Which nitrogen form can also contribute to soil acidification over time?

Ammonium is the form of nitrogen that can contribute to soil acidification over time. When ammonium is applied to the soil, it undergoes a process called nitrification, where it is converted by soil bacteria into nitrate. During this process, hydrogen ions (H+) are released into the soil, which can lead to lower soil pH, resulting in acidification. This is particularly significant in soils that receive high amounts of ammonium fertilizers over extended periods.

This acidifying effect is contrasted with other forms of nitrogen, such as urea, nitrate, and organic nitrogen. While urea can eventually lead to nitrification and thus also contribute to acidification, the initial impact of ammonium directly on soil pH is more pronounced. Nitrate is already in its oxidized form and does not contribute to acidity in the same manner as ammonium, since it does not produce hydrogen ions during its assimilation by plants or microbes. Organic nitrogen can also contribute to nitrogen availability but does so in a way that does not directly result in soil acidification during its breakdown process.

Understanding these processes is crucial for nutrient management practices as it highlights the need to balance different nitrogen sources to maintain soil health and prevent excessive acidification.