Question
I mulch my blueberries with woood chips and I would like to know if it would be benefical to spray with a 5% vinegar solution in order to create an acid soil condition for the blueberries.

Answer
Vinegar is a natural herbicide, and if you are not careful you could kill your plants. We use it full strength as a weed killer in our gravel paths. It will also dissipate rapidly and only act as a temporary solution to your problem.

A better solution would be to test your soil, find your pH and nutrient levels (blueberries like a rich loamy acid soil with a pH around 5.0) and add leaf mold, pine needles, or a non-cedar (cedar is toxic to plants) sawdust, or peat moss (which is very acidic) to bring the pH down. If it is still not acidic enough you can add mined sulfur, usually called soil sulfur, a little at a time to slowly bring down the pH. (It is best to avoid chemical fertilizers, such as nitrates).

Acidity and alkalinity of soils is important, because it affects the availability of soluble salts supplying plant nutrients. If the pH is not correct for your plant, other nutrients may be unavailable.

Acid soils are common in high-rainfall areas.  The frequent rain leaches the alkaline minerals (calcium, potassium, and magnesium) from the soil and replaces them with hydrogen, which makes soil acid.

The difficulty with acid soil is that many of the ohter nutrients needed for plant growth become less available because they are converted into insoluble salts.

Phosphorus especially is tied up in insoluble compounds. Phosphorus deficiency causes plants to grow very slowly and take on a dark, dull, color.

Other elements like aluminum and manganese are water soluble in acid soil, and can become toxic to plants. The microorganism activity that causes decay is lower in acid soils and your organic matter will not break down rapidly.

Acid soils can also be sandy or clay; a sandy soil will leach minerals more quickly than a clay soil.

Test your soil a few weeks after you add any soil ammemdments.  You could also check the pH of your compost, and if you need to, bring the pH of some of it down as well, and then mulch your blueberries with it.

You can check our website for more information on soil building:  http://www.avant-gardening.com