Calcium (40.08)(+)

Calcium is a secondary plant macro-nutrient that is essential for healthy plants. Calcium has bad mobility in plants. Plants require Calcium to build cells. Roots, leaves, stems and fruit require Calcium to grow. Calcium is also needed by plants to fight attacks from pests and disease. It facilitates Nitrogen uptake and is required by plant enzymes.

Factors affecting Calcium availability

• pH - Calcium is less available in acidic soil and more available in alkaline soil.
• Organic matter - higher concentrations of organic matter hold more Calcium as a result of a higher cation exchange.
• High levels of soluble salts due to over fertilization can prevent the uptake of Calcium.
• High Nitrogen fertlisation (plants bolting).
• Inadequate water in the soil can prevent the uptake of Calcium.
• Root damage or poorly developed roots (root rot or nematodes).
• Cold temperatures can prevent the uptake of Calcium.

Calcium Issues

Plants are predisposed to Calcium deficiencies when grown in acidic soils and or during the colder parts of the season (autumn/spring). While most soils will have sufficient Calcium to sustain plant growth, some soils are naturally deficient in Calcium. To establish whether your soil is deficient in Calcium, a soil test can be taken to establish Calcium levels in the soil. Periods of drought or irregular poor watering can resulting in inadequate water availability to the plant which in turn can bring about Calcium deficiency. Damaged roots due to disease or nematodes can result in plants not being able to take up Calcium. High levels of soluble salts in the soil due to over fertilization can also bring about a situation whereby plants are not able to uptake Calcium. Another often overlooked factor is excessive Nitrogen fertilisation. High Nitrogen can bring about growth spurts in plants which create a situation where plants are growing faster than Calcium can be deployed to the growth points. This will result in growth points being deficient in Calcium.

Symptoms

The first tell-tale symptoms that appear is in the new leaves at the growth points. Leaves at growth points appear bubbly, irregular and deformed. Plants suffering from Calcium deficiency tend to stunt. As the deficiency progresses, necrosis will develop on leaf edges and new shoots will die off at growth points.

Untreated Calcium deficiency in chilli plants will result in Blossom End Rot (BER) and/or Stip. BER is unlikely as a result of a Calcium deficiency in the soil, but most likely due to a plants inability to avail itself of the Calcium in the soil. The most common reason for Calcium deficiency being inadequate/erratic watering, due to drought or bad water management (poorly set up irrigation). Root damage due to disease and nematodes can be another factor for a plants inability to uptake Calcium. Another common underlying issue is as a result of high concentrations of soluble sodium in the soil due to over fertilization.

Treatment

Ensure soil pH is within the acceptable range to facilitate Calcium availability (6.5 - 9.5). Adjust soil pH by raising or lowering soil acidity to bring soil into this pH range.

Avoid periods of water shortage with supplemented watering. Avoid over watering and periods of drought.

Cut out supplementing with fertilisers high in Nitrogen.

Mulching can assist with retaining soil moisture as well as insulating soil temperature during colder parts of the season.

Calcium Toxicity

Calcium does not manifest symptoms of toxicity in plants. It can however cause deficiencies in other nutrients (commonly Magnesium, Potassium and Boron) by blocking their uptake. In this event cease supplementing Calcium and supplement with the deficient nutrient(s).