Potassium is one of the most important nutrients in soil. Identified as "K" on the periodic table of the elements, potassium aids plants in processing food and absorbing water, in addition to controlling chemicals. As long as soil is free of sand, high levels of potassium typically exist. However, you can also create homemade potassium to help nourish your plants. This can be accomplished by using basic items such as fruit, ashes and coffee.
Add fruit to compost. Cut potassium-rich banana peels into small pieces, then mix into your compost pile. Place more banana peel pieces into a spray bottle filled with warm water. Allow peels to ferment in the water for two weeks, then spray the liquid on plant soil.
Burn wood. Gather the potassium-rich ashes once the fire is out. Add ashes to soil as you create your compost pile, sprinkling a small amount on each layer. Pause for the ashes to dissolve before advancing to the next layer.
Collect used coffee grounds. Dig 6 to 8 inches beneath the surface of the ground or plant container, then mix coffee grounds into the soil.
When ashes have been added directly to soil, test regularly to verify pH levels are balanced.