When it comes to calcium, many people don’t really consider if and why it can have a significant role in plants as well. However, calcium ions or CA2+ plays a critical role in not only plant growth but also in plant yield as well.

How Plants Use Calcium?

Calcium is a vital substance for plants. It is generally absorbed through the roots of the plant in calcium-rich soil. It is very useful in helping the plants grow and becomes a main constituent of the plant’s cell wall. Without calcium in the plant to hold the cell walls together, the plants would fall apart.

Calcium, when placed on the cell wall, is remarkably stable. This means that once it is attached, it is there for the remainder of the plant’s life. This works out well when it comes to structural integrity because then plant needs a more permanent structure to ensure stability.

Plants generally get calcium from the mineral-rich soil. If the soil has no calcium, they can become deficient, which can cause some noticeable effects in plants. This can be a whitish ring around the leaves, or blossom end rot when it comes to tomatoes. So this is why it’s vital to make sure that your plants get adequate amounts of calcium.

Leaf Absorption Vs. Soil Absorption

The most common idea when it comes to feeding plants calcium is by fortifying the soil. However. That is not the only way for plants to absorb calcium. The plants can also absorb calcium through their leaves. This is referred to as applying Foliar Calcium.

It may seem redundant, as calcium is calcium, right? Not exactly.

Calcium deficiency is a problem, even in many plants, and especially in plants that need more calcium, such as leafy greens. So many believe that applying calcium directly to the leaves will help the plants and thus increase yield. But is there any evidence for this? Actually, yes, There have been many studies done on foliar application of calcium and what the effects are. For instance, this study titled Foliar application of calcium and magnesium improves growth, yield, and essential oil yield of oregano published in 2008 states:
“These results show that Ca2+ and Mg2+ applications can affect the growth and yield of oregano, especially when the plant is grown in acid soils.”

Another study, published in 2006 titled Pre-harvest foliar application of calcium and boron influences physiological disorders, fruit yield and quality of strawberry concluded with this:
“Our studies indicated that pre-harvest foliar application of Ca + B is quite useful for reducing the incidence of disorders and getting higher marketable yield in ‘Chandler’ strawberry.”

So it seems from this that foliar application of calcium not only works but also increases the yield of particular plants as well.

Is a Foliar Application better than Soil Application?

In many instances, it can be. Since with normal soil fertilization, the roots have to work to bring the calcium all the way through the plant, applying the calcium directly to the leaf can cut out the middleman. This can allow the plant to absorb calcium more readily, benefiting the nature of the plantAs shown before, it works out well when compared to soil fertilization. Applying calcium directly to the leaves of the plants appears to cause the plant to grow faster, healthier, and produce more yield. It certainly works better than a traditional soil application. However, that does not mean that a traditional soil fertilization cannot also be used in conjunction with foliar feeding, simply to make sure that the plant does not die.

Calcium toxicity is something that rarely occurs. In such cases, calcium can compete with magnesium absorption, so be aware of that. This type of toxicity was observed with liquid calcium fertilizers such as calcium nitrate where the excess of calcium penetration through the leaf is possible. However, calcium in a form of finely ground mineral sources provides slow release to plant over leaf surface and is unlikely to cause overdose or toxicity.

Sources:

1. WHITE, P. J. (2003). Calcium in Plants. Annals of Botany, 92(4), 487–511. doi:10.1093/aob/mcg164
2. Hepler, P. K. (2005). Calcium: A Central Regulator of Plant Growth and Development. THE PLANT CELL ONLINE, 17(8), 2142–2155. doi:10.1105/tpc.105.032508
3. Singh, R., Sharma, R. R., & Tyagi, S. K. (2007). Pre-harvest foliar application of calcium and boron influences physiological disorders, fruit yield and quality of strawberry (Fragaria×ananassa Duch.). Scientia Horticulturae, 112(2), 215–220. doi:10.1016/j.scienta.2006.12.019
4. Dordas, C. (2009). Foliar application of calcium and magnesium improves growth, yield, and essential oil yield of oregano (Origanum vulgare ssp. hirtum). Industrial Crops and Products, 29(2-3), 599–608. doi:10.1016/j.indcrop.2008.11.004