Q: I have heard that wood ashes can be beneficial in gardens, so I have been dumping the ashes from my fireplace into my garden. How do I know when I have applied enough?
A: Applying a layer of wood ashes to a garden area would be beneficial if you lived on the eastern part of the country, but it is not a recommended practice for northwest Kansas soils. The main benefit of wood ash is to raise the soil pH (making it less acidic or more alkaline). Soil pH is a measure of acidity on a 14 point scale, with 7 being neutral. Below 7 is acidic and above is alkaline. Most of the soil in Rawlins county falls between 7.5-8 pH range, meaning it is very alkaline already.
Soil pH extremes make nutrients unavailable for plants. Most plants tend to thrive in slightly acidic soils (pH 6-7). However, it is important to know the pH preference of whatever you are planting. For example, asparagus is an alkaline loving plant and will grow in soils with a pH up to 8.
Sulfur or other materials may be used on alkaline soils to reduce soil pH to the desired level. Sulfur is available for purchase from garden stores in both powder and pelletized forms. In regions with acidic soils, lime is added to raise the soil pH. Wood ash contains roughly twenty five to forty five percent calcium carbonate (a common liming agent). Adding ash may do more harm than good, particularly since wood ashes change the soil pH much more quickly than most liming products.
The moral of the story is: If your soil pH is 6.5-7 or above, do not add wood ash. 
