LED Lighting Systems for Greenhouses
Updated: Feb 14, 2022
In this article, we will discuss how the target daily light integral (Daily Light Integral) is determined so that greenhouse growers can determine how much additional lighting they need, especially in winter season. LED lighting systems make it possible to provide crops with the DLI value provided in summer for 365 days. Thus, it can be used to grow strong plants at all stages of growth and ensure consistent quality, yield and maximum harvest throughout the year.
Greenhouses located in Guadalajara (20.7°N) or the southwestern United States are expected to receive DLIs of approximately 40 mol/day in the greenhouse and 60 mol/day outside the greenhouse in mid-May. This level of DLI is a tremendous value for any greenhouse, and if these environmental conditions are maintained throughout the rest of the year, excellent quality and yield can be achieved. LED lighting systems are your best alternative to provide these ambient conditions in your greenhouses.
Plants and DLI Requirements
DLI describes the cumulative amount of active PAR that falls into the area over a 24-hour period, expressed as mol · m-² · d-¹ or mol/day. The DLI will change daily and seasonally based on geographic location and therefore the angle of the sun and the length of the day.
We can divide plants into four groups based on DLI requirements: low (some ferns and orchids), medium (bedding plants and flowers), high (perennials and vegetables), and very high (tomatoes, strawberries, cucumber).
The Purdue University chart below represents a quality range for tomatoes and peppers from a lower average DLI – resulting in minimal acceptability – to a higher average DLI that results in better results and consistent yields.
Crops such as tomatoes, cucumbers and peppers can produce salable quality crops in a wide DLI range, but high quality crops can only be produced at high DLI levels. Researchers and growers acknowledge that increasing the DLI level generally increases biomass and fruiting, and this benefit has been observed up to a certain point. Every plant has a maximum DLI limit and going beyond that will not do any good. Insufficient light is a problem that results in great losses in quality and harvest.
Even if the target DLI is provided, this factor alone does not determine the final harvest numbers; In addition to the light needs of the plants, temperature, CO2 levels and fertilization interactions must also be taken into account. Proper care and interventions are just as important as light.
Calculation of Supplementary Lighting Need
Photosynthetic photon flux density (PPFD) is the amount of light imparted to a surface. For example, if the average distribution of PPFD falling on the crop is 300 µmol · m-² · s-¹, a calculation for a 13 mol/day target DLI would reveal that we need to run our lights for about 12 hours that day.
Since DLI is a cumulative value, the additional lighting system does not need to be constantly running. In this way, it is possible for us to benefit from cheaper evening tariff electricity prices for plants such as tomatoes that do not need a certain daily light period for fruiting.
In a sunny areas, the DLI difference between January and May can affect crop production up to 3 times. Specialized LED lighting systems for greenhouses offer you the opportunity to work with constant DLI values and greatly increase your productivity in production. Growers, who can keep their investment costs to a minimum by making the right DLI calculation, have greatly expanded their businesses compared to their competitors in a very short time after meeting maximum quality and harvest.
You can contact us to calculate the correct DLI calculation or the amount of light you need in your greenhouse, facility or smaller and special growing environments. We hope that our article will be helpful to give general information.