Question
I live in Lubbock, Tx. and we have dead cedar branches.  We have burned some of them we wanted to know if we could use the ashes for fertilizer?
                    Thank you, Sharon Miller

Answer
Wood ashes can be a good source of lime, potassium and trace elements, and potenially magnesium but will not replace the need for phosphorus, nitrogen, etc.

You should still have to fertilize the plants/lawns with minimum these nutrients in addition to the wood ashes (see caution note below). However, if your soil is deficient in potassium (which sandy soils typically are for example) then using wood ashes can be a good supplement to a regular fertilizer. Again: READ CAUTION NOTE AT BOTTOM OF PAGE.

One key note, however: wood ashes are rather high in pH. If you already have high soils (which most places have in Tx) then do not use. Normally I recommend having a soil test done before adding fertilizers like these which can seriously affect pH and potassium levels.


In any event, apply no more than 10-15 pounds of ash per 1,000-square feet of lawn (1-1.5 pounds per 100 sq feet of garden bed); at high levels, ash can be toxic to plants. Do not use if soil pH is more than 7.0 or if potassium levels are excessive.

CAUTION - NOTE:

right after you put down wood ashes, do not use commercial synthetic fertilizers (such as ammonium nitrate, urea, ammonium sulfate, etc). These nutrients are very common in almost all commercial fertilizers today. If you mix these fertilizers with wood ashes, you produce ammonia gas. Apply at least 2-3 months apart.

Protect yourself when applying wood ash. Use the same precautions you would use when handling household bleach, another strongly alkaline material. Wear eye protection and gloves. Depending on the fineness of the ash, you may want to wear a dust mask.


OTHER OPTIONS:

Another option for the use of wood ashes would be to add them to the compost pile. Distribute a thin layer between each layer of compost materials when building the pile. In compost piles, wood ash can be used to help maintain a neutral condition, the best environment to help microorganisms break down organic materials. Sprinkle ash on each layer of compost as the pile is built up. Ash also adds nutrients to compost.

If you want to learn about fertilizer nutrients, then here is a good overview:
http://www.suite101.com/article.cfm/18505/106509