Urea vs. CAN: How Nitrogen Form Changes Fertilizer Performance

Urea and Calcium Ammonium Nitrate (CAN) are both widely used nitrogen fertilizers, but the question is not simply which one is “better” or whether one can directly replace the other.

Their real differences lie in:

nitrogen concentration, nitrogen form, nutrient availability, response speed, and their sensitivity to temperature, moisture, and application method.

So in practical crop nutrition, the better question is not:

“Which fertilizer supplies nitrogen more effectively?”

but rather:

“Which nitrogen source is more suitable for this crop, at this growth stage, under these environmental conditions?”

1. The Most Obvious Difference: 46% N vs. 15.5% N

Urea

Typical agricultural urea contains approximately:

46% total nitrogen

Almost all of this nitrogen is present as amide nitrogen.

Its main advantage is clear:

Urea provides one of the highest nitrogen concentrations among solid nitrogen fertilizers.

This gives it major advantages in large-scale agriculture in terms of transportation, storage, handling, and cost per unit of nitrogen applied.

Calcium Ammonium Nitrate

For the fully water-soluble CAN products commonly supplied in the Chinese market, typical specifications are approximately:

• Total Nitrogen: 15.5%

• Nitrate Nitrogen: approx. 14.4-14.5%

• Ammonium Nitrogen: approx. 1.0-1.1%

• Calcium: approx. 19% Ca

• Equivalent to approx. 26% CaO

This type of CAN is therefore primarily a nitrate-based nitrogen fertilizer that also supplies highly available calcium.

If we compare the two purely on nitrogen concentration, the difference is significant.

To supply 10 kg of actual nitrogen, approximately:

• 21.7 kg of urea is required

• 64.5 kg of CAN 15.5 is required

In other words, when calculated on an equal-nitrogen basis, the amount of CAN required is roughly three times that of urea.

This is why the value of CAN should not be assessed simply by looking at nitrogen concentration.

Its real value lies in the combination of:

rapidly available nitrate nitrogen + water-soluble calcium.

2. Why Does CAN Often Produce a Faster Crop Response?

The answer is not that CAN contains more nitrogen.

The key difference is nitrogen form.

CAN: Nitrogen Is Already in a Directly Available Form

Most of the nitrogen in CAN is present as nitrate nitrogen (NO₃⁻-N).

Once dissolved in the root-zone solution, nitrate can be directly absorbed by plant roots without first undergoing urea hydrolysis.

As a result, under suitable root activity and soil moisture conditions, CAN can often generate a relatively fast nutritional response.

This is especially useful for:

• rapid topdressing

• early crop establishment

• recovery from temporary nitrogen deficiency

• fruit and vegetable nutrition

• fertigation systems

Urea: Conversion Is Required First

After urea is applied to soil, it must first be hydrolyzed by the enzyme urease to form ammonium nitrogen.

The ammonium can then either be absorbed directly by plants or further converted into nitrate through nitrification.

The pathway is therefore approximately:

Urea → Hydrolysis → NH₄⁺ → Plant Uptake / Nitrification to NO₃⁻

By contrast, much of the nitrogen in CAN is already present as NO₃⁻.

One of the fundamental differences between the two products is therefore:

CAN provides more direct nitrogen availability, while urea relies more heavily on transformation processes after application.

3. Why Does CAN Often Have an Advantage Under Low-Temperature Conditions?

Low temperatures reduce both root activity and the rate of biological and biochemical reactions in soil.

For urea, nitrogen availability is influenced not only by root uptake capacity, but also by the rate of urea hydrolysis and subsequent nitrogen transformation.

As a result, under early-spring, cool-soil, or highly variable temperature conditions, the crop response to urea may be slower.

CAN behaves differently.

Because most of its nitrogen is already present in nitrate form, it does not need to wait for urea hydrolysis before becoming available.

Its nitrogen supply pathway is therefore shorter and more direct.

This is one reason nitrate-based fertilizers can be particularly useful in:

• early-spring topdressing

• winter and spring greenhouse production

• cool-season vegetable cultivation

• situations where a rapid nutritional response is required

However, one important point must be emphasized:

Low temperatures also reduce plant root activity.

Therefore, it would be inaccurate to say that CAN is “unaffected by low temperatures.”

A more precise statement is:

CAN is less dependent on soil nitrogen transformation processes under low-temperature conditions.

4. Urea Is Not a “Slow-Release Fertilizer”

This is a common misunderstanding in practical fertilizer use.

Conventional urea is a highly soluble nitrogen fertilizer.

It is not inherently a controlled-release or slow-release fertilizer.

The reason urea may sometimes appear to act more gradually than nitrate fertilizer is that it first needs to undergo hydrolysis and subsequent nitrogen transformation.

After urea is converted into NH₄⁺, part of the ammonium can be retained by negatively charged soil colloids.

Compared with nitrate, this can temporarily reduce nitrogen mobility.

However, as nitrification proceeds:

NH₄⁺ → NO₃⁻

the nitrogen gradually enters the mobile nitrate pool and becomes subject to similar leaching risks.

Therefore, rather than simply saying:

“Urea has a longer residual effect,”

a more accurate description would be:

Urea usually produces a less immediate initial nitrogen response, while CAN supplies nitrate nitrogen more directly.

If a genuinely longer nitrogen supply period is required, urea normally needs to be managed through strategies such as:

• split application

• incorporation into soil

• appropriate irrigation

• urease inhibitors

• nitrification inhibitors

• controlled-release or coated fertilizer technologies

5. Their Nitrogen Loss Pathways Are Also Different

Understanding these loss mechanisms is critical for improving nitrogen-use efficiency.

Urea: Ammonia Volatilization Is a Key Risk

When urea is surface-applied and remains on the soil surface, hydrolysis can result in ammonia volatilization under certain conditions.

The risk becomes particularly important under:

• high temperatures

• alkaline soil conditions

• heavy crop residues

• prolonged periods without effective rainfall or irrigation

• situations where urea remains on the soil surface after application

Incorporating urea into the soil, or applying suitable irrigation or rainfall soon after application, can help reduce ammonia volatilization losses.

CAN: Nitrate Leaching Is a Key Risk

Most of the nitrogen in CAN is present as NO₃⁻.

Nitrate is highly mobile in soil and is only weakly retained by soil colloids.

As a result, nitrogen losses can increase under conditions such as:

• heavy rainfall

• excessive irrigation

• sandy soils

• underdeveloped root systems

• large single-dose applications

Under prolonged waterlogging or oxygen-deficient conditions, nitrate may also be lost through denitrification.

So:

CAN is not a fertilizer with “no nitrogen losses.” Its nitrogen loss pathways are simply different from those of urea.

For urea, the main concern is often:

ammonia volatilization

For CAN, more attention should be paid to:

nitrate leaching and denitrification.

6. CAN Also Provides Something Urea Does Not: Calcium

If the comparison focuses only on nitrogen, the practical value of CAN can easily be underestimated.

A typical CAN 15.5 product may also supply approximately:

19% Ca / 26% CaO

Calcium is an essential secondary plant nutrient and plays important roles in:

• cell wall formation

• cell membrane stability

• root tip and growing point development

• fruit tissue structure

• a wide range of physiological processes in plants

For crops such as tomatoes, peppers, cucumbers, strawberries, grapes, apples, and other high-value fruit and vegetable crops, CAN is therefore often used not merely as a nitrogen fertilizer.

Its role is more accurately described as:

a combined source of nitrate nitrogen and water-soluble calcium.

This is one of the most important functional differences between CAN and urea.

7. When Is CAN More Suitable?

CAN is particularly suitable in the following situations:

1. Rapid Topdressing

When crops require a fast nitrogen response, nitrate nitrogen offers a shorter nutrient-availability pathway.

2. Early Spring or Relatively Cool Conditions

When soil nitrogen transformation is relatively slow, directly supplying nitrate nitrogen can help establish a more immediate nitrogen supply.

3. Fruit, Vegetable, and High-Value Crops

Especially when crops require both nitrogen and calcium.

4. Fertigation Systems

Fully water-soluble CAN can be suitable for drip irrigation and other fertigation systems.

However, because it contains calcium, it should generally not be directly mixed in concentrated stock solutions with high concentrations of:

• phosphates

• sulfates

as this may increase the risk of precipitation.

5. Split and Precision Fertilization Programs

CAN is particularly well suited to smaller, more frequent applications matched to crop uptake demand.

8. When Does Urea Have a Clear Advantage?

Urea remains one of the most important nitrogen fertilizers worldwide, and its advantages are equally clear.

1. Large-Scale Nitrogen Supply for Field Crops

For crops such as wheat, maize, and rice, where large amounts of nitrogen are required, the 46% nitrogen concentration of urea significantly reduces transport, storage, and application costs.

2. Production Systems Sensitive to Cost per Unit of Nitrogen

When the main objective is to supply large amounts of nitrogen economically, urea generally has a strong cost advantage.

3. Situations Where Incorporation, Irrigation, or Rainfall Can Be Managed

If urea can be moved quickly into the soil, ammonia volatilization can be substantially reduced.

4. When Combined with Split Application or Nitrogen-Efficiency Technologies

Urea performance can be further improved through:

• optimized application timing

• urease inhibitors

• nitrification inhibitors

• controlled-release technologies

9. Several Practical Points Worth Remembering

CAN Should Not Replace Urea on a Kilogram-for-Kilogram Basis

Because:

46% N is not the same as 15.5% N.

Replacing 100 kg of urea with 100 kg of CAN would reduce actual nitrogen input from approximately:

46 kg N to only 15.5 kg N.

Therefore, the two fertilizers should be compared based on:

cost per kilogram of actual nitrogen + calcium value + crop response speed

rather than simply comparing fertilizer price per metric ton.

High-Nitrate Fertilizers Require Caution in Paddy Fields

Under prolonged flooded and anaerobic conditions, nitrate is more susceptible to denitrification.

For this reason, high-nitrate nitrogen fertilizers are generally not the most appropriate choice for sustained nitrogen supply in flooded rice systems.

CAN Is Better Suited to Smaller, More Frequent Applications

Because nitrate is highly mobile, CAN is usually better suited to:

split applications matched to root uptake demand

rather than large single-dose applications.

Conclusion: It Is Not About Which Fertilizer Is “Stronger” - It Is About Which One Fits the Situation

Urea and calcium ammonium nitrate are both nitrogen fertilizers, but their functions are not identical.

A simple way to understand the difference is:

Urea: high-concentration, economical, large-scale nitrogen source

CAN: nitrate-based, fast-response nitrogen source with water-soluble calcium

If the objective is to provide large amounts of nitrogen economically to field crops, urea will often have the advantage.

If the objective is rapid topdressing, improved nitrogen availability during cooler periods, or simultaneous nitrate nitrogen and calcium supply in high-value fruit and vegetable crops, CAN can offer clear practical benefits.

Modern nitrogen management is therefore not really about asking:

“Which is better, urea or CAN?”

The more important question is:

“At the right crop stage, under the right environmental conditions, which nitrogen form can be delivered most effectively to the active root zone?”

That is the real key to improving nitrogen-use efficiency.

Urea vs. CAN: How Nitrogen Form Changes Fertilizer Performance