Nitrogen feeding & relation of chlorophyll-content, harvest & cannabinoids

Generally the increase seems like linear (the 275mg has about 5x higher Chl content than the 60mg dosis) though there seems to be "a jump" in the middle.

Increasing fertilizer rate led to increased growth and yield but also to a dilution of THC, THCA, and CBGA

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For U2,the highest applied rate, that supplied 283mg N/L, maximized yield; although lower rates delivered higher cannabinoid concentrations in dry floral material.

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Generally, plants with higher fertilizer rates had greener leaves.

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There were signs of foliar senescence beginning around week 6 of flowering when older leaves became chlorotic and ultimately necrotic before harvest. These signs of senescence are typical for cannabis.

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Yield In both substrates, yield increased with increasing fertilizer rate; however, in U2-HP yield reached a maximum, and in U2 yield increased linearly (Fig. 3).

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>> CC = container capacity, lower required a higher fert-frequency

Keep in mind this is organic fertilizer that may not fully instantly bio-available. Plus, they drained 20% out with each irrigation. Thus I doubt the plant consumed all of it fully.

Substrate pH decreased over time in all fertilizer rates and in both substrates (Table 3).

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Therefore, for U2-HP, the optimal rate of this organic fertilizer is between 212 and 261 mg N/L, depending on grower preference for high yield or individual cannabinoid yield. For U2, yield did not reach a plateau over the applied fertilizer rates; therefore, growers may choose to maximize yield using the highest fertilizer rate that supplied 283 mg N/L or chose a lower rate to maximize cannabinoid concentration.

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>> the text continuous to makes some interesting remarks about frequency-of-fertigation

Sadly they didn't monitor nitrite levels in the plant tissue.


Conclusions
"Our results suggest that to produce highyielding, cannabinoid-rich, organic cannabis plants, lower CC coir-based substrates, such as U2-HP, are preferable to those with higher CC, such as U2. The drier substrate produced higher floral yield, GI, THC concentration, THC yield, THCA yield, and CBGA yield than U2, possibly because of higher fertigation frequency or adequate root zone oxygen leading to a more favorable root zone environment. Both substrates generally maintained suitable substrate pH between 5.5 and 7.4 and were effective for cannabis production during the flowering stage. Increasing fertilizer rate was found to have a dilution effect on THC,THCA, and CBGA; therefore, excessive organic fertilizer application during the flowering stage should be avoided despite increased biomass yield. To maximize both yield and cannabinoid yield, the optimal organic fertilizer rate for U2-HP was determined to be within a range supplying 212–261 mg N/L using the Nutri Plus Organic Bloom liquid organic fertilizer during the flowering growth stage. Higher rates within this range favor increased floral yield, whereas lower rates favor higher yield of some cannabinoids. For U2, the optimal rate was one supplying 283 mg N/L to maximize yield; although, lower rates may be desirable to increase cannabinoid concentrations. These recommendations could be generalized for similar organic fertilizer and substrates; however, results may vary with cannabis variety."

Kassiopeija said:

Increasing fertilizer rate led to increased growth and yield but also to a dilution of THC, THCA, and CBGA

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I brought something like this up in another thread. Modern farming has led to a lot of tasteless food as they pump up volume with nitrogen. But it's all about THC and grams per watt. No?

non-organic dwc study

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rkymtnman said:

Frontiers | Optimisation of Nitrogen, Phosphorus, and Potassium for Soilless Production of Cannabis sativa in the Flowering Stage Using Response Surface Analysis

Following legalisation, cannabis has quickly become an important horticultural crop in Canada and increasingly so in other parts of the world. However, due t...

www.frontiersin.org

non-organic dwc study

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You’re moving the goal posts now bro. 5 yard penalty

bk78 said:

You’re moving the goal posts now bro. 5 yard penalty

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the study i posted is 4 years newer. and not sure why you'd use organic ferts in coco anyway ?? i don't see how organic ferts could even be used by the plant if you are giving 4 or more feedings a day??

rkymtnman said:

. and not sure why you'd use organic ferts in coco anyway ??

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Because reaching

I can't seem to find it, but I recently read a study comparing #s of fertigations per day. Basically, 5 fertigations per day yielded 20% more than 2 fertigations per day. More fertigations means the root/soil interface is constantly replenished with optimum nutrition. This is how people who feed at low EC can achieve the same yields as high EC feeds. I've seen at least 3 studies now that indicate cannabinoids decrease at higher EC-more of something isn't always a good thing. Here is an interesting one, showing an increase in bud weight AND cannabinoid content after simulating drought stress: https://journals.ashs.org/hortsci/view/journals/hortsci/54/5/article-p964.xml

Rurumo said:

Here is an interesting one, showing an increase in bud weight AND cannabinoid content after simulating drought stress

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that second study i posted touches on that too: edit: on nute stress, not drought stress

You do hear of increasing cannabinoid levels to some extent by imposing nutrient stress. But this is a complex subject. Nutrient stress may modify the profile of 100 different cannabinoids in 10 different ways. Nutrient stress may also suppress growth, so you may get more potent but smaller buds. A more reliable strategy is producing more cannabinoid quantity through bigger flower mass or weight by proper nutrition

Rurumo said:

I can't seem to find it, but I recently read a study comparing #s of fertigations per day. Basically, 5 fertigations per day yielded 20% more than 2 fertigations per day. More fertigations means the root/soil interface is constantly replenished with optimum nutrition. This is how people who feed at low EC can achieve the same yields as high EC feeds. I've seen at least 3 studies now that indicate cannabinoids decrease at higher EC-more of something isn't always a good thing. Here is an interesting one, showing an increase in bud weight AND cannabinoid content after simulating drought stress: https://journals.ashs.org/hortsci/view/journals/hortsci/54/5/article-p964.xml

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Love simulating me some drought stress

Milky Weed said:

Love simulating me some drought stress

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but depending on its stage the plant may already be senescent, have reduced transpiration etc pp >> less irrigation required anyway.
which, could be another way of saying that watering less during the last weeks is actually a way to reduce water stress. the study in the first posts elaborates on how cannabis dislikes a too moist (or prefers a well-aerated) medium.

i love what this guys says about PK boosters: kinda my thinking all along (not needed and probably hurts)

What About Phosphorus or Potassium Boosting Blooms?
Cannabis requires concurrence of all nutrients to synthesize its cells, including flower cells. Cannabis does need phosphorus for flowers, but extra phosphorus doesn’t boost blooms. If you give extra phosphorus and potassium, while nitrogen is short, cannabis interprets the condition as nitrogen shortage and restricts its growth to meet the lower nitrogen level. The concept of extra potassium during flowering comes from tomato nutrition. When tomatoes and other watery fruits are growing, they take in potassium to make their cells salty so they can pull in water and swell. Even then, only the proportion of potassium taken up by the plant changes and the original nutrient formula would still have adequate potassium to meet potassium demand without a need for change in the formula.