Some interesting Sunday afternoon reading. I get why CBD plants are the focus but it would be nice to see some work on higher THC strains as well.
Cannabis Science and Technology
January/February 2024 Volume7 Issue 1
Pages: 14-17
Cornell University Research on Hemp Responses to Light Treatments, Part 1
This article provides insights on the latest findings from academic researchers exploring the impacts of emerging technology on hemp grown for cannabidiol (CBD).
www.cannabissciencetech.com
"Traditionally, it is recommended to provide 30-40 mol·m-2·d-1 daily light integral (DLI) making this a higher light requiring crop than tomatoes or other fruiting crops. Some information is available in the literature for photoperiodic (such as how short days induce flowering) cannabis. For example, Rodriguez-Morrison, et al. (2021) reported linear increases in flower dry yield as the DLI increased from 8.6 to 77.8 mol·m-2·d-1. Across this broad DLI range a 0.5% increase in yield was reported for every 1% increase in DLI. Amazingly, cannabis responded positively to more light than is provided by the sun on a sunny day in the middle of summer (maximum possible DLI of 65 mol·m-2·d-1). As opposed to typically grown photoperiodic cannabis, autoflowering cannabis cultivars are seed-propagated and do not require short days to flower (photoperiod insensitive).
No information is available in the scientific literature on the response of autoflowering cannabis to DLI.
Results:
When cultivars were grouped together, optimum flower dry weight was reached at 20 mol·m-2·d-1
and did not further increase at higher DLIs. Individual cultivar responses were not statistically significant but exhibited patterns of optimal DLI for yield at 20 mol·m-2·d-1 for AutoCBD and Pipeline and 30 mol·m-2·d-1 for Maverick.
DLI did not significantly impact the percentage of CBD or THC. However, for both cannabinoids there was a pattern for Maverick that increasing DLI led to an increase in CBD/THC, for example, CBD increased from 7.5 to 10% as DLI increased from 15 to 30 mol·m-2·d-1.
The Cornell researchers found that DLI responses of autoflowering CBD hemp are cultivar specific. Some cultivars (such as AutoCBD and Pipeline) appear to have lower DLI requirements than other cultivars (such as Maverick).
In general, these autoflowering (non-photoperiodic) cultivars seem to have lower DLI requirements than photoperiodic hemp, though further research is required to study additional cultivars (especially directly comparing autoflowering to photoperiodic), as well as across a wider range of DLIs."
And another one I found interesting, although they didn't measure light intensity there was a clear reduction of yield in later planted (I'll call it summer) than earlier planted autoflowers (I'll call it spring). Some food for thought and perhaps that's why
@durbin92810 had some March autos do well. I'm hoping my late summer/early autumns also see a benefit.
Role of Planting Date on Yield and Cannabinoid Content of Day-neutral and Photoperiod-sensitive Hemp in Georgia, USA
HortTechnology Volume/Issue: Volume 33: Issue 1 Page(s): 138 – 145 Online Publication Date: 19 Jan 2023 DOI:10.21273/HORTTECH05151-22
Role of Planting Date on Yield and Cannabinoid Content of Day-neutral and Photoperiod-sensitive Hemp in Georgia, USA
journals.ashs.org
Seeding was done on 16 and 30 Mar and 14 and 30 Apr 2020 and 2021
Seedings were ∼3 inches tall and were not pinched when
transplanted on 9 and 25 Apr and 11 and 28 May 2020 and 2021
Conclusions
The impact of planting date on floral yield in photoperiod-sensitive hemp was recently investigated (Linder et al. 2022); however, the effects of planting date of day-neutral and photoperiod-sensitive hemp cultivars planted before the critical photoperiod has not been previously evaluated.
Flower yields of the day-neutral cultivars decreased as planting date progressed during the year and temperatures warmed. In the present study, photoperiod-sensitive cultivars (Von and Whitehouse Cherry) did not initiate flowering despite being planted at a time when daylength would induce flowering. Although photoperiod-sensitive hemp exhibited greater floral yields than day-neutral hemp cultivars, our findings suggest that the day-neutral cultivars would allow growers in parts of the southeastern United States to take advantage of mild spring weather to extend their production season for hemp.