Question about Phosphorus and Sulphur Concentration

jamesvladOctober 30, 2010

A lot of commercial blends pretend to have a high phsophorus concentration for a bloom stage, about 90 ppm or more.

Some people say that in a bloom stage the plant need more phosphorus.

But according to most sources the normal phosphorus concentration is between 30 - 40 ppm of phosphorus. A cocopeat recipe says 37 ppm is enough including in the "bloom stage".

How much phosphorus a tomato plant need in the bloom stage? Is really necesary to rise the phosphorus? Or is just a marketing trick?

For a bell pepper how much phosphorus is necessary?

Another question:

What is the maximum sulphur concentration? Where the tocixity begins?

Last question (sorry):

When we prepare nutrient solution of 40 ppm of phosphorus, this is the "initial concentration", right? Because if we change the nutrient solution every two weeks, when the first week has past, then the phosphorus concentration could be 20 ppm, because the plants are consuming nutrients. I can�t measure the phosphorus concentration, only the total dissolved solids and electrical conductivity. So, I can�t guess how much phosphorus I need to add to mantain the 40 ppm of phosphorus.

Thanks in advance.

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Hi James,

Right, there is quite a contradiction in various information and there has been some confusion about this part for a while. As for the actual needs and uptake of phosphorus by nearly all plants, very little is indeed sufficient. What "science" says is actually needed by plants (simulating a natural soil) turns around 25-30 ppm only. All classical and "historical" formulations use these low amounts as well. The recent but actually contested and somewhat refuted "trend" of adding much higher amounts of phosphorus, up to 90 ppm and even higher is a story of it's own, and I would only give my opinion if explicitly asked:-)

And yet, the phosphorus component (if provided by Monopotassium Phosphate) has not only the role of providing the phosphorus, but the said component also plays a role in acidity and buffering part of the formulation. That is why with a more alkaline base water signature, you can actually go up to 50 ppm if needed. I am not using any different phosphorus proportion for any plant's "blooming stage" and neither with my tomatoes. There is no scientific evidence, that plants need notably higher amounts of phosphorus during bloom or fruiting stage either. In a classical scenario, some extra phosphorus is simply and always provided by increasing the concentration.

Bell peppers can be grown with "standard amounts" of phosphorus as well. But with any pepper formula I would tease out the maximum allowed (before antagonism with calcium may occur) and that means that 50 ppm is still safe but I have been risking 60 ppm with good results when feeding at high concentrations.

Sulphur concentration is usually not a problem as maximal levels before toxicity are relatively high - by the textbook it's as much as 300 ppm. In the context of classical nutrient making, 50 ppm of Magnesium is a recommended maximum, and the relative Sulfur content (provided with Magnesium Sulfate) is thus still safe. In case of use of sulphuric acid I'd recommend to not actually tickle out the 300 ppm but to stay safe under 250 ppm.

Last question: as plants only need and take up little amounts of phosphorus anyway, you in fact don't need to worry about it running short in your solution over time. In case you run a 'filling' for 2 weeks, you most certainly will top off during that period and hence will add some 'fresh' phosphorus as well. In fact the phosphorus part, even if using it in conservatively low amounts - is not exactly what may most likely be missing over time.

Allow me to add a recommendation here: when calculating a nutrient formula, keep in mind that you may alter the concentration during growth. Especially with tomatoes, you may start at only 1.5 mS/cm (for seedlings) and end up with perhaps 2.5 or even 3+ mS/cm - in some case you may even test a rather aggressive feeding strategy and increase even more. Now as for the phosphorus part, - if starting with 50 ppm - you'd obviously end up with the double or the triple. Hence if using the same formula during all stages, but increasing nutrient strength, - keep in mind that you increase all elemental ppm, including phosphorus. In such case, you obviously go with the minimum. If recalculating the formula for each stage- and most importantly according to the respective concentration you use, keep P between 35 and 50 for a more "acidic" formulation (with less pH down correction), and between 25 and 35 for a traditional/conservative (usually with more pH down correction) formulation. If using as much as 50 ppm of P anyway, there is absolutely no need to increase it for the "bloom stage".

Hope this explains it and helps. ;-)

    Bookmark   November 1, 2010 at 7:50AM
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Thanks Lucas. It seems logic to me your explanation. I will reduce the phosphorus concentration to 30. This will reduce cost, obviously a very important factor (Here a bell pepper cost US$0.15 sometimes).
I hope this information can help anyone with the same doubts.
Thanks again.

    Bookmark   November 3, 2010 at 10:46PM
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Eres siempre bienvenido, James! ;-)

30 ppm is a good compromise, I guess. And yes cost factor is what actually brought me to one clue. In commercial growing formulas (if you have insight of what commercial growers are actually using) there is indeed use of much less phosphorus. And in these applications when dealing with thousands of liters, they focus on sufficiency for the same reason.

But you should still keep in mind the acidic buffer ability of monopotassium phosphate that you can juggle around a bit with. Hence you may try the effect of 35-40 on pH in case you want more buffered acidity. There is even one case, where a "recognized manufacturer" came to the insight that in a balanced formula there is indeed no need for high phosphorus, - and they changed their formula accordingly. But with the result, that (as I have heard) many customers struggle with keeping their pH down with the "new and improved formula" ;-)


    Bookmark   November 4, 2010 at 1:46AM
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(US$0.15) That's cheep, I live in the US, and they range from $0.50 to $0.99 ea for green bell peppers, and red, yellow and orange go for as much as $1.99 each. Are you sure that isn't a typo?

    Bookmark   November 4, 2010 at 4:11AM
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According to James' location it's totally plausible, - Bell peppers are not exactly a common vegetable here in Norther Thailand, and yet they are not much more expensive as in El Salvador, which still is one of the poorest countries at the 'Medio Americas'. At my place I can buy as much vegetables as I can barely pack on my bike (bags hanging from both sides of the handlebars included;-), for a few bucks. Very cheap vegetables and fruits, staple food, and standard meals at street cook-shops are in fact a general rule for any emergent country and those under development located at the tropics. Incredibly cheap for anyone who hasn't seen it, even for regular tourists who get a bit off the "gringo or the farang trail" for a change, or get lost on the way back to their resort. LOL

Here's the deal: if farm workers earn only - let's say 25-40 USD (or even less at the far country side), a week - that obviously keeps vegetable prices very low. Btw: any coolie at some country side farm here, makes between 3 and 4 USD a day only. Land prices are relatively cheap and transport is, because in this domain often rudimentary and without any notable logistic- or administrative expenses, cheap as well.

    Bookmark   November 4, 2010 at 5:05AM
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I don't see a problem with any comparison.
$1 united states dollar", is $1 us dollar. No mater what part of the world you live in. If the exchange rate differs in your country (whatever country that is), one USD (united states dollar) still equals one USD. So if there's a problem in the price quoted, it can only be in the interpretation of it. That's why I figure it's a typo.

look at the math. How can One USD (united states dollar), possibly equal less than 1/20th of that at the same time (in the same country). You are saying that "$1 united states dollar' is only worth $0.15 cents, at the same time it's worth one dollar. When you compare one USD to one USD you come up with one USD .

Now if you were saying that one US dollar was only worth 15 cents in that country, that's fine. But it is not one USD anymore. Case in point one dollar in Canadian is diffident than it is in USD. Sure the prices vary, even in different country's. But bottom line you don't make the prices. Even locally they very quite a bit, even season to season.

So you think you know (and have control) of what we pay for produce half way around the world? If so Then I know what you pay also, The way I see it your country is so pour and ignorant that you pay $.047 for one green bean (3 inches long). How do you like that? Am I correct?

I'm the one that goes to the grocery store here, you have no right to decide (nor brain) as to how much things cost here.
USD'[s can be spent everywhere in the world, but are always worth the same when compared to USD's because they are, but have a diffident conversion rate when compared to local currency.

    Bookmark   November 4, 2010 at 7:50AM
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Homehydro, the problem is not the US dollar comparison here in El Salvador. The minimun wage for a countryman is about US$100 a month. In the city the minimun wage is about US$200. Half of the people is living in poverty.
Here a cell phone (with mp3 playing only) cost around US$70.00, in the USA you can get internet and gps for the same price.
Internet for your home (512 kbs) cost US$25.00 a month.

And yes, there are a lot of ignorant people here, I know only 1 person that has hydroponic plants. It looks like nobody wants to know about.

But I can't get how the people can spend US$100.00 for a homemade hydroponic system to produce not more than 6 pounds of tomatoes in one year. Spend US$100.00 to obtain US$5.00 is not a real way to manage money. So if we are going to use hydroponics we have to know what we are doing.

There are a lot of ignorant people around the world, and the USA is not the exception. An example: The attack to the World Trade Center, Irak and Afganistan wars, "The war against terrorism". All the world knew the truth, gringos were the last people to know, always because they think they live in another planet. And of course the Obama fraud, the only "choice" is to vote for republicans: Bush and his friends (Bin Laden including) again ;-)

So, my friend, around the world (including USA) there is abundance of ignorance, more abundance than money, health and well-being.

"I know that I know nothing" Socrates

    Bookmark   November 4, 2010 at 10:21AM
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Sorry, just so you know my last post was not speaking to you when when I was being harsh. What you are referring to is the conversion rate. Yes, there are a lot of country's that a USD goes further than here. That does not make them poor country's (at least in my opinion), it's just about the conversion rate. For instance where I live there are a lot of people that cross the boarder into Mexico (about a 3 hr drive) to buy things, simply because of the conversion rate they can get them much cheaper there using the USD (especially medication). Anyhow I have no idea what the conversion rate is in El Salvador, or even Mexico or any other country for that matter. That's basically why I asked if that was a typo, because $0.15 cents for a bell pepper (even a green one) is cheep to me.

As you mentioned even within the same country, it's not just the conversion rate, but also supply and demand can drive prices no matter what country's money it is being compared to. A USD is a USD, a Peso is a Peso, a Euro is a Euro. But going by what you stated, it appears that technology is expensive in El Salvador, much more so than it is here in the US (goes back to supply and demand). I would like to buy my veggies in your country, but the added shipping cost would make that pointless.

    Bookmark   November 4, 2010 at 7:08PM
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First of all, homehydro - don't ever make people say things in the way you have misunderstood them and hence in a way that they haven't actually said them. No-one ever made the maths with any currency as you demonstrate them, - they are merely your own "homemade" assumptions, reflections and unfortunately wrong conclusions. It is absurd to say "you say that..... " followed by what no-one has ever said, but what YOU extrapolate!

I have been trying to explain things moderately but it clearly sounds like if different prices for various goods linked to different life standards and dire socio-economical conditions in other countries than yours, are way over your head.

Vegetable and fruit prices as others, are simply cheaper (and actually that low) because they are produced and sold cheaper locally. The conversion rate doesn't even matter. Telling prices in USD from my side is just a good turn to make the maths easier. I could tell prices in Baht (and James could use Colon) instead but you would probably get completely lost in conversion then. Different market value of various produce in countries under development is also linked to higher competition in a most favourable climate where "anyone" can grow Bell peppers (for example) in their own garden or patch of land all year long.

Most importantly: In any country with a much lower life standard, various locally produced goods are obviously cheaper in relation to any imported goods. Especially more advanced technology or products that aren't exactly of high demand (including hydroponic supply or specific chemicals) tend to be even more pricy. They may hence turn out to be much more expensive as in the country where they are produced. Now, simply take higher prices for hydroponic material - and way lower prices for produced vegetables and connect the dots!

If you can't make these connections and draw the right conclusions by yourself, at least be smart enough to avoid to have a rather silly showdown on the topic with people who do it naturally as part of their daily life. Instead LISTEN and TRUST (and simply accept) what people from countries with a very different live standard and price range of various goods can tell you. They may have romped around it for many years, while you barely have discovered it in it's amplitude - and not even remotely understood it.

    Bookmark   November 4, 2010 at 11:00PM
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There is differently something called a conversion rate for money, even if you and the people in your country don't want to know about it. Again you are just full of hot air as usual. Of coarse there are local economical and environmental considerations that drive the price for products, that's obviously well known. Do you think you are the only person smart enough to know that? Obviously you and your ego think I'm two stupid to know that. Prices can even vary within the same country and location, even with different seasons. You can even walk across the street into a different store, and the price for the same item there can be different. Do I really need to go through the whole list of variables?

None of that was part of my question, so how does any of that change my original question? I simply stated that I live in the country that the the money equivalent was being compared to. Then I stated what the prices go for locally to me in that same money equivalent. Then I asked if that was a typo (because it struck me as odd). That's it! Then you chimed in as usual like you are the only one on the planet that has a brain. Bottom line you just wanted to belittle me, and to top that off you were so STUPID you didn't even answer my QUESTION. After all how could you? You were not the one that made the statement in the first place. You just wanted to blow your smoke, and pretend like you matter.

P.S. Sorry, you don't get the benefit of the doubt with me any more. You have proven time and time again what your intentions are.

    Bookmark   November 5, 2010 at 3:17AM
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just one thing, here in El Salvador we use US dollars! We used to use "Colon", about 8 years ago the economy was "dollarized", by some ignorant "economist" and "politicians"
There is no conversion rate. The people earn the money in dollars and spend it in dollars.

    Bookmark   November 6, 2010 at 12:11PM
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Your question, homehydro was promptly and amply answered by me and by Jamesvlad. Even in my first sentence - in simplicity first and in detail eventually. The prices ARE THAT LOW and it has NOTHING to do with any of your speculative excursions. It is certainly not about conversion rates as their is any in the "original case" (as fully confirmed by Jamesvlad). I am hopefully not the only-one with a brain here, but you seem to be the one and only with a severe cognition disorder. You just don't want to grab anything that doesn't fit in your own preconceptions in the first place. You are truly ignorant, stubborn and as slow as a snail - so do not try to blame others for being average and hence smarter.

PS: I give a flattened out and dehydrated piece of Yak Dung about what I may get from you. As I never ever got anything intelligent, use- or helpful from your side since you showed up at this place.

    Bookmark   November 7, 2010 at 3:26AM
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Just another bunch of hot air. and again you did NOT answer the question.

"According to James' location it's totally plausible"

That is not a "YES" it is a typo, nor is it a "NO" it is not a typo. That was my question (STUPID), and my only question. Your reply is simply your guess at the answer from your inflated ego. "Totally Plausible" is not confirmation. I already knew it was "totally Plausible," and why it's totally Plausible. I just simply wanted to know if it was accurate (STUPID).

P.S. That makes us even because I have never ever gotten anything "use- or helpful" from you either. Just a bunch of hot air and ego. I'm glad you never got anything "use- or helpful" from me because your just not worth helping.

    Bookmark   November 7, 2010 at 5:03AM
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