Updated: Mar 13, 2020
What if I said that every grower, master grower and head grower use a light quantum sensor for microgreens?
DLI (Daily Light Integral) is used to define the entire quantity of light delivered over the course of an full day. The DLI is describe as the number of moles (particles of light) per day, so the unit is posted in trade journals as "moles/day" or in scientific publications as "mol·m−2·d−1". The daily light integral is a new concept for the indoor controlled agriculture industry but it has the upper hand, especially plant growth is often closely correlated to the daily light integral.
The most common units for measuring light are the foot candle and lux. It is crucial for growers to understand the limitations of these units. Both units add an instantaneous light intensity at the time the reading is taken. Natural light levels are constantly changing and one measurement in time does not accurately means the amount of light a microgreen has received in a day. Most growers, master growers and head growers measure instantaneous light in micro moles (umol) per square meter (m-2) per second (s-1). This "quantum" unit qualifies the number of photons used in photosynthesis that fall on a square meter every second. Yet, this light measurement also an instantaneous reading.
The Importance of DLI in Grow Rooms
DLI ia an important variable to measure in every indoor grow room because it effects microgreens growth, development, yield, and quality. DLI can effect the root and shoot growth. Growers, master growers and head growers who regularly monitor and record the DLI received by their microgreens crop can quickly determine when they need more lighting or less lighting. There are devices that automatically measure and calculate the DLI your microgreens crops are receiving. One of these is the WatchDog weather station produced by Spectrum Technologies. This device is portable and should be placed next to your crop to determine the DLI for that precise area. One more method to measure DLI is to use a light quantum sensor connected to data logger. The sensor measures instantaneous light intensity at some defined interval, which allows you to calculate DLI. No matter which sensors you use, it is important to keep all light sensors level and clean to assure accurate readings.
Microgreens grown under light limiting conditions (a low DLI), commonly have delayed growth and development. We recommend that microgreens growers provide a minimum of 6 to 8 mol·m−2·d−1 of light. But remember, DLI requirements differ between microgreens crops.
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