Nitrogen-fixing cereals
Legumes feed themselves with nitrogen from the air via root bacteria; getting wheat, rice or maize to do the same would remove the need for much fertilizer.
Open in the interactive tree →Most of the world's cereal yield depends on Haber-Bosch fertilizer, and a large part of it is lost as pollution. Researchers try three routes: giving cereals root nodules, putting the bacterial nitrogenase enzyme into plant cells, or engineering root microbes that fix nitrogen next to the plant.
As of October 2026
No cereal that fixes its own nitrogen has been released to farmers. A milestone from 2024 was the discovery of the nitroplast (Science, April 2024), a nitrogen-fixing organelle in the marine alga Braarudosphaera bigelowii, showing that evolution has built such a compartment inside a complex cell. The international ENSA programme, with 12 partner institutions, studies root-nodule symbiosis and microbial partnerships in crops such as maize.
What is missing
- Nitrogenase is destroyed by oxygen, so it needs a protected low-oxygen compartment inside plant cells
- A cluster of bacterial genes (nif) must be assembled and expressed together in plant mitochondria or plastids
- Fixing nitrogen costs the plant a lot of energy (about 16 ATP per N2), which threatens yield
- The signalling for root nodules has not been reproduced in cereals
- Field proof and regulatory approval
Becomes possible once solved
- Self-fertilizing cereals that need little added nitrogen
- Large cuts in fertilizer cost and nitrous-oxide emissions
- Cleaner rivers and coasts with fewer dead zones
- Better yields for smallholders who cannot buy fertilizer
Open steps
- Oxygen-tolerant nitrogenase Medium AI leverageDesign nitrogenase variants or protective compartments that keep working inside plant cells, where oxygen irreversibly destroys the enzyme.
- Full nif gene set in plant organelles Medium AI leverageAssemble the bacterial nif gene cluster and express all its proteins at balanced levels in a plant mitochondrion or plastid.
- Energy cost versus yield Medium AI leverageQuantify and cut the roughly 16 ATP per N2 that fixation costs, so a cereal fixing its own nitrogen does not lose grain yield.
- Root-nodule signalling in cereals Medium AI leverageFind which symbiosis signalling and nodule-organ genes cereals lack or lost, and rebuild the pathway in wheat, rice or maize.
- Nitrogen-fixing root microbes Medium AI leverageSelect or engineer microbes that fix nitrogen next to cereal roots and keep doing so in fertilised, competitive field soils.
Where AI could help
Medium AI leverage. AI can rank nitrogenase designs and nitrogen-fixing microbes, but every design must still be built into plants and tested over growing seasons.
- Design and rank oxygen-tolerant nitrogenase variants and nif gene sets with protein language and structure models
- Screen root microbes and strains for nitrogen fixation from their genomes before any lab work
- Model the energy cost of fixing nitrogen in a plant cell to pick designs that spare yield
- Mine root-nodule signalling papers and omics data for the pathway steps cereals lack
Shown so far
- In August 2025, NFEmbed, a machine-learning model built on protein-language-model embeddings, ranked microbial strains by predicted nitrogenase activity from genome data (R2 0.78 on its test set). source
- In September 2021, an evolution-informed machine-learning pipeline predicted nitrogen-use-efficiency genes, and seven transcription factors were validated in Arabidopsis and one in maize. source
Prerequisites
Unlocks
- Self-fertilizing crops2040s?