Light Deprivation and Supplementation for Greenhouses

By December Kennedy

As cannabis reform continues to grow rapidly across the nation, and moves out of basements and into a regulated and controlled industry built on commercial production, the demand for high quality cannabis grows while the profit margins continue to shrink. auto_light_deprivation_2 (1)This leaves little room for error and an ever-growing need to optimize every opportunity for increased production. The solution to this complex issue is a relatively simple one, employed far before the proliferation of pot shops and commercial grow houses littering the landscape. The answer lies in the light deprivation/supplementation greenhouse design, and those who stand to make the most money in the upcoming boom of national marijuana policy, are the same businesses who employ the latest technology available to the greenhouse cultivation market.

What is Daily Light Integral, and why does it matter?
To understand the need for greenhouse light deprivation and light supplementation first we must determine the plants most basic requirements. Aside from clean air and fresh water, a plant’s most pressing need is also one of the most hotly contested subjects among growers. When to give it and how much light does their plant need?
Daily Light Integral, or DLI, is a measure of the number of photons (light) that hit the plant canopy over a 24 hour period. All crops have their own specific DLI that, once understood, can provide the grower with ample opportunity to manipulate the lighting in their gardens and maximize their plants potential. Once you know what your plant’s DLI is, you can tailor your lighting needs to that plant specifically.How do you calculate DLI? It’s PPFD x hours x 0.0036 = DLI. Daily light integral is expressed as moles of light (mol) per square meter (m −2 ) per day (d −1 ), or: mol∙m −2 ∙d −1 (moles per day).

What is supplemental lighting, and why do I need it?DCIM100GOPROGOPR9721.
Once you have your crops specific DLI, you are then able to supply that crop with the exact amount of light it needs to flourish throughout its entire life cycle. Supplemental lighting, often referred to as simply greenhouse lighting, is artificial (not from the sun) lighting mounted to the structure of the greenhouse itself much like the layout of an indoor grow room. This additional lighting can be tailored to fit your needs precisely and provide the optimum environment for healthy and vigorous growth regardless of rainy or overcast days. Supplemental lighting also ensures the plant receives the correct photoperiods required to grow effectively in each stage of it’s life, through all seasons.
Additional benefits of lighting inside of a greenhouse are two fold, first it provides a more precise level of adjustment based on DLI i.e. longer or shorter light cycles, or continuous light cycles for plants in a vegetative state etc. Additionally, supplemental lighting also offers the benefit of increasing the growing season from one or two harvests a year from outdoor crops, to year around production regardless of the amount of natural light available.

What is Light Deprivation and why is it so important?
To initiate plants into the flowering cycle, and to keep them there consistently, you must meet their DLI while also providing the correct amount of darkness they need to rest and metabolize the sugars that they’ve spent all day making. In an outdoor environment as the seasons wane, the sun begins to set earlier and as the photoperiod lengthens, this triggers the plant to move from the vegetative stage into the flowering stage creating healthy flowering plants. The fall season provides this naturally with an almost identical sun to darkness ratio, and why most indoor growers employ the schedule of 12 hours of light followed by 12 hours of dark. Light deprivation greenhouses are essentially manipulating the seasons to finely tune the optimal environment year round. This allows the plants to harvest the full spectrum provided by the sun, while also controlling the amount of darkness that the plant need to begin flowering sooner and stay flowering consistently, all while being shielded from the sometimes brutal outdoor elements.
sierra_series_4-250x167For smaller hoop houses, light deprivation may mean pulling a heavy tarp over your entire structure to manually block out the light, but in larger commercial production greenhouses, light deprivation can be automated to run off of timers, further increasing efficiency and reducing labor costs. Custom light deprivation/supplementation greenhouses can be built to your unique specifications, of any size and any level of automation, through GroTech Systems available from Gardening Unlimited and their affiliate Dutch Hort.
Light deprivation/supplemental greenhouse growing is truly the best of both worlds and is quickly become the industry standard in places where outdoor growing is either prohibited or just plain illogical due to shortened seasons or inclimate weather patterns. A light deprivation/supplementation greenhouse is the easiest way to increase both productivity and efficiency while also utilizing the energy saving opportunities of harnessing the sun.

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