Environment is everything in indoor growing. Temperature, humidity, light, air, and nutrients all play their role in maintaining the perfect conditions for crop growth and health. When one variable is changed, such as lighting, the rest of the system needs to be recalibrated for the changes.
With years of indoor cultivation being done under traditional sources such as HPS, certain practices and conditions have been ingrained many growers environments that are not necessarily the end goal, but a way to achieve them via they tools they have been implementing.
Here are common issue growers have when coming from HID to LED’s, and how to deal with them.
The number one issue growers have when switching to LED is their grow room temperatures. Leaf temperature is the actual parameter that ambient/air temp is influencing, and different lighting can effect the leaves differently. With HPS and other HID bulbs, they contain 2 forms of heat. Convection heat from the excited gases in the arc tube, and also IR energy that is radiated in the beam of light it’s self. IR heats surfaces on contact, and has the most impact on leaf temperatures. HID growers are forced to lower their ambient temperature to fight the IR heat in order to maintain ideal leaf temperatures.
LED’s do not emit IR and as a result, do not heat up the leaf surface, in addition to their general heat load reduction they offer. To maintain ideal leaf temperature keep metabolic rates high, growers need to run ~5-8˚F higher ambient temperatures than in their HID environments, targeting 78-85˚F. With the higher ambient temperature, internal leaf temperature are maintained in the ideal range and grow is vigorous and nutrient uptake can take place.
Sometimes magnesium deficiency are reported when making the switch. This is because magnesium is a central element in the production of chlorophyll. When we make the move to LED’s, a more chlorophyll targeted spectrum is part of the benefits. But, in order to reap those benefits, we need to match the increased chlorophyll focused reactions taking place.
Common hydroponic fertilizers recipes, usually contain between 40-60ppm Mg. We have found that a range or 75-90ppm of Mg to ideal under LED lighting. The best way to increase only Mg and not introduce more nitrogen, is to add 1gram of epsom salt(Magnesium Sulfate) per gallon of nutrient solution. 1gram/gallon of epsom salt adds ~25ppm of Mg and 30ppm of S, and is usually a sufficient supplement to most fertilizer programs.