How to Naturally Input Potassium Into Soil

Wood ash is a traditional source of soil potassium.

Potassium is a key nutrient for plants, represented as "K" on the NPK ratios found on the labels of chemical fertilizers. Those chemical fertilizers are usually the most direct means of putting more potassium into the soil, but many gardeners are interested in more natural, organic techniques. One of the classic sources of potassium for farmers and gardeners is wood ash, making it a logical choice for naturally putting more potassium into the soil.

Things You'll Need

• Wood ash
• Hoe or roto-tiller
• Iron rake or hand rake

Instructions

1. Stockpile the wood ash from your furnace, fireplace and/or wood-burning stove in a single location. Keep the wood ash stockpile covered to prevent the potassium content from leaching out of the ash.

2. Test your soil to determine its acidity, or pH rating. Wood ash is high in potassium, but is usually stronger in acid-neutralizing calcium carbonate, so using wood ash lowers soil acidity.

3. Till the soil with a hoe or roto-tiller prior to using the wood ash, so as to break up the surface into loose dirt.

4. Spread the wood ash over the soil. Apply no more than 10 to 15 pounds of wood ash for every 1,000 square feet of ground. If you wish to lower the soil acidity, use more wood ash, but avoid raising the pH rating above 7.0.

5. Rake the wood ash into the soil. For large garden plots, use an iron rake. For garden boxes, use a hand rake.

Tips & Warnings

• Some sources of wood and woody fiber are higher in potassium than others. Corn cobs have up to seven times the potassium content of ordinary wood ash.

• Some studies have shown that mixing urine with wood ash makes it a more effective fertilizer. You may wish to use your wood ash stockpile as an outdoor urinal to take advantage of this effect.

• If you wish to create a potassium-rich fertilizer, but avoid the acid-neutralizing effects of calcium carbonate or to add other nutrients as well, incorporate wood ash into a compost heap with nitrogen-rich and/or phosphorus-rich ingredients.

References

• Oregon State University Extension; Wood Ash Can be Useful in Your Garden if Used With Caution; Carol Savonen
• UPI.com: Urine, Wood Ash Potent Fertilizer
• Oregon State University; Fertilize Your Garden; J. Hart et al.
• Improve Your Garden Soil: Potassium and Soil (Potash Fertilizer)