What Are the Differences Between Urea and Ammonium Sulfate? (Applicable Comparison)

Ammonium sulfate and urea are among the best nitrogen fertilizers and provide nitrogen, one of the most important elements plants need. However, these two nitrogen fertilizers have fundamental differences. Before comparing urea and ammonium sulfate, let’s examine the importance and impact of nitrogen on plants.

Nitrogen is one of the three essential elements needed by plants. This element causes vegetative growth, flowering, fruiting, maintaining plant health, and improving the quality of agricultural products. If the nitrogen in the soil decreases, we will see the fall of leaves, yellowing of leaves, poor quality of agricultural products, and insufficient plant growth. For this reason, the necessary nitrogen should be applied to the soil by observing the relevant symptoms.

Urea, ammonium sulfate, and ammonium nitrate are mineral nitrogen fertilizers that are quickly absorbed by plants and can be used in a wide range of soils. Earlier in an article, we compared ammonium sulfate and ammonium nitrate. In this article, we are going to compare ammonium sulfate and urea.

What is urea?

Urea is a chemical compound with the formula CO(NH2)2. It is widely used in agriculture as a nitrogen fertilizer. Urea has 46% nitrogen, which is one of the highest nitrogen content among chemical fertilizers. This substance dissolves easily in water and is quickly absorbed into the soil. Urea fertilizer increases plant growth in the shortest possible time.

Urea is converted into a plant-absorbable form in three steps. In the first step, the enzymes in the soil convert urea into ammonia. After that, the formed ammonia reacts with the water in the soil, and ammonium is formed. In the third stage, ammonium is converted into nitrate through the activity of soil microorganisms. When the humidity and temperature are right, the conversion of urea to ammonium takes between 2 and 4 days. The colder the weather, the slower this process happens.

One of the most important disadvantages of urea is its high wastage. The nitrogen form of urea is nitrate—NO3. Nitrate has a negative charge and cannot form a strong bond with the negative ions in the soil. For this reason, this fertilizer is easily washed away during irrigation and rains and removed from the reach of the plant’s roots.

Also, in the heat of summer, ammonia evaporates from the soil surface and is out of reach of the plant. All these factors make urea fertilizer less effective than it should be. For this reason, farmers have to prepare urea fertilizer several times during the agricultural season, which increases the cost of agriculture.

As we said, urea loses effectiveness at high temperatures and pH. To avoid this problem, it is better to irrigate the ground after fertilizing. Also, it is better to consume this fertilizer in installments and in several stages.

What is ammonium sulfate?

Ammonium sulfate, with the formula NH4 (2SO4), is one of the most widely used nitrogen fertilizers. Its composition consists of 21% nitrogen and 24% sulfur.

This fertilizer dissolves well in water, and due to its slow release, plants are given a stable nitrogen source. The nitrogen form of this fertilizer is ammonium (NH4+). This issue causes ammonium to bind to soil particles, and ammonium sulfate is washed less due to proper binding. Ammonium sulfate has fewer negative effects on the soil than other nitrogenous fertilizers.

The time of using ammonium sulfate is determined according to the type of product, soil conditions, and weather conditions. This fertilizer is compatible with most and can be used in combination with other fertilizers.
Sulfur in ammonium sulfate reduces soil pH, making this fertilizer suitable for use in calcareous and alkaline soils. It also reduces the cost of remediation of these soils.

Comparison of urea and ammonium sulfate

To understand which fertilizer the plant needs, we must consider the soil conditions, the type of plant, and the weather conditions. However, in a general review, we want to compare urea and ammonium sulfate from several points of view in this section.

• The chemical formula of urea is CO(NH2)2 and the chemical formula of ammonium sulfate is (NH4)2SO4 .
• The percentage of nitrogen in urea fertilizer is 46%. If ammonium sulfate has 21% nitrogen.
• Ammonium sulfate contains 24% sulfur, which greatly affects plant growth and health. Urea fertilizer does not contain sulfur.
• Urea is in the category of quick-release fertilizers. If ammonium sulfate is slow-release. The effect of urea is much faster than that of ammonium sulfate; therefore, this fertilizer is suitable for plants that need to receive nitrogen quickly. Of course, for fertilizing with urea, the soil must have favorable conditions. Ammonium sulfate is one of the slow-release fertilizers; over time, it has provided the plant with its nitrogen requirement. Ammonium sulfate fertilizer is suitable for supplying nitrogen to plants during the season.
• Washing and sublimation of urea is high. But ammonium sulfate has little leaching.
• Ammonium sulfate is suitable for use in alkaline and saline soils, but urea fertilizer is not. Urea fertilizer increases the alkalinity and salinity of saline and alkaline soil, making it more suitable for crops that grow in acidic soil.
• Urea fertilizer is cheaper than ammonium sulfate.
• Saline soil leads to an imbalance of nutrients, including sulfur deficiency. Ammonium sulfate contains sulfur and can supply the sulfur needed by the plant.
• Urea has a very high solubility, Which makes it easy for plants to absorb this fertilizer.
• Ammonium sulfate is more suitable for fertilizing trees in tropical regions. Its positive effects on palm trees include the growth of roots and leaves, increasing the health of the trunk, and improving the quality of the product.

In general, ammonium sulfate is a multipurpose fertilizer that is suitable for a variety of agricultural products. Ammonium sulfate, due to its stability in providing nitrogen and sulfur, can adjust the pH of the soil and apply nitrogen to the plant in a stable manner. Using urea in lands with high pH is not recommended Because this fertilizer increases the pH. Urea is a better choice for crops that need a quick increase in nitrogen or grow in acidic soils.

Sometimes, it is better to fertilize agricultural land using a combination of ammonium sulfate and urea. The simultaneous use of these two fertilizers not only reduces the harm of using them separately, but also increases the efficiency of nitrogen absorption.

How to use urea and ammonium sulfate fertilizer

Nitrogen fertilizers such as ammonium sulfate, urea, ammonium nitrate, etc., are applied according to the plant’s needs. How much nitrogen fertilizer is given to the ground per year depends on the age of the trees, the type of plant, the weather conditions, and the soil conditions. In order to understand how much fertilizer to give to the land, we must first understand its needs.

To determine the amount and type of fertilizer, a soil sample should be taken from your land or farm and examined in the laboratory. After the test, the soil’s need is determined, and based on this, the type of fertilizer and the number of fertilization times are determined.
Of course, some farmers fertilize their fields experimentally. Knowing what type of fertilizer to apply under what conditions requires a lot of experience. Nitrogen fertilizers are usually applied to the ground three times a year. Late winter, early spring, and flowering or fruiting stage are the best times to apply nitrogen fertilizer.

Be careful that excessive fertilization not only does not help the growth of plants and agricultural products but also has many disadvantages for the plants.

For example, many grasses grow in the ground because nitrogen fertilizers such as urea are consumed heavily. Excessive fertilization also causes problems with the plant’s flowering and stops the growth of the roots.

The most important harm of excessive fertilization is the entry of nitrates into underground water, which pollutes water and land. Therefore, do not overuse any type of nitrogen fertilizer and fertilize according to the needs of the land.