What are some ways to make soil more acidic?
It is very difficult to permanantly change the acidity of soil. It is like trying to make a small area of the ocean less salty. You could do it but it will soon change back to its original state. That said there are some products that when incorporated into the soil will increase the acidity as they decompose it the soil. Peat moss and Cotton Boll Compost are the two most commonly used and readily available. Pine needles also do the trick but they break down slow unless they have been composted. With all due respect to a previous poster, putting ash of any type on the soil will increase alkalinity (decrease acidity) as it is mostly carbon. Also you can use chemical acidifiers like Sulfer, Sulfer Phosphate, Super Phosphate or similar. If you have a clay soil (common for alkaline soils), these products will chemically bind to the clay particles and quickly become useless. The afor mentioned organic materials will last longer in the soil profile.
Can I say first that changing the PH of soil by any reasonable amount is very difficult and in some cases impossible. Having said that there are things you can do to make it less alkaline than it is at present. Adding organic matter, compost, leaf mulch and pine chips will all help. Do this twice a year, once in spring and again in autumn. Apply a layer at least 3inches thick but not right up to the base of the trunks.The conifers you have planted wil help as their needles acidify the soil when they drop. Found this giving information on how to apply sulphur [Granular sulfur is the safest, least expensive but slowest acting product to use when attempting to lower your soil’s pH. The table below shows the pounds of sulfur needed per 100 square feet to lower the pH to 6.0 in the top 6 inches of soil. Soil pH Sandy Loam Loam Clay loam 5.0 8 10 15 5.5 6 8 10 6.0 3 4 6 To avoid plant injury, don’t exceed 2 pounds of sulfur per 100 square feet per application. Wait at least 3 months to make
Acidic soil amendments that will also improve the soil include: Canadian peat moss Oak leaf compost Coffee grounds Conifer needles and wood chips. If you want to drop the pH fast (and not permanently) with chemicals, you can use sulfur or iron chelates (from a garden center) I would only bother doing any of this if your conifers are showing signs of distress at being in alkaline soil. The usual symptom is iron chlorosis = yellowing and dropping leaves. NOTE: one of the other responders said “wood ash”. This is incorrect. Wood ash is highly alkaline.
