Phosphorus Use From Flower Initiation Onward

[pjlive]

Gypsum as a soil additive: use it or lose it?

The soil additive gypsum is not well understood and has limited uses in the calcareous-soils of Michigan.

www.canr.msu.edu

"In order to adjust soil pH, liming products must contain carbonate (CO3-) which reacts with hydrogen ions to neutralize soil acidity.

• Gypsum is calcium sulfate (CaSO4). While the calcium will displace hydrogen ions, these ions will remain in solution and will not adjust soil pH."

Oh I see what you mean now. Gypsum will help counteract this if you're using enough lime to increase the media's calcium level to a high degree. I use multiple forms of lime and can bring its concentration down somewhat by using a balanced proportion of gypsum. I wrote pH because I was rushing and not thinking about it right at the time. I've always used gypsum for this purpose but don't think too much about the "why" anymore. So, I made a typo or mistake.

But, if you prefer, you can consider yourself trolled if you'd like. Either way is fine with me.

 

[Creeperpark]

I've done it both ways and my view is that an increase in phosphorus will produce more trichrome and bigger buds compared to using less phosphorus. However, the increase in bud size will trap excess moisture in the buds because the leaf stomata are blocked from heavy bud density. Fat buds can't transpire water through the stomata and the water gets trapped in the bud stems. Those small minute leaves in the buds get closed off and squeeze off the gas and water transpiration off completely. For that reason, an increase in Phosphorus can come back and bite oneself on the ass with bud mold. So use enough to get the good bud density and then reduce is my choice today

 

[pjlive]

I've done it both ways and my view is that an increase in phosphorus will produce more trichrome and bigger buds compared to using less phosphorus. However, the increase in bud size will trap excess moisture in the buds because the leaf stomata are blocked from heavy bud density. Fat buds can't transpire water through the stomata and the water gets trapped in the bud stems. Those small minute leaves in the buds get closed off and squeeze off the gas and water transpiration off completely. For that reason, an increase in Phosphorus can come back and bite oneself on the ass with bud mold. So get the good bud density and then reduce is my choice today

I agree with your input 100%. I've decided not to change my ratios. I'm not dissatisfied with moderate to lower than is typical Phosphorus ratios during flower. Plus, I worry too much about potential problems like you mention here.

Thanks for this very detailed personal take, Creeper. I appreciate it!

 

[f-e]

While uncommon, a zinc deficiency is most likely to be caused by a P boost.
I don't see a cannabis study yet, but in some loosely comparable crops, zinc is huge.

 

[pjlive]

While uncommon, a zinc deficiency is most likely to be caused by a P boost.
I don't see a cannabis study yet, but in some loosely comparable crops, zinc is huge.

Yes, see, even another reason for me to be very cautious with it. If I come across a related study I'll be sure to post it.
I'm still flabbergasted over some of the salt growers using crazy high levels for their plants. I feel like I'm missing something, but I'm sure I don't want to test my luck with it either. Lots of different hydroponic styles and experimentation going on out there right now and I'm not convinced all of them are good for the plant.

Thanks for your input f-e. You're always very thoughtful about the plant.

 

[St. Phatty]

Sometimes I mix in the Bone Meal when I'm preparing the soil in the big pots, before transplanting.

Sometimes I add Bone Meal to the Compost Tea the plants get, during flowering.

+ there is Phosphorus in the Bird Guano.

 

[George]

While uncommon, a zinc deficiency is most likely to be caused by a P boost.
I don't see a cannabis study yet, but in some loosely comparable crops, zinc is huge.

I've done this before with P at 50+ and Zn <.120 when using phosphoric acid as a ph down. I had to add quite a bit and got sllammed by Zn literally at the start of he run. It was bad lol.

I use MOST now which has 1.2ppm zinc, basically 10x and I'm hitting 70P plus Phos acid to ph and no stress now. This is a pure coco grow which is the reason for my high P. I'm gonna add more P anf see where i can take it before I see the same signs. Basically trying to see how much P and Ca I can get in there but obviously need to balance zn. According to SlowN, you want like a 10:1 P:Zn but that is on a soil test. I'm not sure 10:1 is a good idea in hydro? How high have you guys gone?

 

[pjlive]

Sometimes I mix in the Bone Meal when I'm preparing the soil in the big pots, before transplanting.

Sometimes I add Bone Meal to the Compost Tea the plants get, during flowering.

+ there is Phosphorus in the Bird Guano.

Yes, thank you St. Phatty! I think I understand you. You're saying in your soil runs you feel comfortable to provide as much Phosphorus as you feel your plants can/will uptake without harming them. I wonder, have you run plants will less available P and, if so, did you notice any difference to the density or productiveness of your flowers? Do your plants seem to take up as much as made available to them without having issues?

I'm running salts, so I have to be a little more cautious. But soil growers can provide overabundances too. Have you ever unknowingly provided too much?

You don't have to answer anything if you don't want to. I'm just curious, so am asking a few more questions.in

 

[pjlive]

I've done this before with P at 50+ and Zn <.120 when using phosphoric acid as a ph down. I had to add quite a bit and got sllammed by Zn literally at the start of he run. It was bad lol.

I use MOST now which has 1.2ppm zinc, basically 10x and I'm hitting 70P plus Phos acid to ph and no stress now. This is a pure coco grow which is the reason for my high P. I'm gonna add more P anf see where i can take it before I see the same signs. Basically trying to see how much P and Ca I can get in there but obviously need to balance zn. According to SlowN, you want like a 10:1 P:Zn but that is on a soil test. I'm not sure 10:1 is a good idea in hydro? How high have you guys gone?

Great response, George. Thank you for your thoughtful input. I'm personally opposed to going over 200ppm in P. In fact, that would be a very rare plant for me to be up that high. But now I see some growers not only meeting that mark, but exceeding it by quite a bit in some cases. When I am up to or over that concentration, it's only for a very brief stretch during Bud Set. I'm coming right back down again during full Flower.

I don't know, though. So, I'm staying right where I know I'm OK without taking any chances for now.

 

[Rurumo]

A study from 2021 called "The Highs and Lows of P Supply in Medical Cannabis" found 30-90 ppm to be the idea P range depending on genotype, with 80% yield efficiency being achieved at 30 ppm. Which means, going up to 90 ppms resulted in only a 20% increase in yield. Bruce Bugbee actually reviewed that paper. I've found that to be a good range for P, but it's so genotype specific.

 

[pjlive]

A study from 2021 called "The Highs and Lows of P Supply in Medical Cannabis" found 30-90 ppm to be the idea P range depending on genotype, with 80% yield efficiency being achieved at 30 ppm. Which means, going up to 90 ppms resulted in only a 20% increase in yield. Bruce Bugbee actually reviewed that paper. I've found that to be a good range for P, but it's so genotype specific.

Yes! And those concentrations seem to be right to me. Definitely.

This isn't a question directly to you -- but why the hell are growers ramping it up over 100% from those levels??? I've seen it, too. Some of them are not getting bad results at all. But, man, I don't know...

 

[f-e]

(Answering in the same vein)
Twice as much? I have seen 3 times as much reported, and it's not even uncommon.

I did ramp up to 100ppm as per that 100/100/200 recommendation. They were having it large during stretch, making huge leaves to store it in. As soon as that phase was over I hit problems though. I suspect I had loaded up on as much as I could. It coincided with 100ppm Ca which seems to follow a similar path.

I seem to be settling around 45ppm P with 0.6 Zn. A ratio approaching 100:1 seemed to prevail on the half dozen bottles I looked at on the shop shelf. Substrate didn't seem to matter to the bottles.

If you push P and Zn a little more, you may in turn need to look at Fe. My personal findings say 1.5ppm Fe will cover 45ppm P and 0.6ppm Zn, but I still went for 3ppm Fe anyway, so I could be a bit more 'happy' with my Zn weighing.

 

[pjlive]

(Answering in the same vein)
Twice as much? I have seen 3 times as much reported, and it's not even uncommon.

I did ramp up to 100ppm as per that 100/100/200 recommendation. They were having it large during stretch, making huge leaves to store it in. As soon as that phase was over I hit problems though. I suspect I had loaded up on as much as I could. It coincided with 100ppm Ca which seems to follow a similar path.

I seem to be settling around 45ppm P with 0.6 Zn. A ratio approaching 100:1 seemed to prevail on the half dozen bottles I looked at on the shop shelf. Substrate didn't seem to matter to the bottles.

If you push P and Zn a little more, you may in turn need to look at Fe. My personal findings say 1.5ppm Fe will cover 45ppm P and 0.6ppm Zn, but I still went for 3ppm Fe anyway, so I could be a bit more 'happy' with my Zn weighing.

Absolutely, f-e. Me too. I've seen it above 300 ppm from talented gardeners growing volume for dispensaries. They don't directly address this question. Maybe that's a clue in itself? That's why I'm so curious. It's screwy but there has to be a reasonable explanation. These people know what they're doing. I think!

I completely agree 350% with everything you've written. I'm in the same exact league when it comes to my use of P. I'm staying on the subject personally because I feel like I'm just missing something obvious. Like, are they modifying other aspects of the grow to accommodate for such high P levels? If so, what are those adjustments and why are they making them? Are they able to stay within the 100mg per gram THC content by doing so? Is it that they don't care about the quality of the bud at all in favor of more production and weight to their buds? It really makes no sense. But I still figure there HAS to be a reason.

Thanks again, f-e. I always appreciate your input.

 

[f-e]

One thing I can't pick out of the data, is frequency of application. Which is a major factor. Also the possible confusion over what the growers were asked.
Here we index soil fertility reports, 0-10 and an index of 5 is 71-100ppm. That should give corn a good return with UK weather. It's conceivable that a farmer fertilising twice a season will be putting on something quite a bit stronger.
I might be making 45ppm available every few hours, and I'm feeding to run off. The farmer driving about with an IBC isn't watering very deep or very frequently. He should probably going quite a higher than me, and perhaps using a slow release source. Which won't be reflected in the figures at all.

When I looked at soil, I used a range of amendments, a calculator, and days of my time. I wanted all my elements at index 5. Almost every amendment contained more than one element though. Never at the ratio I wanted. Hence I took days looking up everything, and how to blend them. Most farmers just get the usual things off the shelf, and might be adding an element they don't really need, just to get one they do. So they don't get the exact profile they wanted, but close enough without the headache I went through, or employing a proper agronomist, who still might not go to great lengths to get it perfect, as costs and tank mixing possibilities must be considered. All this to and fro really makes the average study figures of interest, and the outliers more of a mystery than something to follow. There is just too much going on, to unpick much more from the numbers.

This is a good thread. The question itself shows you are at an advanced level. The production and suggested timing of PK boosters does seem to follow the aptus graph. Yet more and more I find myself in disagreement with them. I have generally found my own way, but have taken a lot of guidance the last 3 years to try and improve my game. It's been disastrous. I do a lot better finding what works for me, than following what works for the industry. This might mean I shouldn't be listened to

 

[pjlive]

One thing I can't pick out of the data, is frequency of application. Which is a major factor. Also the possible confusion over what the growers were asked.
Here we index soil fertility reports, 0-10 and an index of 5 is 71-100ppm. That should give corn a good return with UK weather. It's conceivable that a farmer fertilising twice a season will be putting on something quite a bit stronger.
I might be making 45ppm available every few hours, and I'm feeding to run off. The farmer driving about with an IBC isn't watering very deep or very frequently. He should probably going quite a higher than me, and perhaps using a slow release source. Which won't be reflected in the figures at all.

When I looked at soil, I used a range of amendments, a calculator, and days of my time. I wanted all my elements at index 5. Almost every amendment contained more than one element though. Never at the ratio I wanted. Hence I took days looking up everything, and how to blend them. Most farmers just get the usual things off the shelf, and might be adding an element they don't really need, just to get one they do. So they don't get the exact profile they wanted, but close enough without the headache I went through, or employing a proper agronomist, who still might not go to great lengths to get it perfect, as costs and tank mixing possibilities must be considered. All this to and fro really makes the average study figures of interest, and the outliers more of a mystery than something to follow. There is just too much going on, to unpick much more from the numbers.

This is a good thread. The question itself shows you are at an advanced level. The production and suggested timing of PK boosters does seem to follow the aptus graph. Yet more and more I find myself in disagreement with them. I have generally found my own way, but have taken a lot of guidance the last 3 years to try and improve my game. It's been disastrous. I do a lot better finding what works for me, than following what works for the industry. This might mean I shouldn't be listened to

Or, as a small production residential grower, maybe I should be even more closely listening to you.

I'm following what you're writing. And it makes a lot of sense to me. Some of the growers I've found using unusually high fertigation levels are doing so in in-house runoff systems. I've not considered outdoor soil grows and the feed frequencies and depths of delivery thereof. It was good for me to read this because it helps me understand what's going through a large scale grower's mind a little better. Super of you to take the time to share this with me.

I'm the type that learned to grow in soil a long time ago and gradually moved into a soil-less media base that I don't plan to move away from. Not for cannabis anyway. I do grow in soil outdoors but those grows are very small now. Plus I'm legally limited to the number of cannabis plants I can have going at any one time. I also like to grow various varieties of tomato, pickling cukes, and peppers. With cannabis I don't consider myself an expert, but I know I can grow a good plant and get good feedback from my small group of local friends who are all soil based gardeners. Aside from the base cannabis education I got from a local dealer back in the 80s, I've used brute force techniques to help crack my soil-less grow methods and practices. As has been a typical component to my life, I'm off doing my own things, my way, most of the time. Growing cannabis has proven no different. I'm willing to experiment heavily to determine what works best for me.

Everything in cannabis cultivation is changing so fast. There are now as many professed ways to grow a plant as there are strains. It's insane. But, I want to improve if I can. Soon we're going to have even better LEDs and other new gadgets to help us better control and manage the variables. I like to stay on the cutting edge if I can. Not that I'll use everything. I won't. But I like to know what's what in the community at large.

You'll see how I handle an Auto if you check in every once in a while. Then you can make a better informed judgement on my true abilities. Stay tuned. I'll try not to let you down.