Understanding DLI & choosing optimal supplementation levels

"When I discuss supplemental lighting with old school non-cannabis growers considering switching, I often hear the question, 'Why would I need lights? It’s a greenhouse?'  This is mostly because the ROI on supplemental lighting for traditional crops has never been very attractive. While fruiting crops can justify moderate levels of supplementation, it’s still not widely adopted," said Eric J Harrington, Dir Comm. Salen and Research at California Lightworks.

Yet, cannabis is by far the most light-hungry (and correspondingly fastest growing) plant cultivated commercially. In fact, it is becoming increasingly difficult to compete in the US market growing cannabis in a greenhouse without supplemental lighting.

Understanding DLI
DLI stands for “daily light integral” and is a measure of light in mols (6×1023) of photons. Daily Light Integral is important in greenhouse horticulture because it measures the amount of photosynthetically active radiation (PAR) plants receive each day as a result of both light intensity and duration.  This has a major impact on plant growth and health.

With indoor lighting, light is traditionally measured in instantaneous photosynthetic flux density (PPFD), which is the number of PAR photons that land on a given surface each second. PPFD essentially measures the amount of PAR light that reaches your crop. Each plant species has different PPFD requirements for the best yield.

"Because greenhouses have varying light levels, it is not productive to try to measure the light levels in instantaneous PPFD. Instead, we have to measure the total photons that are transmitted into the greenhouse over a 24-hour period. This is Daily Light Integral," Eric stated.

Read more at californialightworks.com


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