| CPC H05B 45/12 (2020.01) [A01G 7/045 (2013.01); H05B 45/22 (2020.01); H05B 47/16 (2020.01)] | 17 Claims |

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1. A method of operating an LED lighting system to illuminate plants, the method comprising:
providing plural LEDs of the LED lighting system arranged in groups of LEDs, each group of LEDs controlled by a respective LED driver, the groups of LEDs including at least one first wavelength group of LEDs emitting light predominantly at a first wavelength and a second wavelength group of LEDs emitting light predominantly at a second wavelength;
assigning the groups of LEDs and a light sensor into zones;
in a processor of the LED lighting system, determining a relative uptime of the at least one first wavelength group of LEDs and the at least one second wavelength group of LEDs in order to provide a desired ratio of the light at the first wavelength to the light at the second wavelength over a period of time;
instructing the respective LED driver controlling the at least one first wavelength group of LEDs to activate the at least one first wavelength group of LEDs for an active period and deactivate the at least one group of first wavelength LEDs for an inactive period, the active period and the inactive period being selected to cause the at least one first wavelength group of LEDs and the at least one second wavelength group of LED to have the determined relative uptime, the active period and the inactive period being sufficiently long to be perceptible to a human;
in response to determining, based on information from the light sensor that a Daily Light Interval (DLI) corresponding to a total amount of photosynthetic active radiation (PAR) to be received in a photosynthetic active period has been reached, the processor instructing the respective LED drivers of the groups of LEDs to turn off the plural LEDs of the LED lighting system, groups of LEDs assigned to different zones being controlled independently, and the determination that the DLI has been reached being made in respect of the zone to which the light sensor is assigned.
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