Excess nitrogen during fruit growth and development increases disease susceptibility and the softening of fruit. Often leading to a shorter shelf life and fruit that is quicker to rot.
One of the most common deficiency symptoms in strawberries is tip burn, where youngest leaves (at the heart of the plant) and the growing points have necrotic margins, and often deformed or folded in appearance.
Strawberries grown in greenhouses and polythene tunnels are very susceptible to this typical leaf and flower tip burn, especially when the Ca level in the nutrient solution drops below 2mmol (80mg Ca/l). Injury begins on emerging young leaves as necrosis near the tip. As they expand, the leaf blades have light green borders. The next leaves are crinkled, the tips fail to expand fully and turn black.
Calcium supports root development and crop establishment, including the growth of young leaves and buds. It plays a key role in maintaining the physiological stability of plant tissue ensuring good plant structure and health. For example, calcium builds strong cell walls and is vital to cell membrane integrity and permeability. In addition, Ca helps improve the plant’s tolerance to disease and salinity, maintaining good, stress-free growth.
Poor calcium uptake – particularly when it is out of balance with K and Mg supply – leads to necrosis and tip burn. In this trial, petiole necrosis, flower stem lesions and tip burn of runners increased with decreasing Ca and increasing Mg availability in the nutrient solution. Tip burn can be minimized by lowering the EC at night. Calcium uptake and distribution is favored at night when the xylem sap pressure can push water and calcium into the low or non transpiring tissues such as enclosed leaf tips and fruit. Regular calcium supply throughout the production cycle ensures that Ca required for fruit integrity, will find its way into the fruit also boosting yields.
Calcium can help to reduce levels of mould on fruit post harvest when applied pre harvest as a foliar application.
Boron applied with calcium often improves yield and quality. It has been shown in other crops e.g. tomatoes, that adding boron to calcium applications will improve calcium distribution in new tissues in the plant.
Silicon also has an effect on fruit quality and there are indications that it can improve disease tolerance due to its role in reinforcing the cell wall.
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