Calcium (Ca) deficiency can be manifested by symptoms like blossom end rot and tipburn. Sometimes, when a nutrient shortage occurs, the first instinct is to add the nutrient required to fix the problem. This isn’t always the best solution.
Calcium plays an important role in the formation plant cell wall walls. Cell wall formation can’t be completed if calcium doesn’t reach new cells within the required time. As a result, cells can die. This is why calcium absorption from roots to leaves plays a vital role.
Calcium movement in plants
Water is the main factor that moves calcium through plants. Calcium is released when plants transpire. Calcium is only present in plants when water moves. Most calcium deficiencies in greenhouse crops are caused by environmental conditions and not a nutrient problem.
Calcium deficiency can cause problems
There are many environmental conditions that can cause calcium deficiency. These are the most common causes of calcium deficiency.
Low relative humidity. When plants are exposed to low relative humidity, tiny pores called stomata in leaves close. Stomata are responsible in transpiration. Stomata behavior is crucial for calcium movement. It is crucial to know the ideal relative humidity levels for each crop. Additionally, it is important that humidity levels remain consistent and uniform. You can increase the humidity in a greenhouse by running water through the evaporative cool pads or installing a fog system, if needed.
There should be continuous gas exchange, but there must be airflow around the crop. The friction between the leaf surfaces and moving air can reduce the airflow velocity. This creates a “border layer”, which is a layer that is heavy with air and can decrease gas exchange in plants. This can affect calcium uptake in plants.
This decrease in calcium intake is common in greenhouse lettuce. Lettuce has a very tight canopy. The boundary layer is often thickened and exposed to new leaves. To avoid tipburn, it is important to have good airflow above the crop canopy. To improve airflow in lettuce greenhouses, it is often recommended to install vertical fans. Proper airflow is essential in vertical farms. Leafy greens should have a 1 meter per sec air velocity rate in each layer.
Vertical farms have high light intensity. Indoor farm production requires that many variables are controlled in order to ensure crop performance. The light intensity and the boundary layer are two variables that can cause tipburn. The light intensity of plants located near grow lights tends to increase and the space for airflow decreases.
The total daily light integral (DLI), which is the amount of light that plants receive during a given photoperiod, tends to increase over time. Recent research has shown that tipburn occurs when indoor vertical farms are exposed to DLIs that exceed 17 moles per square meter per hour (molm-2d-1) for more than three consecutive days.
High VPD levels. High VPD levels can cause tip burn in some crops, such as tomatoes. Under high VPD conditions, transpiration from roots and leaves increases. When tomatoes have too much VPD, calcium uptake is blocked by the tomato fruit and goes directly to the roots. This is why blossom end rot (calcium insufficient in fruit) can sometimes occur in tomato fruit. However, no symptoms of deficiency appear on the leaves.
Avoiding calcium deficiency
If calcium deficiency is detected in plants, ensure that the fertigation system works properly. Check all fertilizer stock solutions that are kept in multiple tanks to ensure the same solution levels. This will ensure that all nutrients are delivered uniformly to all crops.
Be sure to monitor the environment before adding calcium to any crop. Other nutrient deficiencies can be caused by excess calcium. Foliar calcium must be applied throughout the entire production cycle if the decision is made to use it. If the production environment is controlled properly, foliar calcium applications can be avoided to prevent calcium deficiency.
For more information:
Hort Americas
Chris Higgins is CEO
[email protected]
www.hortamericas.com