Maximum residual acidity is associate with the continuous soil application of

Soil acidity is something that is neutralized by lime or a buffered salt solution to raise the pH to a specified value (usually 7.0 or 8.0) but which cannot be replaced by an unbuffered salt solution. It can be calculated by the subtraction of salt replaceable acidity from total acidity. Maximum residual acidity is associated with the continuous soil application of ammonium sulphate.