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NPK Confusion

Posted by scott123456 5 (My Page) on
Tue, Feb 25, 14 at 22:38

I am trying to become more calculated with my fertilizer and it is very overwhelming and confusing for a beginner. I was wondering, what is the best NPK ratio for vegetative growth and what is the best for blooming? From what I have read about other plants, high Nitrogen is good for vegetative growth, and either high phosphorous or high potassium
(Depending on who you ask) is good for blooming. Not sure if this is the same for peppers or what? Any input would be greatly appreciated .

Also, I understand that a 1-15-1 is 1 part N - 15 parts PHOS � 1 part Potassium. But I don�t understand how a 1-1-1 is any different from a 2-2-2 or a 5-5-5. I f it is truly a ratio then all of those would be a 1-1-1. what am I missing?

Thanks,
Scott


Follow-Up Postings:

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RE: NPK Confusion

N for vegetation, P for flowers and roots, K for general overall health and dealing with extremes.

The ratios are important, but the problems don't normally play a partuntil you get into the higher percentages of each.

For example -- a 5-5-5 or 10-10-10 would probably suffice for a good general fert throughout the season for peppers. But a triple 16 might be a bit too much N to apply maybe more than once or twice per season and I would only side dress with it sparingly.

How are you planting? In pots or in-ground? If in pots, you won't be disappointed with some Osmocote(CRF's) at the beginning and half doses of Miracle Gro All-purpose 24-8-16(3-1-2 ratio) or foliage pro 9-3-6(same ratio) every week. If MG All-purpose, you'll want to find a way to get Ca and Mg into the mix. Most people use Dolomite lime. I use gypsum(Ca) and epsom salts(Mg) because my water is so alkaline. Lime will raise ph.

If in the ground, get a soil test done and you'll find out what that soil needs. In ground, you can never go wrong with lots of aged compost and some organic meals such as blood, feather or cottonseed meal ( all N) , bone meal (P), and kelp meal (K and other micronutes). Worm castings and compost tea is also great stuff for soil.

Kevin

This post was edited by woohooman on Wed, Feb 26, 14 at 0:33


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RE: NPK Confusion

"don't understand how a 1-1-1 is any different from a 2-2-2 or a 5-5-5."

They're the same except for the amount you will apply: package directions will tell the amount for each kind. That is, less of the 5-5-5 than of the 1-1-1.


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RE: NPK Confusion

Similar to the first reply, my rule of thumb is N for vegetation (leaves), P for flowers and fruit, K for overall health and stem and root vigour.

5-5-5 is the same as 1-1-1, just 5 times stonger. ie it has 5% of each nutrient in plant available form, the 1-1-1 has 1% of each nutrient in plant-available form. For indoor growing, I usually use 20-20-20 because I only need 1/8 or 1/4 tsp and that will last an established plant a couple weeks, whereas with 1-1-1 I would need 20X more volume of fertilizer for the same effect, and that just kind of gets sloppy. With 20-20-20, 60% of the fertilizer is plant-available nutrients, whereas 1-1-1 is only 3% nutrients and the rest filler, so after a long indoor grow you would be adding a lot of inert filler to your pots. Outside in the garden it doesn't really matter, and so I usually whatever I can buy a lot of cheaply, which is typically 7-7-7.

I usually use a balanced fertilizer like 20-20-20, but when the plants start to bloom and set fruit I usually replace part of that with something with high phosphorus, like 10-52-10. Somtimes I switch entirely to the high-P fertilizer unless the plant leaves start to yellow, then I add back more 20-20-20 to give the leaves more nitrogen.


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RE: NPK Confusion

NPK :

In an established garden, "P" and "K" tend to accumulate over time, when fertilizers like 10-10-10 are always used. There are TWO reasons for this:

1-- P and K are not used/taken up by the plants as much as N.
2- N , being readily water soluble, tends to leach while P (and to some extent K) bound to the soil and stick around longer. Time and time again, lab tests confirm this.

Because of the above reasons, applying NPK at equal amounts is not the best practice, IMO. According to plant scientists (so I have read) most garden plants uptake NPK at about 3-1-2 ratios, in general.
Furthermore, I, personally, feed my leafy veggies(Onion and cabbage families ..) just "N". Because that is what they need constantly more and I don't want them to flower

JMO

This post was edited by seysonn on Wed, Feb 26, 14 at 10:40


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RE: NPK Confusion

Thanks for all the information everyone!


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RE: NPK Confusion

I grow all the time with equal NPK ratio in hydro. I've tried changing ratio and notice no difference in growth rate or fruit quality.


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RE: NPK Confusion

Seysonn, phosphorus is also very good for bulb growth and quality, which is why people add bone meal (for its phosphorus) when planting or top-dressing spring-flowering bulbs. You might want to try adding P to your onions instead of just N. Unless your soil is naturally rich in phosphorus, I think you will find P fertilizer will really boost the size of your onion bulbs.


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RE: NPK Confusion

The extent to which your N leaches and your P&K stick around is influenced by the sandiness of your soil as well. Sandy soils leach the easiest.

Nutrient uptake and the 'what is best?' question is complex. I think it's different for everyone's soil. If your soil is very high in organic matter and thus the corresponding healthy fungal/bacterial life that assist in nutrient uptake, then you can get great results at a lower NPK level. I think peppers respond especially well in this regard. I have seen impressive plants grown in just manure and compost. At the same time, I have given a lot of chemical fertilizer to plants in poor soil, and they still grew very poorly. I can grow tomatoes that way, but not peppers.


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Wed, Feb 26, 14 at 16:42

The idea that N is for vegetative growth, P for roots, K for the o/a health of the plant (up - down - all around) is misleading and wrong. All plant parts need all the essential elements to grow normally, and you'll find roughly the same ratio of nutrients in all plant parts. IOW, there is as much N, P, and K in roots as in shoots or leaves.

In choosing a fertilizer, the NPK %s aren't very important except to the extent that they determine the fertilizer's RATIO. It's the ratio that primarily determines how appropriate a fertilizer actually is. The volume of fertilizer plants use can vary significantly, but the ratio doesn't vary that much. Here is a chart that shows how much of what the average plant uses, including the high - low range.

I gave Nitrogen, because it is the largest nutrient component, the value of 100. Other nutrients are listed as a weight percentage of N.
N 100
P 13-19 (16) 1/6
K 45-80 (62) 3/5
S 6-9 (8) 1/12
Mg 5-15 (10) 1/10
Ca 5-15 (10) 1/10
Fe 0.7
Mn 0.4
B(oron) 0.2
Zn 0.06
Cu 0.03
Cl 0.03
M(olybden) 0.003
To read the chart: P - plants use 13-19 parts of P or an average of about 16 parts for every 100 parts of N, or 6 times more N than P. Plants use about 45-80 parts of K or an average of about 62 parts for every 100 parts of N, or about 3/5 as much K as N, and so on.

You can see that plants use about 6X as much N as P, and about 3/5 as much K as N ..... so why supply fertilizer in a 1:1:1 ratio when plants don't USE it at that ratio? When the calculations that take into account that P %s are reported as P2O5 and K as K2O are done, 3:1:2 ratio fertilizers provide almost exactly 6X as much N as P and 3/5 as much K as N - that's not an accident. Examples of 3:1:2 ratio fertilizers are 24-8-16, 12-4-8, 18-6-12, 9-3-6 .....

I'll post what I think our nutritional supplementation goal should be. I'd be interested if anyone can think of a more ideal goal to shoot for:

The goal for fertilizing containerized plants can easily be described. You should work toward ensuring that all the nutrients plants normally secure from the soil are in the soil solution at all times, in the ratio at which the plant actually uses the nutrients, and at a concentration high enough to ensure no deficiencies yet low enough to ensure the plant isn't impeded in its ability to take up water and the nutrients dissolved in water. This goal is easily achievable using one water soluble synthetic fertilizer (containers). You CAN use organic forms of nutrition, like fish/seaweed emulsions or various types of meal, but that makes it much more difficult to achieve the goal.

When growing in the ground, it's not as easy. Maintaining even close to ideal fertility levels is not possible w/o a soil test. It doesn't matter what you choose to apply, it's going to be little more than a SWAG if you haven't had your soil tested. Often, fertilizing can do more harm than good; this, because more often than not you're over-supplying the nutrients that are already adequately abundant, and an excess has the same potential to limit as a deficiency. If you want your peppers grown in the garden or beds to grow their best - get your soil tested and follow the testing facility's recommendations.

Al


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RE: NPK Contusion

Thanks, Al. Nice to see you over here.

Dennis


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Wed, Feb 26, 14 at 17:59

Thanks! I saw the post in the "Most Recent Posts" box & thought I'd see if there was something I could add.

Best luck with this year's crop!

Al


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RE: NPK Confusion

Thanks Al.
What I said was principally leading to the same conclusion. The reason, I say to cut back on P and K in garden application (Not in soil less container) is based on the notion that most established garden soils have more of what is required P and K. So what is more likely to become deficient is N.


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RE: NPK Confusion

Al: Just a question. Are you trying to say that what most horticulturists and botanists say what each MACROnutrient and it's general attributes is incorrect and, for example, if I throw a triple 30(as opposed to a 21-0-0) on my lawn that it WON'T be more apt to seed rather than just green up the blades of grass? Again, just an example. Or that I can feed my carrots a a 24-8-16 and they won't split roots?

Kevin


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Wed, Feb 26, 14 at 20:30

That was several questions. Find me a botanist or horticulturist that subscribes to the up - down - all around ditty for how NPK is used by the plant. ;-)

"If I had a nickel for every time I heard: “Nitrogen is for leaves, phosphorus is for roots and flowers and potassium is for stems,” I would be rich.

Growers have long believed that they need to use high-phosphorus fertilizers at planting and during the flowering period for sufficient root and flower growth. The fact is growers need to supply all plant parts with essential elements at required amounts to achieve optimal growth. If healthy flowers or roots are analyzed for nutrient content, not only is phosphorus present, but so are all the other essential elements.

So how did this myth start? High-phosphorus fertilizers such as Blossom Boosters and Plant Starters were developed many years ago when greenhouse growers were still planting in mineral or field soil. Since some mineral soils quickly tie up soluble phosphorus, high-phosphorus fertilizers were needed to flood the soil with phosphorus so that plants could take up an adequate amount of the nutrient before it was fixed by the soil and unavailable to the plants." ~ Fred Hulme, Ph.D.

Source - there are a LOT of them.

The results of using any fertilizer on a lawn w/o a soil test are unpredictable.

Why would your carrots split roots if you use 24-8-16 unless they're too wet? If you're thinking excess N (is what I'm guessing), remember that the NPK %s on the box have no bearing on how much N a plant gets. That's on the grower, how heavy-handed HE is, if he's supplementing with fertilizer. You can as easily over-supply N with 5-5-5 as with 24-8-16.

Al


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Wed, Feb 26, 14 at 21:04

Deleted duplicate post .......

This post was edited by tapla on Thu, Feb 27, 14 at 22:16


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RE: NPK Confusion

" Find me a botanist or horticulturist that subscribes to the up - down - all around ditty for how NPK is used by the plant. ;-) "

"If I had a nickel for every time I heard: “Nitrogen is for leaves, phosphorus is for roots and flowers and potassium is for stems,” I would be rich. "

So, you've read and heard it tons of times also, correct?

All those people that have written it and said it, you don't think at least ONE was a botanist or horticulturist???

:P

Kevin


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RE: NPK Confusion

remember that the NPK %s on the box have no bearing on how much N a plant gets. ..(Al Tapla)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Are you saying that if I apply 5-5-5 OR 23-0-0, my tomatoes are going to get the same amount of "N"?.

If, "YES", I have to disagree.
I don't know how plants choose to up taks P and K, but I am pretty sure that they cannot control their appetite for N. Isn't that why excess N causes BURN( Extremely dark foliage )??

Not being a botanist, but having been born and raised on the farm, I know that plants will take as much N as they can get. I THINK, probably the reason is that N is READILY soluble in H2O and as plants take moisture, with it automatically Nitrogen goes into their system, DEPENDINDG ON THE AMOUNT OF N PRESENT. .


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Thu, Feb 27, 14 at 8:11

Are you saying that if I apply 5-5-5 OR 23-0-0, my tomatoes are going to get the same amount of "N"?.

No, I'm saying it's the grower's responsibility to make sure the grower supplies the right amount of N. Using 5-5-5 doesn't preclude toxic levels of anything. Fertilizer is supplied and used by the plant as a function of N. If you supply N at lower than ideal levels, the plant will use other elements accordingly - in reduced amounts. It's impossible, using 1:1:1 ratios or high-P formulations to avoid having some nutrients in excess and some at deficiency levels as a function of N, and you can't make a plant take up more of any one element than it needs, unless it's at the expense of other necessary elements (antagonistic deficiency). You can easily supply the right amount of N using either 23-0-0 or 5-5-5. The problem is, you can't supply a favorable ratio of either P or K using either. If 5-5-5 and 23-0-0 were both soluble synthetic fertilizers, looking at the general directions on a box/bag you would find that following directions would yield a solution with roughly the same amounts of N, even though the EC/TDS levels of the solution would allow (but not suggest) a larger amount of N when using the 23-0-0; but that's simply because it doesn't have P or K as contributors to EC/TDS.

In this case, it does no good to have this discussion about plants in the ground unless we know what the soil contains, but for container culture, the conversation would be relevant.

Kevin - you can't always trust in consensus. Consensus is just a convenience that most people will allow themselves so they don't have to think. It's easier to believe than think. That toxic levels (more than a plant needs) of N stimulates weak, succulent, elongation in many plants doesn't mean that N is "for foliage". N is as important to roots, shoots, and fruits as P, K, all the secondary macros and the micros. The same is true of other elements. A plant can't grow normally without all the essential elements, so how can one be more important than another for particular organs? If you consider it for a few seconds, it all makes perfect sense.

Al

This post was edited by tapla on Thu, Feb 27, 14 at 10:55


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RE: NPK Confusion

Lots of people might be surprised to learn that most soil testing labs don't normally include a N test routinely. N fertility levels are then based primarily on the crop being grown. More emphasis is actually given to "Topdressing" N for certain crops like corn to ensure adequate amounts are present at pollination time when it is most needed. I believe more research would show that this same principle applies to other crops, especially peppers. By withholding N application until time of initial blossom set I believe one can significantly increase pepper fruit yield. Unless one has mitigating circumstances such as applied manure ( or if you had a plant tissue analysis), I would simple base the N application on the generalized plant needs.

Other nutrients are more tricky. If I were seeding and crop I'd apply some P2O5 regardless if the soil test indicated P in the excessive range. Reasons were mentioned above.

What surprised me in this thread is the slight mention of liming the soil. If your soil pH is out of wack for the crop you are growing you may as well ignore other nutrients. I'd place limestone, calcitic or dolomitic right behind water in importance. If you concentrate too much on the micros and have not provided for the macros you are wasting money.


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RE: NPK Confusion

I'm enjoying this thread quite a bit. I absorb scientific discussions about pepper growing the way plants absorb fertilizer.

from what I'm reading, I think I wanna stop using my current fert and go for something with a 3-1-2 nutrient ratio.

Al, while we have you here, what are your thoughts on using added mycorrhizae with container gardening, namely in your famous 5-1-1 mix?


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Thu, Feb 27, 14 at 14:15

I have mixed emotions. If we were sure we could keep the beneficial fungi thriving in a container, there wouldn't be much of a downside other than the fact that your soil would break down faster. The problem is, root systems often develop relationships with the fungi, and that reduces the size of the root system needed to support the entire organism, so if anything happens to the viability of the fungi (like high root temps [mycorrhizal fungi are very heat sensitive], soggy soil conditions, application of a high-P fertilizer, someone applying something fungicidal to the foliage ....) the roots are suddenly abandoned by their symbiotic partner and the plant left struggling or shedding parts in order to survive.

I'm not suggesting what anyone SHOULD do, but I don't bother. I always see plenty of fungal hyphae in my containers in spring and fall, but hardly ever in summer - because they don't tolerate high temps well - especially the manufactured fungi. In fact, you really can't tell if the product you buy is active. Being left too long in a greenhouse or a truck during transportation can easily kill all the fungi in any given lot. Some people say they love them, but I don't think they're necessary or very beneficial in container culture. If you fertilize regularly and use a soluble fertilizer with all the elements essential to normal growth, it's going to be difficult to beat that program, mycorrhizal fungi or not.

Al

This post was edited by tapla on Thu, Feb 27, 14 at 21:05


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RE: NPK Confusion

thank you.

you should visit the pepper forum more often.


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RE: NPK Confusion

Indeed, great discussion, Al.
Thanks for stopping by and dispensing such great information.

Josh


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Thu, Feb 27, 14 at 21:59

Thanks for the kind words, guys! I don't usually spend time here, but I caught Scott's "NPK Confusion" out of the corner of my eye in the Most Recent Posts box & thought I might be able to add to his confusion. ;-)

Al


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RE: NPK Confusion

Now that Al is around, let me ask couple more questions:

What is the mechanism by which plants take the nutrients ? I don't think they are like us, humans to have breakfast then wait til lunch ...then have dinner. They should be continuously doing this. Maybe it has to do with the light ?

More importantly, do they decide what to take or what not to take ? Say, certain amounts of NPK (at a given ratio) are dissolved in water. Can they just take the water and leave the any of the NPK behind ? I am assuming an ideal pH here and absence of other elements. Do they have preference to take more or less of those elements? My thinking is that they have a preference for "N"itrogen.


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RE: NPK Confusion

WOW! Thank you all so much for all the information! Al, believe it or not this has cleared up a lot of things for me, it did not add to my confusion at all. This is a very interesting discussion and exactly what I was looking for. I am a scientist by heart (and profession) so it is usually not enough for me that something worked (or is the consensus), I want to know why it worked and what can be done to improve upon it. I have a pretty good understanding of human physiology, but when it comes to plants I have a ton to learn. I guess the only thing I’m still caught up on is a question that is similar to, or possible the same as seysonn’s. Do plants pick and choose what they absorb, or must they take up whatever is in the soil? If they do pick and choose (maybe a concentration gradient of some sort?) then as long as there is not a deficiency, I would assume the plant would be fine. How would a surplus cause a problem? On the other hand, if they do not pick and choose, and are forced to take up whatever is in the soil (I doubt it), then how would you balance the micros in the correct ratio? It seems like an impossible task (I do not even think there is a fertilizer that has all the micros and macros in the correct ratio commercially available). I have to believe that there is some sort of mechanism that determines what nutrients a plant takes up. They have lived for millions of years in many different soil types in nature. Are there any good reads you could recommend on this mechanism?
Thanks,
Scott


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RE: NPK Confusion

I can take a short answer stab at that Q since there is much info available to support theories and more coming to light. Plants don't pick and choose- thus the symptoms of excessive nutrients. Uptake is dictated by roots and to some degree by the types of roots. Rick Snyders research with tomato Blossom End Rot linked the problem of Ca uptake to lesser numbers of new root hairs likely brought on by one type of stress.

Once nutrients are in the plant it is clearly evident that they all move thru the plant at different levels. Thus you'll see certain deficiencies in new tip growth, others lower on the plant. The problem is that any nutrient, especially trace elements, can be adequate in the soil and still be deficient in the plant. pH, which I mentioned earlier, is a major player in that.


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Fri, Feb 28, 14 at 9:13

If we allow for a little anthropomorphism we can say that to some degree plants do pick and choose what they absorb, but that ability is quickly altered as soon as the ratio of nutrients in the soil solution becomes skewed. I think it was in this thread that someone mentioned they think that plants can't control their N uptake. Well, they CAN if N is appropriately represented in the soil, along with appropriate representation of the other elements. If there is an excess of ions belonging to one element, it can affect the uptake of the other elements to the degree of toxicity. For instance, if there is too much Fe (iron) in the soil, the plant won't be able to take up enough Mn. The plant can't precisely tell the difference between Fe and Mn, so if there is too much Fe, it takes up Fe instead of Mn. That's why fertilizer RATIOS are important.

1:1:1 fertilizers supply about 2.5X as much P as a plant can/will use. The excess P can do a lot of things, like cause deficiencies of K, Ca, Z, Cu, Fe, or raise pH unnecessarily, or contribute to the TDS/EC (level of salts in the soil solution) unnecessarily, w/o actually providing anything but limitations. See why fertilizer ratios ARE important?

How plants take up nutrients is sort of complicated, but I'll take a stab at explaining it. We know that nutrients are taken up in the form of inorganic or organic salts or ions, which may exist in either in free state or bound to soil particles. These salts can come from OM in the soil, a dead fish, or from a box of Miracle-Gro - the plant doesn't care because it's nutritional diet is salt (salt is what's left after an acid and a base react).
One way they absorb: Root cells in contact with soil particles secret hydrogen ions which have a + charge. H+ ions easily displace cations like K+, Na+ ions that are bound to soil particulates. These ions enter the soil solution and thus are made available so the root system can hopefully absorb the required ion. The relative retentive capacity of the soil particles isn't absolutely fixed, there is an order of preference of ions to be released. IOW, some ions are more tightly held than others but H can replace any of the ions easily. Once dissolved into the soil solution, the plant takes them up readily - as long as the cultural conditions are favorable - not too wet/dry, plenty of air in the rhizosphere, not too hot/cold .....

Another way nutrients become available has to do with root respiration.Roots continuously respire irrespective of day or night and during the process produce significant quantities of CO2, which dissolve into the soil solution, producing carbonic acids. Immediately they ionize into H+ and bicarbonate ions. The H ions exchange with any bound cations on clay particles, which go into the soil solution and make the bound cations available for the roots.

Land plants have extensive root system with innumerable growing tips (apical meristems). Most of the (from soil) nutrients are absorbed dissolved in water by the growing meristems. These nutrients are ultimately actively transported to the xylem. From the xylem they move upward in the transpiration stream and get distributed to all the plant's living parts.

Al


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Fri, Feb 28, 14 at 9:45

Once nutrients are in the plant it is clearly evident that they all move thru the plant at different levels. Thus you'll see certain deficiencies in new tip growth, others lower on the plant. This has more to do with mobility than the rate at which they move through the plant, and it ties into the BER thing. N, P, K, and Mg arte very mobile in the plant, so when there is a deficiency of any of these nutrients the plant "steals" what it needs from other parts, usually older parts or parts not producing optimal returns.

S, Cu, Fe, Mn, Mo, and Z are somewhat mobile in the plant, so deficiency symptoms might appear anywhere on the plant.

Ca and B are immobile. These nutrients must be in the nutrient (respiration) stream at all times or the plant exhibits deficiency symptoms immediately. This is why BER often occurs in rapidy growing plants. The demand for Ca outstrips the plant's ability to transport enough Ca, so cells are formed improperly. More often than not it's a physiological issue, but it makes sense that damaged root tips might be a cause or contributor. Because the plant can't mobilize Ca & B and borrow it from various parts, deficiency symptoms show up in the new growth. Since periods of drab weather and/or cool temps and/or high humidity and/or soggy soil conditions can slow the nutrient (transpiration) stream, these conditions can also cause or contribute to BER.

Cool how all this stuff works, eh? ;-)

Al


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Very cool indeed Al! Thanks again for all the info. I guess I'll have to rethink the plan of mixing in bat guano, worm castings, mineral dust, and compost haphazardly this year. You saved me a lot of money lol. Do you have any recommendation to get the micro nutrients in the soil in the correct ratio?

Also is the Ca and Mg in my harder water available to the plant or do I not need to worry about correcting the ratios for that?

Thanks,
Scott


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Fri, Feb 28, 14 at 15:30

You are growing in the ground - right?

Al


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RE: NPK Confusion

Well, maybe ideally it is better to arrange every elements in correct ratios. But in real life and practice it is not possible to run a garden bed like a laboratory. In case of in ground gardening, you may have ample amounts of P, K or CA etc , that you have no control over it ; You can add certain elements but you cannot take them away. So I subscribe to the notion that plants do pick and choose and have priorities in picking and choosing, to some extent. The prioriy of plant is to grow foliage. That seems to be the building block to facilitate other functions. So maybe, that is why(probably) plants have a good appetite for nitrogen. Lets say that in a laboratory condition, instead of providing NPK at 3-1-2 ratio we provide them at 6-1-2 ratio . Are the plants going to use them at 3-1-2 ratio ?


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Sat, Mar 1, 14 at 0:48

It may not be possible for the average hobby grower to run a garden like a laboratory, but being able to recognize situations with the potential to limit your plants and eliminating the limitations to the greatest degree possible is what defines our ability as growers. If you have ample amounts of P, K, and Ca in your soil like you alluded to, there probably isn't a need to reduce the supply of those elements, but there would be advantage in altering the ratio of other nutrients in the soil solution to one that meshes nicely with the volume of what is preexisting so the plant CAN take up nutrients appropriately. For instance, if there was a high level of soluble Fe in soils, it would make acquiring Mn difficult, so to prevent an antagonistic deficiency of Mn (because of Fe in greater than luxury concentrations, you might add an appropriate source of Mn to bring the ratio back into balance, or perhaps add materials that change pH and in doing so make certain nutrients more or less available. So our gardens and containers CAN be treated like they are laboratories, and if we get it right, be better for the effort.

Making up an untested thesis to fit what we THINK we are observing seldom meshes with what we actually know to be true. Experience is at its most valuable when it's used as a practical application to justify (prove to be true) something we've already learned. Because it seems to sound good or simply because we like it is hardly reason enough to hold to an unproven thesis.

Plants do prioritize, and a plant's priority is to pass its genes down to future generations; so it stands to reason that for energy distribution, the order of priority runs first to blooms, then fruits, leaves, stems, and roots, in that order.

If you provide nutrients at a 6:1:2 ratio, the plant will WANT to use nutrients at roughly the rate provided by 3:1:2 ratio fertilizers, but will be prevented from doing so because when N is available at levels above luxury range, the plant will be taking up extra N instead of taking up the amount of (mainly) K, B, Cu, and Z it needs for normal growth - as it would if N was in balance with the rest of the nutrients plants need. You can see that excessive N also usually means complications related to deficiencies of N's antagonists.

Al


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RE: NPK Confusion

OK. So, although uptake of NPK at 3-1-2 ratio is optimal, but plants will not follow that rout necessarily. That was my point.

Second, Although the plants' ultimate mission is the survival of its gene, dictated by the genetic code (even, in mammals), but it have to develop some kind of maturity first to do that. So to get to that point it needs to grow foliage, to get ready to manufacture nutrients and develop a good root system and then come blooming and fruiting.
But if a plant does not have the resource (adequately) and it is deprived , to some extend, then it will hurry up its mission. We see this often in pot bound/root bound and Not-so-healthy plants. So that is why, uptake of nitrogen is a bigger priority for plants.Any also, MAYBE WHY, as gardeners apply more N early on and cut back on N at flowering and fruiting stage.


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RE: NPK Confusion

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Sat, Mar 1, 14 at 12:35

.... although uptake of NPK at 3-1-2 ratio is optimal, but plants will not follow that rout necessarily. That was my point. That's like agreeing that a daily multiple vitamin + a vitamin C tablet + 2 glasses of milk is an excellent way to provide certain nutrients for a child, but if you feed the child copious quantities of some other vitamin, it won't get the nutrition it needs. I think your original statement is a given, and illustrates the importance of supplying nutrients in the right ratio. This is more important in containers where the o/a fertility level needs to be more concentrated than for plants growing in the ground; this, because of the disparity in the size of the root systems.

If a plant normally uses 6 parts of nutrient A for every 2 parts of nutrient B and 4 parts of C, and you're supplying 12 parts of N to 2 and 4 parts of B and C respectively, the plant isn't going to just start using the 12:2:4 instead of the 6:2:4. It's going to use a little more A and a little less B & C - maybe something like 8:1:2. Having 1 nutrient's availability out of sync with the other nutrients impacts nutrition in ways more far-reaching than just as it relates to that 1 nutrient that's out of balance.

The reasons to avoid having anything in the soil in excess are. it unnecessarily adds to the o/a EC/TDS levels, which makes it more difficult for plants to take up water and therefore nutrients (that are dissolved in water); it can change soil pH, and an excess of 1 or more nutrients can cause deficiencies of other nutrients.

When it comes to plant nutrition, we need to let go of the idea that if a little bit is good, a little more must be better - it doesn't work that way. An excess has the same potential to limit as The difference between deficiency and toxicity of many nutrients is small.

We tend to think that N is the most important nutrient because it's most used, but cells can't form w/o Ca, and photosynthesis isn't possible w/o Mg ....... the list goes on. So why is N more important than Ca or Mg. Look at the picture holistically and you'll see that all nutrients are equally important because all are needed for normal growth. We could even make an argument that N is LESS important than many other nutrients because it's very mobile in the plant and the plant can rob its parts of N to produce new growth, even if there is no N available for uptake. That's a silly argument if you understand plant nutrition, but still, there is a lot of validity in it.

Plants don't need N exclusively for foliage, they need N in the right proportion to and along with all the other nutrients. There are a number of ends that can be accomplished by manipulating nutrition, but first we need to understand how the plant works.

Al


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RE: NPK Confusion

No Al, I am container gardening only at this point.

Thanks again,
Scott


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