Nutrient Mixing

[Chato]

This is an article that appeared a few years ago in Urban Garden Magazine which is now no longer in publication. I thought it was worth posting as it's something many of us could learn or be reminded from. I didn't write nor take credit for this article. Chato   Original Article

 

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 (www.flairform.com), explains why…

 

Multi-part nutrient guidelines

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

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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?

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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.

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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).

 

Be 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.

[The Hash Nibbler]

Cheers Chato saw this awhile ago, but a great read.  

 

Remember to always check to see what your Nute Manufacturers recommend, as they are all different.

 

Some are Chelated, some are salt based........etc.........

 

Peace. Nibbler.

[conman]

Thanks Chato,

Very useful information there!

phosphate first, good to know.

 

Peace,

Con

[Vape]

Thanks Chato,

 

Who would have thought to put 'B' first..  ???????

 

ill be doing that from now on...  as a noobie trying Coco for the first time.. priceless info.. cheers!

 

Vape

 

Peace!

[Ford Fairlane]

Great post, thanks Chato