Sweet Basil Requires an Irradiance of 500 μ mol·m−2·s−1 for Greatest Edible Biomass Production

Abstract

<jats:p>Energy conservation in controlled-environment agriculture is a major concern for both commercial and research facilities as well as extraterrestrial facilities for food production. Supplying optimal irradiance by using electrical lighting for the greatest edible biomass production potentially is the greatest draw on energy during earth-based or extraterrestrial food production in controlled environments. Our objective was to determine the optimal irradiance for greatest edible biomass production of three cultivars of basil (<jats:italic>Basilicum ocimum</jats:italic> L.) in a controlled-environment production system. Seedlings of the three cultivars were transplanted into soilless medium, one plant per pot, and grew for 17 days in reach-in growth chambers maintained at 25 ± 4 °C with a 16-h photoperiod. Canopy-level irradiances of 300, 400, 500, and 600 μmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup> were provided by cool-white fluorescent and incandescent lamps. Shoot growth was measured as height, diameter, and number of leaves 0.5 cm long or greater; and edible biomass was measured as leaf fresh weight, shoot fresh weight, and shoot dry weight. There was no irradiance × cultivar interaction, but main effects of irradiance and cultivar were observed. Plant growth and edible biomass production were least at 300 μmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup> and greatest at 500 or 600 μmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup>. In several cases, 400 μmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup> yielded intermediate growth or edible biomass. Within the main effect of cultivar, Italian Large Leaf produced greater edible biomass than ‘Genovese’, and ‘Nufar’ yielded an intermediate amount of shoot fresh weight and dry weight. Under our environmental conditions that included ambient CO<jats:sub>2</jats:sub> concentration and ambient relative humidity, the rate of growth peaked at 500 μmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup>, and no additional accumulation of edible biomass occurred at 600 μmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup>. Based on our results, canopy-level irradiance of 500 μmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup> provides maximum edible biomass production of basil in a controlled-environment production system.</jats:p>

Growth and Photosynthetic Capacity of Basil Grown for Indoor Gardening under Constant or Increasing Daily Light Integrals

“…Although studies have compared growth and quality responses of edible plants grown with sole-source lighting under different DLIs (Beaman et al, 2009;Dou et al, 2017Dou et al, , 2018Ferreira Fernandes et al, 2013;He et al, 2001;Walters and Currey, 2018), most research has been conducted to address the needs of commercial growers who aim to maximize yield. Therefore, leafy greens for commercial production are typically grown with target DLIs in the range of 10 to 20 molÁm -2 Ád -1 , whereas 30 molÁm -2 Ád -1 are commonly targeted when producing fruiting crops like tomato [Solanum lycopersicum (Beaman et al, 2009;Dorais et al, 2017;Kang et al, 2013)]. However, providing DLIs in those ranges is not likely to be a feasible strategy by indoor gardeners because 1) the recommended light intensity for human comfort results in less than 1 molÁm -2 Ád -1 of light and 2) the cost for fixture installation and maintenance to provide sole-source lighting is not expected to result in an economic return and may limit the willingness of consumers to invest in lamps and electricity (Halleck, 2018;U.S.…”

“…Recommended DLIs for commercial basil production range between 13 and 35 molÁm -2 Ád -1 (Beaman et al, 2009;Dou et al, 2017;Moya et al, 2014;Somerville et al, 2014;Walters and Currey, 2018). However, when using cool-white fluorescent lamps in an indoor environment not designed for plant production, the recommended light intensity for human comfort and function is %7 mmolÁm -1 Ás -1 , resulting in a DLI of 0.6 molÁm -2 Ád -1 using a 24 hÁd -1 photoperiod [adapted from U.S. General Services Administration (2013)].…”

Nutrient Solution Strength Does Not Interact with the Daily Light Integral to Affect Hydroponic Cilantro, Dill, and Parsley Growth and Tissue Mineral Nutrient Concentrations

“…Based on their growth responses to DLI, parsley is classified as a medium-light plant (optimum DLI between 10 and 20 mol·m −2 ·d −1 ), whereas cilantro and dill are categorized as high-or very high-light crops (optimum DLI between 20 and 30 mol·m −2 ·d −1 or >30 mol·m −2 ·d −1 , respectively) [17]. When our data are taken together with other research on culinary herbs [15,17,18], they reinforce the impact of PPFD on culinary herb shoot mass, having direct implications for the profitability of commercial operations, as herbs are sold on a per-unit-mass basis. Light is less-or not limiting in the late spring, summer, and early fall for culinary herbs when ambient and greenhouse DLI are high [12].…”

Continuous and Intermittent Light at Night, Using Red and Blue LEDs to Suppress Basil Downy Mildew Sporulation

“…Many new horticultural top lighting systems employ red (l max 660 nm) and blue (l max 450 nm) LEDs to efficiently deliver light for photosynthesis in crop production (Radetsky, 2018). Light levels ranging from 150 to 500 mmol • m -2 • s -1 have been reported as effective for basil production, with photoperiods of 14 to 16 h (DLI: 7.56 to 28.8 mol • m -2 • d -1 ) (Beaman et al, 2009;Dou et al, 2018). Considering the energy efficiency improvements available with many horticultural LED luminaires relative to the incumbent HID systems, they may also be cost-effective for controlling basil DM sporulation at night.…”