By: Dan Gillespie, Technical Specialist
Tipburn is among the most common issues experienced in controlled environment lettuce production. Tipburn occurs as browning of the edges or tips of new young leaves (Figure 1).
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| Figure 1. Tipburn on young lettuce leaves |
Tipburn in lettuce is most often caused by calcium deficiency. However, this deficiencyis usually not a result of insufficient calcium in the nutrient solution. To understand why tip burn occurs (and how to avoid it), we need to understand how calcium travels through the plant
Calcium moves through the plant differently than nearly all other nutrients: It requires mass flow of water. Think of it as a hose that must be turned on for the calcium to move into the plant. Mass flow is driven by transpiration, so high transpiration rates will enhance calcium uptake and translocation, whereas, low transpiration rates will decrease calcium uptake and translocation. When a head of lettuce grows, the growing point becomes enclosed by older mature leaves, creating a high humidity microclimate. This microclimate results in decreased transpiration, which leads to the tip burn.
The first step in preventing tipburn is ensuring that calcium is not lacking in the nutrient solution and that your fertilizer formula has a proper ratio of potassium, calcium, and magnesium. Source water with calcium concentration above 40 ppm is typically a good candidate for one-part fertilizer systems such as Jack’s Nutrients 12-4-16 RO or Jack’s Nutrients 15-5-20 Tap. However, source water with lower concentrations of calcium will typically require the use of a two-part fertilizer system, such as Jack’s Nutrients Part A 12-4-26 and Cal Nit Part B 15-0-0. Additionally, nutrient solution electrical conductivity should generally not exceed 2.5 mS/cm, as high soluble salt levels will decrease water and calcium uptake. Note that all Jack’s Nutrients provide the proper balance of nutrients.
As stated above, even when calcium levels in the nutrient solution are adequate, tipburn may still occur. Improve airflow around the growing tip with the use of vertical airflow fans.Vertical airflow should provide just enough air movement to gently move plant leaves (0.3-0.5 m/sec). This will eliminate the microclimate and facilitate calcium uptake.
If vertical airflow fans cannot be installed, another option to prevent tipburn is increasing night time humidity above 95%. High nighttime humidity leads to increased root pressure, and thus, increases water and calcium translocation to the growing point of the plant. However, this strategy can increase the threat of fungal diseases that thrive in high humidity environments.
| Product Name | Item Number | |
|---|---|---|
| Jack's Nutirents 12-4-16 RO | 33-12416 | |
| Jack's Nutirents 15-5-20 Tap | 33-15520 | |
| Jack's Nutirents 5-12-26 FeED Part A | 33-51226 | |
| Jack's Nutirents 15-0-0 Boost Cal Nit Part B | 33-79080 |
