Calcium is an essential secondary macronutrient for most plants, but even more important for horticultural fruit crops, such as tomatoes or peppers.
Tomato calcium must be provided from pre-flowering, because it affects a large number of plant processes, and not only to give consistency to the fruits and avoid what is called tomato blossom end rot.
In this article we summarize how much and when to use calcium for tomatoes.
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Calcium intake in tomato
According to the literature, the production of 100 t/ha of tomato requires approximately 175 kg/ha of calcium. At this figure we must always count on the calcium provided by irrigation waterwhich in many cases is not negligible.
Calcium and other nutritional parameters in water are measured in meq/L, but with this simple table we convert it to kg/m3 of irrigation water.
| Meq/L | Irrigation volume (m3/ha) | |||
| 10 m3 | 20 m3 | 30 m3 | 40 m3 | |
| 1 | 0.2 | 0.4 | 0.6 | 0.8 |
| 3 | 0.6 | 1.2 | 1.8 | 2.4 |
| 6 | 1.2 | 2.4 | 3.6 | 4.8 |
| 9 | 1.8 | 3.6 | 5.4 | 7.2 |
Knowing that one hectare of tomato can now consume 5,000 m3 for 10,000 plants, for water at 6 meq/L typical of southern Spain, more than 600 kg of calcium are added.
Amount of calcium for tomatoes that must be supplied
Generally speaking and from water of average quality, it is usually supplied about 20 kg/ha of calcium nitrate by irrigationthe most common and efficient way to provide this element.
If we go to a smaller scale, in liters, 0.5 g/L of calcium nitrate is provided. We pass it to the following equivalent table:
| liters of irrigation water | grams of calcium nitrate |
| 1 | 0.5 grams |
| ten | 5 grams |
| 100 | 50 grams |
| 1000 | 500 grams |
Calcium corrector for tomatoes
There are not many sources of calcium compared to those of potassium or other elements, but more effective forms emerge where complexes, phytohormones and surfactants are added that improve their assimilation.
And it is that calcium is one of the most complicated elements to introduce into the plant, and for its absorption it needs water readily available to the plant, transpiration and new roots.
Some of the most commonly used forms of calcium are:
- Calcium nitrate: one of the most commonly used forms in agriculture, providing 27% CaO (calcium oxide) and 15.5% nitrate nitrogen.
- Calcium chloride: not recommended in cases where the water is very saline, because chlorine in high concentrations is harmful. However, its assimilation both in fertigation and by foliar application is very good.
- Complexed calcium: Calcium is protected by organic complexes such as acetate, gluconate or citrate, among others. Its foliar application is interesting, because it increases its assimilation by the leaves.
Foliar applications of calcium are only recommended in the early stages of plant development, during flowering or the first fattening of fruits, because its assimilation is complicated and its transport downwards (phloem) is almost non-existent.
Therefore, to cover calcium needs, it is always recommended via fertigation, from the roots to the aerial part, transported through the xylem.
In case they are done foliar applications of calcium in tomatowe recommend an amount of 500-1000 cc/hl (100 L of water).
Function of calcium in tomato cultivation
After nitrogen, phosphorus and potassium, calcium is the second most important macroelement. This nutrient is essential in tomato cultivation for maintaining cell structure and stabilizing the plasma membrane.
That is to say, it is the glue and the protective shield of the cells to keep the leaves and fruits strong and resistant.
In addition, calcium maintains the balance of salts in the “cellular juice” and, together with potassium, regulates the opening and closing of stomata.
Calcium Deficiency Symptoms
There are 2 clear symptoms of calcium deficiency in a tomato plant. The first case is seen in the head of the plant, near the apex, where new leaves form. The second case, much more obvious, is at the fruit level, with a brown spot appearing at the base or bottom of the tomato (apical rot).
Leaf symptoms: Calcium deficiency appears in the crown of the plant, where the leaves are wrinkled, forming easy to detect lumps, with the tips and edges turned down. This only happens on new leaves.
Fruit symptoms: When there is no adequate supply of calcium to fruits, the furthest part, the base of the fruit, rots. Within a few hours, a dark brown spot forms which gradually rots the fruit. It is commonly referred to as peseta, blossom end rot or apical rot.
Photography: Chris Burnett – Web: Almanac