I’m Dr. Bruce Bugbee, professor of Crop Physiology at Utah State University. AMA about cannabis cultivation!

What are your thoughts on organic vs synthetic fertilizers?

I am not a fan of organic fertilizers. I should record a video with my thoughts about this. In my opinion organic agriculture is not always good the for environment, and it is not always good for human health. Other than that, Organic is great for recycling wastes back to gardens and farm. This recycling can save the planet!

I'd personally love to see such a video. I have a lot of internal conflicts with organic vs synthetic that I am trying to wrangle with so I'd love to hear some more expert opinion on the matter as it pertains to cannabis.

Thanks for all of the comments. I am inspired to do a video describing my thoughts on this. Organic agriculture is an excellent principle because of recycling, but I do not like prohibiting the use of pharmaceuticals for plants any more than pharmaceuticals for people.

I always see recommended online that liquid fertilizers must always be pH adjusted, even if the feed is going into soil. However, I've really only seen this suggested in cannabis growing communities, and when I researched this further, I came to the conclusion that substrate pH matters a lot more and that the nutrient solution won't end up changing it very much. Assuming starting with a good soil, is it even necessary? I would love any insight you have on when pH adjusting a nutrient solution is and isn't necessary (excluding hydroponics of course). Thank you!

this is a good but the answer is complex. We use media with peat to help buffer pH changes. And because our tap water is high bicarbonate, we use an acidifying fertilizer (higher fraction of ammonium ion). This fertilizer is pH 2.8 in our concentrate tank and it reduces the tap water pH from 7.8 to 6.8. This helps, but we further reduce pH with a separate acid injector. This is not always necessary, but it helps to control the media pH.

Here is an important point: Big commercial growers of ornamental crops (30 to 100 acres under glass) often use only ONE fertilizer for all of their crops. We also use only one fertilizer for the many crops in the Utah State University Research Greenhouses. Cannabis is mostly unique because of a higher demand for P during flowering.

Dr Bruce! We love you on our discord server (The Sticky Dojo). We use your YouTube material and wisdom to help many new growers.

My question for you: if you were going to grow a 4x4 grow tent, what light features would Dr Bugbee look for? High efficiency > spectrum tuning? What PAR level would you want for a 12/12 flowering schedule?

Thanks for all you do! Please come for Thanksgiving dinner one day!! <3

High efficacy (the technical term for efficiency) is more important than spectrum. High efficacy means more light and less heat! Spectrum shapes the plant, but high light increases yield.

In field grown citrus there has been great success using Mylar to reflect light underneath the canopy, it reduces pathogens (fungal and bacteria) and boots growth. Could you see a method like this working for cannabis?

Yes, Mylar is an effective reflector of photosynthetic photons, and it work well in citrus because many of the photons hit the ground. However, In a more closed cannabis canopy only a few photons hit the ground--- so Mylar would be less effective in cannabis.

Ok guys, Bruce has left the building! This is Chris at Apogee Instruments, but for the record, Bruce was doing all the typing during the session. That was an incredible experience to sit here watching him answer complex question after question off the top of his head. You guys should look closer at Bruce's Curriculum Vitae to really appreciate the lifetime of knowledge he brings to the table. https://www.apogeeinstruments.com/our-founder-dr-bruce-bugbee/

It's exciting to think of the advances that will come in Cannabis research with Dr. Bugbee and other researchers now on the case. I'll keep an eye on this thread and try to get Bruce to answer some of the unanswered questions later as he gets time. He is a very busy guy, pulling double-duty as a full-time professor at Utah State University and President and Founder of Apogee Instruments. We don't get him here at Apogee much because his passion is the research at his USU lab.

That said, each of the products at Apogee Instruments were inspired by some aspect of his research over the years and have to meet his quality standard. Most of you probably know our PAR meters, but I invite you to check out some of our other products we make that might help with your grows like our temp sensors, soil O2 sensors, our chlorophyll meter and more. We are also just about to release a couple new products, a DLI meter and all-in-one Greenhouse monitor that will be game-changers... but enough of the shameless plugs. Check out www.apogeeinstruments.com

Thanks again for all the great questions. Some of my tech support staff and Bruce's grad students might hang around for a while and answer what we can. If you want to meet Bruce personally, he should be at our Apogee Instruments booth quite a bit at MJBizCon in Las Vegas in October.

And one last plug for the class Bruce is currently producing at Utah State University. It is a paid class that is open to anyone for enrollment, but the amount of high-level content they are producing is HUGE! If you are serious about your grows you should definitely check it out at cannabis.usu.edu.

Thanks again for a great session and best of luck to everyone!

-Chris

I notice USU has research farms all over the state. Where have you guys been practicing growing cannabis?

The research in my laboratory is almost exclusively in growth chambers and greenhouses; but we work closely with USU extension personnel to do studies in the field. We have several plots around the state, mostly in remote fields.

Hi Dr Bugbee!

• If you were running cannabis at 1000 umol/m2/sec with white light that has a very high CRI (so with deeper reds) and wanted to overdrive the plants to 1400 umol/m2/sec but you only have one wavelength to do this. What would you pick ignoring the PPE of the LEDs: blue (which has poor leaf penetration and strong photomorphogenesis effects which we may or may not want), green (85-90% absorption with good leaf penetration), red (gets in to lower leaf penetration again at higher lighting levels), or far red (half is reflected, may drive the PSI separately for greater photosynthesis)?

• What are you thoughts on using chlorophyll florescence for real time monitoring of photosynthesis levels? I do this with a spectroradiometer but most people in to cannabis have no idea about this technique. How about monitoring the 570/531 nm photochemical reflectance index in a grow chamber?

• What are you thoughts on using the newer spectral sensors as full spectrum quantum lights sensors to drive down the $500 cost of something like the SQ-520 (I use one of these and love it). There is a 10 channel one out that covers PAR fairly well (the AS7341) that costs $5 in quantity.

In recent published papers (see Kusuma et al. 2020 and 2021) we have recommended a combination of white and red LEDs. the exact fraction of red is about 70 to 90% of the photons. I think most people know, however, that the high fraction red photons is associated with photobleaching of flower tips. This photobleaching (white tips) interacts with intensity (PPFD) and genetics (cultivar). We are doing additional studies o this now.

We also use chlorophyll fluorescence, using a meter from Optiscience, This is a powerful technique (see papers by Zhen et al. 2020 and 2021) , but we prefer the more comprehensive measurements of photosynthetic rate, using a single leaf or whole canopy photosynthesis systems.

What kind of IPM protocol are you using or is pest management necessary when using growth chambers?

We have fewer problems in growth chambers but we still have pest issues. Because we are not selling our research crops we can use the full range of agricultural pharmaceuticals. Although my last name is two insects, and I studied entomology in graduate school, I defer to my professional colleagues on the best IPM approaches. Some day we will have more products approved for use on cannabis.

To begin i know this is a lot. I’ve watched and listened t almost everything i could on you. If you can’t reply to all of them i think question 3,1,13,6,10,8,7, in this order of importance would provide the most help to the community. Thankyou so much for your time i know you have taught me and I’m sure many others so much

1. in your opinion is defoliating or lollipoping beneficial or harmful. If you could go more in depth that would be awesome.
2. Why are blurple lights not as good as other LED and have been phased out ?
3. Many people say red light is not good for plants but I’ve heard you say it is the best by far. -Same with that plants don’t ignore green light and it interrupts the photoperiod. Be. - Same with that you in studies have found it difficult to show any result from using UV. -None of these are questions but would love to see it in writing by you to cite people who claim all/each are wrong and I’m an idiot.
4. What are your thoughts on “water-only” soil that is just top dressed with nutes
5. Do you think organic can be as good as synthetic or visa versa
6. At what point if any during seedling/ veg growth or even flower do you think someone should raise ppfd
7. Do you think other than a plant being shorter/taller (as mentioned in your interview with tad hussey) there is a benefit to using different spectrums at different stages of growth.
8. What % of the effect of light would you said is strength vs spectrum. (My guess is 85/15 or so)
9. Do you believe leaves “tacoing” where they fold up like w taco is from there being to much light.
10. What do you consider a max dli and/or ppfd/m²
11. Why do you not mulch your plants? I figured from water retention alone it would be worth it?
12. Do you believe things like compost tea, sprouted seed tea, plant ferments are actually beneficial.
13. From your research what do you think the ideal ppm of each of the 16 essential nutrients is ideal for cannabis. Obviously some cultivars require more/less of some but generally speaking.
14. Why do you think the trichomes are different on outdoor compared to indoor even with same ppfd and dli (not sure if in examples I’ve seen spectrum is the same. But the difference seemed more than what I’ve seen spectrum do indoors)and even environment conditions. Part 2: do you think a light will ever be able to equal the sun?

These are all good questions. I don't have time to answer all of them right now; but we are now teaching a university level course through USU that discuss these topics in more detail. The course is web site is cannabis.usu.edu.

But I can answer one important questions here: Red LED are the most efficient color and have a high absorption by photosynthetic pigments. BUT adding about 10% whate LEDs provide some blue photons and some green photons. Green photons penetrate leaves better then blue and red photons, so they are more valuable than most people think. See the 2005 article by Terashima et al. on the value of green photons.

Would u be able to answer just these 3? Or any that you choose?

Many people say red light is not good for plants but I’ve heard you say it is the best by far. -Same with that plants don’t ignore green light and it interrupts the photoperiod. Be. - Same with that you in studies have found it difficult to show any result from using UV. ?

From your research what do you think the ideal ppm of each of the 16 essential nutrients is ideal for cannabis. Obviously some cultivars require more/less of some but generally speaking?

At what point if any during seedling/ veg growth or even flower do you think someone should raise ppfd?

This is really an economic decision. It depends on the cost of electricity and the value of the yield. But reemember that cannabis is worth abouot $2 per gram, and electricity costs only about a penny per mole of photons (I think I have a video on this topic). So more photons is almost always cost effective. Yield is usually about 0.2 to 0.3 grams per mole of photons.

Do you believe leaves “tacoing” where they fold up like w taco is from there being to much light.

I am circling back to your list- all good questions. #9. folding of leaves. We have not seen this from high DLI -- as long as the nutrisnts are not excessive. Leaf folding is usually more associated with excessive nutrient levels.

Why do they make pot so strong now? You can't even find stuff that can be smoked casually anymore.

Good question. There is now good evidence from pharmacology studies that super high THC , without some CBD, is hazardous. But I guess some people like drinking Everclear alcohol!

How do you guys measure the exact rate of plant growth when you are trying to compare things like the effect of lights, temperature, climate, and root zone medium?

Do you just run whatever test you plan on running and then compare them at the end?

good question. We use multiple techniques, include continuous measurement of photosynthesis of whole communities of plants (see Monje and Bugbee, plant cell and environment). We also use a lot of digital imaging using automated cameras. we are now working with IR cameras do we can photograph the plants during both the day and night. Stay tuned for future publications!

You've recommended a DLI somewhere around 60 when growing cannabis with ideal levels of CO2. Do you have any thoughts on what DLI would be a good target with typical ambient CO2 levels, for homegrowers who aren't supplementing CO2?

I made a video that answers questions about the 9 cardinal parameters for plant growth. https://youtu.be/JwtkHxv_3pU .

But the short most direct answer is that the maximum DLI without co2 might be more like 40 or 50 moles per m2 per day.

First timer here.

1. How essential is lollipopping? Is it better to not stress the plant as much?

2. When defoling, should I try cut the minimal amount possible?

3. When in flower, should I cut off most leaves so the plant can focus on the buds, or should I not trim the leaves and just let the plant swell and trim after drying?

Please answer this

I recommend minimal pruning. Unless it is necessary to improve airflow in the bottom of the canopy. But getting more fans is better than pruning. We do prune the shoot tip meristem in early flowering stages to improve branching. But we do not remove the lower leaves, which contribute photosynthates and remobilize nutrients until harvest.

So in short if you have adequate airflow you should not prune as it would be a net negative to the plant.

The argument i see for pruning slot is that the plant will waste energy and the top buds will not be as good?

Is that flase

There is no evidence that the lower leaves suck energy for the upper leaves. Even then they are turning yellow. Nutrients are beneficially remobilizing at this time.

wait you "top" the plant in early flowering?

I'd bet the marketing guy, Chris, messed up the word and Prof. Bugbee actually said veg. No way no way are they actually topping during flower since there is no more "branching" that occurs at that point, it's all stretch.

I am doing all my own typing. I wish I could type faster. Pinching the meristem more subtle than removing leaves and stems. And we do this right at the transition from veg to flowering.

Hi Professor!

​

Love your videos, what are your thoughts on flushing? I don't believe I've seen one on that yet.

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There's lots of wild theories out there about this one.

Yes, this is a hot topic. In my experience, flushing only helps if the plants were overfertilized to start with. We thus do not flush in our studies. A recent study by RX Green technologies (Flushing Trial) found that users preferred cannabis that was not flushed (zero days of flushing).

My colleague Jim Faust at Clemson is studying flushing. He found a decreased yield and a small increase in cannabinoid concentration with increasing flushing (called leaching in horticulture terminology). This is likely due to what we call "yield dilution". Higher flower mass dilutes the concentration of cannabinoids.

Huge fan! I've read and watched a lot of your work. Many thanks!

Specifically when cultivating hemp, what is the major differences in growing for fiber vs resinous tricomes and what are some tips for maximizing each of those objectives?

There are big differences in the genetics. Fiber Cannabis "hemp" is much taller then medial hemp. Fiber hemp is studied in Agronomy departments, Medical hemp is studied in Horticulture department.

Many factors affect trichome density and cannabinoid content. See our course at cannabis.usu.edu

If you give cannabis as much light, nutrients, soil, space, and CO2 as it wants, is there an upper limit to how fast it can grow, and if so, what is it?

Yes, see my video on tis topic: https://youtu.be/JwtkHxv_3pU

Max yield is ultimately limited by the quantum yield of photosynthesis. Our models estimate a maximum of 1 gram dry biomass per mol of photons. I have a video on "turning photons into food" that discusses this.

I've been growing in the 50/50 Peat and vermiculite. How often do you have to add dolomitic lime throughout the grow?

You add dolomitic lime just once when the media is mixed. The release rate is gradual, usually 7 to 21 days. Long term pH control depends on the bicarbonate in your tap water. and the ammonium/nitrate ratio in your fertilizer.

Which keyboard layout do you find superior, QWERTY -or- DVORAK?

Good cannabis question: DVORAK is clearly superior.

What’s your thoughts on the red to far red ratio or R:FR

In nature it’s usually around 1:1.5 from what I’ve seen

But many led companies claim a low rate has a negative impact on plants could u go into that?

The answer is complex, but increasing FR photons also increase stem and peti9ole elongation in cannabis, and the taller plants are usually undesirable.

We have applied FR only during veg to increase photon capture, and then turn off the FR LEDs during flowering to keep the plants short. FR photons are photosynthetic (see papers by Zhen and Bugbee). They are great for lettuce, which doe not get too tall, but they must be applied carefully.

Hi Dr. Bugbee,

Many nutrient manufacturers have separate nutrients for vegetative cycles and for bloom cycles, some use entirely different base nutrients, others use a different ratio of their base nutrients, and still others recommend adding a PK booster to their base nutrients. Some nutrient companies recommend using their enhanced PK nutrients for just a couple weeks during the transition phase, others recommend starting after ~4 weeks in flowering, some recommend to use their bloom nutrients as soon as preflowers form. Have you found a benefit from using enhanced PK formulas for flowering? If so, what application time and rates did you find the most effective? For reference, I am in hydroponics, coco coir specifically, so I have significant control over root zone nutrients. My current nutrient schedule is Jack's 321 which has an NPK of 3:1:4 with 50ppm phosphorous at full strength.

From my understanding, these plants accumulate P during their vegetative stages and can then move it into the flowers as necessary, I can see that this may cause a problem with plants that are sent to flower after a very short veg cycle, perhaps causing a need for enhanced PK fertilizers in those conditions.

I suppose this also depends on what the purpose of nutrients in plants are. Are we just trying to provide enough nutrients to avoid any deficiencies so as to not limit plant growth, or can providing additional nutrients above required amounts accelerate plant growth?

Thank you for doing this AMA!

Good question . We are studying this now. Here is what we know so far: 15 ppm P is adequate during vegetative growth, but unfertilized cannabis flower are a strong sink for P and accumulate more than 1% P in the flower buds. This is not needed to any physiology function, and it is stored, partly as phytic acid. The flowers can be such a strong sink for P that they suck P from the leaves, and this can create a P deficiency in the leaves. So we now recommend going to 50 ppm about 4 to 5 weeks prior to harvest.

The other nutrients stay the same throughout the life cycle.

Hi Dr. Bugbee, thank you for taking the time to do this.

My question is: We know the importance and role light plays to a plant, but how important is darkness? Is the 12/12 light cycle the only standard for a flowering cannabis plant or can we utilise a light cycle such as 11/13 with 13 representing the hours of darkness. Are there any benefits to reap from an extra hour of darkness in the flowering stage?

We are studying this now. Some cultivars flower well in with longer photoperiods and this allows us top give them more light and thus increase yield. We have not found that shorter photoperiods accelerate flowering, at least in the cultivars wee have studied. Future plant breeding will give us cultivars that can take much longer photoperiods. Larry Smart at Cornell is leading a group studying genetic manipulation on cannabis plants.

Are there any heirloom strains availble anymore? Has there been so much hybridization that sativa, indica are merely more marketing than true descriptions of a plants ancestry?

Professor Larry Smart at Cornell University just published an excellent paper on the heritage and the genetic links among cannabis strains. I cannot remember the journal, but if you use google scholar and search for Larry Smart cannabis" you should find it.

Hi Dr. Bugbee. I'm a former reporter for the Herald Journal and actually interviewed you several times for various science stories. Now I live in Colorado and work in the cannabis industry.

My biggest issue in growing on my own has been finding the right container size for strong roots. Any thoughts on the ideal container size during seedling/veg/flower for the best roots and when to transplant?

The bigger the better for pot size. But a rule of thumb is to use a pot big enough so that you only need to water once a day. About 40 years ago my colleagues grew a large tomato plant in a 500 mL container, but they had to continuously water with nutrient solution to keep with with nutrient and water demand.

Federal legalization of cannabis will have a huge effect on research opportunities. When federal legalization inevitably happens, what research topics excite you most?

We are now starting to study crop steering. We have previously published papers on this approach called phasic environmental control.

This means applying precision stress during specific life cycle stages to improve quality. We are using this approach in fruit trees to increase sugars in the fruits.

So far, growers have been generous in funding our research. But Federal funding will be more stable.

Dr. Bruce, I am a big fan and have been following your work for some time now, thank you for all you continually do. I've been running a setup for over 3 years now detailing the difference between light spectrum and their genotype changes for certain strains. I had 4 very different light sources in each room, all other variables remained the same (vpd, temp, nutrients, genetics). I was running a few of the same clones in each tent so that I could identify only the changes that occurred from each spectrum (380-740nm). I did this for 7 cycles before i found out the light recipes that worked best for all categories (smell, taste, effect, vigor, bulk).

I found this selected light recipe and tuning has worked best with every cultivar that I have grown since then, and I have changed all my lighting combos. The problem is, no light company has got it right and I have to end up making a combination from 2 different lights and put them on dimmers/timers to mimic the sunrise/sunset effect in nature. My DLI is very close to natures output, and your instruments are the only way I can go beyond PAR and grow without being blind to wavelengths that we do not see.

How hard is it to get the general industry to understand PAR is only a part of the picture, instead of DLI? It seems any time I try to talk to someone about the difference, they shrug off any info because of "blurple" lights, and it gets frustrating. It seems like the industry is stuck in the hps days and they are afraid to change up a working system. Is this something you also notice or battle in the industry?

Also, second part, do you plan on making a light that will offer such range and control?

Thank you for your education and your wonderful instruments that let me see the unseen!

-Cheers!

DLI is the key metric driving growth and yield. But as you know, with indoor agriculture it can be derived by multiplying by the photoperiod.

I am not a fan of lights without any green photons. If you cannot see your plants you cannot diagnose disorders. The best fertilizer is the footsteps of the farmer. Without green photons to see the plants these footsteps don't help. Yes, you can wear a head lamp, but I like to see the whole canopy.

Dr. Bruce Bugbee !!! I can't thank you enough for all the knowledge you drop.

I once heard that CBD requires dark time during the grow cycle to develop correctly. During the winter time I like to run autoflowers 24/0 light. I'm curious if there is any truth that CBD requires dark time to develop optimally.

I'd love to hear your thoughts on different light cycles for autoflowers in general too. 24/0 vs 18/6. If we are calculating DLI properly do you suggest 24/0 has no downside?

Thank you!

I am not aware of evidence that CBD synthesis is increased in darkness. Cannabinoid sysntesis requires lots of ATP , which is produced from photosynthates, but more light usually means more cannabinoids.

Continuous light can be used with autoflower cultivars, but we have not specifically done studies with autoflowering cultivars.

Are there any NDVI & multispectral imaging guidelines for monitoring cannabis plant health en-masse that are specific to cannabis? Any indices that were found especially useful for cannabis plants?

I am not aware of any unique imaging recommendation for cannabis. NDVI and PRI both work well in cannabis. See the Apogee Instruments web site for a discussion of these sensors.

In what ways will cannabis cultivation change in the future?

It will change dramatically when high THC Cannabis becomes legal at the Federal level.

Thank you for the time!

There's lots of questions here so I'll cut to it.

What is the specific type of Powdery Mildew that attacks cannabis as a host, and what is the best way to combat/control/prevent that particular variety?

We have found that a high level of Silicon in the root zone almost completely inhibits PM.

We add Si both in the media, using rice hulls and wollastonite, and in the liquid fertilizer using potassium silicate. my student present posters on each of these approach at the American society for horticultural science last month in Denver. See ASHS.org

Dr. Bugbee,

Do you have any insight into future Cannabis trends for the home grower?

Also, what makes you excited to come to work everyday?

Changes in the legality are the biggest factor for home growers. And the legal climate is changing faster than the global climate!

Working with so many excellent people gets me out of bed each morning. I hope I can sty healthy for many more years.

Hey Bruce! Love the videos you’ve put out, very informative. Thinking about taking your course to round out my experience growing cannabis with a scientific understanding of the plant.

• what is your opinion on the most effective IPM throughout both veg and flower? As in organic sprays like spinosad/eco-1 from arbico organics, predatory mites/nematodes, etc.

• what is your opinion on living soil? I know you prefer half peat half vermiculite, but the industry is seeing a shift towards solventless extracts and living soil/no till flower capturing a higher cost vs hydro/salt grown plants.

• do you have a set feeding schedule/favorite nutrient line? These days I do roughly 80% organic feed (pre amending soil before planting with organic inputs/brewed compost teas/recharge/mammoth microbes) but do supplement with some traditional salts and amendments in the reservoir (Jack’s 3-2-1 and Epsom salts), so I would say I’m 80/20 organic/inorganic. Would love to hear your thoughts on feeding in soil vs inert media.

• any opinion on the new LED bar style lights that offer 3 way spectrum control (white/red & IR/blue & UV)?

• what is your favorite strain to grow/consume, or do you just love the study of this plant? Curious what varieties you guys grow out in your studies, and if you rotate them based on what’s available or if you have your own breeding program, or a stash of old seeds.

Thanks for doing this! Hope you’re having a great day.

• R

regarding media components: there are many excellent options, including Rockwool.

Coconut coir is also good. We use peat because it has such a long history of use in container culture and it buffers nutrients and pH.

They key is an appropriately dilute nutrient solution coupled with rigorous pH control.

UVA or UVB ?

From what I have seen UV has been mentioned on your videos but never into great detail.

I have seen UVA and UVB products is there a clear winner?

We have not found that supplementing with either UVA or UVB increase cannabinoid synthesis. Supplemental UVB is highly damaging and can decrease photosynthesis and yield, however.

We are continuing to study this.

Does green light affect photoperiod.

I see a lot of people in cannabis use green headlamps or similar because they say it dosnt affect photoperiod. I find this hard to believe do you have any information?

Green photons penetrate deep into leaves and they have a powerful effect on phytochrome. We are studying this now. Green headlamps should be used with caution.

But since our eyes see green photons so well, the green color is still the best choice for human vision at night.

Aloha from Hawaii!!

My questions are:

1. If a plant is showing Nitrogen toxicity(Clawing, dartkening leaves) & is about to flower, should I not be worried too much since the plant uses a lot of N during the flower stretch?
2. If a plant has N toxicity and I see it mostly built up on specific leaves(they are darker and clawing) is it a good idea to remove those leaves?
3. Have you ever worked with strains from Hawaii?
4. Have you ever worked with novelty strains such as Freakshow / American Bastard Cannabis ?

Thank you!

We use a very dilute nutrient solution. I have seen many more problem with nutrient toxicity than with nutrient deficiency. The EC of our solution is 1.4, and the leachate EC should also be about 1 to 1.4.

It is better to make the plants work a bit to get the nutrients. This is part of precision stress. Low nutrients help us get green leaves right up to harvest.

The fertilizer that you showed on your video (The blue 20-10-20 Jacks) is pretty hard to find unless you buy in bulk for commercial. I can't seem to find any 20-10-20 water soluble fertilizer. Is there another fertilizer that you would recommend?

Peters also sells this same fertilizer. Any brand will work. You probably need to buy a 25 pound bag however.

Can I assume you are answering these questions in your crop of Big Bugbee OG?

Can you send a few seeds of this new genetics? It sounds dangerous.

Hey love your videos! Is there a place that we can get access to the results of your research? I would like to know the effect of temperature on yeilds and the effect of the different light types on yeild.

We are studying the interactions between temperature and light now in our canopy gas exchange systems. This is part of "crop steering". See also cannabis.usu.edu. This is an on line course with up to date research results. The tuition payments all go to fund graduate students.

What's the difference between the Apogee MQ500 full spectrum meter and the epar meter? Would it make sense to get both?

The quick answer is yes. Both PAR (traditional, 400 to 700) and ePAR (400 to 750) are going to be used for many years. As President of Apogee Instruments, I recommend stocking up on both models!

I'm curious why adding lime and gypsum to build the soil would be better than adding it to the irrigation? Seems like one could get more consistent results with irrigation.

Steady state addition of nutrients in irrigation water is always better than slow release fertilizer, BUT the carbonates in lime are minimally soluble so they are difficult to add in irrigation water. They form calcium carbonate which plugs emitters and filters.

We also have used a separate injector to add either KOH or acid for pH control.

What range should the runoff pH be in the peat/vermiculite media?

We regularly monitor leachate pH. The optimum is between 5.6 and about 6.3.

This is the optimum regardless of the media type. We control pH in our recirculating hydroponic systems at 5.8 to 6.0.