Regular use of the following fertilizers increases the acidity of soil? (a) Ammonium sulphate (b) Potassium nitrate (c) Urea (d) Superphosphate of lime. ?

When it comes to understanding how different fertilizers affect soil acidity, it's important to look at their chemical composition and how they interact with the soil. Among the options you've provided, ammonium sulfate is the one that significantly increases soil acidity.

Why Ammonium Sulfate Affects Soil Acidity

Ammonium sulfate contains ammonium ions (NH4+), which, when applied to the soil, undergo a process called nitrification. During nitrification, ammonium is converted into nitrate (NO3-) by soil bacteria. This process releases hydrogen ions (H+) into the soil, which leads to an increase in acidity. The more ammonium sulfate you apply, the more hydrogen ions are released, thus lowering the soil pH.

Comparing Other Fertilizers

• Potassium Nitrate: This fertilizer provides potassium and nitrate without significantly affecting soil acidity. It does not contribute to the release of hydrogen ions, so it tends to maintain a more neutral pH.
• Urea: While urea can also be converted to ammonium in the soil, its effect on acidity is less pronounced compared to ammonium sulfate. The conversion process does not release as many hydrogen ions, so it has a more neutral impact on soil pH.
• Superphosphate of Lime: This fertilizer is primarily used to supply phosphorus and contains lime, which actually helps to reduce acidity. It can raise the soil pH rather than lower it.

Practical Implications for Soil Management

Understanding how these fertilizers affect soil pH is crucial for effective soil management and crop production. If you're aiming to lower soil pH for acid-loving plants, ammonium sulfate can be a useful tool. However, if you're looking to maintain or raise soil pH, you might want to consider using potassium nitrate or superphosphate of lime instead.

In summary, among the fertilizers listed, ammonium sulfate is the one that increases soil acidity due to the release of hydrogen ions during the nitrification process. The others either have a neutral effect or help to raise the pH, making them suitable for different agricultural needs.