Features
New research shows red-light application could improve yield in some tomato crops

New research is emerging that suggests adding far-red light during the entire photoperiod alongside the standard PAR light can increase yield in some tomato crops.

According to a May press release, lighting firm Signify, together with Wageningen University & Research and Nunhems, recently conducted research that shows the use of far-red light can produce an additional yield of almost one fifth in tomatoes, depending on the variety. The far-red light needs to be added during the entire photoperiod alongside the standard PAR light.

“It is well-known that the different colors within a light spectrum can influence the development of plants. In fact, crops may react differently to the various colours of light at different times of day,” the press release states. “Therefore, this study sought to find the most appropriate time for the application of far-red light. They found that far-red was by far most effective when added throughout the entire photoperiod.”

The press release says the outcome confirms the opportunities that far-red light presents, but it is not a clear and straightforward equation. 

“We now have more insight into the impact of far-red light during different periods of the day,” said Phillips Horticulture LED Solutions plant specialist Erik Stappers. “The next step is to focus on the ratio between far-red and PAR light to find the ideal balance between growing optimization and energy efficiency.” 

Additional yield
The best result observed was a 16 per cent increase in yield, however, major differences between varieties make the outcome uncertain for growers. 

According to the press release, the 20-week study shows that all far-red treatments give more sink strength, which means that more sugars flow to the fruits. However, this only led to a significant increase in harvest if the far-red was dosed during the entire photoperiod – in this case, 16 hours a day.

The research partners say they conclude the plant is not more sensitive to this light in the morning or in the afternoon. Far-red light requires more energy than PAR light, which means that the long duration that far-red has to be added leads to higher energy consumption.

Ratio between PAR and far-red

“The question now is the level at which the use of far-red becomes advantageous in relation to the extra energy consumption,” the press release continues. “If a relatively low percentage of far-red light produces additional yield, then the researchers expect it may become appealing.”

“We continue to tweak it to find the ideal light recipe for tomatoes,” said Elena Jiménez, Plant Pathology researcher at Wageningen University, in the release. “Besides additional yield in kilos, higher quality and better taste may also come into play in the future.”

Philips Horticulture LED Solutions, Nunhems and Wageningen University & Research have been working together for approximately seven years to research the ideal light recipe for tomatoes. Various light recipes are being tested in relation to energy consumption, light spectrum, additional yield and uniformity.