Calcium is one of the most important nutrients plants absorb from the soil, used more than phosphorus. It's often called „soil sweetener”, cause it loosens its structure and contributes to sweetness of fruit and veg. It also enhances natural defense mechanisms of plants against pests and parasitic fungi.

The problem with calcium is its low solubility and mobility in soil. This means that deficiency is not always related to its low concentration, but often to other factors such as: soil acidification due to extensive use of synthetic fertilisers, saturation with magnesium and potassium, that compete for the same ion channels, or wiped out microlife, which is largely responsible for root system expansion, and uptake of less soluble compounds.

However, poor, sandy soils in many parts of the world lack proper levels of calcium PERMANENTLY, which means fertilisation becomes a necessity. Calcium is also removed within a few seasons by crops such as tomatoes, potatoes or corn, so it needs to be replaced eventually.

This is usually done by adding gypsum, dolomite lime, but both materials are nonrenewable, which means their mining contributes to irreversible destruction of natural environment. They also have wrong Ca:Mg ratio, and that means another correction is necessary to prevent deficiencies in plants.

But I'm happy to say, that there's a sustainable alternative for small time gardeners, and simple at that: eggshells! They contain on average 96-98% calcium carbonate (CaCO3), and can be collected on a daily basis, and used to fertilise garden beds or potting soil once in a while at ZERO COST, adding both calcium and carbon to the soil!

The only thing you need to do is to store them, dry them and grind them into powder like I've done here!