How does salt build up occur?

Hi. Can someone explain to me how salt build up occurs in the media? Is it because of ph fluctuations or feeding at a high strength when the plant doesn’t need that much? or is it due to feeding too many times in a row instead of doing a watering every couple of feedings? I just need to know how salt build up occurs and is there more than one way that salt build up can happen. any info is greatly appreciated thanks

A lot of nutes are salt based some more than others. Most nutrient lines that are salt based recommended flushing every so often and will say it on the feed schedule chart. If you fed them so you didn’t need to flush they wouldn’t be getting enough


Synthetic nutrients are salt based and are delivered in a solution as dissolved solids. Those salts solidify and bond to the soil material over time.


Im using advanced nutrients MGB ph perfect are those considered synthetic?

Im thinking of switching to biobizz line of nutes and media. Since its all organic, can i basically feed them with every watering?

Unless it has that, its synthetic.

yeah the nutes im using are not organic but biobizz has the certificate. Guess I’ll be switching for my next grow. Thanks :slight_smile:

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This is the ingredient list for PH Perfect Grow
Ingredients: Potassium nitrate, magnesium sulfate, monopotassium phosphate, ammonium sulfate and potassium sulfate.
You need to refer to bottle’s label for %
Info from the products safety data sheet

To a chemist, salt is generic term for a compound. Salt based just means it uses these. Salt buildup means there is ecxess. It can be for several reasons like too much, lockout, or coming out of suspension.

Im curious as to what issue you’re trying to correct? There are a lot of issues that simply switching from synthetic to organic won’t fix.

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I came here to say this. “Salt” the way we use it in gardening is not “salt” the way we understand it generally. Salt, sodium chloride, is actually really toxic for plants. While “salt” is an inconvenience which can manifest much larger issues. It is often prevented by watering to runoff - which reduces the amount of expended nutrients (salts) in the soil.

Here’s a little tidbit from the internet generally;

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The problem in having is that every time I feed my runoff ec keeps going up. last thursday i gave it a feeding at 1.58 EC and runoff came back at 1.66EC. On Friday I gave it the same feeding and runoff came back at 2.06EC so im not sure why it keeps going up. Does mean the plant is not eating?

There are many forms of salt. Perhaps a better term in minerals.

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Livestock industry they are called trace minerals.

Your runoff numbers are not at a point that can harm plants but more ‘salts’ are going in than coming out. Generally, for optimum feeding one would monitor runoff until the numbers hit a point that tells you to either run water only until it drops or to perform a flush.

Example: feeding at 2.0 EC in, out is 2.2. Next feeding is 2.5: call that your ‘trigger’ point. Go to water only until EC drops back below 2.0 then resume feeding.

Or, seeing runoff numbers going up; reduce input EC and feed every watering.

The plant will uptake nutrients at different rates depending on the life cycle of the plant and the environment it’s in. Lights, temps, VPD, airflow etc. all play a role in nutrient uptake.


To a farmer, salt buildup doesnt allow nitrogen uptake.

All roots go through osmosis of some type, simple to me, roots drink water, with salt build up, its hatd to get a drink, thus no nutes,

But isnt 2.2 already a bit too high? With what I’ve read from this forum and other forums, you normally dont want to go over 1000ppm (2.0ec) So why do I want to increase the next feed to 2.5 if runoff is already at 2.2?

Depends on element in excess. Most of the time this isn’t an issue with nitrogen. Download Mulders chart to which elements antagonize and stimulate others.


It occurs due to drainage or lack of. Why are mediums so talked about. If i have read and learned from you peeps, straight coco isnt a soil. And when used without personal addittives does not have the issues of salt buildups.

Well actually it does: coco tends to sequester calcium and magnesium which is why many buffer their coco with cal mag before use.

This depends on a lot of factors including age and size of plant, light intensity and environment. Soil for example if measured will regularly exceed 10 EC but won’t harm plants. In soilless media this number goes way down: my usual advice is to feed in coco until runoff hits around 4.0 then water only until it hits 2.0. Most cannabis plants can generally tolerate that.

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