Editing Soil pH (section)

===Decreasing the pH of alkaline soil===
The pH of an alkaline soil can be reduced by adding acidifying agents or acidic organic materials. Elemental [[sulfur]] (90–99% S) has been used at application rates of {{convert|300|-|500|kg/ha|abbr=on}} – it slowly oxidises in the soil to form [[sulfuric acid]]. Acidifying fertilizers, such as [[ammonium sulfate]], [[ammonium nitrate]] and [[urea]], can help to reduce the pH of soil because ammonium oxidises to form [[nitric acid]]. Acidifying organic materials include [[peat]] or [[sphagnum]] peat moss.<ref name="Cox2010">{{cite web |title=Solutions to soil problems. II. High pH (alkaline soil) |url=https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1954&context=extension_curall |last1=Cox |first1=Loralie |last2=Koenig |first2=Rich |year=2010 |publisher=[[Utah State University]] |location=Logan, Utah |access-date=10 September 2023}}</ref>

However, in high-pH soils with a high calcium carbonate content (more than 2%), attempting to reduce the pH with acids can be very costly and ineffective. In such cases, it is often more efficient to add phosphorus, iron, manganese, copper, or zinc instead because deficiencies of these nutrients are the most common reasons for poor plant growth in calcareous soils.<ref>{{cite web |url=https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5293776.pdf |year=1998 |title=Soil quality indicators: pH |website=[[United States Department of Agriculture|USDA]], [[Natural Resources Conservation Service]] |access-date=10 September 2023}}</ref><ref name="Cox2010"/>