Balancing nutrient supply in leafy vegetables will not only improve color and appearance, but also ensure maximum marketable yield, says Dean Konieczka of OMEX® Agrifluids.
Few growers will have any qualms about rolling out a nutrition program for the basic macronutrients such as nitrogen, phosphorus and potassium, but many will wish they had the same degree of confidence in managing calcium nutrition.
Calcium deficiency is a significant problem in leafy vegetables and salad leaves, tip burn the most common symptom. A collapse and death of the cells, causing breakdown of the leaf tissue and the all-too-familiar browning effect, it can generate serious economic losses through loss of quality and marketability.
Testing of the affected tissues usually reveals low levels of calcium, but the cause of the imbalance isn’t always clear: is it due to poor transport within the plant? Or insufficient calcium absorption?
It’s both. Insufficient movement of water through plant tissue can lead to tip burn, but sometimes the plant can’t acquire sufficient calcium in the first place.
Understand what’s caused it, and then a grower can decide how best to manage it.
What’s the crop?
On closed-head lettuce, or brassicas, tip burn usually appears in the center. This is a sure sign that calcium transport is the culprit.
Calcium isn’t mobile in the plant’s phloem. Crops cannot move it around the plant. Instead, calcium moves with water in the xylem. Parts of the plant with the highest water loss also exhibit the highest throughput of calcium. And because calcium absorption is controlled by the plant hormone auxin, parts of the plant that enjoy high levels of auxin also absorb the most calcium.
Let’s look at the closed-head variety. Tip burn is occurring in the newest leaves, where auxin levels must be high. We can deduce that this isn’t a problem of inability to absorb calcium; instead, it suggests there’s not enough calcium reaching those leaves.
Here, the focus should be on insufficient water movement — either because the surrounding air is cool and moist (little water loss from leaves), or thought hot and windy conditions increasing water loss from outer leaves.
In these circumstances, a foliar calcium application will be wasted, because it’s not going to reach the all-important core. The outer leaves will absorb calcium, but they don’t need it; and the plant won’t be able to move the excess internally.
Solving this type of tip burn needs a dual approach: make calcium available in the root zone, where it can be drawn to the right part of the plant; and try to manage the crop to maintain a more even flow of water through the plant. The latter is easier to enact where crops are protected.
Careful selection of nutritional products is also helpful. How many of you have experienced the frustration of seeing no effect from a calcium application? OMEX® Cell Power® Calcium Gold contains the unique LoCal® technology — developed by our British partners Levity Crop Science — which directs the plant to use calcium in a different way. This allows lower rates of calcium to be applied, while producing greater effect.
What about loose-head varieties?
Here, tip burn usually appears on the outer leaves — and isn’t due to water transport. Instead, it’s because auxin levels in these older leaves, where cell division has stopped, have declined. This reduces the leaf’s calcium-absorbing ability.
Again, foliar calcium applications in these circumstances will lead to frustration: those fresh new leaves in the center, packed full of auxin, will absorb it, with no effect on the calcium-deficient outer leaves.
Thankfully, the remedy is the same. The LoCal® technology within Calcium Gold uses a calcium transport stimulant that emulates auxin, allowing all parts of the plant to take advantage of enhanced calcium levels.
What’s more, growers can also choose to incorporate a valuable dose of micronutrients at the same time, by applying Cell Power® Calcium Platinum. It adds critical micronutrients such as copper, iron, zinc, manganese, boron and molybdenum to the formulation, providing growers with a unified solution to remedy other micronutrient deficiencies in the same application.
Learn more at www.OMEXusa.com.
The product names and brands referenced here are registered and trademarks of OMEX® Agrifluids, Inc.
© OMEX® Agrifluids, Inc. 2021.