What is the Difference Between Ammonium Sulfate and Urea?

Ammonium sulfate and urea are two important fertilizer types that differ in their chemical composition, nitrogen content, and effect on soil acidity. Here are the key differences between the two:

1. Chemical Composition: Ammonium sulfate is an inorganic compound with the chemical formula $$\left( {N{H4}} \right)2}S{O4$$, while urea is an organic compound with the chemical formula $$CH{\left( {NH2^ - } \right)_2}$$.
2. Nitrogen Content: Urea has a higher nitrogen content (46%) compared to ammonium sulfate (20.6%). This makes urea a more cost-effective option in terms of $/N (dollars per unit of nitrogen).
3. Effect on Soil Acidity: Ammonium sulfate creates more acidity in the soil than urea. This means that when using ammonium sulfate, more limestone may need to be applied to neutralize the acidity. Urea, on the other hand, does not produce acid when added to water, making it a more preferred option for nitrogenous fertilizers.
4. Application: Ammonium sulfate is a superior fertilizer when applied prior to a permanent flood, while urea is a superior fertilizer when applied after permanent floods.
5. Volatilization: Urea has a higher tendency to volatilize (evaporate) compared to ammonium sulfate. This can lead to the loss of nitrogen from the soil, making it less efficient as a fertilizer. To mitigate this issue, some farmers use agratane, a urease inhibitor, to help reduce volatilization.

In summary, urea is generally preferred over ammonium sulfate due to its higher nitrogen content, lower acidity, and more balanced effect on soil pH. However, ammonium sulfate may be more suitable for certain applications, such as before a permanent flood.

Comparative Table: Ammonium Sulfate vs Urea

Here is a table comparing the differences between ammonium sulfate and urea:

Ammonium sulfate is an inorganic compound with the chemical formula (NH4)2SO4, containing an ammonium cation linked to a sulfate anion. It is a widely used nitrogen source for microorganisms' cultivation. On the other hand, urea is an organic compound with the chemical formula CO(NH2)2, produced by reacting carbon dioxide with ammonia. It is a sustainable and cheaper alternative nitrogen source.

Urea has a higher nitrogen content compared to ammonium sulfate. However, ammonium sulfate has the added benefit of containing sulfur, which is essential for plant growth. Ammonium sulfate has a lower pH and is acidifying, while urea is neutral and does not significantly affect soil pH. Ammonium sulfate is less prone to volatilization than urea.

In terms of cost, urea is generally cheaper compared to ammonium sulfate in terms of $/N. Watershed management and fertility management plans should be considered when applying these fertilizers to avoid potential losses and maximize nutrient uptake by plants.