LIT_115: Andrew et al. (2021) — solar-grazing pasture yield derate & LER, Oregon agrivoltaic

LIT_115: Andrew et al. (2021) — solar-grazing pasture yield derate & LER, Oregon agrivoltaic

Source

https://doi.org/10.3389/fsufs.2021.659175 — original source (opens in a new tab; the file is not redistributed)

Andrew et al. (2021) — Herbage Yield, Lamb Growth and Foraging Behavior in Agrivoltaic Production System

The best-evidenced, lowest-derate agri-PV food pairing: solar grazing. Pasture DM ~9–33% less under a dual-use solar farm than open pasture, but lamb liveweight is COMPARABLE (higher forage quality offsets lower quantity), and combined land-use efficiency reaches LER 1.68–2.04.

Two-year replicated grazing trial (Oregon State University, Corvallis, OR, 44°34’N) comparing weaned-lamb growth and pasture production between a 1.4 MW / 2.4 ha commercial agrivoltaic farm (sheep grazed under east-west PV rows 6 m apart) and adjacent open pasture. The NI-load-bearing result: whole-system pasture production was 9–33% less under panels (38% lower over the entire period, concentrated in the fully-shaded strips), yet spring-lamb liveweight production was statistically comparable (solar 1.5 vs open 1.3 kg ha⁻¹ d⁻¹, P = 0.67) because forage quality rose under shade. Land-equivalent ratio (dual use vs single use) was 1.68–1.81 for herbage and 1.97–2.04 for lamb — i.e. combining solar + grazing on the same land is ~1.7–2× as land-productive as either alone. Net grazing return was only 1.6% ($17 ha⁻¹ yr⁻¹) lower under panels. A PROXY for NZ (Oregon, temperate; data_quality: medium) — grazing/pasture is the NZ-relevant pairing; the derate can flip to a gain in hot/dry conditions via improved water-use efficiency.

Summary

Peer-reviewed original research (Frontiers in Sustainable Food Systems, CC BY) reporting a two-year (spring 2019 + 2020) replicated grazing experiment at the Rabbit Hills Solar Farm near Corvallis, Oregon — one of the first studies of livestock (rather than crop) production inside a commercial agrivoltaic (dual-use solar) system. Weaned Polypay lambs were grazed on 0.1 ha plots either under east-west single-axis PV rows (6 m apart, giving 50% fully-shaded / 50% partially-shaded ground) or in adjacent open pasture, in a randomized complete block design with three replicates. The team measured herbage dry-matter production and mass on offer, lamb liveweight gain and liveweight production per hectare, botanical composition and nutritive value of forage, foraging behaviour, water intake, and computed a Land Equivalent Ratio and net grazing return. For Neobiome Intelligence the value is the under-panel food-yield derate for the pasture/grazing pairing — the parameter the model needs to co-locate solar generation with food production on the same parcel without double-counting the land. The headline is favourable: a modest and highly design-dependent herbage penalty (9–33%, driven by the fully-shaded strips) that does not translate into a livestock-output penalty, plus a strong land-productivity multiplier (LER ~1.7–2.0). It is an Oregon proxy (context: both — feeds the D02 food-yield layer and the thesis FEW-nexus/agrivoltaic argument), read verbatim from the open-access primary; figures are source-verified but flagged medium for the geographic transfer to NZ.

Key claims

- claim: "WHOLE-SYSTEM YIELD DERATE (the model figure): 'On average, the pasture production was 9–33% less in agrivoltaics systems than open pastures (P < 0.01).' Restated in the Discussion: '...consequently leading to 9–33% less in solar pastures than open pastures.' → retained-yield ratio ≈ 0.67–0.91 vs open pasture (derivation, not verbatim)."
  source_location: "Results — 'Pasture Dry Matter (DM) Production' p.5 ('On average, the pasture production was 9–33% less...'); Discussion — 'Shade and Animal Trampling Reduced the Pasture Production...' p.8 (restatement)"
- claim: "FULL-PERIOD DERATE (abstract headline): 'Over the entire period, solar pastures produced 38% lower herbage than open pastures due to low pasture density in fully shaded areas under solar panels.' → ~0.62 retained over the whole period, dominated by the fully-shaded strips (derivation)."
  source_location: "Abstract p.1"
- claim: "LIVESTOCK OUTPUT IS COMPARABLE despite less herbage: 'The liveweight production between solar (1.5 kg ha−1 d−1) and open pastures (1.3 kg ha−1 d−1) were comparable (P = 0.67).' And 2019 growth: 'weaned lambs grew at 120 and 119 g head−1 d−1 under solar panels and open pastures, respectively in spring 2019 (P = 0.90).'"
  source_location: "Abstract p.1; Results — 'Lamb Production' p.5 (120 vs 119 g head⁻¹ d⁻¹, P = 0.90; 1.5 vs 1.3 kg ha⁻¹ d⁻¹, P = 0.67)"
- claim: "2020 lamb parity confirms the pattern: 'lamb liveweight gains and liveweight productions were comparable in both solar (89 g head−1 d−1; 4.6 kg ha−1 d−1) and open (92 g head−1 d−1; 5.0 kg ha−1 d−1) pastures (all P > 0.05) in 2020.'"
  source_location: "Abstract p.1; Results — 'Lamb Production' p.5"
- claim: "MECHANISM — quality offsets quantity: 'Overall, solar pastures had greater (P < 0.05) CP content than open pastures'; the Discussion concludes 'higher forage nutritive value in solar pastures during the same period offset the lower herbage mass, leading to similar lamb liveweight gains in both systems.' i.e. the yield derate is a HERBAGE-MASS derate, not a livestock-nutrition derate."
  source_location: "Results — 'Botanical Composition and Nutritive Value of Herbage on Offer' pp.5–7; Discussion — 'Lamb Production Did Not Differ Despite Lower Herbage on Offer in Solar Pastures' p.9"
- claim: "LAND EQUIVALENT RATIO (dual-use land-productivity multiplier): 'Land use efficiency of herbage DM yield (kg DM ha−1 y−1) and lamb liveweight production (kg ha−1 d−1) in agrivoltaics was 1.81 and 2.04, respectively in 2019. The LER of herbage DM yield was 1.68, while the LER of liveweight production was 1.97 in 2020.' (LER assumes solar energy yield ratio = 1, i.e. panels arranged to maximise energy.) Conclusion: dual-purpose management 'enables increasing the land productivity up to 1.81 for pasture production and 2.04 for spring lamb production.'"
  source_location: "Discussion — 'Land Equivalent Ratio and Net Economic Return of Solar Grazing' p.8; Conclusion p.10. LER formula + energy yield-ratio = 1 assumption: Materials & Methods — 'Land Equivalent Ratio (LER) and Net Return of Spring Grazing' p.3"
- claim: "NET ECONOMIC RETURN barely differs: 'Averaged across the years, our net return from grazing was $1,046 ha−1 year−1 in open pastures, and $1,029 ha−1 year−1 in solar areas.' i.e. 'Our net returns for grazing in solar pastures were 1.6% ($17 ha−1 year−1) less than in open pastures' (USDA 2018 lamb price $316.19/100 kg; spring-grazing net only, PV revenue excluded)."
  source_location: "Discussion p.8 ($1,046 vs $1,029 ha⁻¹ yr⁻¹) + p.10 (1.6% / $17 ha⁻¹ yr⁻¹); pricing basis — Materials & Methods p.3"
- claim: "SITE & SYSTEM CONFIGURATION (the design the derate is conditional on): trial at Oregon State University, Corvallis, OR (44°34'N, 123°18'W, 78 m a.s.l.), spring 2019 & 2020, within the Rabbit Hills Solar Farm — 'a 2.4 ha, 1.4 MW agrivoltaic farm which combines sheep grazing with solar energy production. The 1.65 m wide photovoltaic panels are oriented east-west, and tilted south at an 18° angle. The lowest edge of the panel is 1.1 m above the ground, and rows of panels are 6 m apart.' Row spacing gave '3-m fully shaded and 3-m partially shaded areas', so plots were '50% open (partially shaded) and 50% fully shaded areas.' Fertilised 50 kg N/ha as urea (Feb 2019 & 2020)."
  source_location: "Materials & Methods — 'Site' p.2 (location, Rabbit Hills 2.4 ha / 1.4 MW, panel geometry); 'Experimental Design and Grazing Management' p.2 (6 m spacing, 3 m + 3 m, 50/50, 50 kg N/ha)"
- claim: "PER-AREA breakdown (⚠ apparent internal labelling inconsistency — do NOT lift as a per-strip derate): '2019 total herbage yield ... was 3,609, 2,893, and 3,700 kg DM ha−1 for open pastures, partially shaded, and fully shaded solar pastures, respectively'; '2020 ... 8,700, 3,079, and 8,579 kg DM ha−1 for open pastures, partially shaded and fully shaded solar pastures, respectively (P < 0.01).' As transcribed these show the PARTIALLY-shaded strip lowest and the fully-shaded strip ≈ open, which conflicts with the paper's prose attributing the loss to the fully-shaded areas — a probable strip-label swap in the results text; only the whole-system 9–33% / 38% figures are used for the model."
  source_location: "Results — 'Pasture Dry Matter (DM) Production' p.5 (Figure 2)"
- claim: "DERATE CAN FLIP TO A GAIN in hot/dry via water-use efficiency (cited within-site evidence): 'from ungrazed pastures under the solar panels within the same site, Adeh et al. (2018) reported a 90% increase biomass per unit area, and 330% increase in water use efficiency under the solar panels during late spring-summer.' Lambs under panels also drank less: in late-spring 2019 'lambs in open pastures consumed 0.72 L head−1 d−1 more water than those grazed under solar panels (P < 0.01)' (no difference in 2020, P = 0.42). ⚠ The +90% / +330% figures are attributed to Adeh et al. (2018) [ungrazed, same site], NOT a grazed result of this study."
  source_location: "Discussion — 'Shade and Animal Trampling...' p.8 (Adeh et al. 2018 cite: +90% biomass, +330% WUE); Abstract p.1 + Discussion — 'Lambs Spent Their Time Predominantly Under Shade...' pp.9–10 (0.72 L head⁻¹ d⁻¹ water)"
- claim: "STUDY-CONDITION CAVEAT (why the open-pasture baseline is itself low, and what the ratio transfers): 'the current study was conducted on an unimproved, grass-dominated pasture established over 20 years ago and managed with no (e.g., irrigation) or low inputs (e.g., fertilizer, lime). We expect that the pasture conditions are representative to most grazed agrivoltaic systems in Pacific Northwest.' Both open and solar pastures 'did not compare favorably to the biomass yield from young, unirrigated pastures in the same location where annual forage production was 13.4 t DM ha−1 y−1 (Wilson, 2020).'"
  source_location: "Discussion — 'Lamb Production Did Not Differ...' p.9"
- claim: "FRAMING (cited context, not this study's own measurement): agrivoltaics 'have the potential to increase global land productivity by an impressive 35–73% (Dupraz et al., 2011)'; and the herbage LER here 'is quite comparable to LER of grass-clover pasture (1.67–1.70) reported by Trommsdorff et al. (2021).'"
  source_location: "Introduction p.2 (Dupraz et al. 2011, 35–73%); Discussion — 'Land Use Efficiency in Agrivoltaics...' p.10 (Trommsdorff et al. 2021, 1.67–1.70)"

Neobiome Intelligence relevance

This source resolves the under-panel food-yield derate the NI model needs to co-locate PV generation and food production on the same parcel (the agri-PV / agro_pv pathway), for the pasture / solar-grazing pairing — the best-evidenced and lowest-derate agri-PV food pairing, and the NZ-relevant one given NZ’s pastoral base.

What it supplies to D02 (food-yield layer):

• A whole-system herbage derate of 9–33% (retained ratio ≈ 0.67–0.91 vs open pasture; ~0.62 over the full period when the fully-shaded strips dominate). Derivations from the verbatim figures above.
• Crucially, the derate is a herbage-mass derate, not a livestock-output derate: lamb liveweight production per hectare was statistically comparable (higher forage quality under shade offset lower quantity). For a livestock-based food-self-sufficiency calculation, solar-grazing land can be treated as near-parity on meat output.
• A Land Equivalent Ratio of ~1.68–2.04 (herbage + lamb) — the quantitative anchor for the land-conflict-resolution claim already on agro_pv (which currently cites the Fraunhofer LER ~1.6–1.8 from OT_050); this is field-measured corroboration from a livestock system.

Recommended modelling treatment (see Notes): apply a pasture food-yield multiplier of ~0.85–0.95 open-field-equivalent with an irradiance/aridity modifier (North-Island/dry-east trending toward 1.0 or a gain, South-Island/cool-cloudy trending toward a larger derate), rather than a flat constant. Suitability order for agri-PV food pairings: pasture/forage > shade-tolerant horticulture > arable staples.

Caveats for the modeller: (1) it is an Oregon proxy (data_quality: medium), transferable as a ratio between the two treatments on the same low-input pasture, not as an absolute yield; (2) the open-pasture baseline is itself an old, unimproved, low-input pasture (13.4 t DM/ha/yr from young unirrigated pasture at the same site by comparison), so the ratio, not the levels, is what transfers; (3) the derate is conditional on the panel geometry (6 m rows, 1.65 m panels, 1.1 m clearance, 50/50 shade split) — different agri-PV densities (see the sibling density source in this batch) shift it.

Research targets

Resolves the under-panel yield-derate leg of RT_108 (pasture / solar-grazing pairing) — the food-yield-tradeoff component the RT called out as pending. No new research targets opened (minimise-RTs policy). The RT_108 umbrella stays open for the remaining legs addressed by the sibling sources in this batch (agri-PV density, land-retention fraction, NZ cost NZD/kWp, NZ consent pathway) and until the modeling work wires the parameters; the NZ-specific pasture-yield-under-panel gap folds into that open umbrella rather than a new RT.

Documents to retrieve

• None.

Research gaps

• NZ-measured under-panel pasture-yield derate (this Oregon result is a proxy) — folded into the open RT_108 NZ-calibration umbrella; not a standalone new RT.

Retrieval provenance

• Upstream source: open-access peer-reviewed article, Frontiers in Sustainable Food Systems 5:659175 (2021), DOI 10.3389/fsufs.2021.659175, CC BY. Publisher full text.
• Located by: the RT_108 agri-PV integration retrieval pass (worklist research_to_retrieve_agripv_integration_2026-07-25.md; see the retrieval record held with the project) on 2026-07-25 — target 108c, “under-panel yield derate (pasture/grazing pairing)”. The exact retrieval prompt is captured in that worklist, not reproduced here.
• Read: verbatim, via pdftotext -layout on the downloaded + hydrated PDF (12 pp). Unlike a typical AI-prepared raw, every figure in key_claims is quoted directly from the authoritative primary and carries an exact source_location — the values are source-verified, not AI-extracted-and-unverified.
• Verification status: data_quality: medium reflects geographic proxy transfer (Oregon, 44°34’N temperate maritime → NZ analogue), not unverified extraction. The one figure NOT this study’s own measurement — Adeh et al. (2018) +90% biomass / +330% WUE — is flagged in key_claims as a within-paper citation. sha256 verified against the raw (499e4c4f…).

Notes

• PROXY, data_quality: medium. Oregon, USA (Corvallis, 44°34’N), temperate maritime — a reasonable NZ analogue (the paper’s own peer reviewer was Massey University), but not NZ data. Transfer the derate ratio, not the absolute yields.
• Modelling recommendation: pasture food-yield multiplier ~0.85–0.95 open-field-equivalent nationally, with an irradiance/aridity modifier (not a flat number). Rationale: (a) whole-system herbage loss measured at 9–33% here; (b) livestock output was near-parity, so for grazing the effective food-output derate is smaller still; (c) the sign is climate-dependent.
• The derate can flip to a GAIN in hot/dry conditions via improved water-use efficiency and reduced heat/evaporative stress — same-site ungrazed pastures showed +90% biomass and +330% WUE in late spring–summer (Adeh et al. 2018, cited within this paper). NZ mapping: North Island / dry-east regions trend toward ~1.0 or a gain; South Island / cool-cloudy regions toward a larger derate — hence the aridity modifier.
• Suitability order for agri-PV food pairings: pasture/forage > shade-tolerant horticulture > arable staples. Pasture/grazing is the lowest-derate, best-evidenced, most NZ-relevant pairing (this source); shade-tolerant horticulture is intermediate; arable staples (e.g. soybean/maize) are the worst-affected.
• ⚠ Cross-pairing figures are NOT in this PDF. the retrieval pass’s cross-checks against Weselek, Campana, Sturchio et al. (arable and horticulture derates) are abstract-level reads of OTHER papers, not downloaded and not this source — they are deliberately excluded from key_claims and must not be attributed to Andrew et al. (2021).
• ⚠ Per-area (per-strip) numbers carry an apparent internal labelling inconsistency (partially-shaded strip shown lowest, fully-shaded ≈ open, contradicting the prose) — only the whole-system 9–33% / 38% figures are used for the model.
• Cross-refs: agro_pv (the technology page this evidences — currently carries the Fraunhofer LER 1.6–1.8 and the INT_002 <5%-land-loss framing; this is field-measured LER + a livestock derate). Feeds D02.

Connections

Links to

Technologies (1): Agro-PV (Dual-Use Solar + Agriculture)

EDT domains (1): D02: Smart Food Systems & Agriculture

Sources (1): OT_050

Referenced by

Technologies (1): Agro-PV (Dual-Use Solar + Agriculture)

EDT domains (1): D02: Smart Food Systems & Agriculture