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What comes first Part A or Part B when mixing nutrients? Article from UrbanGarden Mag

Discussion in 'Hydroponics' started by Chronic Monster, Jun 20, 2011.

What comes first Part A or Part B when mixing nutrients?

  1. Part A ~ 1st

  2. Part B ~ 1st

  1. Came across this article in my morning reading, was hoping to get some feedback from my fellow farmers,
    +rep for all thoughtful comments

    Know Your Nutrients: Rights and Wrongs

    Making up your nutrient solution is a regular job for hydroponic growers – and most of us probably think we know what we’re doing – right? Just like how most of us are familiar with the phrase, “falling at the last hurdle”! Because unless you know exactly how to deploy your hydroponic nutrients, that’s exactly what you could be doing. Shortcuts are all too tempting to fall into when you’ve been growing for a while. And if you’re not making up your nutrient solution properly you could well be impeding the performance of your nutrients. This is particularly important for growers using multi-part nutrients (e.g. two-parts and three-parts) as these can be more complex than many gardeners think.

    Bob Taylor, chief chemist of Flairform, explains why…

    Multi-part nutrient guidelines

    1. Do not combine concentrated nutrients in too little water.

    Think about it for a second. Two and three-part nutrients come in separate “parts” for a reason! If they come into contact with each other when still concentrated (or in too little water) you will see a white precipitate form (Fig 3.1) and, depending on the formulation, this can happen well within a minute or so. Try this for yourself – mix an equal volume of each part in a glass, undiluted. You’ll quickly see precipitate start to form. The majority of the precipitate is typically calcium sulfate. Now, add more water and see if it will dissolve. The longer you delay dilution, the more difficult (or impossible) dissolution becomes. Your plants can only use nutrients that are fully dissolved in the water. So all that precipitate represents food that your plants can no longer access. Along with poor pH control, this is a cause of the white precipitate within the body of the nutrient (Fig 3.6b). Therefore, to prevent this, always add the majority of water before combining nutrients. Additionally, always stir well before each subsequent part is added. Note that the source of white precipitate above the water line, on the surface of media and equipment (e.g. clay pebbles), is salt deposition from evaporation. Notably, the amount of precipitation from this source is greater at higher (EC) nutrient concentration.

    2. Which comes first: A or B?

    My advice is that you should always add the part containing the phosphate first. This is because the addition sequence of each nutrient ‘part’ can affect nutrient stability, particularly if your water has high alkalinity. “Alkalinity” (bicarbonate & carbonate) is the component of natural waters that causes high pH. Adding the nutrient dose to high alkalinity water can decrease the stability of several nutrient species (including calcium, sulfate, iron, copper, manganese, zinc). Therefore, rather than trying to pre-adjust the pH of the water (often a very difficult task – pH adjustment is better done after all nutrients and additives have been added), it is preferable to first add that part of the nutrient that lowers pH the most. This is usually the part that contains the phosphate. In two-part nutrients this is usually part “B”. So there you have it. “B” comes before “A” after all! However, make sure you check with your particular brand. Note that the “part” without any phosphate will normally have relatively little impact on pH. Secondly, it usually contains the iron, which is highly unstable at pH levels much above ~6.5. Note: in three-part nutrients the phosphate is sometimes dispersed across two bottles. Therefore, if you really want to be accurate, determine which contains the highest concentration of phosphate, and add that first.

    3. Add equal amounts of each part.

    Avoid “roughly measuring” out the nutrient dose. An excess of one nutrient species does not compensate for deficiencies in another. In the case of a two-part, ‘under’ dosing part ‘B’ (for example) could cause a deficiency in over half the nutrients required (i.e. P, K, S and all of the trace elements excluding iron). This problem is compounded with two and three-parts because the dose volumes for each part will be roughly one-half to one-third (respectively) of what it would otherwise be if using a one-part. Therefore, without appropriate measuring equipment, when small tank volumes are being used the dosing error can be significant.

    To some growers, the additional complexity of two and three-part formulations is an interesting challenge. To others, who want to make their lives a little simpler, the idea of dosing using multiple parts isn’t so appealing. Certainly, using a high quality one-part formula readily ensures an optimal balance of nutrients and, as a result, one-part nutrient products are increasing in appeal among growers.

    Whatever type of nutrient you prefer, you should always follow these dosing guidelines:

    Thoroughly stir the nutrient.

    Always stir immediately after the addition of nutrient, additives or top-up water. Doing so will eliminate high zonal concentrations of the less soluble nutrient species. Further, it removes zones of extreme pH (either high or low), thereby preventing the destabilization of nutrients that are unstable outside of the optimum pH window of 5.0-6.5 (Fig 1.11).

    vBe diligent with pH.
    This is probably the most crucial area of nutrient management.

    Be cautious when using additives with a high pH.

    I don’t mean to be alarmist here as it’s important to note that essentially all additives will affect nutrient pH at least slightly. The best technique to adopt with those that elevate pH significantly (e.g. silica, PK additives) is to add them to the water and adjust the pH down to ~6 prior to adding the nutrient. Another less preferred but common alternative is to pre-dilute the additive in a separate volume of raw water prior to adding to the nutrient solution, then quickly lower the pH to below 6.5 once this solution is added. Note that a white cloudy precipitate (calcium sulfate) may form when the pre-diluted additive initially merges with the nutrient solution (Fig 3.6a). However, because the initial particle size of the precipitate is small, it will usually re-dissolve if the pH is immediately re-adjusted.
  2. sfzoo


    I always mix A first. My logic was they labeled it 'A'...which comes before 'B' in most cases.

    he makes an interesting point about phosphate lowering pH and its relation to stability of the trace elements.

    If it is in fact true, that alkaline waters lead to unstable trace elements(he mentions iron among others that are unstable above 6.5)..then we should be trying to reduce the pH first w/ nutrients that have this effect(as opposed to pH adjusters), usually part B. Which begs the question, why did the company label it B, and not A?


    i've noticed that when i add my silica, usually at the end, i'll notice a white cloud. It mixes up well enough that i won't see it soon after, anyone notice this too?
    Chronic Monster likes this.
  3. I actually have a different opinion on a few things and would like to share them.

    I do not think nutrient mixing is beyond anyone. If you can add and subtract I could teach you how to calculate the levels on an infinite number of products mixed at any level. I do not think growers under estimate the complexity of nutrient mixing but I do believe that many find the simple approach more to their liking.

    I spent nearly 30 months in research before uncovering the truth on nutrients and how it all works. It is just a simple thing but you don't know what you don't know and this is one of those things hydroponic growers really should know.

    ppm = [(Element%) x (10,000) x (ml of nutrient)] / [(ml of water) + (ml of nutrient)]

    The P on a label represents P2O5, which is 44% Phosphorus. To get the true ppm of phosphorus multiple the final value by 0.44.
    The same thing goes for the K on the label representing K2O. This is 83% Potassium, so multiply by 0.83 to get this number.

    Products that contain high levels of Nitrogen or Calcium will generally produce a higher tested EC than you will predict using a calculator and 500 conversion. Products that contain high levels of phosphorus will test a lower EC than predicted. Most A+B systems test around x1.6 higher than the predicted ppm on a 500 conversion. This includes unlisted elements, trace, and just imperfect testing equipment (as the nutrient companies can base their levels on the mass of salt to volume of water, but are not required to list everything).

    I know this might sound totally crazy but perhaps the companies that made the nutrients know what they are talking about and put them as A+B for a reason. One before the other from their perspective.

    I think the reasoning here is that the part A, generally a Cal Nitrate, contains low levels of the more chemically reactive elements Phosphorus, Magnesium, and Sulfur. The part A will reduce the pH of the solution, at 5ml per gallon I see a drop of about 0.6pH of the solution, so they are both acidic. Perhaps by taking your alkaline tap water from 7.0+ to down under 6.8pH that the addition of a more acidic solution, the phosphorus dominant one, results in a less of "adding an acid to a base" reaction causing precipitates (even if only short lived).

    This sounds like some bizarre ass advice considering that most every A+B growers adds the A first with no trouble. Considering all the people just on Canna and AN Sensi... I dunno... I'm not buying this.

    I think this is more a result of A+B systems holding a grower into a very specific ratio of elements for the entire grow forcing them to supplement the system in order to alter these ratios if they are not appropriate for their strain "out of the box." Realizing that we are basically mixing 2 parts into a 1-part solution, many growers are opting for other 1 part solutions that have good results and a balanced ratio, like CNS 17. These systems sell $20 on the gallon, while $25 will only net you 1L of A and 1L of B, and despite being less concentrated than the A+B system we still get about twice the elements for the same price using the same total number of ml per gallon.

    It just makes more sense if you're going to be supplementing your system not to be messing with two extremely reactive products before tossing in more Cal-nitrate, phosphates, or magnesium. For people who decide they don't want to mess with too many extra bottles of crap they find that 3-part GMB systems offer very decent control over each element ppm when used in different ratios. Given the proven track record in cost efficiency and results this puts the power back into the gardeners hands.

    3-part systems are superior to 1-part systems in the reduced need for supplements... but you need 2 extra bottle which is the same as two extra supplements. Essentially, a 3-part is just a 1-part system with two well designed additions and that makes them a very good choice for any hydro grower who understands their plants and the element ppm requirements.

    I have found A+B systems to be more work than you need to do, more money than you need to spend, and to provide too little control over your profiles despite having good results. If you find an A+B you like, then by all means, stick with it! Personally, I feel my growing talents evolving out of this genre.

    This is all good advice I can get behind. I never knew that white cloud was calcium sulfate. I think I might start adding my Silicate before adding my Epsom Salts to the reservoir to keep the amount of available sulfate minimized. Might even start doing that before the Bloom component later in flowering.

    An interesting read. Thanks for posting.

    :banana1sv6: <-- right?
    Chronic Monster likes this.
  4. jyip


    Interestin thread,, i think they r labeled, a,b, and watnot 4 a reason,,, but i have been wronga a zillion times or more...

    i do know u should mix ur nutes ina small amount of water and then pour the into res do to reactions n stuff...

    good info chronicmonster
    Chronic Monster likes this.
  5. swisscheese

    swisscheese Guest

    I get the white silica cloud when I add it to my nutes. Also thought I read somewhere that I shouldn't use phosphoric acid as a ph down after adding the silica. Not sure.
    Chronic Monster likes this.