Organic Fertilizer has less Salt?

[Bretts]

I recently asked what fertiliser do you get the most bang for your buck. In this I mean what fertiliser gives the most nutrients compared to salt residue which can be harmful to some trees.
A recent comment on a forum suggests that Organic fertiliser is lower in salt and although it is hard to pin down with some searching on the Internet it seems that could be true.
Any thoughts?

[Joel]

Brett,

The salts are the fertilizers. Sodium Chloride is one of the bad ones that are needed in extremely low quantities or else it become harmful. You know NaCl as table salt....

Joel

[Bretts]

It does seem to be a complicated subjest Joel. I have been finding statements that organic fertilisers don't cause as much salt buildup.
Here is one I just found.

Organic fertilizers are more complex chemical substances that take time to break down into forms plants can use. These are know as slow-release fertilizers. Gardener's should apply organic fertilizers to media before plant reaches the rapid-growth phase. Organic fertilizers usually have a low salt index, so larger amounts can be applied at one time without causing injury to plant roots.

http://www.indoor-gardening-guide.com/a ... izers.html
I continually find the staement. If salt build up is an issue then use Organic fertiliser!

[bonscythe]

Hi all,
Going along with what Joel stated before, I was thinking something along the lines of that as the organic ferts have a lower N:P:K (usually) they would have less salts, and that would leave a lower chance of damage but at the cost of less ferts.
It would be a case of convenience and cost I guess..

[Bretts]

I had considered that Scythe but something tells me it is not that simple? Organic fert must be broken up by microbes in the soil and it only breaks up what it needs? It is also stated that cheap chemical ferts are bad at building up salts. This is all little bits of info from here and there like I said it is hard to pin this answer down but majority states there is a difference in salt content or maybe just residue?
Maybe it is just a lower NPK as you say? I have found statements saying organic is milder and more can be used but if that was the case I can't help but think they could be just diluted less? Organic has been stated as less expensive? But is it really just a matter of organic fert being spread further in application rates which makes their salt content less?

[Joel]

Good point Brett.

I think the main emphasis is that organic compounds are not "ready to use" to the plant. They need to react with particles in the soil, the air, micro or macro organisms before they form a suitable salt that can be used by the plant. Even if they simply have a low solubility, that means they can only be used in small amounts, despite the amount given to the plants. Chemical fertilizers are already a totally soluble salt. Stick it in water, it dissolves. This means it is affecting the osmotic pressures inside the cells of the roots, perhaps causing water to not be absorber, or even expelled by the plant.

Since you are already reading, may i suggest looking up ionic exchange rates?

Cheers,
Joel

[63pmp]

Which salts are you talking about Brett? Are you talking about the white crusts that form on pots and the surface of soils? Or the minerals that plants absorb?

Maybe you could break the topic up so that we can look at different areas of nutrition.

Joel is correct about organic fertilizers, the nutrients are not available to plants until microorganisms have assimilated them into usable forms. For example, nitrogen in organic material is in the form of proteins and amino acids and other complex molecules,like DNA. Micro-organisms absorb the organic compounds and then break up the molecules to extract energy and nutrients. They process the organic nitrogen into usable inorganic forms such as nitrate and ammonium. So good are they at this they can produce excessive amounts which can be released back into the environment, or stored in special cellular organs, (which are released back into the soil environment upon cell death).

Paul