahoma State University Extension lists an EC of 2.0–4.0 mS/cm and a pH of 6.0–6.5 for hydroponic tomatoes. That is considerably stronger than lettuce. Many growers start near the lower end of the range while plants are young.
Nutrient choice
A complete hydroponic nutrient with a fruiting or bloom formula, or a three-part system that lets you shift the balance as plants flower, suits tomatoes better than a leafy-green formula.
Container size
Use the largest lightproof container you can, such as a 5-gallon bucket or larger tote, for one plant. Compact or dwarf varieties are easier to manage than tall indeterminate types.
Topping up
- Measure EC before each top-up. If it has risen, add plain water; if it has fallen, add fresh solution.
- Add only enough to reach the lower roots. Never refill to the top and submerge the air roots.
- Top up in small amounts regularly rather than large amounts occasionally.
Support
A Kratky container gives roots very little to anchor in. Stake or cage the plant so its weight does not pull the net cup out of the lid.
Related guide: Kratky nutrient solution for different crops.
Sources
- Kratky, B.A. (2009). Three non-circulating hydroponic methods for growing lettuce. Acta Horticulturae 843: 65–72.
- UC Master Gardeners of Orange County, UC ANR. Kratky Hydroponics: Soil-Free Growing Method.
- Dunn, B. and Singh, H. Oklahoma State University Extension. Electrical Conductivity and pH Guide for Hydroponics (HLA-6722).
