Question

What is acidic soil caused by?

Answer 1

Increase in hydrogen ion concentration...

Explanation:

Acidity in soil is caused by the increase of `H^+` ions in the soil. This can come anywhere from acid rain or from invalid uses of fertilizers. Surprisingly, ineffective use of nitrogen fertilizers is the main cause of acidic soil in countries such as Australia. I suggest you read a scientific article to find more about this issue:

http://soilquality.org.au/factsheets/soil-acidity