Calcium problems in limestone soils


Although it would not be included within the primary macroelements (such as nitrogen, phosphorus and potassium), calcium is a very important element in plant nutrition. The lack of this element causes deformed fruits, with rottenness and stains that cause a great destruction. However, the problem is not in quantity but in quality … 

Despite the fact that we have been in agriculture for centuries and now, in the 21st century, we have technical improvements to achieve the yield we want from plants, even today doubts arise regarding the activity and characterization of certain minerals.

One of them is calcium, considered as a secondary macronutrient (such as magnesium and sulfur), and of vital importance for most plants.

This element appears in the soil in many forms, whether in mineral form (silicates, gypsum, carbonates, phosphates, etc.) or organic. The latter is important from the point of view of plant nutrition, since it is part of the organic matter of the soil.

What the plant is interested in is the calcium ion (Ca2 +) that can be free in the soil or in the adsorbent complex. As it has a positive charge and the clay or humic compounds have a negative charge, their complexation (neutralization) occurs, they unite and form particles known as clay-humics.

Regarding this, there is a very graphic image that will raise doubts:


Calcium is a not very mobile element that nevertheless has a lot of influence on the proper development of the crop. It has a decisive role in the functioning of cell membranes. It is involved in the formation of a large number of enzymes, regulates the acid-base balance inside the plant, etc.

The problem with calcium , as we will say throughout this article, is its lack of mobility and the difficulty that the roots have in absorbing it, even many times in a chelated state.

For the root of a plant to be able to absorb calcium adequately, the following circumstances must be met:

  • That the plant has new roots with absorbent hairs (where the Caspary band has not yet formed).
  • Adequate control of perspiration in the plant and direct availability of water.
  • That the soil has active calcium and is not precipitated or immobilized by antagonists.

Taking stock of the aforementioned, if we make an adequate application of water and the soil has an adequate amount of organic matter ,  the roots will be favored and will create greater absorbent hairs (through which the calcium can be absorbed and translocated to the fruit).


Even having made a correct calcium amendment, it may be that there are inopportune circumstances to reduce its assimilation at the root level. Whether it is the soil pH , the presence of antagonists or the state of the roots, it is common to see calcium deficiency states due to their lack of mobility.

One of the peculiarities that calcium has is that its deficiency is presented differently depending on the crop. We give you an example with images.

Blossom end rot in tomato or blossom end rot in tomato crop

Blossom end rot or blossom end rot  in tomato

Apical rot of pepper or peseta 

Blossom end rot or blossom end rot on pepper

Apical burn in lettuce or tip burn

Tipburn or calcium deficiency in lettuce

Bitter pit in apple tree

Bitter pit or calcium deficiency in apple

And some more like melon vitrescence, black heart in celery, etc.


As a curiosity to tell you that calcium deficiencies (blossom end rot) have been detected in fruits where the soil had significant levels (even above normal) of calcium. Of course, if we could separate and analyze that calcium in the soil, we would realize that it is mostly made up of oxalates and carbonates. That is, calcium not soluble and not assimilable by the plant.


Although we have already seen the importance of calcium in the plant (and the damage of deficiency and excesses), we have to say that not only is this element essential for plant growth, but it also has an action on the soil , since be it from the physical, chemical or even biological point of view.

On the other hand, it must be said that this positive function for the soil only appears when there is active calcium (Ca2 +) in the soil, and not as carbonate (CaCo3).

  • Calcium is a flocculating element, forming a clay-humic complex with complexed calcium.
  • Improves the balance between the outside atmosphere (the gaseous complex) and the atmosphere inside the soil.
  • It improves the circulation of water inside the soil, avoiding the clogging of the pores and their content in air or water.
  • It raises the pH of the soil (positive if we have an acid soil a priori).
  • It is a useful food source for microorganisms and plants in the soil.
  • Improves root respiration and nutrient uptake.
  • It works by reducing the aggressiveness or virulence of certain diseases originating in the soil, such as fusariosis.


One of the great determining factors of calcium in agriculture is that its quantity does not imply good absorption by the plant. Calcium is an element with a great immobilization capacity and with many antagonistic elements that slow down its mobility and block it in the soil.

In fact, a good amount of calcium in the soil (due to the type of structure and the pH it has) coupled with a good calcium fertilizer does not imply that problems related to the lack of this element do not appear. How is this possible?

The problem with calcium is not in its low availability, but in its assimilation and transport.

However, to further curl the curl, there is a current trend that defends that the lack of calcium does not cause these rottenness, but the consequence . To put it another way, calcium deficiency appears when there is already a visual symptom of the problem.

This only makes us think that calcium has the disadvantage of knowing the exact moment of its application. According to the line that the research has followed in reference to the lack of calcium in the fruits, the ideal time to apply this element is just after the fruit set. That is, the demand for calcium appears when the plant organ is growing (and not only the fruit, but also leaves, meristems, etc.).

So if you observe apical rot or other effects as a result of calcium deficiency, do not apply it, you are late.

Have you ever had problems related to calcium deficiency?

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