ROLE OF CALCIUM IN APPLES
Calcium is a secondary plant nutrient, which is required by plants for healthy growth. Calcium is not a primary nutrient like nitrogen, phosphorus and potassium, but it is essential for healthy plant growth. It helps in formation of new plant tissue, such as shoot tips, root tips and new leaves. Calcium is the most important nutrient for post harvest quality of the fruits. Calcium acts as glue between cell walls, so it is responsible for holding together the cell walls of the plant. Fruit with low calcium levels at harvest are soft and of extremely poor quality. Without adequate amounts of calcium, apple plants experience number of plant disorders viz. Bitter Pit, Cork Spot, poor storability etc.
KEY ROLE OF CALCIUM
• Strengthen Cell Wall Structure.
• Regulates enzymes and Hormonal Processes.
• Participates in plant cell elongation.
• Calcium boosts fruit quality.
• It delays the softening of the fruit.
• Regulates opening of stomata, prevent the plants from stress during drought.
• It helps the plants against diseases.
• Calcium helps in producing plant tissues.
• Ensures normal root system development.
• Helps in fruit storability.
• Also helps in pH adjustments.
Calcium deficiency is caused due to low availability of calcium to the plants. Low transpiration rates and water stress can result in calcium deficiency. Calcium is immobile in the plant, so the needed calcium is taken through the soil solution and transported to the plant’s new growth.
Low calcium levels can result in;
• Bitter pit.
• Poor keeping quality.
• Lenticel Breakdown.
• Cork spot.
• Poor root development.
Most of the commercial fruit growers now spray their apple trees with calcium nitrate or calcium chloride, to reduce the incidence of Bitter Pit, Internal breakdown and cork spot. Calcium chloride is the most preferred form of calcium used for foliar application. Spraying calcium nitrate close to harvest can delay coloring in red delicious apples. Calcium nitrate spray is not advised; since a number of varieties have suffered lenticel damage as a result especially in Tydeman’s Early Worcester.
Foliar application of calcium should be done at two weeks interval starting from 3 weeks after petal till harvest. Ideally 6-8 sprays should be done before harvesting the fruit. Start with low dose and increase the dose with gain in fruit size.
1. Calcium chloride (29% Ca) 400-600gms per 200 liters of water. (do not mix Captan or Boron with Calcium Chloride)
2. Calcium Nitrate (19% Ca) 1000gms-1200gms per 200 liters of water.
SOURCES OF CALCIUM
1. Gypsum 22% Calcium
2. Calcitic Limestone 32% Calcium
3. Dolomitic Limestone 22% Calcium
4. Calcium Nitrate 19% Calcium
5. Hydrated Lime 46% Calcium