[spurr]

I wanted to expand on the issue of CEC and bulk destiny for a minute because it's an important topic and many claims about efficacy of CEC in peat and coco are false. The reason is that facts about CEC functions in soil does not translate into CEC functions of peat and coco due to their low bulk density.

I agree that CEC is an important consideration in terms of cation exchange/reservoir and pH buffering, if the bulk destiny of media is above ~ 0.25 g/cm^3 to above 0.5 g/cm^3. However, if people use only coco (~ 0.10 g/cm^3) or only peat (~ 0.15 g/cm^3) than the bulk density will be low and thus the CEC won't 'do it's job'. Mixing in perlite and vermiculite doesn't increase bulk density to any worthwhile degree.

For reference, bulk density of good, humus-rich and biologically active soil (e.g. "chernozem") is ~0.5-1.25 g/cm^3; and average bulk destiny for regular soil is 1 g/cm^3 to 2 g/cm^2. Once bulk density exceeds 1.6 g/cm^3 roots can not penetrate soil well.

Considering most people here (in the synthetic fert forum) do not add organic matter (OM) with high bulk destiny to peat or coco they have low "effective CEC" (i.e. the CEC that is useful). To increase bulk density (and thus effective CEC) of peat or coco we can add OM with high bulk density or we can intentionally compress the media (but compressing isn't a good idea). For those who do not want to add OM to coco or peat addition of sand will increase the bulk destiny, but using sand is less than ideal.

Adding humus rich compost is good because it is high in CEC (from the humus and clay often found in compost) so compost helps in two ways: (1) it increases CEC and (2) it increases bulk density. Along with compost and vermicompost I add micronized aluminosilicate zeolite powder ("zar-min") to my media to also increase CEC because zeolite has some of the highest CEC one can provide; the other being humus. Adding said zeoltie is also good because it is "paramagnetic" rock powder, and increasing paramagnetism of media is a great thing to do (but out of scope of this thread).

Using good humus rich vermicompost is a good option in place of compost to increase bulk density and CEC at the same time.

Both vermicompost and compost provide lots of other benefits to media and plants besides bulk density and CEC. Of the two, fresh and humus rich vermicompost is probably the better choice (adding compost or vermicompost from 10-20% by volume is a good goal, I use 10% vol/vol)

For quick reference:

Bulk destiny:

• soil = ~0.5-2 g/cm^3
• s.peat = ~ 0.15 g/cm^3
• coco = ~0.10 g/cm^3

CEC

• soil (humus/clay rich) = ~5-20+ meq/100g
• s.peat = ~60-80+ meq/100g
• coco = ~30-60+ meq/100g

[OsWiZzLe]

https://www.canr.msu.edu/vanburen/e-896.htm

[OsWiZzLe]

https://docs.google.com/viewer?a=v&q=...vTeMYcFEQgf_ug

[OsWiZzLe]

Coir Dust, A Viable Alternative to Peat Moss

https://flrec.ifas.ufl.edu/Hort/Envir...0potential.htm

[OsWiZzLe]

https://www.informaworld.com/smpp/945159584-24047777/content~db=all~content=a905417 032~frm=abslink

Properties of coir dust, and its use in the formulation of soilless potting media

Author: Kevin A. Handrecka

Abstract
Data from two experiments have shown that for adequate growth of Petunia 'Celebrity Salmon' in soilless potting media based on or containing coir dust it was necessary to amend the media with Ca, S, Cu and Fe. When coir dust is used as a direct replacement for natural peat, about 10 mg/L medium extra N per week must be provided. The high K content of coir dust means that fertilizers need not contain as much K as is normally used for plants in media based on other products. The high Cl content of some coir products requires that they be leached if they are to make up a high proportion of a medium.

The low CEC of the coir products (21-30 m.m (+)/L, compared with 78 m.m (+)/L for a peat), indicates a low ability to retain cations and to buffer against pH change. Two coir products had lower air-filled porosities than did the peat tested and they retained more water at 10 kPa suction.

[spurr]

hey bro,

Coir Dust, A Viable Alternative to Peat Moss

https://flrec.ifas.ufl.edu/Hort/Envir...0potential.htm

yea that is a good read, I think it helped to start interest in coir in commercial horticulture years ago, and the references cited are good too. Coir dust = coir pith, the same stuff we know as coco coir.

[spurr]

Originally Posted by OsWiZzLe

https://www.informaworld.com/smpp/945159584-24047777/content~db=all~content=a905417 032~frm=abslink

Properties of coir dust, and its use in the formulation of soilless potting media

Author: Kevin A. Handrecka

Abstract
Data from two experiments have shown that for adequate growth of Petunia 'Celebrity Salmon' in soilless potting media based on or containing coir dust it was necessary to amend the media with Ca, S, Cu and Fe. When coir dust is used as a direct replacement for natural peat, about 10 mg/L medium extra N per week must be provided. The high K content of coir dust means that fertilizers need not contain as much K as is normally used for plants in media based on other products. The high Cl content of some coir products requires that they be leached if they are to make up a high proportion of a medium.

The low CEC of the coir products (21-30 m.m (+)/L, compared with 78 m.m (+)/L for a peat), indicates a low ability to retain cations and to buffer against pH change. Two coir products had lower air-filled porosities than did the peat tested and they retained more water at 10 kPa suction.

That too is a good paper, but AFAIK, they tested coir pith without flushing it first, and coco coir we buy today is generally flushed by the manufacture, e.x. bontinacre cocogrow.

The info about the CEC is sound also, in that coco has reduced CEC vs. peat; besides the topic of both having low bulk density.

spurr...your formula appears to have a lot of calcium and not a whole lot of S, at least to me. Could you comment on these levels and why you think they are appropriate?

Would you also comment on what EC you run in veg and flower? How much citric acid do you use and where do you source it?

Would you also comment on your use of PGRs?

[spurr]

sure, but not today, sorry.

[ImaginaryFriend]

Subscribed. Dense thread. Thanks to everyone for the work.