Crops adapt their photosynthesis to agrivoltaic shading, Hohenheim study finds
A University of Hohenheim study of five crops at five German sites found dark respiration fell 12 to 46 per cent under agrivoltaic and agroforestry shade.
Photo by Mark Stebnicki on Pexels
Five arable crops grown under real solar arrays and tree rows in Germany adjusted their leaf physiology to the reduced light, according to a University of Hohenheim study published in the European Journal of Agronomy. Under agrivoltaic shading and agroforestry shade, the plants cut dark respiration by 12 to 46 per cent and lowered their light compensation point by 20 to 54 per cent, meaning they burned less carbon in the dark and needed less light to break even. The university announced the results on 18 August 2026; the paper itself went online on 28 July 2026 and appears in the October 2026 issue.
The paper, “Partial shade effects of dual land use systems: Harnessing plant acclimation to drive sustainable farming solutions”, is open access under a CC BY 4.0 licence as article 128268 in volume 181. Jennifer Moore is first author, with Lisa Pataczek and Andreas Schweiger of Hohenheim’s Institute of Landscape and Plant Ecology, and Onno Muller and Christoph Jedmowski of Forschungszentrum Jülich. Germany’s Federal Ministry of Food and Agriculture and Federal Ministry of Education and Research are listed as funders; no grant numbers are published.
What agrivoltaic shading did to the plants
The work measured barley (Hordeum vulgare), maize (Zea mays), cabbage (Brassica oleracea), potato (Solanum tuberosum) and field bean (Vicia faba) across five German locations in 2023 and 2024. The shade was not simulated. It came from existing agrivoltaic and agroforestry installations, each paired with a fully sunlit reference plot on the same site. Measurements were taken on the leaves with an LI-6800 portable photosynthesis system, using light response curves to derive four parameters.
| Parameter | What it measures | Result under shade |
|---|---|---|
| Dark respiration (Rd) | Carbon the plant burns when no light is available | Reduced by 12 to 46 per cent across sites |
| Light compensation point (LCP) | Light level at which photosynthesis balances respiration | Reduced by 20 to 54 per cent across sites |
| Light-saturated assimilation (Asat) | Maximum carbon fixation rate in full light | Variable, depending on crop and system |
| Apparent quantum yield (AQY) | Efficiency of carbon fixation at low light | Variable, depending on crop and system |
Source: publisher abstract, Moore et al., European Journal of Agronomy 181 (2026), article 128268. The percentage figures are cross-site ranges covering all five crops; the paper does not publish a per-crop breakdown in its abstract.
Both reductions point the same way: the plants shifted their break-even point downward, which is what shade acclimation looks like. “That shows a clear physiological adaptation to partial shading,” Moore stated. Schweiger, who heads the Plant Ecology department, put it more broadly: the crops “have a considerably greater capacity to adapt than we had assumed”.
The two shading systems did not behave alike. Photosynthetic performance was comparatively stable under photovoltaic modules and fluctuated more under trees, which the researchers attribute to the irregular shade patterns cast by canopies. “Our results show that shade is not simply shade,” Moore stated. Maize, the one C4 crop in the set, was the most sensitive to reduced light, because C4 photosynthesis cannot reach its capacity when light is short.
What the study does not show
The researchers are explicit that physiology is not yield. Yield data varied by site and crop and showed no uniform pattern, and the abstract states the responses “do not directly translate to yield outcomes”. Moore also cautions that areas of permanently heavy shade should be avoided where possible. The team proposes dark respiration and the light compensation point as selection traits for breeding shade-tolerant varieties, which is a research recommendation rather than an available tool.
Prior field evidence on yield under panels is mixed, and the closest comparison comes from the same university. Weselek and colleagues reported in 2021 on the Heggelbach agrivoltaic pilot near Lake Constance, where photosynthetically active radiation was reduced by about 30 per cent under the array. Across 2017 and 2018, yields under the panels ranged from minus 19 to plus 3 per cent for winter wheat, minus 20 to plus 11 per cent for potato and minus 8 to minus 5 per cent for grass-clover, relative to the reference plot. Direction depended heavily on the weather.
A 2022 meta-analysis by Laub and colleagues, which shares a co-author with the new study, found most crops tolerate a reduction in solar radiation of up to 15 per cent with a less-than-proportional yield decline, while berries, fruits and fruity vegetables benefited at reductions up to 30 per cent. Maize and grain legumes lost yield strongly even at low shade levels, which is consistent with the new physiological finding on maize. The land-use case for the approach is set out in our coverage of an Indian trial where an agrivoltaic insect net house lifted land use 2.5 times, and in research suggesting agrivoltaics could power AI data centres on comparatively little land.
One wording point matters for accuracy. pv magazine’s account states the team “installed photovoltaic modules above” the crops. The German release says the opposite: the shade conditions were not artificially created but came from real agroforestry and agri-photovoltaic systems already in the ground.
Background
Agrivoltaics in Germany traces to the APV-RESOLA project, which Fraunhofer ISE ran with the University of Hohenheim, BayWa r.e., EWS Schoenau, the Demeter farming community at Heggelbach, KIT and the Bodensee-Oberschwaben regional association, funded by the Federal Ministry of Education and Research and completed on 30 June 2019. The Heggelbach array, built in 2016 near Lake Constance, put 720 bifacial glass-glass modules totalling 194 kilowatts peak on mounts five metres above 0.3 hectares of arable land. Land-use efficiency there reached 160 per cent in 2017 and 186 per cent in 2018.
Policy caught up in stages. DIN SPEC 91434, issued in May 2021, set the German technical definition, requiring that agricultural yield after construction reach at least 66 per cent of the reference and capping permanent land loss at 10 per cent for high-mounted systems and 15 per cent for interspace systems. The 2023 Renewable Energy Sources Act classed agrivoltaics as a special solar installation and attached a bonus for arrays with at least 2.10 metres of clearance, tapering from 1.2 cents per kilowatt-hour for 2023 awards to 0.5 cents for awards from 2026 to 2028. Solarpaket I, in force since 16 May 2024, created ring-fenced auction volumes for these installations, but the Bundesnetzagentur confirmed on 18 August 2026 that those provisions remain inapplicable pending EU state aid approval.
Germany publishes no official figure for installed agrivoltaic capacity. The most solid public series is auction awards in the relevant categories, which ran to about 1,328 megawatts between 2023 and the July 2026 round, awarded rather than built. Fraunhofer ISE puts the technical potential for high-mounted agrivoltaics in Germany at roughly 1,700 gigawatts peak, with levelised costs of 7 to 12 cents per kilowatt-hour. The largest German installation, Vattenfall’s 76 megawatt-peak park at Tuetzpatz on 93 hectares, was commissioned without subsidy on 10 September 2025. Against that build-out, the Hohenheim finding narrows a practical question that site planners keep hitting: not whether crops survive under panels, but which of them adjust, and how far the shade can go before adjustment stops working.
Sources: European Journal of Agronomy; University of Hohenheim; pv magazine; Agronomy for Sustainable Development; Agronomy for Sustainable Development; Fraunhofer ISE; Bundesnetzagentur
Featured image: photo by Mark Stebnicki on Pexels (free Pexels license).
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I specialize in sustainability education, curriculum co-creation, and early-stage project strategy. At WINSS, I craft articles on sustainability, transformative AI, and related topics. When I’m not writing, you’ll find me chasing the perfect sushi roll, exploring cities around the globe, or unwinding with my dog Puffy — the world’s most loyal sidekick.
