Most compost is acidic, esp. oak leaves and pine straw, but it takes time for it to break down. Here in FL, the soil is very alkaline and sandy. It is popular to layer dry dog food, pine straw or hay, and unscented kitty litter under plastic after thoroughly wetting it down. The plastic keeps the moisture in and the critters out, the dog food breaks down into protein, the kitty litter (clay) improves the moisture content of the soil, and the hay or pine straw (or even newspaper) forms acidic compost. In extreme cases, there is some kind of sulfur you can add to the soil to lower pH. Sometimes gardening here is like hydroponics!

The most effective organic method of reducing the pH of soil, is the addition of peatmoss as an ammendment. Other organic material can also be used, such as sawdust, composted leaves and conifer needles, wood chips, leaf mold and cotton seed meal. These require more time to increase the Hydrogen, Aluminum & Sulphur ions because, as the acidity increases, the microbes in the soil become less effective in breaking them down.
Most plants will tolerate the addition of ground rock sulphur, which is often used in agriculture to reduce the alkalinity of soil.
Out of curiosity, what plants are you planning for the area?
Blueberries, Rhododendrons, Cypripedium acaule?
Rainfall, in excess of plant moisture reqirements, also tends to increase the acidity of soil. Acid rainfall (the root of all vegetation failures and pollution, so some pronounce!), has no significant effect on soil pH.
Rb

Hi,

Thanks for the replies!

I blanketed the area with some white pine needles last week, so hopefully that has some effect over the winter! :)

There are lots of plants that I hope to grow in the area, once the soil is right... Epigaea repens, Trientalis borealis, Blueberries, Gaultheria procumbens, Arctostaphylos uva-ursi, Cornus canadensis... and some others.

Thanks again!
God bless,
Jeff

I think liquid coffee is acidic. This is also a good topic for the compost/soil forum and maybe the organic gardening forum since you do not wish to go chemical. A gardening friend of mine uses pine needles and oak leaves and his plants look great. Literature and websites with instructions on care of blueberries should have some good tips on acidifying the soil.

I doubt you need to do much to increase acidity - all the plants you mention will do fine in a pH range of 5.5-6.5. Most plants, even acid lovers - tolerate a relatively wide range of soil pH. My soil is naturally at 6.0-6.3 and all manner of acid loving plants thrive. However, if your soil is very sandy, increasing organic matter will certainly improve moisture retention and incorporating peat moss is a great way of achieving that as well as lowering pH. Be sure to incorporate it well into the soil - if on the surface and it dries out, it becomes hydrophobic and repels water.

Compost is pretty much neutral in pH but it is by far the most desired form of organic matter. Contrary to coventionally held gardening wisdom, pine needles, other conifer needles or bark or oak leaves used as mulch do not significantly change soil pH. Soil pH is a factor of mineral content and rainfall, not organic matter. There is a slight increase of acidity at the soil surface that lasts only until decomposition occurs, but it does not penetrate deeply. Decomposition of organic matter is the big neutralizer.

FWIW, it is extremely difficult to significantly alter soil pH for long term effect. Soils have a buffering capacity that resist change - more so in clay based soils, less in sandy soils. But with your pH levels, you really don't need to alter anything. Incorporating peat moss as an amendment before planting is probably your best route.