As Medicinal Cannabis Cultivation consultants we are often asked what is the minimum Daily Light Integral (DLI) for Medicinal Cannabis cultivation in a greenhouse.
Definition of Daily Light Integral (DLI)
Daily light integral is a measure of the amount of light received in a particular area over a 24 hour period. DLI can also be defined as the amount of Photosynthetic Active Radiation (PAR) received each day. It is expressed as moles of light (mol) per square meter per day. e.g. Mol/m2/day. Daily light integral (DLI) impacts plant management decisions and will have an impact on water requirements and yield.
Measuring Daily Light Integral (DLI) – Mol/m2/day.
- It is important to know that the DLI outdoors varies depending on latitude, the time of year and the amount of cloud cover.
- When the DLI is low it would be wise for growers to maximise the amount of natural light that can reach the crop.
Throughout the year, outdoor DLI ranges from 5 to 60 mol/m2/day, however, in the greenhouse, values seldom exceed 25 mol·/m2/day due to glazing material, structure shading, seasonality, cloud cover, day length, and other greenhouse obstructions. The DLI can then be supplemented with other forms of light such as Metal Halide (MH), High-Pressure Sodium (HPS) or Light Emitting Diodes (LEDs).
Calculating your supplemental DLI is easy using the following equation:
DLI = ((Average intensity over a 24-hour period, in μmol·/m2/second)*(3600*24)) / 1,000,000
Medicinal Cannabis Cultivation and Minimum Daily Light Integral (DLI) | Standards | Requirements
First, we need to discuss DLI values outdoors, which vary depending on latitude, time of year, and cloud cover and varies between 5-60 mol/m2/day. For forest floor plants, DLI may be less than 1 mol/m2/day, even in summer.
In greenhouses, 30-70% of the light will be absorbed or reflected by the glass and other greenhouse structures. DLI levels in greenhouses therefore rarely exceed 30 mol/m2/day. Indoor grows, values between 20 and 30 mol/m2/day are common.
Why this focus on DLI? When replicating natural sunlight, cannabis cultivators aspire to achieve two important goals. The first being consistency of the grow and the second being quality of the grow, to ensure the active ingredient content is uniform. To achieve these goals, it is critical to have optimal light management in place, as natural light fluctuates constantly throughout the day and varies from season to season. Light exposure is the most important variable affecting plant growth and it is therefore important to measure the amount of light your plants receive. We use the measurement of Daily Light Integral (DLI), particularly with commercial farmers and greenhouses growers.
Light particles or photons, particularly those with a wavelength between 400 and 700 nanometers (nm) provide plants with energy for photosynthesis (the process of converting water and carbon dioxide into sugars and oxygen). The DLI influences plant growth, vitality and yield. A rise or fall in the DLI will affect the plant roots system, branching, flowering, leaves and stems. Some advantages of having optimal DLI are improved crop yields, more predictable results, the better quality of your plants and can lead to faster, better results to help reduce your research and growth cycle.
References, Publications and Journal Articles:
Publisher: American Society for Horticultural Science
HortScience, 2012 – journals.ashs.org – Publication date: July 2012; Volume/Issue: Volume 47: Issue 7; Pages: 856–860
- Photosynthetic daily light integral during root development influences subsequent growth and development of several herbaceous annual bedding plants
Publication: Commercial Greenhouse Production
Authors: Ariana P Torres and Roberto G Lopez
University: Purdue University
Department: Department of Horticulture and Landscape Architecture (Purdue University)
I. Daily Light Integral: A useful tool for the U.S. Floriculture industry.
Author: James E. Faust
Other terms: photosynthetically active radiation (PAR)
Australian Courses for Medicinal Cannabis Cultivation:
Page last updated on June 14, 2019.