Calcium Fertilizer

Calcium Fertilizers are chemical substances that either contain calcium in cationic form Ca+2 or produce it after it is transformed. Its main purpose is to enrich calcium nutrition in plants (since this mineral is a major component of the cell wall), promote cell division and growth, and directly affect fruit quality.

When to use Calcium Fertilizers

To answer that, there are a few things you need to know about calcium.

Most soils have enough calcium accessible to plants, as it is released through the weathering of its minerals, with no need to add more of it with fertilizers. Soils with high CEC, or clay soils, usually have more calcium available because calcium, a positively charged ion, is retained by the clay particles and organic matter of the soil.

Tropical acid soils, with low pH and high concentration of aluminum, tend to be low in calcium as it is not properly retained in the soil and can easily be leached with high rainfall.

Another important characteristic is that it has limited mobility in the soil and in the plant. It’s contact with the root is by mass flow, which means it requires water. It is then taken up from the soil solution and directed to the shoot via the xylem, also with water. As a result, one important factor to determine whether there is Ca+2 available for the plants is irrigation. Too much water can cause leaching and also damage the roots, and not enough water can prevent the mass flow.

How SMART FERTILIZER SOFTWARE can help in assessing the Calcium levels

By uploading lab tests such as soil, water and tissue into our software, it is possible to get an instant evaluation of your field conditions. For example, the soil test is assessed, and the software will estimate if the levels of the nutrients are low, adequate, high or excessive. This is fundamental in order to understand what to apply precisely, in fact if the calcium levels are already high, it is quite a large waste to apply more.

Also, calcium can be provided to the soil via multiple materials. Some particular ones are limestone and gypsum. These are not applied with a fertilization purpose but with the aim of raising the pH and therefore making the soil less acidic. Therefore, it could happen that plants potentially have all the calcium required for their growth in the soil, but often it is simply in a form or condition that is making it not available to them.

Also, calcium is a component of other fertilizers, for instance phosphorus fertilizers such as calcium phosphate and nitrogen fertilizers like calcium nitrate.

However, there are situations where calcium fertilizers need to be applied. For instance, when growing leguminous plants, because they require a much higher amount of calcium, and with lawns as whenever the grass sheds its roots it needs calcium for root growth. Also, as a result of its limited mobility in the plant, some crops with more demanding storage organs such as tomatoes and apples can show signs of calcium deficiency and require fertilizer application.

Some signs that your crop needs calcium administration are:
– Longitudinal chlorosis on the leaf edges
– Curling of young leaves or shoots
– Underdeveloped roots
– Apical rotting or Blossom-End Rot (BER)

Image by Scot Nelson


– Depressed dark areas on the fruits

John Kempf • The American Fruit Grower

– Tip burn of the new leaves
– Fruit deformation

Photo Mark Bolda, UCCE

– Stunted plants
– Distorted, cupped leaves with interveinal chlorosis

As we could see in the pictures, calcium deficiencies could appear very often, and when they show up, it is often too late to sort out the issue. Therefore, a periodical tissue sampling and SMART FERTILIZER SOFTWARE test tool is a powerful weapon as it can instantly evaluate if the calcium levels are low, adequate, high or excessive.

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Types of calcium fertilizers

Insoluble sources of calcium

  • Agricultural lime – Calcium carbonate
  • Agricultural Gypsum – Calcium sulphate dihydrate
  • Superphosphates
  • –  Single Superphosphate
  • –  Triple Superphosphate
  • –  Thermophosphate

Soluble sources of calcium

  • Nitrogen Fertilizers – Calcium nitrate
  • Calcium chloride
  • Calcium chelates


Usually calcium deficiency is not directly related to the amount of the nutrient in the soil, but to specific characteristics of the crop. Consequently, calcium is normally applied in its soluble form as a foliar fertilizer.

Once again, given its limited mobility in the soil, it is commonly applied directly to the deficient organ, for example, calcium chloride can be applied to the fruit. Calcium nitrate on the other hand can damage the fruits if applied directly on it, so it is applied on the leaves, such as on tomato leaves.

Identifying the nutrient deficiency and using the right dose of the foliar fertilizer is essential to keep the crop healthy and productive. With the SMART FERTILIZER software, you get an instant evaluation of the nutrient status of the crop and detect eventual deficiencies, simply by uploading a tissue test to the system. Understanding the nutrient requirement of the crop and how it is being uptaken is crucial in creating an accurate fertilization plan.

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  • Recommends the ideal fertilizer mixture/ blends
  • Saves up to 50% on fertilizer costs
  • Comprehensive data on hundreds of crop varieties
  • Interprets test results for any extraction method

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