Which amendment lowers soil pH?

Which amendment lowers soil pH?

• A. Lime
• B. Sulfur
• C. Nitrogen
• D. Phosphorus

Answer: (C)

Lowering soil pH means increasing soil acidity, which is done by adding acidifying amendments. Elemental sulfur is the standard amendment to decrease pH. Soil bacteria oxidize sulfur to sulfuric acid, releasing hydrogen ions and gradually lowering the pH over weeks to months. Lime, in contrast, adds calcium carbonate and raises pH, so it’s used to make soils less acidic. Phosphorus fertilizers have little effect on pH. Nitrogen can contribute to acidification when applied as ammonium-based forms because the nitrification process releases hydrogen ions, but this effect is variable and not the primary method for reliably lowering pH.

Lowering soil pH means increasing soil acidity, which is done by adding acidifying amendments. Elemental sulfur is the standard amendment to decrease pH. Soil bacteria oxidize sulfur to sulfuric acid, releasing hydrogen ions and gradually lowering the pH over weeks to months. Lime, in contrast, adds calcium carbonate and raises pH, so it’s used to make soils less acidic. Phosphorus fertilizers have little effect on pH. Nitrogen can contribute to acidification when applied as ammonium-based forms because the nitrification process releases hydrogen ions, but this effect is variable and not the primary method for reliably lowering pH.