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Re: Osmocote release rate

Neil Frank wrote:
> While the release may be 'somewhat' controlled when completely submerged, I
> suspect that it probably releases very _quickly_. I would be interested in
> someone figuring out how to determine the rate of release and how long it
> takes before the capsules are emptied. Or to compare an osmokote substrate
> with an 'equivalent' amount of other NPK fertilizer.
<more good stuff snipped>
It seems 'osmokote', like the 'plant sticks' use urea-formaldehyde resin
as a binder and time release mechanism. The release rate will vary with
the resin consistency and pH of the water. Physical consistency of the
resin can vary from 'glass' to the weak sponge used in most 'fertiliser
sticks', so a "suck and see" approach is easiest by far. 
The big advantage I can see with these products is they provide an easy
'no mess' way of getting extra fertiliser deep into the substrate of an
established tank. As Neil points out later, if you later disturb the
substrate things will get messy :). All the products should break up
quickly in terms of a plant tank. My guess is the NPK ratio and price
are the real concerns. The danger with these beasts is its easy to over
I found some 'Jobes' brand spikes, intended for ferns, with less P than
most (NPK 16-2-6). I broke one up and used it with some Crypt's hoping
to give them a little extra boost- they responded well, but I'm not sure
exactly what helped.