Farming without synthetic fertiliser

Could major crops be grown without synthetic nitrogen fertiliser?

No major cereal has yet been shown to match fertilised yields without synthetic nitrogen fertiliser across sites and seasons. A Sierra Mixe maize landrace from Oaxaca, Mexico, gets a large share of its nitrogen from bacteria living in its root mucilage, and a company sells microbial products for maize. Their field results vary from site to site and year to year. Engineering cereals to fix nitrogen themselves has only reached early laboratory steps. The perennial grain Kernza yields less than wheat in the report reviewed.

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WHERE WE AREPilots

Close. Early pilots are running in the real world.

Nitrogen fixation by bacteria living in a maize landrace has been measured in field studies, and gene-edited microbes have raised nitrogen uptake in maize under controlled conditions. Commercial microbial products are on sale for maize, but their yield and nitrogen benefits vary between sites and seasons, and the reviewed trials are small and in places company-linked. No cereal has been engineered to fix nitrogen itself, and the sources reviewed do not show a major crop matching fertilised yields without synthetic nitrogen across sites and seasons. The stage is pilot.

The tech tree

Everything recorded on Vrulum that this future needs, oldest foundations at the top and the goal at the bottom. Lines show what each step requires.

What it takes: Farming without synthetic fertiliser Unlocked Being researched Locked
  1. 2014Nitrogen-fixing cerealsPilot and early commercial Unlocked.
  2. 2017Perennial grainsPilot and early commercial Unlocked.
  3. 2017Gene-edited cropsPilot and early commercial Unlocked.
  1. 2018Nitrogen fixation measured in a maize landraceDone Unlocked.
  2. 2021Active nitrogenase protein made in plant tissueIn progress Being researched.
  3. 2024Gene-edited microbes raise nitrogen uptake in maize under controlled conditionsDone Unlocked.
  4. Date not recordedCommercial microbial products tested on farmsIn progress Being researched.
  5. Date not recordedEngineered cereal fixing a useful share of its own nitrogenNot started Locked.
  6. Date not recordedPerennial grains yielding as well as annual wheatIn progress Being researched.
  1. GoalFarming without synthetic fertiliserGoalRequires: Nitrogen-fixing cereals, Gene-edited crops, Perennial grains, Nitrogen fixation measured in a maize landrace, Gene-edited microbes raise nitrogen uptake in maize under controlled conditions, Commercial microbial products tested on farms, Active nitrogenase protein made in plant tissue, Engineered cereal fixing a useful share of its own nitrogen, Perennial grains yielding as well as annual wheat. Locked.

The road so far

2 of 6 steps done, 3 in progress.

  1. Done · 7 Aug 2018Nitrogen fixation measured in a maize landrace

    Van Deynze and colleagues report that a Sierra Mixe maize landrace from Oaxaca, Mexico, gets 29% to 82% of its nitrogen nutrition from the air by the nitrogen-difference method. The %Ndfa estimate gave 31% to 55%. Nitrogenase activity was found in aerial root mucilage, where bacteria live. The genetic basis of the trait and the source of the bacteria are unresolved. [1]

  2. Done · 12 Nov 2024Gene-edited microbes raise nitrogen uptake in maize under controlled conditions

    Gene-edited, non-transgenic Klebsiella variicola and Kosakonia sacchari strains raised 15N in maize chlorophyll under 15N2 labelling in a sterile, nitrogen-free pouch system (p < 0.001). Nif-knockout control strains did not. Field estimates from the same work were small and uncertain. [2]

  3. In progressCommercial microbial products tested on farms

    The product PROVEN 40 is sold for maize. In an on-farm comparison across 58 fields, yield did not differ significantly when 39 to 45 kg N/ha of fertiliser was replaced by the product (p = 0.871). The trial estimate of nitrogen supplied by the product was 21.2 kg N/ha, with a 95% confidence interval of -0.16 to 42.6, which includes zero. A University of Kentucky review of corn trials found a general lack of yield response to these products and reported no nitrogen credit values. [2][3]

  4. In progress · 4 Jan 2021Active nitrogenase protein made in plant tissue

    Jiang and colleagues tested 32 NifH variants in Nicotiana benthamiana leaves. Two were consistently detected in soluble leaf extracts. The first protein purified from tobacco was inactive until its iron-sulphur cluster was rebuilt in vitro, and later preparations showed only low activity. The authors name iron-sulphur cluster availability in plant mitochondria as a bottleneck. No whole-plant nitrogen fixation was shown. [5]

  5. Not startedEngineered cereal fixing a useful share of its own nitrogen

    Rogers and Oldroyd propose an initial target of 25 to 50 kg fixed nitrogen per hectare for engineered cereals. They state that it is unlikely that any current approach will deliver fertiliser-equivalent levels in the short term. One generation of maize takes about a year, which slows testing. [4]

  6. In progressPerennial grains yielding as well as annual wheat

    Kernza, a perennial grain, is grown on some farms. A SARE-funded final report states that Kernza grain yields remain lower than wheat. In the 2023 season, one irrigated grower field gave about 480 lb of grain per acre, while two dryland fields gave close to none, and the report links one of these failures to dry conditions. These are single-farm results and do not give a wheat comparison. [6]

Why it matters

Nitrogen that leaves a field can pollute water and add to nitrous oxide emissions. Crops that need less synthetic nitrogen could cut these losses and farm costs, but only if yields hold up. Most of the open questions are about whether results seen at a few sites can be repeated across many farms and seasons.

What stands in the way

  • Measured nitrogen fixation in field trials is small and uncertain, and the confidence interval for nitrogen supplied by one commercial product includes zero.
  • Yield responses to commercial microbial products are inconsistent. In a North Central region study of 61 site-years, only two showed a positive yield benefit.
  • Plant-made nitrogenase has shown only low activity in vitro, no whole-plant nitrogen fixation has been shown, and iron-sulphur cluster supply in plant mitochondria is a bottleneck.
  • Engineered cereals have a proposed initial target of 25 to 50 kg fixed nitrogen per hectare, and the authors do not expect fertiliser-equivalent levels in the short term.
  • Testing is slow, because one generation of maize takes about a year.
  • Farmers have little reason to cut fertiliser unless yields hold up, and the effects of drought on the bacteria are not known.
  • The climate benefit is not yet established, because effects on nitrous oxide emissions and nitrate leaching have not been measured for the current products.

Signals to watch

  • Replicated multi-site field trials of microbial products that report nitrogen supplied with confidence intervals.
  • Independent trials, not run by the company that sells a product, reporting yields with and without fertiliser over several seasons.
  • Peer-reviewed evidence of active nitrogenase in the cells of a cereal, with whole-plant nitrogen fixation measured.
  • Measured nitrous oxide emissions and nitrate leaching in systems that use less synthetic nitrogen.
  • Perennial grain yield data reported across several sites and seasons, compared with annual cereals.

Sources

  1. peer reviewed paper
    Nitrogen fixation in a landrace of maize is supported by a mucilage-associated diazotrophic microbiota
    Allen Van Deynze, Pablo Zamora, Pierre-Marc Delaux et al.. PLoS Biology, 7 Aug 2018.
  2. peer reviewed paper
    Genetic remodeling of soil diazotrophs enables partial replacement of synthetic nitrogen fertilizer with biological nitrogen fixation in maize
    Rafael Martinez-Feria, Maegen B. Simmonds, Bilge Ozaydin et al.. Scientific Reports, 12 Nov 2024.
  3. other
    Biological N fixation products for corn: update
    John Grove, Chad Lee. University of Kentucky Martin-Gatton College of Agriculture, Food and Environment, Grain and Forage Center of Excellence, 24 Mar 2025.
  4. review article
    Synthetic biology approaches to engineering the nitrogen symbiosis in cereals
    Christian Rogers, Giles E. D. Oldroyd. Journal of Experimental Botany, 31 Mar 2014.
  5. peer reviewed paper
    Exploiting genetic diversity and gene synthesis to identify superior nitrogenase NifH protein variants to engineer N2-fixation in plants
    Xi Jiang, Lucía Payá-Tormo, Diana Coroian et al.. Communications Biology, 4 Jan 2021.
  6. other
    Exploring the production costs, utility, and value of by-products in Kernza perennial grain production: Final report for FNC22-1331
    Brandon Kaufman, Morgan Kaufman. Sustainable Agriculture Research & Education (SARE), 2024.

Last reviewed 21 Oct 2026.