Loving the thoughts this provokes!
So to touch the canopy size vs cannabinoid content:
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Not a favorite study, a vague hit-piece on P again, quoting a 200 mg/ml solution as bad (no shit) and 30 mg/ml as a proper limit (in veg) and no mention of P in flower
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Table 6… c’mon guys show us all of the data, even the outliers. I want to grow outliers!
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No one is phasing nutrient solutions over time, over a run, like nature does. The one big lie is that we should feed a constant nutrient solution over the run. Funded research gets done. Who’s funding??
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School of environmental sciences involved = REDUCE P = genetic selections with low P chosen to show results is a natural motivation.
Anyways, then look at the notes:
- While the cannabinoid concentrations in the floral tissues in our study did not respond to nutrient solution NPK concentrations, other studies indicate that plant mineral nutrition can affect production of secondary metabolites in cannabis (Caplan et al., 2017a; Saloner and Bernstein, 2021). There appears to be an inverse relationship between cannabis yield and potency, with cannabinoid concentrations decreasing as plant inflorescence yield increases. Inflorescence from plants supplied with 160 mg L–1N had approximately 30 and 20% lower concentrations of THCA and CBDA than plants supplied with 30 mg L–1N (Saloner and Bernstein, 2021). However, while nutrient stress and deficiency may enhance inflorescence cannabinoid content, this method is not ideal for optimising overall plant productivity as plants supplied with 160 mg L–1 N yielded twice that of those supplied with 30 mg L–1N.
So in the end, you can double yield and increase total cannabinoid weight with a higher N supply, and economically speaking this looks good - you’d divide the cannabinoid weight harvested by the energy used to get it, and come up with a $ value. You’d get more cannabinoid per watt. But if you’re a hobby shop grower, you might get bored of chasing data efficiencies and look for the real summit, effect-per-unit-hit.
Look at this one too:
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Considering effect of N availability in the plant tissue: We have recently demonstrated that an optimal N nutrition, and high concentration of N in the plant, do not correlate with high secondary metabolism in cannabis (Saloner and Bernstein, 2021). Rather, we claimed, that the main factor governing the decrease in cannabinoid and terpenoid production is the tissue N content, which increase gradually with the increase in N supply (from 30 to 320 mg L–1) (Saloner and Bernstein, 2021). This suggestion, supported by results for numerous other plants (Bryant et al., 1983; Coley et al., 1985; Fritz et al., 2006; Palumbo et al., 2007; Massad et al., 2012; Albornoz, 2016), supports the carbon-nutrient balance hypothesis which states that under low N content production of N-rich primary metabolites and hence growth are restricted, and plant metabolism and energy expenditure shifts from creating N-containing metabolites to the production of metabolites that do not contain N
You know, like THC:
Edit, and CBG
- … indeed confirm that the production of secondary metabolites in the cannabis inflorescence is highest under low N concentration in the inflorescence and in the plant, and decreases with the increase in inflorescence (and plant) N concentration (Figure 7A).