What causes "acidity" in soil and is clay more alkaline or more acidic usually?

Question

and how can you make it more acidic or alkaline ?

Thanks for your answers!

Answer 1

Clay soils are usually about a pH of 7. This is neutral. To make the soil more acidic add sulphur to the soil. To make it more alkaline add lime. Both these products are available at good garden centres.

Answer 2

Acidity is caused by the minerals that are present,as well as what other plants are or have grown on the soil,Oaks and pines for instance acidify soil.Clay can be either alkaline or acidic.To increase acid you can use an azalea,Camellia,rhododendron fertilizer for fast results.Some people add sulfur, but it is slow to break down into an effective form.To add alkalinity use agricultural lime.I like the pellet form.The dust is very fine ,and blows everywhere including all over you.