Making the most of Calcium (Ca) as a soil plant nutrient.

Calcium is a secondary nutrient and is taken up by the plant as Ca²⁺ it is the fifth most abundant element in the Earth’s crust and is a vital nutrient for optimal plant and animal growth. In spite of this, it is often overlooked and undervalued by both agriculturalist and farmers alike. A number of health and growth problems, such as blossom-end rot, in intensive crop production can be attributed to Ca-deficiency.

Functions of Ca

• Necessary for cell wall development and strength.
• Hot dry weather is not beneficial for Ca-absorption.
• Low levels of Ca in the leaf make the plant susceptible to foliar damage from heat stress.
• Ca is important for the active transport of K for the regulation of stomatal openings.
• Low Ca-levels in leaf means poor control of the stomata even with high K levels.
• Low soil levels of Ca will lose yield and quality, their production costs will increase, and profitability will decrease.
• Soil-Ca improves soil structure and porosity, improves air and moisture movement, enhance soil biology and promotes root growth within the soil.
• Not only does Ca strengthen plants’ cell walls and bind cells together, it is important for cell division and elongation.
• Plants also need Ca to assist with their uptake and translocation of other important nutrients, and
• Ca helps plants to release stress and increase their tolerance to pests and diseases.
• Finally, Ca helps increase the shelf-life of fresh produce.

Increasing Soil-Ca levels

There are four common sources of Ca that can be used to be applied to soil to improve soil pH and Ca-levels

• Lime – calcitic and dolomitic
• Hydrated lime
• Gypsum
• Ca-Salts e.g., Calcium Nitrate and Calcium Chloride

While lime is good for reducing soil acidity, supplementary soluble Ca is often required to meet the immediate crop and soil Ca requirements that is largely immediately insoluble. Gypsum is good for treating sodic soils and sub-soil acidity. It is more soluble than lime, but it is still relatively insoluble. Should a soil or crop require immediate Ca-availability, it may be best to apply the necessary quantities as a soluble Ca source.

The Table below illustrates the solubility of different lime and calcium sources

Conclusion:

Consult with a trusted Kynoch Agriculturalist expert before deciding on which Ca salt is needed. This is because the nitrates and chlorides in these Ca salts may actually be undesirable and detrimental to either the soil or crop quality if not applied appropriately.

Source:

Reference: Fertilizer Handbook, 2007. FSSA; Bornman, JJ

Compiled by:

Hugh Smith, Agriculturist at Kynoch Fertilizer

FAQ: The Role of Calcium in Agriculture

What is the important role of calcium in plants?

Calcium plays a crucial role in plants by contributing to cell wall structure, stabilising cell membranes, and facilitating the transport and retention of other nutrients. It is essential for root development, enzyme activity, and overall plant health. Calcium also helps in mitigating the effects of stress conditions such as salinity and drought.

What is the purpose of calcium in fertiliser?

The purpose of calcium in fertiliser is to supply plants with an essential nutrient required for their growth and development. Calcium-containing fertilisers, such as lime, gypsum, and calcium nitrate, help in correcting calcium deficiencies in the soil, ensuring robust plant health and optimal crop yields.

What is the purpose of calcium in soil?

Calcium in soil improves soil structure by enhancing the aggregation of soil particles, which promotes better water infiltration and root penetration. It also helps in maintaining a balanced soil pH, which is crucial for the availability and uptake of other essential nutrients by plants.

What plants benefit from calcium?

Many plants benefit from calcium, including:

• Tomatoes: Prevents blossom end rot.
• Peppers: Enhances fruit quality and prevents blossom end rot.
• Lettuce: Promotes leaf development and prevents tip burn.
• Cabbage and Broccoli: Supports healthy head formation and overall growth.
• Fruit Trees (e.g., apples, citrus): Improves fruit quality and storage life.

Why is calcium important in crops?

Calcium is important in crops because it strengthens cell walls, promotes healthy root and shoot development, and enhances resistance to diseases and pests. It also aids in the uptake of other essential nutrients, improving overall plant health and productivity.

What are the symptoms of calcium deficiency in plants?

Symptoms of calcium deficiency in plants include:

• New Growth: Distorted, twisted, or curled leaves.
• Blossom End Rot: Dark, sunken spots on the bottom of fruits like tomatoes and peppers.
• Tip Burn: Margins of leaves turn brown and die, commonly seen in lettuce.
• Root Issues: Poor root development and increased susceptibility to root diseases.
• Stunted Growth: Reduced growth rate and overall plant vigour.

What happens when plants get too much calcium?

When plants get too much calcium, it can lead to an imbalance of other essential nutrients, particularly magnesium and potassium. Excessive calcium can cause nutrient deficiencies, poor plant growth, and reduced crop yield. It can also lead to soil alkalinity issues, affecting nutrient availability.

How do I know if my soil needs calcium?

You can determine if your soil needs calcium through soil testing, which will measure the calcium levels and soil pH. Symptoms of calcium deficiency in plants and poor soil structure can also indicate a need for calcium supplementation.

Does calcium stimulate plant growth?

Yes, calcium stimulates plant growth by supporting cell division and elongation, strengthening cell walls, and enhancing root development. It also plays a role in nutrient uptake and stress resistance, contributing to overall plant health and productivity.

How to give calcium to plants?

To give calcium to plants, consider the following methods:

• Lime: Apply agricultural lime (calcium carbonate) to raise soil pH and supply calcium.
• Gypsum: Use gypsum (calcium sulfate) to add calcium without altering soil pH.
• Calcium Nitrate: Apply calcium nitrate as a fertiliser for a quick calcium boost.
• Foliar Spray: Use a calcium solution to spray directly on leaves for rapid absorption.
• Organic Sources: Incorporate crushed eggshells or bone meal into the soil.

How much calcium is needed for plant growth?

The amount of calcium needed for plant growth varies by plant species and soil conditions. Generally, soil calcium levels should be maintained between 1,000 to 2,000 ppm (parts per million). Regular soil testing and monitoring are essential to determine the specific calcium requirements of your crops.

What is the main function of calcium?

The main function of calcium is to provide structural support to plant cells by strengthening cell walls and membranes. It also regulates nutrient uptake, enzyme activity, and signal transduction pathways, playing a vital role in overall plant growth, development, and stress tolerance.