Potassium bicarbonate 99.7% (KHCO3) is also known as potassium hydrogen carbonate or potassium acid carbonate. Potassium bicarbonate is a white, alkaline solid used in fire extinguishers, wine making, to make soft drinks, to neutralize acids and also used as a leavening agent in baking.
It’s naturally present in humans, animals, plants and virtually all living organisms. As a base, potassium bicarbonate is at the high end of the pH scale, 8.0 – 8.6pH.
Potassium bicarbonate is an accepted fungicide in organic farming. As a foliar spray, it has been found to stop and inhibit the growth of fungal pathogens and the spores (Alternaria blight, apple scab, black spot, blights, botrytis, downy mildews, moulds, phytophthora, powdery mildew, and Septoria leaf spot) on many plants and crops. Found to be most effective as a preventative measure.
It’s very effective on mildews as it uses various modes of action against them causing them to desiccate and collapse, as the mildews have a low resistance to potassium bicarbonate. Plants also benefit form the extra intake of potassium.
Directions for use:
Potassium bicarbonate is a “contact” fungicide, therefore contact needs to be made with infected areas.
Preventative foliar 1g – 3g KHCO3 per litre of rain/dechlorinated water. Spray as a preventative on a fine mist every 10-14 days through the vegetative stage of growth and up to two weeks into the flowering stage of growth.
Heavily Infected plants might require a more aggressive approach 3g-4g KHCO3 per litre or rain/dechlorinated water at 4-7 day intervals misting the entire plant including underside of leaves and stems.
A spreader/wetting agent (eg JADAM wetting agent at 1ml/1l) added will ensure proper surface coverage and the potassium bicarbonate will be even more effective. Refrain from using a wetting agent about 30 days prior to harvest.
Application without a spreader/wetting agent can be applied and still be very effective. Spray on a very fine mist so droplets hold on the leaf surface. Move around, misting evenly, returning to where you began to fine mist areas you might have missed. *Do not over spray one area and cause droplets to run, this could lead to the potassium bicarbonate been ineffective.
Application rates above 4g/1l showed signs of pistils browning. Leaf burn on tips of older plants was noticed at the higher dosage. Young seedlings and clones also showed burns on the edges and tips of the leaves.
Application late in flower might be needed when plants are most susceptible to mildews and botrytis. Refrain from using a wetting agent about 30 days prior to harvest.
- Outdoors foliar spray at the coolest time of the day, early mornings or at sunset. One can foliar spray without a wetting agent after rain while plant is still wet. This will ensure proper coverage as the rain on the plant will act as a spreader helping the KHCO3 make contact with all spores.
- Indoors foliar spray at lights off with fans off and then put fans back on after foliar spray. If you have high humidity at lights off you can foliar spray during lights on, but will need to either raise or dim lights or use a soft light when foliar spraying and while plants dry. Ensure plants are dry before increasing light intensity again or switching on – wet spots might cause burns.
Potassium bicarbonate (KHCO3) should be stored at room temperature, upright and in a sealed container away from moisture. KHCO3 is very hygroscopic and will draw moisture from the air.
Safety and precautions:
Good hygiene and safety practices should be used when handling and working with this material. Good hygiene practices include but are not limited to: wearing suitable gloves and/or eye protection, washing hands and affected skin immediately after handling.
- Avoid breathing in dust
- Avoid contact with skin and eyes
- Wash skin and contaminated clothing and tools after use
- Cause eye irritation
- Cause mild skin irritation
- Harmful if inhaled
- May cause respiratory tract irritation
* Potassium bicarbonate is incompatible with all types of water-soluble fertilizers and other chemicals and needs to be applied on its own as a soil drench for correcting low medium pH.
* For use on plants and crops.
* Keep out of reach of children and animals.