# ph not so important?



## Stone (Nov 2, 2011)

Just read a study where 2 species of fern that evolved on alkaline soils and
were said to need alkaline media to grow found that they grew equally well
with Ph values of 5.5 and 7.5 as long as the Ca/Mg ratio was in the range of 
2 to 10. In other words that the percentage of Ca was 20 to 100 times that of Mg.
In onother study, wheat plants were fed nitrate, nitrate/ammonium and ammonium forms of N. The nitrate fed plants had the greatest root growth,
The NH4/NH3 plants about 15% less and the ammonium plants about20% less.
More evidence Nitrate is preferable to ammonium?


----------



## Ray (Nov 2, 2011)

Got a reference on those articles? Sounds like interesting reading.

A few months ago I read an article in Greenhouse Grower magazine discussing the use of nitrate and ammonium fertilizers at different times to control the growth of bedding plants. I am not solid on my recollection of the details, but I believe there was a statement that "it's been long known" that ammonium nitrogen sources lead to internode elongation, while nitrate sources do not.


----------



## Rick (Nov 2, 2011)

We were having debates along this line in Bjorns' thread on Urea use.


As long as the pH is not really out of wack (<5.0, >9.0) you are probably not going to see much trauma.

What apparently is more important than the pH is the alkalinity value. The two are closely linked, but not always in step.

Within the above thread I posted links to a couple of articles on nitrate vs ammonia use. One was plant pH physiology and the other was fertilizer selection. The basic take home of the articles was that plants favor nitrate under low alkalinity (pH usually less than 7), while preferring ammonia at higher alkalinity (pH usually more than 7).

I've also been posting a lot on the importance of Ca and Mg. Much of it based on leaf tissue and leaf litter analysis around the world.

and yes, Ca is almost always higher than Mg, but more importantly is that Ca is almost always higher than K. On top of that, plants are able to selectively uptake K out of systems with high Ca present. So its not just a matter of offering nutrients in the correct ratio, but also limiting the absolute amount of some (particularly K).


----------



## keithrs (Nov 2, 2011)

That Ph range is pretty close to optimal to what most plants can uptake nutrients from most Ph charts I have looked at.....


----------



## Rick (Nov 2, 2011)

keithrs said:


> That Ph range is pretty close to optimal to what most plants can uptake nutrients from most Ph charts I have looked at.....



Yes

So if water can be extracted from these soils it would be interesting to see how the alkalinity values compare.


----------



## dodidoki (Nov 2, 2011)

While I use about 1/4 part lime stone in mix for all paphs and use Ca nitrate as fertilizer, no root problem or rot at all.


----------



## Rick (Nov 2, 2011)

dodidoki said:


> While I use about 1/4 part lime stone in mix for all paphs and use Ca nitrate as fertilizer, no root problem or rot at all.




Use of "lime stone" can be real difficult to determine if it has any effect on the hardness and alkalinity/pH of the system.

It depends on how course and hard the stone is. Which also varies in composition of Ca/Mg.

Generally the finer it is ground up the more likely it will actually effect the chemistry of the potting mix. Need to get something close to the order of sand to make a big difference. Pelletized dolomitic lime is getting close to this extreme since it is powdered dolomitic limestone formed into tiny pellets using an organic polymer binder. You can actually launch the pH for a short time to >10 with this stuff when it breaks down all at once.

If the chips are 1cm or bigger the effects get progressivly less for actuall pH or alkalinity shifts in the potting mix.

If roots are directly attached or in contact with large chips, then the plant would probably be able to get something out of it chemistry wise. 

I also use large chips (1-2 cm) to maintain good drainage and aeration and not even wory about chemistry effects.


----------



## Stone (Nov 2, 2011)

Ray said:


> Got a reference on those articles? Sounds like interesting reading
> 
> 
> A few months ago I read an article in Greenhouse Grower magazine discussing the use of nitrate and ammonium fertilizers at different times to control the growth of bedding plants. I am not solid on my recollection of the details, but I believe there was a statement that "it's been long known" that ammonium nitrogen sources lead to internode elongation, while nitrate sources do not.



Yes Ray. Not so much articles but a Ref. book.( Growing Media by K.A. Handreck, University of New South Wales Press. Sydney 2052 Australia)
Its full of no bullshit scientific info. hundreds of tables,charts, chapters on 
nutrients, fertilizer practice and so on. Im sure the information is generally available but its good to have it all in one book.


----------



## Stone (Nov 2, 2011)

Rick said:


> We were having debates along this line in Bjorns' thread on Urea use.
> 
> 
> As long as the pH is not really out of wack (<5.0, >9.0) you are probably not going to see much trauma.
> ...



I also read that Coconut products in particular are so high in native K as to throw Ca out of balance.


How do you go about reducing K in otherwize good fertilzers containing calcium nitrate without reducing the rest?


----------



## Rick (Nov 2, 2011)

Stone said:


> I also read that Coconut products in particular are so high in native K as to throw Ca out of balance.
> 
> 
> How do you go about reducing K in otherwize good fertilzers containing calcium nitrate without reducing the rest?



The amount of K in CHC can vary a lot which is why thourogh washing in freshwater (at the very least) is reccomended. Also Bob Wellenstein has a writeup on the ANTEC site about soaking CHC in CaNitrate and Mag sulfate solutions to suck the K and Na out of CHC.

You are correct in that you cannot reduce K only out of a fertilizer. basically I reformulated by cutting the overall amount of the fertilizer of choice, and offsetting the nitrogen loss with addition Calcium nitrate.

So for instance since I was using the MSU RO mix which reccomends 1/2tsp per gall to get ~ 100ppm N, I cut it back to 1/4tsp MSU to cut the K in 1/2, but added back a 1/4tsp per gal of calcium nitrate AND 1/4 tsp per gal of Mag sulfate. MSU already has some Ca/Mg, but at lower concentrtions than K, so I both reduce K and bump up Ca/Mg. Also instead of using straight RO water I'm using diluted well water to also add even more Ca, Mg, and silicates.

This is for a weekly feeding. During the rest of the week I water with dilute well water with no fert added.


For fall/winter I've already cut back to 1/8 tsp of each.


----------



## Stone (Nov 2, 2011)

Rick said:


> The amount of K in CHC can vary a lot which is why thourogh washing in freshwater (at the very least) is reccomended. Also Bob Wellenstein has a writeup on the ANTEC site about soaking CHC in CaNitrate and Mag sulfate solutions to suck the K and Na out of CHC.
> 
> You are correct in that you cannot reduce K only out of a fertilizer. basically I reformulated by cutting the overall amount of the fertilizer of choice, and offsetting the nitrogen loss with addition Calcium nitrate.
> 
> ...



Good idea.
I use a locally made 2 part hydroponic feed with N/Ca seperate from the rest.
I find it generally excellent so I'll just cut part 2 or increase part 1 and add
a pinch of Mag.sulphate. Should be enough trace elements, but just to make
sure I like to some diluted home made organic fert. I can't help myself


----------

