Calcium nitrate: keys to its use in agriculture

The calcium nitrate is considered as one of the universal fertilizer. A fertilizer that is present in most irrigation heads and is widely used. In fact, considering that in many parts of Spain we have limestone soils, it still continues to be used in large quantities. The plants require calcium but how much? Let’s see it. 

When we talk about calcium nitrate or lime nitrate (also known as that), we are mentioning an inorganic fertilizer whose formula is Ca (NO 3 ) 2. 

Within this salt we will only find calcium, nitrogen and oxygen. The first 2 components mentioned, plants (except for nitrogen with legumes), cannot obtain it by themselves, so they need special contributions.


Podredumbre apical o blossom end rot

This topic is quite recurrent in Gardenprue and we will comment on it again. It must be taken into account that both NH4 + (ammonium) and this calcium are absorbed by mass flow (with water). For this reason, it is important that to facilitate the absorption of the latter by the roots of the plant, the hydric conditions of the soil are good and, in addition, there is not much presence of ammonia.

[alert style = »green»] Hence it is always said that peseta problems are caused by a lack of calcium . However, this phrase is not well said at all. There is no specific lack of calcium in the soil, but simply the plant cannot assimilate it. Why? [/ Alert]


  • Excess humidity
  • Environmental humidity defect
  • A large amount of light that increases the growth of the plant and dilutes the volume of calcium in sap.
  • High temperatures with a variation in humidity.


  • Soils with a large amount of ammonia (NH4 +).
  • Large accumulation of salts and high osmotic potential in the soil ( high conductivity ).
  • Antagonisms with other elements (magnesium, ammonium, other cations, etc.).

That is why the calcium nitrate provided must be linked to climatic conditions that we can barely control, and to practical conditions that we do have direct action on, such as subscriber conditions .

The cause of peseta is also linked to the low transpiration rate of the fruits . Low transpiration rate means that calcium is not mobilized to the fruits in the moments of greatest need (fruit set and initial development). For this reason, blossom end rot appears at the base of the fruit, where it is most difficult to reach calcium.


In most of the bags that we are going to find the nitrate of lime we will find the following:

  • Total nitrogen (N): 15.5%
  • Calcium (CaO): 26%

These values ​​can vary in decimal places. Normally we will always find nitrogen between 14.4 and 14.5%, and calcium between 26 and 27%.

If we get into issues of meq / L , very common in greenhouse crops where conductivity is used, it should be noted that each meq of calcium that is provided, also includes 1 meq of nitrogen.

In terms of mmol / L , for every 1 mmol of calcium supplied, 2 mmol of calcium is added. This is very important when establishing fertilizer plans, since nitrogen contributions must be controlled. Very often they are excessive and affects both the plant and our pocket.


It is a way of knowing what and how much we pay. It is something different from fertilizer units and has its advantages and disadvantages. With this first working system, you know how much water you add. At least, it is a known parameter.

With fertilizer units it is an unknown value. Suppose you have to add 10 FU of nitrogen. In how much water? It is something that we do not know and whose data we have to provide.

If we transform the mmol of calcium nitrate to a known value system, for example, the grams of compost per cubic meter of water , then we have to do the following calculation:

1 mmol / L of calcium nitrate · 182 mg / mmol = 182 g / m3 of water.


Imagine that a horticultural plant in our garden, such as a pepper or tomato, needs, for example, 10 meq / L calcium. The most common way to provide this calcium is undoubtedly with calcium nitrate .

Imagine that you are going to water your tomatoes with 1,000 liters of water. How many kg of this fertilizer do I add?

10 meq / L of calcium is 5 mmol / L, since its valence is taken into account.

We return to the formula from before:

5 mmol / L of calcium nitrate · 182 mg / mmol = 910 grams / m3 of water. That is, almost 0.9 kg for those 1,000 L of water. With this, the plant is more than supplied with calcium. And that’s not counting the calcium in the irrigation water …


It is not necessary to generalize, because each crop demands different needs. Calcium is a nutrient that is used in excess since many times the large amounts that water contributes are not taken into account, simply because a water analysis is not done .

A very pure water, understanding pure with a fairly low conductivity (below 1), can have between 1 and 2 meq / L of calcium. If for one hectare in each irrigation 40,000 liters of water can be supplied, we can be adding to our soil between 1 and 2.5 kg / ha of pure calcium.

This, in terms of calcium nitrate , would be around 3.70 and 9.25 kg / ha.

For an intensive pepper, with an expenditure of 4,000 m3 of water per season, we would be talking about 1,000 kg of calcium nitrate, with a price of € 400.

Therefore, the calcium intake is variable and must be done taking this into account. A water analysis is worth much less than these € 400 that we are counting.

[alert style = »green»] Normal doses for an average crop are between 300 and 800 kg / ha, according to the recommendations of the fertilizer houses. [/ alert]


As we said in its day about the incompatibility between fertilizers , calcium nitrate is a very messy fertilizer.

It can be mixed with most composting solutions, with the exception of all those that contain sulfates (ammonium sulfate, magnesium sulfate, potassium sulfate, etc.) and phosphorus (phosphoric acid, monopotassium phosphate, monoammonium phosphate, etc.).

Welcome to The GardenPure! My name is Ryan Heagle, and I’m the founder of The GardenPure, I spent the first part of my adult life teaching and then living in Australia in various business ventures, the first of which was a business devoted to the sale of house plants.  I am now a full time blogger. I am a self taught gardener.

Ryan Heagle

Welcome to The GardenPure! My name is Ryan Heagle, and I’m the founder of The GardenPure, I spent the first part of my adult life teaching and then living in Australia in various business ventures, the first of which was a business devoted to the sale of house plants.  I am now a full time blogger. I am a self taught gardener.

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