In the past, we’ve discussed how everything from clouds to wind causes light fluctuations on our crops that result in a photosynthetic process that is very dynamic. But a dynamic photosynthetic process isn’t always the most efficient.
Take C4 crops, for example. When genetically modified to react and adjust to transitional periods of light more efficiently, some will experience a whopping 40% increase in photosynthetic productivity.
Based on that research, one might expect micro naps or flickering the lights on crops grown indoors to stimulate an outside environment better to be a futile pursuit.
Not so fast, says Kevin Folta, professor in the Horticultural Sciences Department at the University of Florida.
A Big Problem For Indoor Gardens And Those That Use Supplemental Lighting
Just because some crops struggle with light fluctuations doesn’t mean all crops do. In fact, by modifying C4 crops to react to changes in light in the same way C3 crops do, the woes of a dynamic photosynthetic process appear largely eliminated. With about 85% of all plant species falling under the C3 category, the bigger issue most gardeners face isn’t light fluctuations, but the poor photorespiration rates C3 crops struggle with when in hot and dry climates.
While LEDs have greatly helped offset the costs and electricity demands of growing crops indoors, it certainly hasn’t eliminated it and never will. In essence, the sun is a free source of light, and using it as much as possible for your lighting needs is going to save you significant money. But from cannabis plants sensitive to cross-pollination to the advantages of supplemental lighting in greenhouses, indoor gardening and grow lamps aren’t going away. This makes finding ways to cut down on their electricity needs a highly sought out endeavor.
One solution may be micro naps.
“Flicking the lights on and off can save energy without hurting indoor agriculture harvests”
With most crops able to handle reasonable light fluctuations, Kevin Folta and his colleagues wanted to see if mimicking natural light cycles outside could reduce electricity consumption without hurting yields. To test their idea, they studied kale, turnip, beet, and thale cress seedlings by exposing them to various on/off cycles with 5 seconds of light, followed by a dark period lasting between 10 to 20 seconds showing the most success.
At 5 seconds of light followed by 10 seconds of darkness, energy consumption was cut by 30% with no effect on seedling productivity. When increased to 20 seconds, energy consumption was cut by 60% — however, a slight effect on seedling production was seen. Kevin and this team theorize that five-second/ten-second flickers are the most optimal because only they override a plant’s regular rhythm. Other light cycles from 6 hours on/off to just 30 minutes of light followed by 30 minutes of darkness all resulted in the plants acting as if they were only grown in the dark.
“Five-second pulses just keep the ‘clock’ starting and stopping to the point where it never really gets going,” Folta told Anthropocene. “The ‘clock’ never really moves, and the plant just adjusts to the external environment without paying attention to that internal information.”
The Next Step
With light cycles ranging from just five to ten-second flickers having no negative impact on plant productivity while reducing energy consumption by up to 30%, micro naps may earn themselves a vital place in indoor gardening.
Questions linger, though, and that’s why Folta and his team plan to study different wavelengths and light intensities to determine the ideal low-energy conditions for indoor crops. Until then, the question is whether indoor growers should test the practice for themselves.
However, you may want to hold off simply because of the unknown wear-and-tear this practice may have on our lights. Unlike other grow lamps like HIDs, LEDs with dimming capabilities handle being turned on/off much better thanks to PWM. However, the effects that rapid on/offs have on thermal cycling/shock is tricky to say. While some LED fixtures might be able to handle repetitively being cycled between low temperatures to high temperatures, others might not. Fortunately, they can be tested and designed to handle these frequent naps, but that’s if this problem even exists.
At the end of the day, Folta and his team have made great progress on a very exciting prospect that could very well be one of the keys to long-term sustainable gardening.