What is it?
Potassium is an important nutrient for the plant’s growth process that takes place on a cellular level. It is required for good stem, root, and leaf development.
Signs of Deficiency
If a plant does not get sufficient Potassium it will not thrive. Its lower leaves will turn yellow and curl at the tips first. Eventually, the whole leaf will turn brown. The stems and branches may get weak and break.
There are a couple of excellent organic sources of Potassium. Granite meal is probably the cheapest and is a good choice. This has a Potassium content of around 20. But you will only get about 4 a year because it is slow acting. My Favorite choice is Green Sand which also has over 20 trace minerals. This has a 7% but you only get about 1 a year over 6 or 7 years. Green Sand is even slower acting than Granite Meal. Sul-Po-Mag has a K of 22 and Wood Ash has a K of 5, but both of these will affect the pH of your soil. Be sure to have a soil test before using either.
Other fertilizers that have potassium in more modest quantities include:
- Worm Castings,
- Alfalfa Meal,
- Cotton Seed Meal.
What I would do if my plants showed a deficiency in potassium is immediately water them with a organic hydroponic solution that has the highest value for potassium. Then I would work some Granite meal in around the base of the plant. I would water once a week with the hydroponic solution.