There are plenty of nutrient deficiency symptoms growers can encounter, but the most common (and obvious) one is a change in leaf color.
“The nutrient deficiency they’re most likely to see is when the plant is much lighter in color,” says Dan Jacques, Grower Services Manager for Sun Gro. “There are a number of deficiencies that can look similar, so the best thing to do is get media and tissue analyses to help confirm what the nutrient deficiency might be.”
Spotting the signs is the easy part—confirming the cause is harder. Insect damage and disease can produce symptoms that look just like a nutrient deficiency, so growers need to rule out those other issues before assuming a deficiency is the culprit.
Confirm Before Correcting
Even when growers or grower specialists can identify symptoms visually, the diagnosis isn’t completely reliable until it’s backed by testing. That’s a tough pill to swallow for growers who want to fix the problem right away, but acting too soon carries a real risk.
“Growers can do more harm than good if they try to correct for a deficiency they don’t have,” Jacques explains. “They could damage the plant because they may have caused an excess of specific nutrients which also can pose a problem for the plant.”
Guessing wrong doesn’t just waste their time, but it can make the original problem worse. That’s why growers should confirm their diagnosis by working closely with a grower specialist or someone well-versed in plant nutrition.
“We can narrow the diagnosis down very well,” he says. “In the rare case that the diagnosis and testing are not 100% accurate, the treatment we recommend will at least not hurt the plant. But most times, it helps.”
Sometimes, the grower specialist nails the diagnosis on their first try. Other times, there’s more than one problem at play, which is exactly why that extra layer of expertise matters. A second or third look can catch issues a grower would otherwise miss.
Matching the Fix to the Cause
Once a grower’s diagnosis is confirmed, it’s time to take corrective action.
“That could be adding fertilizer or modifying the pH of the mix,” Jacques says. “On top of that, they need to determine why the problem is occurring in the first place.”
But corrective action isn’t one-size-fits-all. Growers could be dealing with a one-time mishap or a long-term problem, and while the symptoms may look similar, the course of action differs slightly.
The right fix depends on whether the deficiency is a one-time slip or a sign of an ongoing issue with the growing setup.
Jacques breaks down each scenario:
- One-time occurrence: “Let’s say a grower has a one-time occurrence of too much lime in the mix,” he says. “Since the pH is running higher than normal, the future corrective action there would be to make sure the lime rates are accurate in the mix they’re using going forward. Other corrective action for the plants already in the mix would be needed, such as applying additional micronutrients, which are the most likely to be affected with high pH conditions”
- Long-term problem: “A longer term issue would be if the water quality brings the pH up too quickly in the mix or suppresses the pH,” he says. “That would impact the availability of the nutrients, so the grower would want a grower specialist to make the right recommendation for which types of fertilizer to use or how they should treat the water.”
A solution for one-time occurrences would be making a simple amendment to the growing mix. Long-term solutions, however, point to a deeper problem—they require growers to adjust the water quality, temperature, or crop selection.
When the First Fix Doesn’t Work
In some cases, a grower will take corrective action that doesn’t fully resolve their crops’ nutrient deficiency. After they do what the grower specialist recommends, they still may need to add more than one additional nutrient.
“That typically happens when you’re trying to diagnose without fully testing the growing media and plant tissue,” Jacques says. “It could be a critical situation where the grower just wants to get some kind of treatment on their crops prior to getting the final results of the test.”
Jacques has seen firsthand how quickly a diagnosis needs to change. He recalls one instance where he diagnosed what looked to be a nutrient deficiency—but when the grower didn’t see the results they expected after treatment, it became clear something else was going on. The real culprit turned out to be disease.
“If you have a disease problem, you have to suppress it through chemical use or changing how you grow your plants for future corrective action,” he explains. “That’s what will remedy the long-term issue.”
Above anything else, the main takeaway Jacques wants growers to remember is the importance of testing.
“It’s easy for growers to visually assess what the problem is, but they don’t really know for sure what they’re dealing with until they test their growing media and plant tissue,” he explains. “I’ve been saying this to growers for more than 30 years. If the foliage is yellow, we can tell you which nutrient to add to green up the plant. But the only way to get the full story is through testing.”
Growers can trust their eyes to spot the problem, but must trust the test to solve it.