However, UV light stimulates resin production and metal halides (MH) emit more UVB light than HPS lamps. The bud has pretty much stopped growing by then so the reduced light output of the MH would not affect yields too much. Does it make sense to use MH lamps during the last few weeks of the bloom to stimulate more trichome/THC production?
Or is there a better way to add UV light to the end of the bloom phase?
Potency increases with more UVB light, so it would be a good idea to increase the amount of UVB they are receiving.
I like your idea of replacing the HPS lamps with MH during the last one to two weeks of flowering. Your reasoning ? that flowering growth has slowed so that MH lamps, which emit considerably more light than HPS lamps, would increase the quality ? could work. It’s worth a try.
There are several ways you could make the switch over to MH lamps. You could replace the HPS bulbs with HPS-MH lamps. They work with standard HPS ballasts. Conversion ballasts can accommodate MH or HPS lamps at the flip of a switch.
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