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Wood Ash: How to Make Your Own Fertilizer

By Jon Frank

Wood ash can be a resource for making your own super fertilizer: You’ve heard of super foods — foods especially endowed with nutrition that merit special attention. I would like to suggest a simple, effective fertilizer you can make yourself.

Often overlooked and many times deprecated because it was over-applied — it is time to give wood ash its due. If you burn wood for home heating you already have a ready supply. If not, all it takes is a bonfire and you are in business. I like to incorporate plenty of charcoal in combination with the wood ashes.

This approach is more closely aligned with the creation of Terra Preta. To cut the dust, I like to mix wood ashes with moist leaf mold. You may want to en­hance your fertilizer by mixing 1 pound of kelp meal and 1 pound of sugar for every 20 pounds of ashes. If phosphorus is low in your soil, add bones to the bonfire and crush them with the charcoal.

I suggest using anywhere from 5 to 50 pounds per 1,000 square feet. Avoid using on soils with a pH above 7.8. The use of wood ash does not replace soil test and fertility recommendations; rather it supplements it and reduces the overall need to purchase costly off-site inputs. The beauty of using wood ash is that the spectrum and ratio of minerals present in the ash have already been preselected by plants. Its fine dust is very fast-act­ing in soil. Wood ashes are very rich in trace and secondary minerals, without adding nitrogen.

wood ash
Straight wood ash on the right and wood ash mixed with ground up charcoal on the left. Both will benefit most soils.

Beyond Wood Ash

To create an optimum growing environment in your garden take these actions:

  • Keep the mineral levels in your soil well supplied;
  • keep soil-applied nitrogen very low;
  • keep the soil consistently moist, and
  • make your own super fertilizer.

And now for the word of caution. Externally applied nitrogen is a safety net. Its use should not be discontinued in the following situations:

  • Indoor growing — Greenhouses and high tunnels are very intensive and require more production to remain profitable.
  • Commercial grain production — Don’t even think about it.
  • Soils heavily sprayed with herbicides and pesticides — The microbial system struggles in this environment and requires applied nitrogen.

For more information about fertilizer, visit the Acres U.S.A. bookstore or subscribe to Acres U.S.A. magazine.