Anyone who’s ever driven past a cornfield after a windstorm, observed corn stalks after a late spring frost, or tried to get control of pests chewing up leaves knows how many above-ground factors there are in the success of a crop.
But great farmers also know the importance of what happens below the surface to overall crop health — and eventual yields.
It’s why the depth of a crop’s root system can be so significant to an overall nutrition program. And it’s one aspect that’s often overlooked. But farmers who gather data on their plants’ root systems, develop plans for improving root depth, and optimize their crop nutrition programs alongside root depth data can be one step ahead when it comes to overall crop nutrition.
From the time a seed is planted, that plant’s root system evolves. As roots dig deeper into the soil, the plant’s ability to absorb water and nutrients shifts.
So you should adapt your nitrogen applications according to those changes.
Why does root depth matter?
There are several factors at play — weather, soil type, and increasingly, root depth — that affect whether nitrogen is actually available to a plant after application.
It’s not good enough to blindly apply nitrogen and expect that your crop is absorbing it all. With more information at hand about what’s happening in both the plant and the soil, you can better time your nitrogen applications to maximize your plants’ uptake.
These days, this is more important than ever as we’re starting to learn more about what it takes to develop a deep root system — and in which regions this might be a bigger issue.
“In Nebraska, for example, and north Kansas and some parts of the I-states, depending on the soil type and weather patterns, it’s often hard to develop a deep root system,” says Kylen Hunt, who’s in charge of business development at GroGuru, which uses permanently installed, year-round soil sensors for continuous root zone monitoring. “This is especially true if we get a lot of rain or moisture early, and the crops don’t have to work hard to develop a deeper root system.”
How can root depth impact irrigation or nutrient management?
As any farmer who’s ever watched a freak hailstorm take down a field of seedlings knows, timing is everything.
Increasingly, growers are learning how to align irrigation and nutrient application timing with when it will be most beneficial to the crop.
According to Kylen, many farmers often aren’t sure when to start irrigating after a rainstorm, for instance. Knowing more about their crop’s root depth could help that decision-making process.
“Another trend I’m seeing is farmers simply don’t know when to turn the pivot on after a rain,” he said. “When a farmer has no idea how deep their roots really are, they have no idea how deep that moisture made it into the profile, so they don’t know where the plants are actually drawing water out. What typically happens is they’ll start to pivot when the top eight inches dries down. But when the top eight inches start to dry down is actually when the roots are continuing to grow down. If we irrigate too soon, we stop the deep root development.”
Okay great, you might be thinking. That’s for irrigation. What does this have to do with nitrogen applications?
Well, as we’ve written about before, those who use fertigation can take a few lessons from the water management playbook. The best, most impactful nitrogen applications are those that are applied based on the strongest data. What the root depth zones look like on your farm can be part of that equation.
For example, Kylen says, if fields are holding too much moisture (from excess rain, irrigation, or both), there’s a risk of water-induced compaction, which makes it harder for water to push through to the root zone. This starts to remove oxygen from the soil profile, which then limits nutritional uptake.
Then when you come through with that pre-planned nitrogen application … the plant isn’t actually getting what it needs.
In other situations, plants can take up way too much of the nitrogen, which is its own problem.
“It’s easy to over-apply nitrogen, which really causes the plants to shut down,” Kylen says. “Folks in the regenerative ag market call this ‘nitrogen flooding.’ It gets to the point where the plant will draw in so much nitrogen in that little limited area that it’ll actually damage the plants. It’s just a harder, more stressful environment for the crop.”
Farmers need to optimize their nitrogen programs according to data about whether the plant actually needs that extra application. Otherwise, the downstream impact could mean lower crop health and eventually lower yields.
How root depth can impact nitrogen application decisions
Root depth can also help explain some of our recent N-Time recommendations. This summer, our N-Time data delivered recommendations to many of our users to apply nitrogen in June, then slow down applications in July and August.
From what we’ve observed ourselves and from conversations we’ve had with others out in the field, like Kylen, roots can be pretty shallow in June. With a lot of rainfall in the spring, root systems didn’t have the chance to push very deep into the soil. When nitrogen was applied, all that continued rainfall was pushing the nitrogen down into the soil profile — past the root zone.
Then, later in the season, as rain slowed down and the roots got the chance to push deeper, they started to tap into all that nitrogen in the soil profile. Farmers could take advantage of the nitrogen that was already there — and avoid making an extra fertigation pass.
We know what you might be thinking:
But wait, I always make a fairly heavy nitrogen application on the front end of the season, then fertigate only once or twice toward the end of the season. You’re saying to apply more in June?
This won’t always be the case for every farmer in every region. But this year we believe that was the case for many of our N-Time users.
Growers who follow those data-backed recommendations are more likely to avoid wasted nitrogen, reduce runoff, and save on input costs.
How to leverage technology to monitor root system depth and optimize nitrogen applications
In a situation like the one above, a farmer not using technology to drive decision-making might end up applying unnecessary nitrogen, or not applying nitrogen during periods of temporary nitrogen stress. This threatens to reduce profitability by either wasting nitrogen or reducing yield potential.
But thanks to new innovations, farmers no longer have to rely so much on guesswork. With the right technology in place, they can monitor their root depth — then apply nitrogen appropriately, based on what plants need during certain points in the season.
Probes like the ones Kylen uses at GroGuru, can enable continuous root zone monitoring and irrigation management. This can help you more effectively observe what’s happening in the soil profile — and more quickly see the impact of irrigation decisions you make. It can also help you understand water levels, which can better inform your nitrogen decisions.
These probes do not, however, measure nitrogen content in the soil. To optimize your nitrogen management, a tool like N-Time can take real-time data about crop conditions, and turn it into actionable insights.
If, for example, heavy rains have compacted soil and reduced a plant’s ability to uptake nitrogen in their root zones, our satellite imagery — which is extremely sensitive to crop nitrogen status — can pick up that subtle shift. From there, N-Time could deliver a recommendation to either apply more nitrogen, or to hold off on that extra application you had planned.
Crop conditions, weather events, and root zone depth all evolve through a season. Your nitrogen plans should adapt alongside those changes too.
For questions or more info about integrating N-Time into your operation, reach out to the Sentinel team today.
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