Quick flush?

[ppm Charlie]

How does one know if salts are building up? I have reused soil over and over and over yet I don't see a difference from one grow to the next unless I run new genetics....even when using Fox Farms for nutrients. I no longer use the brand as I grow in soil, coco, hydro and find it's easier on me to use 1 brand for all 3 mediums. I know I could use Fox Farm for hydroponic grows but I personally don't like how it turns my root zones a dyed brown color. If you are watering correctly with run off, is a flush even actually needed since you hypothetically are flushing it little by little with each watering?

I believe if you see "white" powdered buildup in the drain holes of the pot, in the lower part of the fabric of a fab pot, or white powdered buildup on the surface of the soil media, one would assume that salt buildup is occurring. Salt buildup can occur for a number of reasons, however, the most common reasons are over-nuting without flushing to 20% overflow waste or using mix water high in TDS (i.e. hard water - TDS = 250+ with dissolved limestone, bicarbinate and carbonate minerals mainly).

In a purely simple and ideal sense, salt buildup should be able to be avoided in soilless systems (non-organic soils - pure peat/perlite or pure coco/perlite) by watering/nute to 20% overflow to waste. However, each situation is different. I believe an RO, distilled or "clean water" flush once in a while possibly helps in some situations where a grower is using only nutes with no organic contribution (composted material).

For organically grow crops in containers, flushing probably has little effect on the soil media because the fertilizer (cations, organically derived nutes) are bound more tightly in the compost and organic substrate by bacteria and fungi. Those organically derived nutes cannot be washed away by simple 3X "flushing". It would take a vast amount of water and a long time to rid an organic compost soil of it's organically derived nutes.

Generally, it is my experience that re-using soilless media is not that good an idea (I just dump mine in the outdoor garden or compost pile). In a system of soilless media (pure peat/perlite or pure coco/perlite) where chemical nutes are used, it is possible to re-use the soilless media, however, the media must be adequately flushed of the residual nutes that are left over so that it is returned to it's pre-nutrified state. That's a lot of work. Easier to buy new soilless media.

 

[ppm Charlie]

Tap water from the City of Detroit Water & Sewerage Department. They provide water for a large portion of the multi-county southeast corner of Michigan, about 700,000 residential customers plus businesses. Water comes from intakes on the Saint Clair River and in Lake Saint Clair with back-up intakes in the upper Detroit River just below where Lake Saint Clair empties into the river.

Rooting around with google searches and the TDS was running about 140 in 2013 and varied a bit depending on which fresh water plant was tested. Probably more recent testing and numbers but I figure that is close enough for now and I did not want to go through even more pdf files.

Go online an look at the water system's most recent tests for the EPA certification. Public water systems must test routinely to keep certification. You will find all you want to know there. Or, you could just call the water plant and ask for the results.

 

[Melville Hobbes]

Interesting arguments on both sides........
But here is my question - Would it do any harm to flush??

You can damage the roots through osmotic stress, but it should be minimal, and if you are getting lockouts due to buildup you're better off flushing. The plant can recover from the stress more easily.

Edit: I misremembered (took a cup and a half of coffee to remind me)-It was turgor pressure, not osmotic stress. Still don't have the references though.

 

[Krissi Carbone]

This has become too abrasive a thread lol I'm scared to comment on anything so I plead the 5th! I'm sure there is a middle ground here somewhere

 

[ppm Charlie]

You can damage the roots through osmotic stress, but it should be minimal, and if you are getting lockouts due to buildup you're better off flushing. The plant can recover from the stress more easily.

Maybe...can you point to past research to supports this? I have never understood that osmotic stress on roots is a problem where water is in abundance - maybe for drought stress osmotic root stress is a factor, not for flushing though where there is an abundance of water.

 

[ppm Charlie]

This has become too abrasive a thread lol I'm scared to comment on anything so I plead the 5th! I'm sure there is a middle ground here somewhere

Ohhh...come on @Krissi1982 ! Everyone's "two-cents" is valuable. Spill, girl!

I think it is clear though that there is not general agreement one way or the other.

 

[Emilya Green]

In a purely simple and ideal sense, salt buildup should be able to be avoided in soilless systems (non-organic compost soils - pure peat/perlite or pure coco/perlite) by watering/nute to 20% overflow to waste. However, each situation is different. I believe an RO, distilled or "clean water" flush once in a while possibly helps in some situations where a grower is using only nutes with no organic contribution (composted material).

I have recently started to respond when I see this 20% advice, after I took the math apart and looked more carefully at the claim.

Let's assume for the sake of the argument that we all agree that it takes a 3x the container sized flush to properly clear the salts that have been building up. If we assume that creating extra runoff over time is as efficient as doing a single setting flush, lets examine carefully what we are proposing.

It will take 5x 20% runoffs sessions to equal 1 container of flush, or 15 watering sessions to create the equivalent of a 3x flush. Each time you do a nute pass in one of these 15 watering sessions, you add back more salt... something that the fresh water 1 session 3x flush does not add.

Conclusion: A 20% extra runoff watering does NOT properly flush your soil. Sorry. It is a myth.

 

[Melville Hobbes]

Maybe...can you point to past research to supports this? I have never understood that osmotic stress on roots is a problem where water is in abundance - maybe for drought stress osmotic root stress is a factor, not for flushing though where there is an abundance of water.

Sorry, no. I didn't find the info myself. I got it from a post on another forum where a member had posted screenshots of a paper. Guess I should have said that.

 

[Emilya Green]

sometimes old science can get in the way of common sense. It is times like these, that we probably need to re-examine the old science with fresh data. It is my point of view that the drought stress idea needs to be re-examined, especially when the scientific papers describing it are talking about field crops and not container crops.

 

[Krissi Carbone]

The sun will come out tomorrow....

I personally try not to flush at all unless it is absolutely necessary so I have no good input to give. I have not researched this nor do have I worked at the local water department and seen numbers first hand...I am merely here to listen to all this information and provide comic relief.

I do know one thing...the main goal was/is to help out @Frazer so for that, F, I apologize I have nothing to offer you

 

[ppm Charlie]

I have recently started to respond when I see this 20% advice, after I took the math apart and looked more carefully at the claim.

Let's assume for the sake of the argument that we all agree that it takes a 3x the container sized flush to properly clear the salts that have been building up. If we assume that creating extra runoff over time is as efficient as doing a single setting flush, lets examine carefully what we are proposing.

It will take 5x 20% runoffs sessions to equal 1 container of flush, or 15 watering sessions to create the equivalent of a 3x flush. Each time you do a nute pass in one of these 15 watering sessions, you add back more salt... something that the fresh water 1 session 3x flush does not add.

Conclusion: A 20% extra runoff watering does NOT properly flush your soil. Sorry. It is a myth.

I think when people "flush" in soilless situations they flush repeatedly in one session 3X, 5X, 10X, etc., and measure TDS the effluent water overflow waste water. When that TDS number is reduced significantly they quit the flush. I do not think flushing in an "organic mix soil" has much effect at all.

 

[DiamondLevelGrower]

The real problem is.....there's 2 different kinds of "flushes" that are being talked about and many might think one is being talked about and not the other. Flushing salts = good when done right at the right times....flushing nutrients final 2 weeks of flower = Bro science and borderline plant neglect.

 

[Emilya Green]

I think when people "flush" in soilless situations they flush repeatedly in one session 3X, 5X, 10X, etc., and measure TDS the effluent water overflow waste water. When that TDS number is reduced significantly they quit the flush. I do not think flushing in an "organic mix soil" has much effect at all.

Why do you think that? Salt can dissolve in water in soil just as easily as in a soilless mix.

 

[Emilya Green]

The real problem is.....there's 2 different kinds of "flushes" that are being talked about and many might think one is being talked about and not the other. Flushing salts = good when done right at the right times....flushing nutrients final 2 weeks of flower = Bro science and borderline plant neglect.

it is confusing isn't it? It helps if you call the thing at the end forced starvation and let flush retain its original meaning, flushing the soil with 3x the container size.

 

[DiamondLevelGrower]

it is confusing isn't it? It helps if you call the thing at the end forced starvation and let flush retain its original meaning, flushing the soil with 3x the container size.

Mic Drop!!!

 

[ppm Charlie]

sometimes old science can get in the way of common sense. It is times like these, that we probably need to re-examine the old science with fresh data. It is my point of view that the drought stress idea needs to be re-examined, especially when the scientific papers describing it are talking about field crops and not container crops.

Regarding the 20% to overflow waste - I think I would like to see solid evidence of overflow not working to minimize salt buildup. If you can point to researched evidence that says that 20% overflow to waste is not effective in reducing salt buildup - I would be sold. However, if it is just your personal opinion ("common sense") then I do not think you are as persuasive as you can be. I agree with you on the field-crop vs container assertion. Where are the drought studies of crops and, specifically cannabis crops, for drought stress iideas n containers?

 

[ppm Charlie]

The sun will come out tomorrow....

I personally try not to flush at all unless it is absolutely necessary so I have no good input to give. I have not researched this nor do have I worked at the local water department and seen numbers first hand...I am merely here to listen to all this information and provide comic relief.

I do know one thing...the main goal was/is to help out @Frazer so for that, F, I apologize I have nothing to offer you

I want more comic relief! @Krissi1982 ! Any wild two-year-old-boy stories to make us all happy and laughing again? When ever I see one of those "off-topics" it just warms my heart because I remember helping raise my grandson and that was a PILE of work!

 

[ppm Charlie]

it is confusing isn't it? It helps if you call the thing at the end forced starvation and let flush retain its original meaning, flushing the soil with 3x the container size.

Very good comment - we all need to define terms so we are all on the same page. I like the term "forced starvation".

 

[ppm Charlie]

Sooo... @Emilya ...do you flush at all in your organic garden at any point before harvest? What are your recommendations? I am interested because I am using GeoFlora products on some of my crop-horde and need the experienced advise you can provide. Should I feed them all the way to harvest or slack off top-dress feedings toward harvest?

I know GeoFlora is the easy way to go and that you "build" your organic soils individually, piece-by-piece - however - as a beginner here...inquiring minds want to know. Do you flush before harvest or slack off top-dress feedings before harvest?

 

[Emilya Green]

Regarding the 20% to overflow waste - I think I would like to see solid evidence of overflow not working to minimize salt buildup. If you can point to researched evidence that says that 20% overflow to waste is not effective in reducing salt buildup - I would be sold. However, if it is just your personal opinion ("common sense") then I do not think you are as persuasive as you can be. I agree with you on the field-crop vs container assertion. Where are the drought studies of crops and, specifically cannabis crops, for drought stress iideas n containers?

Charlie, I didn't say it doesnt help minimize... but can it possibly eliminate salt as well as a 3x flush? The math says it cant. Maybe 1/15 of a flush every time you water is enough to keep the salt from totally locking out nutes at the end... I am not willing to chance it when flushing is so easy to do.

Then you hit my button. You want researched documented evidence (you mean a published paper) on a plant that is illegal to grow in most of the world. Sorry Charlie (had to get that in) those papers simply do not exist... yet. I would like to think that a lot of the work, research and experiments just like the sciency crowd uses, will someday contribute to those "official" studies. Until then, you have to rely on the results found in our journals... scientific studies in their own right.