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Old 11-12-2017, 06:54 PM #21
mushroombrew
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Quote:
Originally Posted by Douglas.Curtis View Post
'Proper' pH depends on the type of system your plants are in.

Roots-out systems, where the roots dry out between waterings, have a natural pH drop during the dry out period. 'Proper' pH range will vary with each system but top and bottom pH (edit: of your nutrient solution) will generally be 5.5 to 6.1.

Roots-In systems, where the roots are constantly exposed to the nutrient system, do not have a 'dry out' induced pH swing. Best results are obtained by setting the pH at 5.4 and letting the pH naturally rise as the plants eat nutrients. Res size determines how fast this swing occurs. 5.4 - 5.8 is where you're going to find the best results with these systems.

Just figured I'd clarify.
I would say it is also strain dependent. Mag hungry OG's don't like 5.6(Mag valley)

I have run 5.2-5.5 and 5.8-6.0 with OG's and they perform the same.

If you do run 5.2 I suggest letting it drift up to 6.0 periodically.

Staying at any specific pH is not beneficial. As growers find out using dosers for pH control.

Lastly the higher the TDS the less pH matters. Real easy to kill plants under 600ppm if pH is off.
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Old 11-12-2017, 06:59 PM #22
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Thanks. I now measured pH of 70% coir + 30% seramis, leached with 2 times pot volume of tap water (0,2mS/cm) and 1 volume RO. It is 6.3.

In my initial post I wondered if any charts exist for coir, thinking it might well be a bit different in coir compared to the posted chart which is for a specific mix. But there is one more variable I read about here: How much available nutrient vs pH depends a lot on what molecule the ion is part of, if part of sulfate it is soluble at much higher pH than if oxide, it says.

Coir has the highest CEC of all potting mix materials per volume, and what counts for potted plants is per volume not per weight. And as Bunt said, CEC mainly affects divalent ions, most monovalent ions remain water soluble.

Testing pH of fertilized soil might be a good idea. Due to Coir and my usual fert both being a bit high on K and seramis adding to the K I decided to add some Ca+Mg (an N), found a suitable bottle called "Magne-Cal". I should buy that first before testing.
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Old 11-12-2017, 09:47 PM #23
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Quote:
Originally Posted by Douglas.Curtis View Post
'Proper' pH depends on the type of system your plants are in.

Roots-out systems, where the roots dry out between waterings, have a natural pH drop during the dry out period. 'Proper' pH range will vary with each system but top and bottom pH (edit: of your nutrient solution) will generally be 5.5 to 6.1.

Roots-In systems, where the roots are constantly exposed to the nutrient system, do not have a 'dry out' induced pH swing. Best results are obtained by setting the pH at 5.4 and letting the pH naturally rise as the plants eat nutrients. Res size determines how fast this swing occurs. 5.4 - 5.8 is where you're going to find the best results with these systems.

Just figured I'd clarify.
thanks DC this information helps.
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Old 11-12-2017, 10:41 PM #24
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Quote:
Originally Posted by mushroombrew View Post
I would say it is also strain dependent. Mag hungry OG's don't like 5.6(Mag valley)

I have run 5.2-5.5 and 5.8-6.0 with OG's and they perform the same.

If you do run 5.2 I suggest letting it drift up to 6.0 periodically.
I always use a pH drift from 5.4 (with drops down to 5.2'ish) up to 5.8-6.0 and then back to 5.4. OR, with roots out systems I do the opposite with a 5.8-6.0 starting pH and regular drops to 5.4, along with occasional drops to 5.2.

Yes, you're correct strain matters. Some strains hit 5.2 for a few days and spit male flowers. Bleah!
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Old 11-13-2017, 12:09 AM #25
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I am running Drip DTW, Drip Recirc, Flood & Drain, DWC and Aero. Different strains like different environments (media vs no media). All share the same feeding schedule more or less.

But check this out. I have a new vert setup.
https://www.icmag.com/ic/showthread....343303&page=51

Drip feed on the top. Water drips down through all the pots.

Well the pH stabilizes around 5.8 within 24hrs of a water change. And Stays there. So I use no acid during the week. Same strain, same nutes. Trips me out. All the other systems drift.


It's super fun seeing all the changes in phenotype expression with the same strain in 5 different systems!
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Old 11-13-2017, 06:49 PM #26
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Quote:
Originally Posted by Daniel_Norway View Post
Thanks. I now measured pH of 70% coir + 30% seramis, leached with 2 times pot volume of tap water (0,2mS/cm) and 1 volume RO. It is 6.3.

In my initial post I wondered if any charts exist for coir, thinking it might well be a bit different in coir compared to the posted chart which is for a specific mix. But there is one more variable I read about here: How much available nutrient vs pH depends a lot on what molecule the ion is part of, if part of sulfate it is soluble at much higher pH than if oxide, it says.

Coir has the highest CEC of all potting mix materials per volume, and what counts for potted plants is per volume not per weight. And as Bunt said, CEC mainly affects divalent ions, most monovalent ions remain water soluble.

Testing pH of fertilized soil might be a good idea. Due to Coir and my usual fert both being a bit high on K and seramis adding to the K I decided to add some Ca+Mg (an N), found a suitable bottle called "Magne-Cal". I should buy that first before testing.
Ah you now see the limit of my knowledge here. I was under the impression peat had a higher CEC. Couldn't even recall if the reference I read was volume or weight.

Interested to see your measurements of fertilized coir.

If no one more classically educated chimes in, I would suggest contacting glow on his website, manicbotanix.
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Old 11-13-2017, 07:32 PM #27
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Yep I collected a few credible sources for CEC values. Finding them per volume is much harder, and all coir data is a bit scarce:


Sources (I think you can find all by googling except Bunt):
[AY-238] Agronomy Guide AY-238, Purdue University, Cooperative Extension Service
[Bunt] A C Bunt "Media and Mixes for Container-Grown Plants", UK 1988;[Mattson] "Totally Potted - Making the most of your media" by Neil Mattson, Asst. Professor and Floriculture Extension Specialist, Cornell University Dept of Horticulture
[Miller] J.H. Miller & N. Jones 1995: Organic and compost-based growing media for tree seedling nurseries, World Bank Technical Paper No. 264, USA;

[Milos] "The cation exchange capacity of industrial minerals and rocks of Milos island", Geological Society of Greece 2007
[NSW] "Cation exchange capacity" NSW Government 2002;

[Yavapai] "Horticultural Substrates - Common Substrate Components" K L Trainor (BS Agriculture, Ph D Biology) 2009, Yavapai College;
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Old 11-13-2017, 07:38 PM #28
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That's weird. Dragged and dropped pic which looked fine but didn't appear in the post, and it deleted one source and added blank lines and deleted a space before [Mattson] which is the source of coir CEC per volume. I try again with pic, now without drag-n-drop:
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Old 11-14-2017, 08:36 PM #29
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While searching for info on how different Manganese compounds might depend differently on pH, I found this extremely useful document from the University of Wisconsin. Table 3 indicates MnO and MnSO4 are equivalent and they don't seem to differentiate between them so I suppose they are. But some much more interesting quotes:
  • "Manganese toxicity is common in acid soils below pH 5.5. On the other hand, manganese deficiency is most common in soils with a pH above 6.5. One of the main reasons for liming acid soils, especially for legumes, is to prevent manganese toxicity. The amount of manganese in solution decreases 100-fold for each unit rise in soil pH (as from 5.0 to 6.0). Where manganese deficiency exists as a result of high pH, it is easier to correct the deficiency by adding a manganese fertilizer than by attempting to acidify the soil."
  • They seem to say the left chart applies to mineral (loam) soils and the right chart to soils with >6% organic matter but that exact shape depends on amount of organic matter - so it doesn't sound like the right chart is for soilless media or hydroponics but for soils high in organic matter: "Soils high in organic matter (more than 6.0%) and near neutral in pH (above pH 6.5) may be deficient in manganese. As the organic matter content increases, the amount of exchangeable manganese decreases due to the increased formation of organic matter and manganese complexes." And in fact Bunt says that what Lucas & Davis pointed out in 1961 was that organic soils have optimal pH range 5,0-5,5, i e 1,0-1,5 units lower than mineral soil. So the righ chart applies in principle to all organic soil mixes, with some variations.
  • "Foliar applications of manganese reduce chemical fixation [in organic soils] by reducing contact with soil particles."
  • "Manganese treatment is recommended if the soil tests less than 10 ppm. When soil organic matter exceeds 6.0%, the availability of manganese is based on soil pH. Manganese is recommended if the pH is above 7.0."
They are focused on outdoors soils which I suppose has relatively infrequent fertilizing, so I'm thinking if one applies liquid fert at every watering or slow-release fert there might be enough Mn. And the text gives hope coir will work fine up to pH 7.0, and that mine with 6.3 hopefully is ok.

Some growers here recommend max 6.1 or 6.2. Have you tried higher and seen deficiencies?
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Old 11-15-2017, 01:27 AM #30
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Hi Daniel.

Here's some good info on coco coir.

https://hortamericas.blogspot.com/201...ry-if-its.html

https://www.uaex.edu/publications/PDF/FSA-6097.pdf

https://www.extension.uidaho.edu/nurs...CN%20ratio.PDF
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