danas, Author at Sun Gro

Nutrient Deficiencies: Stop Guessing, Start Testing

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.

Why Some Growing Media Trials Fail — And It’s Not the Media

From a grower’s perspective, a growing media trial is fairly simple: they’re growing the plants they always do in a new growing media.

“The word ‘trial’ makes it sound like a complicated process, but it’s really not,” says Stephanie Cruz, grower specialist for Sun Gro. “It’s as simple as putting a plant in a different growing media and seeing how it performs compared to everything else.”

From there, the grower evaluates how the plant performs. On the ornamental side, that means looking for differences visually. On the food production side, if the grower is selling transplants, that means ensuring the plants grow uniformly across the growing media.

When the results aren’t what the grower anticipated, it’s easy to blame the growing media. “It’s visible,” she explains. “It’s something you can see with your eyes and it’s where the roots grow.”

So, what really goes wrong? Cruz points to three culprits: irrigation practices, water chemistry, and fertilization.

1. Irrigation Practices

Irrigation is one of the main reasons why growing media trials fail. Whether it’s overirrigating or underirrigating, both negatively impact how plants perform in a trial. Luckily, there are clear warning signs growers can watch for each one.

Overirrigation: A clear sign growers are overirrigating their plants is when algae builds up at the top of the substrate. “If you’re irrigating and also dosing in fertilizer, you will have a lot of algae float to the top of the substrate,” Cruz says. “The plants will also stay pretty small.”

Another common sign of overirrigation is stunted plant growth and roots that aren’t growing as well in the pot.

Underirrigation: When plants don’t get enough water, that stunts their growth as well. Irrigation is a huge cost for growers, especially where labor is concerned. Some growers will put a sprinkler in the middle of their growing field and hope it irrigates all of their plants.

“If they’re able to have control over how much water goes into each container, that would be really helpful in how we evaluate the substrate,” Cruz adds.

Irrigation is especially tricky for growers that cultivate different plant species at different stages in the growing cycle. This could mean that two-week old plants in one-gallon containers are placed next to large, vigorous plants that are bigger than the pots themselves.

2. Water Chemistry

Water chemistry doesn’t leave the same visible clues, as there’s no algae buildup or stunted root to point to. The water can look, feel, and behave normally while working against the growing media beneath it.

“You want to understand what’s in your water, mainly your alkalinity, because that will affect how you can actually control the pH in your growing media,” Cruz explains.

Alkalinity in water neutralizes acids, which leads to increasing substrate pH if it’s too high, and causes the pH to crash if it’s too low.

High alkalinity. When water has high alkalinity levels, it raises the pH in the substrate, breaks down pesticides, causes iron deficiency, and keeps the plant from absorbing the nutrients it needs.
Low alkalinity. When water has low alkalinity levels, it makes the pH in growing media more likely to spike or crash. As a result, toxicities and nutrient deficiencies become much more common.

3. Fertilization Practices

Like water chemistry, fertilization problems can hide in plain sight. A grower might be feeding their plants correctly on paper and still see poor performance because how and when the fertilizer is applied matters just as much as what’s in the mix.

According to Cruz, having a regular fertilizer regime is essential for getting your plants the nutrients they need. This is especially important during growing media trials, as each supplier will have a different amount of starter fertilizer charge.

“You’ll want to keep that in mind when you’re fertilizing,” Cruz says. “Just to make sure you’re continuously monitoring electric conductivity (EC) in the root zone by doing pour-through tests.”

Once a grower performs a pour-through test, they can tell whether their plant has too much fertilizer, too little fertilizer, or the pH is wrong.

Here’s how the test works:

Water the plant normally. Then wait an hour and pour a small amount of pure water on top.
Catch the drip water. Hold a plastic cup or saucer under the plant to catch the water that drips from the bottom.
Test the water. Check the pH and EC in the water sample collected.

If growing media has low EC, it means the plants aren’t getting enough salt from the fertilizer. This can result in stunted plant growth and yellowed plant leaves from not getting enough nutrients.

On the other hand, if growing media has high EC, it means the plants are getting too much fertilizer. This can cause plants to wilt even if the growing media is still moist and their leaves to yellow.

Across all three variables, the pattern is the same: what looks like a media problem is actually a management problem. The growing media trial isn’t a test of the media at all. It’s a test of everything the grower does around it.

Why CEA Is Poised to Lead the Transparency Conversation

Heavy metals are often found in field soils, but, even in tightly controlled greenhouses and vertical farms, these elements can enter the growing space. They do so through substrate materials (coco coir, perlite, and peat), irrigation water, and recycled inputs. Because CEA systems are enclosed, inputs can be closely monitored and controlled.

CEA does not guarantee clean inputs by default. But it does give growers the tools and control they need to find and fix problems that traditional agriculture cannot detect. That distinction matters to the consumers who are paying attention.

Understanding Food Traceability and Input Requirements

Grocery stores have started tightening supplier requirements around traceability and input documentation. Major retailers are increasingly requiring suppliers to document not just what they grow, but how they grow it.

Alongside retailer requirements, the Food Safety Modernization Act (FSMA) adds another layer of pressure. Section 204D specifically focuses on improving traceability and responding quickly to food contamination. There are 24 foods on the Food and Drug Administration’s (FDA) Food Traceability List that requires manufacturers, processors, and packers to keep additional documentation.

Cucumbers, leafy greens, herbs, peppers, tomatoes, and strawberries—all key CEA crops—are included in the rule. For growers, meeting these requirements starts with the inputs themselves.

Here’s what documentation looks like in practice:

Certificate of Analysis (COA): An official document from a third party that confirms that food products, substrates, and water meet quality, safety, and regulatory standards. It verifies heavy metals, microbial counts, and pesticide residues.
Substrate sourcing: For commercial produce growers, all purchased substrates and soil amendments must go through a validated treatment process or must be handled like untreated materials.
Water quality records: Water used to grow, harvest, and pack produce must be documented by produce growers. They should closely monitor and record their water source, use practices, and testing schedules—they should also address any heavy metal contamination that could occur in their water systems.
Pesticide use: Growers must note what pesticide they applied, when, and at what rate.
Chain of custody: Many retailers want to trace a product back through every input. The benefit of a closed-loop CEA system really comes into play here.

CEA growers who build these documentation practices aren’t just staying compliant, they’re building an advantage that field growers can’t match.

How This Affects Growers

For many growers, the bigger question is practical: What does building this documentation actually cost?

The average cost of a COA depends on crop type and what growers are testing for. Tests can range anywhere from $10 to $800 per sample. Here are a few tests growers typically complete:

Basic Microbial Screen: Tests for common pathogens like E.Coli, salmonella, and listeria.
General Food Safety Screen: Combines microbial testing with checks for yeast, mold, and coliforms.
Pesticide/Heavy Metal Panel: Tests for pesticide residues and heavy metal concentrations like lead, cadmium, arsenic, and mercury.
Nutritional Analysis: Documents macro and micronutrient content. This test is more about label and compliance claims than food safety.

A few other factors determine total cost as well, including test frequency, rushed lab results, and the accreditation of testing facilities.

These costs add up fast, but as consumers become more aware of where their produce comes from, the cost of not testing can climb even higher.

As retailers crack down on these requirements, suppliers who don’t have proper documentation can easily lose the contracts they have. Some retailers established traceability deadlines in 2025, well ahead of what the FDA requires.

While the official FSMA compliance deadline was pushed back from January 2026 to July 2028, the real deadline has already passed. Retailers are already making decisions based on documentation readiness, meaning growers who wait until 2028 could already be falling behind and losing contracts.

Breaking Down the CEA Advantage

Since CEA inputs are controlled by the grower, they’re much easier to document. Here’s a brief breakdown of how documentation looks for CEA growers specifically.

COA: With controlled and consistent inputs, growers can test their produce one time and apply their results repeatedly across growing cycles.
Substrate sourcing: CEA growers choose and purchase substrates carefully, making it much easier for them to document treatment history than traditional field growers.
Water quality records: Hydroponic and recirculating systems have water source and quality tightly controlled. This makes it easier for CEA growers to identify contamination before it reaches the crop.
Pesticide use: CEA growers typically use fewer pesticides than field growers—applications are made in a confined space. This gives growers a clear and well-defined paper trail.
Chain of custody: Every input in CEA systems enters through a controlled point, often making end-to-end traceability straightforward.

CEA doesn’t guarantee clean inputs. But it does give growers the tools to prove it, and that’s what buyers are asking for.

Why More Growers Are Moving Indoors

As the world population grows, food demand grows alongside it. According to a report from Global Market Insights, the controlled environment agriculture (CEA) market will reach $168.7 billion in value by 2032. These numbers indicate that growing indoors will gain more traction over the next decade.

Climate change is a key driver of this growth, as it makes traditional farming challenging and unreliable.

In the U.S., certain fruits and vegetables can only grow in specific states year-round due to their required growing conditions. Take strawberries, for example. Approximately 90% of strawberries grown in the U.S. come from California due to its warm, sunny climate and fertile soil.

A strawberry shipped thousands of miles arrives with barely a week of shelf life left. And since that strawberry was harvested a week prior, it loses most of its flavor and ripeness before it even reaches the grocery store shelf.

The Case for Indoor Growing

Growing produce in greenhouses and indoor farms makes shelf life less of a concern.

When fruits and vegetables are grown locally, they’re typically harvested the day before—sometimes sooner. This means the crop in question will taste better, fresher, and last much longer.

Purchasing produce that’s past its peak is one of the largest contributors to food waste. As soon as lettuce starts to brown and wilt, it typically gets thrown in the trash. The longer it takes for lettuce to reach that point, the less food will go to waste.

This ties directly back to food miles, or the total distance food travels from the farm to the final consumer.

While vertical farming has plenty of promise, it has earned a polarizing reputation in the CEA industry.

Addressing the Elephant in the Room

CEA is leading the charge on local food production, but despite its potential, the industry hasn’t gotten good press in the last decade.

Growing food indoors—especially in vertical farms—is not easy or inexpensive. Unlike greenhouses, which use both sunlight and supplemental lighting, everything in a vertical farm is completely controlled.

Growers generate CO2 and lighting while controlling temperature and automation to match their crops’ specific growing needs. To get a vertical farm off the ground, it needs high capital investment from outside vendors. On top of that, operating costs are higher than greenhouses, high tunnels, and traditional farming. Combined, both of these factors have been the primary cause of 14 indoor farm bankruptcies in 2025.

Regardless of the bad press vertical farms have received in recent years, many CEA professionals still believe that this sector of the industry has a bright future.

“What’s emerging now is not a failed industry, it’s a filtered one,” Nona Yehia, co-founder and CEO of Vertical Harvest Farms, wrote in a LinkedIn post. “The question is no longer whether vertical farming can exist. The question is who is willing to build it properly, because the need is not theoretical.”

Choosing the Right Growing Media and Market

The need for greenhouses and vertical farms is undeniable. But the growers that succeed match the right crop to their growing environment. Commonly used growing media in CEA operations for the following crops include:

Tomatoes: Rockwool, coir, organic peat-based media.
Leafy greens: Rockwool, coir, peat-based media, deep-water culture.
Strawberries: Rockwool, coir, peat-based media.
Microgreens: Peat-based mixes, fiber mats.
Cucumbers: Rockwool, coir, organic peat-based media.
Mushrooms: Compost, peat.
Peppers: Rockwool, coir, organic peat-based media.

But matching the crop to the right growing media and environment is only a piece of the puzzle. Choosing the right crop also means understanding the market it’s going to.

Take microgreens, for instance. Since it’s a high-value crop, microgreens primarily appeal to chefs and health-conscious consumers. Not every grocery store has a customer base willing to pay that premium, which means distribution decisions are just as important as growing media and environment.

Leafy greens, on the other hand, appeal to almost every consumer segment. By moving through grocery store chains and food service distributors in large volumes, leafy greens are the ideal crop for most indoor growing operations.

Strawberries shipped from California with a week-long shelf life aren’t going away any time soon. But when a greenhouse or vertical farm gets it right, those strawberries have more competition.

The future of food probably isn’t a field in California. It might be a greenhouse or a warehouse less than two miles from your grocery store.

Choosing the Right Growing Media for Your Greenhouse

For greenhouse growers in floriculture and controlled environment agriculture (CEA), growing media is often treated as a cost to manage rather than an input to optimize. As a result, many operations opt to reduce the upfront cost through cheaper mixes or substitutions.

While a lower price is ideal for any grower, using cheap growing media can have expensive consequences.

Energy and labor are the most prominent pain points for greenhouse growers. But growing media directly influences both. By investing in the right one, growers gain stronger operational efficiency and long-term ROI.

Peat vs. The Competition

In the last decade, soilless substrates have grown increasingly popular due to sustainability concerns around peat. While many greenhouse growers have tried coconut coir and rockwool as an alternative, peat-based media continues to have the edge in the market.

Peat has an ideal balance of water-holding and aeration. Its smaller pore spaces hold water, while the larger ones hold air, making it easy to maintain that balance.

The ideal pH level for crops tends to range between 5.5 to 5.8. Peat has a starting pH between 3 and 4.5 due to its natural acidic chemical property. This makes it easier for growers to amend pH with lime to reach optimal levels.

Adding lime to peat enables the pH to resist change throughout the growing cycle and remain in an optimum range. This is a huge benefit for peat, especially compared to coconut coir.

Coconut coir starts at a pH level of 5.5, and that number tends to rise when other amendments are added to it. It’s much easier to raise pH levels than to lower them when it comes to reducing labor and the risk of crop stress.

Putting Sustainability in Context

There have been continuous peat shortages dating back to 2020, forcing many growers to look for sustainable growing media solutions. While peat accessibility is a strong concern in European countries, it’s less of an issue in North America.

Peat bog can be restored in 15 to 20 years in Canada, where it can take 100+ in Europe. This means European growers are using peat much faster than it can be restored—they don’t have the flexibility to gradually transition to other mixes like North American growers do.

Still, peat isn’t the only growing media with an environmental footprint.

Rockwool and coconut coir carry their own sustainability baggage, and at a higher price point. On top of being more expensive, rockwool—a manufactured substrate made from spun mineral fibers—goes directly to the landfill after one use. Coconut coir is composed of ground-up coconut husks from Sri Lanka and Thailand—using coconuts there isn’t beneficial for the local ecosystem either.

While growers in North America aren’t currently facing the same peat concerns, the status quo isn’t permanent. This underscores why they should start paying attention to biochar sooner rather than later.

The Case for Biochar

To combat the growing concerns around peat’s sustainability, Sun Gro released biochar mixes. Biochar eliminates the need for perlite—a mined, nonrenewable material—with a renewable resource derived from wood chips, plant residues, and agricultural waste. Sun Gro’s biochar aggregate comes from 100% soft wood waste streams.

Beyond sustainability, biochar brings agronomic benefits that growers can measure.

For instance, biochar offers the same structure, aeration, and drainage as perlite. It also improves nutrient holding, water holding, and reduces ammonium toxicity. The reduction in irrigation lowers labor and energy costs, two of the biggest overhead costs for greenhouse operations. Plus, when added at a high enough percentage to the mix as an aggregate (15%+), growers may experience better rooting and overall plant performance.

Biochar has the potential to be the future of growing media. However, many greenhouse growers are hesitant to use biochar since they’re accustomed to using perlite mixes. As perlite becomes more expensive, biochar may be their only option.

That’s not to say that biochar is inexpensive by any means. Currently, biochar mixes are about the same price as perlite ones, but that won’t always be the case—growers could see biochar become the more cost-effective option within a few years.

At the very least, Sun Gro aims to keep the price consistent so biochar mixes are in line with perlite mixes in the future.

Growers likely won’t move away from peat completely. But instead of using peat-perlite mixes, they will start using peat-biochar and peat-wood fiber mixes instead to help offset their need for perlite or to stretch their peat supply without compromising the quality of their mix.

Peat-based growing media isn’t going away, but the inputs surrounding it are changing rapidly. Growers who treat those changes as an opportunity—rather than waiting until perlite prices force their hand—will protect their margins when it matters most while maintaining or even improving their plant quality.

Sun Gro’er Blog

Author: danas