What is it?
Acidification is where the pH level of soil decreases and reduces plant vigour. While soil acidification is a natural process (especially in higher rainfall regions), agricultural practices can greatly accelerate the rate of acidification.
Strongly acidic soils are defined as those having a pH less than 4.5 (in water), with a pH of 7 being neutral.
Soil acidity occurs naturally in higher rainfall areas and can vary according to geology, clay mineralogy, soil texture and buffering capacity. Agricultural production also increases acidity through unbalanced nitrogen cycling (excessive use of nitrogen fertilisers and nitrogen leaching) and the continued removal of alkaline plant/animal materials (grain, hay, wool, meat).
A diagrammatic representation of the causes of soil acidity showing the importance of product removal and nitrate leaching in the process