Finding the optimal photoperiod and light intensity combination for indoor growing
Source: VFD.com
spectrum, photoperiod and intensity) can optimize crop quality and yield, reduce energy consumption and production costs and increase energy use efficiency (EUE). This study aimed to investigate the influence of different combinations of photoperiod and light intensity on the yield, growth and lighting-energy use efficiency (L-EUE) while maintaining a constant DLI on four leafy vegetable crops, namely crispy lettuce (Lactuca sativa L.), green kale (Brassica oleracea L.), pak choi (Brassica rapa L.) and lettuce var.
Three different light regimes with a DLI (9.75 ± 0.15 mol m⁻² day⁻¹) were used for the experiment, obtained by simultaneously varying photoperiod and light intensity, as follows: 14 h day⁻¹ and 190 μmol m⁻² s⁻¹ (14/190), 18 h day⁻¹ and 150 μmol m⁻² s⁻¹ (18/150), and 24 h day⁻¹ and 115 μmol m⁻² s⁻¹ (24/115). Continuous light exposure (24/115) yielded the best morphological results for both lettuce cultivars, whereas pak choi showed higher leaf width at higher light intensity and a shorter photoperiod.
Conversely, differences in light use efficiency (LUE) were observed only in pak choi with the shorter photoperiod (14/190), resulting in higher LUE values than in the continuous day (24/115) treatment. The use of 24/115 and 18/150 is a valid strategy to increase L-EUE for the crops used in this study, but additional research with higher DLI is needed to further investigate the effects of different combinations of light intensity and photoperiod in commercial settings.
Why this matters: For operators, this is a water-management story. The useful signal is that direct substrate measurements can help cut drain loss materially without giving up yield or fruit quality, which is exactly the kind of controllable efficiency gain a facility can build on.
Frequently Asked Questions
Why does substrate sensing matter in free-drain strawberry systems?
Because drain percentage tells a grower what already happened, while substrate moisture and EC data show root-zone conditions directly. That makes it easier to cut water loss without guessing.
What is the operator takeaway from this trial?
If the thresholds are understood well enough, growers can reduce drain water materially while protecting yield and fruit quality, which makes sensing an operational tool instead of a reporting tool.
