Cornell University scientists have developed genetically engineered tomato plants that turn red-purple when nitrogen becomes scarce, giving farmers a visible warning that crops may need fertiliser.
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crops → develop → fertiliser
Called RedAlert, the plants have moved beyond greenhouse experiments and are being tested under real-world conditions at Cornell’s Musgrave Research Farm in Aurora, New York.
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plants → call → Aurora
Visitors saw the experiment on July 30 during the 2026 Aurora Farm Field Day, which showcased agricultural research.
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which → see → research
According to a September report in the Cornell Chronicle, the plants produce betanin, the red-purple pigment found in beets, when deprived of nitrogen.
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plants → accord → nitrogen
Researchers hope these living sensors could help growers identify nutrient shortages sooner and apply fertiliser more precisely.
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growers → hope → fertiliser
The plants are not intended to enter the food supply.
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plants → intend → supply
Instead, they could eventually be planted alongside conventional crops to monitor nitrogen availability in a field.
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they → plant → field
RedAlert tomatoes: how nitrogen deficiency triggers a red-purple colour change
The project is part of Cornell’s Centre for Research on Programmable Plant Systems (CROPPS), which investigates ways to engineer plants to communicate information about their surroundings.
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which → trigger → surroundings
Plant scientist Margaret Frank first conceived the idea behind the colour-changing tomatoes.
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Frank → conceive → tomatoes
Initial work on the nitrogen-sensing system involved researchers Brandon Williams and Yinan Wu, while doctoral students Jacob Belding and Ava Forystek developed the RedAlert Living Sensors.
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Belding → sense → Sensors
Their invention won the Graduate Runner-Up award at the 2025 Collegiate Inventors Competition, receiving $5,000, according to the National Inventors Hall of Fame.
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invention → win → Fame
RedAlert uses a biological signalling pathway through which plants detect nitrogen availability around their roots and transmit information to their shoots.
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plants → use → shoots
The engineered plants respond by producing betanin, making nitrogen stress visible through a change in colour.
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stress → engineer → colour
Nitrogen-deficient plants can develop yellowing leaves, but RedAlert is designed to offer a different visual signal that researchers hope could help growers recognise nutrient shortages earlier.
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growers → develop → shortages
In its 2025 report on the invention, the Cornell Chronicle reported that shades of redness reflect varying gradients of available soil nitrogen.
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shades → report → nitrogen
However, the researchers are still analysing field data to establish how reliably colour intensity corresponds to nitrogen concentration under real growing conditions.
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intensity → analyse → conditions
The potential agricultural benefit is reducing unnecessary fertiliser use.
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benefit → reduce → use
Cornell’s 2025 report noted that farmers can apply up to 50% more nitrogen than needed.
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farmers → note → nitrogen
Excess nitrogen can run off into groundwater and lakes, contributing to harmful algal blooms.
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nitrogen → run → blooms
A visible biological sensor could help growers identify where fertilizer is needed instead of relying solely on soil measurements that may not capture differences across an entire field.
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that → help → field
Cornell’s 2026 field trial tests RedAlert under real growing conditions
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trial → test → conditions
The 2026 experiment at Musgrave Research Farm marks the project’s second field season at the site.
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experiment → mark → site
During the first season in 2025, researchers planted the sensor tomatoes among corn.
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researchers → plant → corn
The plants distinguished low-nitrogen conditions from conditions with sufficient nitrogen.
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plants → distinguish → nitrogen
A secondary experiment aimed at using the tomatoes to predict corn yields proved more difficult because the two crops require different management practices.
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crops → aim → practices
For the 2026 season, researchers established a separate plot containing RedAlert plants alongside non-engineered tomatoes.
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researchers → establish → tomatoes
The experimental plants received 3 nitrogen treatments: a low dose, a standard dose and a recovery treatment that began with low nitrogen before receiving a standard amount.
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that → receive → amount
The season presented challenges.
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season → present → challenges
Powdery mildew and hot conditions early in the growing period made measuring plant characteristics more difficult.
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measuring → make → characteristics
Nevertheless, researchers observed recovery in plants that had experienced early nitrogen stress.
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that → observe → stress
Green leaves emerged after nitrogen was added to mature plants, particularly in a new line being tested.
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nitrogen → emerge → line
Doctoral student Sam Mosher, who is leading the field trials, highlighted the importance of observing recovery in mature plants, which greenhouse experiments rarely grow to that stage.
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experiments → lead → stage
Researchers are analysing soil and leaf samples to investigate whether nitrogen levels explain the observed colour differences.
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levels → analyse → differences
They are also using low-flying drones and handheld spectrophotometers to measure plant colour systematically.
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They → use → colour
The 2026 Cornell Chronicle report noted that visitors asked whether the intensity of the purple-red colour reliably matches nitrogen concentration.
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intensity → note → concentration
Mosher said that if nitrogen proves to be the driver of local colour changes, the new line would be a promising sensor candidate.
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line → say → changes
The field data are still being analysed, so the relationship requires further verification.
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relationship → analyse → verification
Can nitrogen-sensing tomatoes help farmers reduce fertiliser waste?
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farmers → sense → waste
Researchers hope sentinel plants could provide a more continuous picture of nitrogen availability across agricultural fields.
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plants → hope → fields
Unlike occasional soil tests, living sensors could potentially reveal changes as plants grow, helping farmers decide when additional fertiliser is necessary.
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fertiliser → live → changes
…and 6 more, not listed.
The Aporia
