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, promotes cell division and growth and directly affects 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 the plants 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, and the reason for that is, being a positively charged ion, it 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 poor on calcium, once it is not properly retained on the soil and with high rainfall it can easily be leached.

Calcium has limited mobility in the soil and in the plant. Its contact with the root is by mass flow, which means it requires water, and then it is 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 mass flow.

This nutrient is usually applied in the soil through limestone and gypsum, with no fertilization purpose (but aiming to make the soil less acid), and as a component of other fertilizers, for instance, phosphorous fertilizers such as calcium phosphate and nitrogen fertilizers like calcium nitrate. Therefore, another reason why plants commonly have all the calcium required for their growth already available to them.

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 lawn, 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 also require fertilizer application.

Some signs that your crop needs calcium administration are:

Grass
- Longitudinal chlorosis on the leaf edges
- Curling of young leaves or shoots
- Underdeveloped roots
Tomato
- Apical rotting or Blossom-End Rot (BER)
Apple
- Depressed dark areas on the fruits
Strawberry
- Tip burn of the new leaves
- Fruit deformation
Vegetables
- Stunted plants
- Distorted, cupped leaves with interveinal chlorosis

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, it is commonly applied directly on the deficient organ, for example, calcium chloride can be applied on apples. Calcium nitrate on the other hand can damage the fruits if applied right on it, so it is applied on the leaves, such as on tomato leaves.

Identifying the nutrient deficiency and using the right dose of foliar fertilizer is essential to keep the crop healthy and productive. With the i-Plant Nutrition, you get an instant evaluation of the nutrient status of the crop and detect eventual deficiencies such as Calcium simply by uploading a tissue test to the system. Understanding the nutrient requirement of the crop and how it is being up taken is crucial to creating an accurate fertilization plan.