Literature review: Kale response to shading

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• kale OR borecole OR “Brassica oleracea var. acephala” OR “Brassica oleracea var. sabellica” OR “Brassica oleracea var. palmifolia” OR acephala OR sabellica OR laminate OR “cavolo nero” OR “Tuscan kale” OR “curly kale” OR “Red Russian"

• Agrivoltaic: "agrivoltaic”; “agrivoltaics”; “agrophotovoltaic"; “agri-PV”; “agro-PV”; “solar sharing”; “photovoltaic greenhouse”; “solar panel”; “photovoltaic”; “dual land use”; “semi-transparent"
• Shade net / cloth: “shade net”; “shade cloth”; “shading net”; “shade screen”; “shade house”; “shade structure; “netting”; “insect net”; “mesh"
• Colored / photoselective: “photoselective”; “colored net”; “red net”; “blue net”; “light quality”; “light spectrum"
• Other shading: shading; shade; “low light”; “reduced light”; “light intensity”; “shade tolerance”; intercrop; intercropping; agroforestry; “alley cropping”; greenhouse screen”; PAR; “light interception”

Inclusion and Exclusion Criteria

• Papers must be written in English (not only the title, abstract, keywords)
• Source should be a peer-reviewed journal article, peer-reviewed conference paper or proceedings paper, or a peer-reviewed or edited whole book
• Papers are included if:
  • kale-specific results are reported in multi-crop studies
  • studies report kale growth, yield, morphology, physiology, quality, water use, microclimate, or pest/disease response caused by reduced/altered light from:
    • agrivoltaic systems (all types and configurations)
    • open-sided overhead shade nets or cloth, including colored/photoselective nets
    • enclosed environments that are compared with each other when they differ mainly in light (e.g., shading in greenhouses)
    • covers that surround the crop (e.g., low tunnels), only if light was measured and related to growth or yield
• Papers are excluded if:
  • pest, disease, or yield effects are caused by a cover that surrounds the crop (like in netting, low tunnels, covers) rather than by shading
  • indoor studies that only vary lamp or LED light intensity or spectrum with no shading structure

From Wikipedia:

Kale (/keɪl/), also called leaf cabbage, belongs to a group of cabbage (Brassica oleracea) cultivars primarily grown for their edible leaves, but it is also used as an ornamental plant. Its multiple different cultivars vary quite a bit in appearance; the leaves can be bumpy, curly, or flat, and the color ranges from purple to green.

Notes: The main producing provinces are: Ontario (1,331 t) British Columbia (566 t) Quebec (373 t) Manitoba (182 t) Also reported in: Saskatchewan (27 t, E), Nova Scotia (15 t), New Brunswick (8 t), Alberta (3 t), and Newfoundland and Labrador (3 t). Prince Edward Island data for total production is marked F in Statistic Canada’s data which means “too unreliable to be published." Saskatchewan data for total production is marked E which means “use with caution."

To add:

• Expected diameter
• Expected height
• Typical leaf mass

• Publication Year:
• Country:
• Location:
• Climate:
• Kale:
• Growing period:
• Shading category:
• Method:
• Main findings:

• Publication Year: 2025
• Country: Tanzania and Kenya
• Location: Tanzania: Sustainable Agriculture Tanzania (SAT)'s Farmer Training Centre, Morogoro (lat. −6.7413, long. 37.5494, elevation: 537 m); Kenya: Latia Agribusiness Solutions (LAS), Isinya, Kajiado County (lat. −1.6850, long. 36.8308, elevation: 1,646 m)
• Climate: tropical and semi-arid (for both study areas)
• Kale:
• Growing period:
• Shading category: Agrivoltaics
• Method:
• Main findings:

• Publication Year: 2025
• Country: United States
• Location: AV Photovoltaic Dual-Use Research Project site at the UMass Crop and Animal Research and Education Farm in South Deerfield, Massachusetts
• Climate: 2016 (hot and dry), 2017 (cold and wet), 2018 (warm and wet)
• Kale: Curly Kale (Brassica oleracea var. sabellica)
• Growing period: three growing seasons from 2016 to 2018
• Shading category: Agrivoltaics
• Method: solar panel configuration is a south-facing 40° fixed-tilt array with inter-panel gaps of 0.6 meters, 0.9 meters, 1.2 meters, and 1.5 meters; lowest edge of each PV cluster is 2.3 meters; proponents planted kale, Swiss chard, pepper, and broccoli; data collected: harvestable leaves per plant and fresh weight per leaf; calculated data: modeled irradiance
• Main findings: Kale was the only crop with a consistent (marginally significant) linear increase in harvestable leaves per plant as inter-panel spacing increased; full-sun controls gave more and heavier kale leaves in 2017 (cold and wet) and 2018 (warm and wet), while agrivoltaic full-sun beds were equivalent in the 2016 (hot and dry) season.

• Publication Year: 2024
• Country: Brazil
• Location: State University of Mato Grosso do Sul — Cassilândia University Unit (latitude: 19°07′21″ S, longitude: 51°43′15″ W, and altitude: 516 m)
• Climate: tropical rainy climate with rainy summer and dry winter
• Kale: Brassica oleracea var. sabellica L. (Georgia cultivar)
• Growing period: January 13 to 24, 2022 (microgreen), March 17 to April 19, 2022 (baby leaf)
• Shading category: Shade net
• Method: "The experiments were conducted in a completely randomized design in a factorial arrangement of 4 × 2 (four environments × two substrates) for experiment 1 and 4 × 5 (four environments × five substrates) for experiment 2, both with six replications. Both experiments have non-air-conditioned protected environments: two screens (3.5 m height) and two greenhouses (4 m height). For the two screens:(1) agricultural screen with black monofilament screen with 18% shading, (2) agricultural screen with black monofilament screen and 30% shading. For the two greenhouses: (1) greenhouse covered with a 150-micron low-density polyethylene (LDPE) film and an Aluminet® aluminized screen with 35% shading under the LDPE film, (2) greenhouse covered with 150-micron low-density polyethylene (LDPE) film and 42–50% shading LuxNet® aluminized screen under the LDPE film
• Main findings: Microgreens grew most under the 35% screen and had the most pigments under the 42-50% screen; baby leaf grew most under the 42-50% screen, and the 35% screen gave higher pigments (chlorophyll and carotenoid) in pure Carolina Soil® substrate.

• Publication Year: 2022
• Country: not reported (assumed to be United States based on authors’ affiliation)
• Location: not reported
• Climate: not reported (but study considered kale growth through wintertime)
• Kale: Brassica oleraceae [Toscano Lacinato kale (also known as “dinosaur” kale)]
• Growing period: October 2019 to March 2021
• Shading category: Agrivoltaics
• Method: The proponents set up an agrivoltaic greenhouse ’test cell’ with two PV panels forming part of the roof and glazing (transparent polycarbonate) between; they measured one year of microclimate data (relative humidity, internal air temperature, incident solar radiation, wind speed, and wind direction); they developed heat/moisture and shadowing models; they had 3 growth experiments with 'Toscano Lacinato' kale in the test cell vs adjacent outdoor control and conventional greenhouse; data collected: dry mass by allometry; data calculated: modeled photosynthetic rate
• Main findings: Kale grown in the control (unprotected) died due to exposure to snow and prolonged freezing temperatures. Kale grew in the test cell through winter but only plants directly under the glazing grew well; the cell was below freezing only 36.6% of the time compared to the ambient.

• Publication Year: 2022
• Country: Germany
• Location: Mecklenburg Lake District
• Climate: "Overall temperature increased from an average of 12.9 °C in the first week to 19.6 °C in week 6 of the experiment. Analogously, minimum temperature increased from only 3.5 °C to above 10 °C from week 4 onwards. Hot days were absent during the experiment, reaching a maximum of 28.3 °C."
• Kale: Brassica oleracea var. sabellica L. (Winterbor F1 cultivar)
• Growing period: May 20, 2020 (sowing) to July 1, 2020 (harvest)
• Shading category: building shade; indoor behind glass
• Method: pot trial; kale pots were placed outdoors on the N, E, W, and S sides of a residential building and indoors behind S- and E-facing windows; there were 6 locations total, 6 replicates with 10 pots each; data collected: plant height, water use, flavonoids, hydroxycinnamic acids, carotenoids, chlorophylls, glucosinolates
• Main findings: "Plants grown inside (southern and eastern location) were in average 83 and 12% higher than their outside grown counterparts (south and east, respectively) during the first two weeks of cultivation. During growth, differences between location vanished until week 4.”

• Publication Year: 2021
• Country: United States
• Location: SunPower Research and Development Ranch, 28058 Mace Blvd, Davis, California 95618( 38.531751° latitude, -121.694959° longitude)
• Climate: typically has winter
• Kale: Brassica oleracea cv. ‘Toscano’
• Growing period: trials were conducted during spring and summer; April 12, 2017 to October 13, 2017 (first trial) and March 28, 2018 to July 6, 2018 (second trial)
• Shading category: Agrivoltaics
• Method: Kale (along with chard, broccoli, peppers, tomatoes, spinach) seedlings were positioned within a single-axis tracking PV array, 1.2 m height, with 7%, 55%, 62%, and 85% of full sun, and under full sun (control); data collected: PAR, canopy air temperature, and harvested biomass
• Main findings: Kale yield was the same in all PAR conditions across 55% to 85% of full sun, and 15%-23% less than control (over three harvests). Authors suggested that kale can be planted throughout the solar array as long as light levels are at least 55% of full sunlight.

• Publication Year: 2019
• Country: Brazil
• Location: Mato Grosso State University – Nova Mutum (Latitude 13º49′44″ S, Longitude 56º04′56″ W, and altitude 460 m)
• Climate: tropical with average annual rainfall of 1,900 mm and average temperature (low) 24 °C and (high) 34 °C
• Soil: Dystrophic red-yellow latosol
• Kale: Brassica oleracea var. acephala hybrids Hi Crop (Takii, Brazil) and Kobe F1 (TopSeed)
• Growing period: not reported
• Shading category: shade-net, coloured-net
• Method: randomized blocks, 2 hybrids (Hi Crop, Kobe F1) x 6 environments (tissue-non-tissue (TNT), white polyester organza mesh (47 g m-2), red mesh, silver mesh, and black mesh), 4 replicates: open field vs low tunnels (1 meter high) covered with nonwoven TNT (15 g m-2), white organza (47 g m-2), red Chromatinet®35%, silver Aluminet® 50%, and black Sombrite®35%; data collected: air/soil temperature (thermocouples), luminosity (lux at 2:00 pm), yield
• Main findings: Kale planted in the open field had the lowest plant height values; higher plant height values were recorded in the black Sombrite®35% and silver mesh tunnels Aluminet® 50%. Heavier fresh weight (leaves) was observed in the white organza tunnel, 22.8% higher than in the open field and 9.89-42.19% higher than other meshes. The authors recommend using organza for kale cultivation in high-temperature regions.

• Publication Year: 2017
• Country: Kenya
• Location: Trans-Nzoia district, Western Kenya, at the settlements Botwa, Hututu, Wehoya, Yuya, and Sinoko, 15 km east of Kitale town (01°00’N 35°00’E), 1800–1900 m above sea level
• Climate: mean annual temperature is 19 °C; average yearly rainfall is 1000–1200 mm (from mid-March to October)
• Kale: Brassica oleracea var. acephala
• Growing period: not reported
• Shading category: Agroforestry tree shade
• Method: On-farm survey: 20 small kale fields (20-100 m²) in 5 settlements classified as shaded by trees (at least 2 meters high) or open; data collected: pest abundance (aphids, caterpillars), natural enemies (ants, spiders, predatory beetles), aphid parasitism, predation on diamondback moth eggs and surrogate caterpillars, bird predation on aphids
• Main findings: Shade fields had fewer aphids and caterpillars and more spiders and predatory beetles than open fields; ant abundance and predation parasitism rates did not differ. The authors attributed pest reduction mainly to natural enemies but suggested that microclimatic effects on pest physiology and changes in plant or soil quality may also have contributed, although these were not measured in their study.

• Publication Year: 2017
• Country: Brazil
• Location: State University of Mato Grosso do Sul – University Aquidauana Unit (Latitude −20°27'00” South, Longitude-55°40'12” West, and altitude 174 m)
• Climate: tropical humid climate and annual average temperature of 29°C
• Kale: Brassica oleracea var. acephala (Georgia cultivar)
• Growing period: July to September 2009
• Shading category: shade-net
• Method: agricultural greenhouse with polyethylene film vs. agricultural screened nursery with black monofilament screen (Sombrite®), both with 50% shade; 72-vs-128 cell trays x 6 substrates (cassava branches/cattle manure mixes); data collected: plant height at 16, 23, and 30 days, stem diameter, and seedling dry mass at 40 days
• Main findings: The screened nursery produced more vigorous seedlings than the polyethylene greenhouse, with substrates containing 80% and 100% cattle manure.