The Myth of Low N

[desertsquirrel]

nice link grapeman.

 

[desertsquirrel]

bump

 

[spurr]

Also im confused myself about urea/ammonicals for the same reason you say, the long period of nitrification.

Ammonium is the 'main' ammonicial nitrogen source, and it's used immediately by plants. A good ratio for NO3:NH4 in fertigation water is at between 10-20; I am using 13 now. When co-applied NH4 will potentate uptake of NO3 by roots, but after some time, NH4 will hinder NO3 uptake.

Plant cannot self-regulate uptake of ammonicial N, but they can nitrate N, to a degree (re some amino acids in phloem). Thus if the plant cannot move enough sugar to the roots, fast enough, the NH4 will not be converted soon enough, and can burn roots and cause other expressions of phytotoxicity.

In a garden with high Co2 it's a good idea to 'hedge bets' and use a low NO3:NH4 ratio. I have never used below 10, but I plan to try 8. In most Ag lit. below 4 is considered too low and can/will hinder the plant. The reason being there is mounting scientific evidence that plant given only NO3, or a vast majority of NO3, are only benefited by Co2 for a short time (days/weeks), re increased growth rate, etc. However, with plants given only NH4, or a majority NH4, the plants were continually benefited by Co2 over time.

Also, the process of nitrification is pretty quick in many cases, re conversion of NH4 into NO3, by microbes in media and water.

However i think that that refers only to soil as once the conversions have started (as soon as NO3 becomes NO2) its unusable.

That's backwards, a main route of nitrification is NH3 > NH4 > NO2 > NO3. The element NO3 is nitrate and NO2 is nitrite. cite: http://www.rpi.edu/dept/chem-eng/Biotech-Environ/Environmental/nitrification.html

It seems that urea must be a usable form of N seeing as it is a main source of it in Advanced products, presumably the nutrients used in the tissue samples.

It's lightly usable in organic form, but it's fairly quickly converted into ammonium (NH4) by some microbes (ex., bacteria) in media and water.

This is also probably the reason your finding good results with Pure Flowers, as phosphites are actually poisonous to plants but easily converted to phosphates in the rhizosphere.

This is not wholly accurate. Phi (phosphites) are only "easily converted to phosphates [Pi]" under high pH conditions (re chemistry). It takes weeks for media microbes to convert enough Phi into Pi, so the plant can get enough P from the Pi to not be P deficient. See the links in my sig for more info, along with an article I wrote on this topic.

I posted pics from studies of plants given only Phi as a P source, in soil, and they all suffered severely from P deficiency. Yet those given Pi, in the same soil type, thrived (side-by-side grow of grass). And that's in soil rife with live microbes, but the pH was not > ~8, which is the pH best to speed conversion of Phi into Pi.

The story in hydro is worse, because often there are far fewer microbes than live soil. And because pH in hydro is not sufficiently high to speed conversion of Phi into Pi. Thus application of Phi to rez (for the rhizosphere) will provide little P (as Pi).

Phi is good for some things, one thing it is not good for is a source of P. In fact, when a plant is P deficient, and it's given Phi along with Pi, the Phi will hinder uptake of Pi; making the plant even more P deficient!

 

[spurr]

Oh yea, I haven't read through this whole thread yet, but I use ~120-140 ppm N (NH4 + NO3) from veg until the last week before harvest. It seems I get much better yields this way, not to mention I get heather plants which means higher rates of photosynthesis vs plants lower in N.

 

[spurr]

One other thought, I know of at least one (two I think) papers that found there may be a positive correlation between N levels in leaf tissue and THC quantity (during flowering).

 

[spurr]

Not saying anyone is wrong but I have always wondered...if marijuana actually self regulates how do people manage to nute burn it? And why don't people just load it up with the major nutes and let it pick and choose what it wants to eat? Why would people flush?

Cannabis and other plants can automatically self-regulate uptake of only some elements (ions) and only by degrees, not turn off uptake completely.

I have written about this topic a few times, and posted quite a few good studies, the cliff notes are that some amino acids in the phloem 'lightly' hinder uptake of nitrate, some 'strongly' hinder uptake of nitrate and some do not affect uptake at all.

Plants cannot self-regulate uptake of ammonicial forms of N, which is why they can burn roots and cause phytotoxicity.

Plants can self-regulate (to a degree) uptake of NO3, Pi, Ca (IIRC), a some others.

People burn plants because plants will take up ions, even if the plant is 'trying' to hinder the uptake. And the issues of osmotic pressure can 'overpower' the plants attempt to hinder uptake of NO3 (for example), AFAIU.

Plants take up elements in excess of what they need, aka "luxury" elements. And plants can store some elements for later use, mostly mobile forms of elements, though.

 

[spurr]

perhaps cannabis can only regulate nutrient uptake in an organic "live" soil based environment (where actual breakdown occurs) and not in a "hydroponic" chemical nutrient regiment where the nutrients are immediately available to the plant.

See what I wrote above re selective uptake by plants, however, just to point out: plants like cannabis do not need to have nitrogen and phosphorous broken down into inorganic forms. Plant can use DOM (Dissolved Organic Nitrogen; often as amino acids) and DOP (Dissolved Organic Phosphorus) as N and P sources, in place of NH4, NO3 and Pi.

 

[spurr]

Nute burn is caused by plants growing too fast. This causes cells to elongate and eventually burst, looking like they have been "burned."

That sounds like you are describing when N:Ca ratio is too high, and leaf growth (from N) outpaces movement of Ca into leaf for cells. No?

Nute burn often also occurs when too many ions are provided, esp. for a element that is plant immobile, or weakly mobile, ex., boron, calcium, etc. Other cases are root burn when the plant is unhealthy and given too much N (as NH3 or NH4), or when the EC is too high in the rhizosphere.

 

[spurr]

Cannabis only self-regulates nitrate nitrogen uptake. Too much phosphorous, potassium, or ammoniacal nitrogen will "burn" a plant.

They also can self-regulate upatke of Pi (P), as well as some other elements too IIRC. I think not K, but I am unsure, I cannot recall.

 

[desertsquirrel]

Awesome to have your input spurr. Im going to have to read your posts tomorrow when im less tired though. haha.

thanks.

 

[grapeman]

This is not wholly accurate. Phi (phosphites) are only "easily converted to phosphates [Pi]" under high pH conditions (re chemistry). It takes weeks for media microbes to convert enough Phi into Pi, so the plant can get enough P from the Pi to not be P deficient. See the links in my sig for more info, along with an article I wrote on this topic.

I posted pics from studies of plants given only Phi as a P source, in soil, and they all suffered severely from P deficiency. Yet those given Pi, in the same soil type, thrived (side-by-side grow of grass). And that's in soil rife with live microbes, but the pH was not > ~8, which is the pH best to speed conversion of Phi into Pi.

It amazes me that such sophomoric comments, by a pseudo self appointed, self proclaimed researcher, based on a back room grow, is given credence.

 

[spurr]

Love you too grapeman! I <3 Grapeman

Nice try with the logical fallacy (attack) "Ad Hominem", but you should know better than to use logical fallacies. However, in case you don't, here is what Ad Hominem means, and here is a good list of logical fallacies you should stop using (you shouldn't be using any logical fallacies).

What I write is generally respected and accepted, and often questioned and challenged (which are good things when done honestly) because I base what I write on fact, on science and on many, many studies, as well as my personal experience. And with respect to phosphites, from conversations with *your* source of phosphites who agree with me and not you.

 

[spurr]

Awesome to have your input spurr. Im going to have to read your posts tomorrow when im less tired though. haha.

thanks.

Yur' welcome, hope you find it useful.

 

[grapeman]

No spurr - I just read your stuff and laugh. You tried to grow using phi and you suffered a P shortage. LOL. And that is the extent of your studies. LOL.
Therefore you determine that phi is not to be used. Yet, people that farm for a living (you know, folks who determine that each penny spent needs to return 2 pennies) use a ton of phi. They just know what they are doing and how to do it.

 

[Cannabologist]

- I can absolutely agree based on anecdotal observations with these claims about low N being a myth.

- Cannabis needs, uses, and loves lots of nitrogen (as well as potassium and calcium).

[FONT=&quot]- I am unconvinced fan leaves *should* be allowed to yellow during the final stages/part of flowering, and whether it actually has a beneficial impact on finished buds, taste, etc., and instead high nitrogen levels be maintained throughout nearly all stages of growth, even up to harvest.[/FONT]

 

[1971]

so what is the conclusion of this theory? are you guys running higher N? looking at spurr's nutrient profile he links in his profile, i see that he is running approx. 140 ppm. would this be considered high? I don't think so.

 

[thefatman]

IMHO
When Spurr says 140 ppm that means the actual calculated ppm of the nitrogen used in a diluted form. Is it really any different than mixing a 100x concentrate containing 420 ppm of nitrogen diluted in 300 gallons rather than 100 gallons? No. It is just the way some choose to look at it in what they consider a better way. To me it just seems like a way for people to mix different preformulated commercial fertilizers or to add more of a few specific salts to a preformulated commercial fertilizer to try to get close to what they desire rather than to just mix what they want from scratch and get nearer to what they desire. To each his own way. Perhaps I just misunderstand Spurr's reasoning though behind his methodology or reason for same.

 

[spurr]

@ 1971,

You're correct that words such as "low" and "high" are arbitrary. To me, "high" yet sufficient N is ~150-200 ppm. I use ~140 ppm N from veg to harvest, but I have tested and I am testing lowering EC later in flowering, which would lower N ppm.

@ thefatman,

I'm unsure what you are suggesting is my position. You're correct when I write "140 ppm N" I mean the elemental ppm of total nitrogen (ammonicial + nitrate); it's the best way to quantify what one is giving their plants. However, I do not prefer using pre-made commercial fertilizers, like General Hydroponics. I made my formulation for General Hydroponics so the vast majority of cannabis growers that do not want to make their own mix(es) from base salts can have a (truly) scientifically sound cannabis specific fertilizer formulation using off the shelf bottles.

 

[1971]

well, for example, is the bloom recirc formula i found:
Nitrogen 293
Phosphorus 80
Potassium 350
Magnesium 91
Calcium 268

now when i put this into hydrobuddy, it gives me a much too high EC. so if initially i mixed it to 100 gallons, i can dilute in half again to arrive at an EC i am more comfortable with. after halving again, would the ppm's then be half of what they were originally? i know, i'm retarded for even asking

beyond those questions, and excuse me for being a bit tired, i am curious as to the reasoning behind the high N and Ca ppm's. your formula gets thrown around quite a bit but not the reasoning for picking those numbers. not because i am trying to debate them, but because i'd like to learn more

 

[thefatman]

@ 1971,

You're correct that words such as "low" and "high" are arbitrary. To me, "high" yet sufficient N is ~150-200 ppm. I use ~140 ppm N from veg to harvest, but I have tested and I am testing lowering EC later in flowering, which would lower N ppm.

@ thefatman,

I'm unsure what you are suggesting is my position. You're correct when I write "140 ppm N" I mean the elemental ppm of total nitrogen (ammonicial + nitrate); it's the best way to quantify what one is giving their plants. However, I do not prefer using pre-made commercial fertilizers, like General Hydroponics. I made my formulation for General Hydroponics so the vast majority of cannabis growers that do not want to make their own mix(es) from base salts can have a (truly) scientifically sound cannabis specific fertilizer formulation using off the shelf bottles.

Another fertilizer formulator/mixer. Righteous.