Creating the Perfect Nutrient Solution in Veg and Flower
The performance of a nutrient solution is not guaranteed by simply using a quality brand. Proper dosing procedures and ongoing maintenance are necessary to obtain maximum performance.
1. Always use a professional liquid nutrient, ideally one formulated specifically for use with the medium being used. Be sure to use the associated additives as overall performance will often depend on these. The order in which you add different components is important, and so is the timing—seedling, vegetative or bloom. ALWAYS follow the dosage chart!
2. Use clean and sterile water. This helps to prevent diseases. Use either fresh reverse osmosis water (ideal due to its low nuisance salt content) or fresh treated tap water.
3. Add nutrients and additives to water: Always add the majority of water before adding nutrients and additives. Never mix any nutrients or additives together in their concentrated form. Once a nutrient or additive is added to the water, stir well before adding the next. High pH additives should be added last, pre-diluted into a cup of water before being added, quickly stirred and the pH checked (Fig 2).
4. Measure the nutrient solution’s strength (EC) and pH. Check this once the total solution is made and ‘before’ feeding to the plants. For most species, use the following as a guide:
- pH: Maintain between 5.0 to 6.5. Within this range all essential nutrient elements will remain soluble and available for root uptake (see Fig 1). To adjust pH, add pH Down (often required) or pH Up (rarely required). Add little by little until the pH falls within the correct range. To measure pH use a digital pH meter that has been calibrated in pH Buffer 4.0 and pH Buffer 7.0 (essential for accuracy).
- Nutrient strength (EC): Test using a conductivity (EC, mS, cF) or TDS meter (see conversion chart right). For seedlings or clones use 0.6 to 0.9mS. For vegetative phase use 1.3 to 1.8mS. For flower use 1.8 to 2.4mS (Use the lower levels during heatwaves or if plants are stressed). The ‘meter’ reading indicates the concentration of salt based solutions. Hence, a higher reading implies a higher concentration. Therefore, if your meter’s reading is too low, simply add more nutrient. Obviously if it is too high then add more water. TIP: Always stir the nutrient solution well before taking readings.
- For recirculating hydroponic systems only: As plants grow they simultaneously remove both water and nutrients from the nutrient solution. Ensure the water level is kept relatively constant. When this is done, the concentration (EC) will be relatively predictable. It will move up or down depending upon the size and growth rate of plants and the salinity of the top-up water.
5. Tepid solution. Use a nutrient thermometer to monitor the temperature of your nutrient solution. The ideal is 20 °C (68 °F). Too warm and you risk promoting root diseases or suffocating the root zone with low dissolved oxygen levels. Too cold and you will shock the roots and slow plant metabolism to a crawl. Your nutrient solution should feel sort of “silky” and tepid—neither warm or cold.
6. Water thoroughly. When hand watering or top feeding, do so slowly, evenly and gradually. Aim for around twenty percent of the nutrient solution to run out of the bottom of the pots. Run-off helps to keep the root zone cleaner with less salt build-up.
- Dry patches from automated top-feeding: Water the surface of the medium at as many points as possible otherwise areas of the root-zone will risk being left un-watered. Devices such as water-rings or spray nozzles are a good alternative to single point drippers.
7. Check run-off. For run-to-waste coco coir or soil systems, periodically collect some of the run-off and check its EC. If it measures more than 0.5mS (500 µS or cF 5.0) above the EC of the input nutrient solution then consider flushing through with a milder solution (or even pure water) to help clear the root zone of excess salts. For example, if the nutrient solution has EC 1.7mS but your run-off measures 2.3mS (or more) then it is time to flush.
8. Hard Water Problems: Hard water is typically alkaline—and so are many nutrient additives! “Alkalinity” is what typically drives nutrient pH above and beyond 6.5. This is the point at which many trace elements (e.g. iron) begin to destabilise. FloraMax Ca-Mg-Fe will “protect” the nutrient if pH spikes within the range of 6.5 to 10.
For more see page 45 of the FloraMax Hydroponics Manual.
© Andrew M Taylor