Perennial grains

Also known as Perennial grain crops, Kernza, Perennial rice, Intermediate wheatgrass

Perennial grains are cereal crops that live for several years and regrow from the same roots, so farmers do not have to replant them every season. Kernza and perennial rice are the best-documented examples, but yields tend to fall as stands age and soil carbon gains have not been shown at scale.

Pilot and early commercialReported, unverifiedReviewed 21 Oct 2026
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In plain language

Most grain crops are annual. A farmer ploughs the field, sows seed, harvests once and starts again the next year. Perennial grains are different: the plant survives for several years, its roots stay in the soil, and the field is not ploughed and resown each season. Two examples are Kernza, a perennial wheatgrass bred at The Land Institute in Kansas, and perennial rice, which a 2022 study tested on farms in Yunnan, China.

The attraction is fewer field operations each year and less soil disturbance. The trade-off is that the plants have to keep producing grain after their first harvests, and so far yields tend to fall as the stand gets older. Whether these crops store more carbon in soil than annual crops is still being tested, and the answer so far is mixed.

Technical explanation

Perennial grain breeding selects for seed yield, seed size and the share of plant biomass that becomes grain, while also building in persistence across seasons. The Land Institute reports that five breeding cycles in Kernza, the perennial wheatgrass also known as intermediate wheatgrass, raised seed yield by 145% and average seed weight by about half. The page does not give units, trial years or sites, so the figure is best read as an organisation's summary of breeding progress rather than a verified field result. A Land Institute report released in March 2022, as cited by a trade article published in April 2022, counts 3,957 acres of Kernza in the United States and Canada in 2021 and gives a yield of over 400 lbs per acre, more than double the 2019 estimate.

Stand age is the main agronomic problem. Ding and colleagues (2025) measured a 23.4% fall in grain yield from year one to year two in intermediate wheatgrass. The fall was linked to lower seed mass rather than fewer seeds, and the authors associate it with earlier and slower canopy senescence. The work is correlational, so the mechanism is a working hypothesis. For perennial rice, Zhang and colleagues (2022, Nature Sustainability) report in their abstract that the crop averaged 6.8 Mg/ha over four years against 6.7 Mg/ha for replanted annual rice. The University of Illinois press release reports that yield began to fall in year five, so resowing after four years is recommended. The labour and input figures and the year-five comment come from that press release, because the full text was not accessible for this record.

Soil effects are mixed. Four years after planting, Sprunger and colleagues (2017) found no significant difference in large or medium particulate organic carbon at 0 to 10 cm between intermediate wheatgrass and winter wheat, although the wheatgrass had much more root carbon. The Nature Sustainability abstract, as summarised in its metadata, reports that four years of perennial rice cropping increased soil organic carbon and nitrogen, which is a different result from the wheatgrass study. Van der Pol, Crews and Cotrufo (2025) tracked labelled plant material over 27 months in controlled chambers and estimate that 9.5% of root carbon inputs may be stabilised in the soil. Their labelled litter was grown in a chamber in a greenhouse setting, so field conditions may differ.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Demonstrated Shown in a published experiment, test or shipping product.

In intermediate wheatgrass, grain yield fell 23.4% from year one to year two. The authors link the fall to lower seed mass rather than seed number, in a correlational study.

Sources: [7] · Abstract · medium confidence

Four years after planting, soil under intermediate wheatgrass did not differ significantly from winter wheat soil in large or medium particulate organic carbon at 0 to 10 cm, although the wheatgrass had more root carbon.

Sources: [5] · Abstract · medium confidence

In a 27-month isotope-labelling study of Kernza in controlled chambers, the authors found 3.5% of root carbon in mineral-associated organic matter and 6% in a particulate fraction, implying that 9.5% of root carbon inputs may be stabilised in soil. The labelled litter was grown in a greenhouse-setting chamber, not in the field.

Sources: [6] · Abstract · medium confidence

Reported, unverified Stated by a company or team but not independently confirmed.

The Land Institute reports that five breeding cycles raised Kernza seed yield by 145% and average seed weight by about half; the page gives no units, trial years or sites.

Sources: [3] · Breeding summary · medium confidence

In 2021 Kernza was grown on 3,957 acres in the United States and Canada, up from an estimated 500 acres in 2019, according to a Land Institute report as reported by Food Business News.

Sources: [4] · medium confidence

Kernza grain yield in 2021 was over 400 lbs per acre, more than double 2019 estimates, according to the same Land Institute report as reported by Food Business News.

Sources: [4] · medium confidence

In the 2022 Nature Sustainability study, perennial rice averaged 6.8 Mg/ha per harvest over four years against 6.7 Mg/ha for replanted annual rice; according to the press release, yield began to fall in year five.

Sources: [1], [2] · Abstract (via Crossref); press release yield summary · medium confidence

Press coverage of the perennial rice study reports that farmers used almost 60% less labour and spent nearly half as much on seed, fertiliser and other inputs as with annual rice.

Sources: [2] · Economic and labour claims · medium confidence

The perennial rice authors say more research is needed on carbon sequestration and greenhouse gas balances, as reported in press coverage of the study.

Sources: [2] · Caveats · medium confidence

The Nature Sustainability paper's abstract reports that four years of perennial rice cropping increased soil organic carbon and nitrogen.

Sources: [1] · Abstract (via Crossref metadata summary) · medium confidence

Limitations and open problems

  • Yields fall as stands age. Ding and colleagues (2025) measured a 23.4% drop from year one to year two in intermediate wheatgrass, associated with lower seed mass.
  • Kernza yields remain modest. A trade article reporting a Land Institute report gives more than 400 lbs per acre in 2021. The Land Institute's own page gives a 145% seed yield gain over five breeding cycles but no trial details.
  • Early soil carbon gains are not established. Sprunger and colleagues (2017) found no significant difference at four years and say that, on sandy, low-CEC soils, a difference above 15% would need more than four years to show.
  • The perennial rice yield comparison covers only the first four years. Yields fell in year five, and press coverage reports that significant exposure to cold limited regrowth, with no temperature threshold given.
  • Carbon and greenhouse gas balances for perennial rice are still under study, according to the authors as reported in press coverage.
  • Commercial scale is small. A trade article reporting a Land Institute report gives 3,957 acres of Kernza in the United States and Canada in 2021.

Possible future uses

Speculative

Ideas, not predictions. None of these has been demonstrated.

  • Perennial grains on dry or low-input land where repeated tillage is costly, although no trial data for such settings was reviewed for this record.
  • Using the same perennial breeding approach for other cereals, which is a research goal rather than a demonstrated result.
  • Perennial rice in frost-free regions beyond Yunnan, which the researchers suggest could work across a broad range of frost-free locations, according to the paper's abstract and press coverage.

Timeline

  1. Mar 2017Sprunger and colleagues report no early soil carbon gain under intermediate wheatgrass compared with annual winter wheat, four years after planting. Sources: [5]
  2. 2020The Land Institute reports a 145% gain in Kernza seed yield over five breeding cycles. Sources: [3]
  3. Apr 2022Food Business News reports a Land Institute report, released in March 2022, that counts 3,957 acres of Kernza in the United States and Canada in 2021, up from about 500 acres in 2019. Sources: [4]
  4. 7 Nov 2022Nature Sustainability publishes Zhang and colleagues' study of perennial rice on farms across Yunnan Province, China. Sources: [1], [2]
  5. 27 May 2025Van der Pol, Crews and Cotrufo publish isotope-labelling results on soil organic matter formed from Kernza plant material. Sources: [6]
  6. 26 Nov 2025Ding and colleagues publish a study linking leaf senescence to age-related yield decline in intermediate wheatgrass. Sources: [7]

Futures this could help bring about

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How far away?

Farming without synthetic fertiliser

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Related breakthroughs

Glossary

Perennial crop
A plant that lives for more than one growing season and regrows from the same roots, rather than being sown again each year.
Intermediate wheatgrass
A perennial grass that is being bred into Kernza, a grain crop.
Particulate organic carbon
Carbon held in partly decomposed plant material in soil, measured in particle size fractions.
Stand age
The number of years a perennial crop has been growing in the same field.

Sources

  1. peer reviewed paper
    Sustained productivity and agronomic potential of perennial rice
    Shilai Zhang, Guangfu Huang, Yujiao Zhang et al.. Nature Sustainability, 7 Nov 2022. DOI: 10.1038/s41893-022-00997-3. Accessed 21 Oct 2026.
  2. university press release
    Farmers in China, Uganda move to high-yielding, cost-saving perennial rice
    ScienceDaily, Nov 2022. Accessed 21 Oct 2026.
  3. other
    Kernza Perennial Grain Yields are Increasing
    The Land Institute (Kernza), 2020. Accessed 21 Oct 2026.
  4. news
    Kernza, a grain used by General Mills, increases in acreage
    Jeff Gelski. Food Business News, 11 Apr 2022. Accessed 21 Oct 2026.
  5. peer reviewed paper
    Perennial grain on a Midwest Alfisol shows no sign of early soil carbon gain
    Christine D. Sprunger, Steve W. Culman, G. Philip Robertson et al.. Renewable Agriculture and Food Systems, 23 Mar 2017. DOI: 10.1017/S1742170517000138. Accessed 21 Oct 2026.
  6. peer reviewed paper
    Mechanisms of soil organic matter formation for perennial grain Kernza under contrasting nitrogen management
    Laura K. van der Pol, Timothy E. Crews, M. Francesca Cotrufo. Frontiers in Soil Science, 27 May 2025. DOI: 10.3389/fsoil.2025.1548577. Accessed 21 Oct 2026.
  7. peer reviewed paper
    Association between leaf senescence dynamics and age-related yield decline in the perennial grain crop intermediate wheatgrass
    Qiansu Ding, Xiaoxing Zhen, Jacob M. Jungers et al.. Annals of Botany, 26 Nov 2025. DOI: 10.1093/aob/mcaf307. Accessed 21 Oct 2026.

Revision history

3 changes since this profile was created.

Changes on 21 Oct 2026
Published on owner instruction (content loop iteration 12 and comparisons batch 3)71040a9
Sources and claims re-checked against originalsfbb434c
Initial profile drafted from primary sources7e66249