andrew ward wrote:
Reference is made in this article to 'fertiliser chemicals being loosely bonded to the zeolite and are slowly released to the plant. Nutrient loss due to leaching from excessive watering is reduced. Burning efects of high nitrogen frertilisers are bufered by the high initial uptake and slow release by the zeolite thus protecting early root development. Good water absorption and desorptiohn (10% - 15%) is beneficial during summer and aides the release of nutrients, encouraging a more even growth rate in plants.'
This is what Zeolite is added to the mix to do. It will not "Lock Up" the nutrient, but it holds on to it and releases it more slowly to the plant to use, so preventing fast and total leaching. Most of the nutrient added to the potting medium is therefore available to the plant. Not all as there will still be some leaching, if not your medium is to heavy and not allowing water to pass through it. Zeolite is a handy aditive to most Bonsai mix, as we should all be using a fast draining Medium. One point that was mentioned to me years ago was that Zeolite remained wet for to long. As this worried me I did a test on it's water holding capability. I half filled a bucket with Zeolite and wieghed it, then filled the bucket with water and left it to sit for 24 hours. I then drained the water from the bucket and weighed the Zeolite again. I then placed the Zeolite into a plant pot, leaving it again for 12 hours, before again weighing the pot. Result = the wet Zeolite was nearly twice the weight of the dry Zeolite so it took up water nicely. Weight of the Zeolite 12 hours later was nearly the same as the initial dry weight, meaning it had released the water again for the plants use. Overall result, Zeolite will not result in a wet potting medium.
andrew ward wrote:As I understand, excessive use of Zeolite can lead to nutrient becoming 'locked' within the honeycomb structure of Zeolite and therefore it becomes a matter of balancing Zeolite as one of the components used in our bonsai mediums.
As explained above Andrew, Zeolite in any quantity will not lock up nutrient. The process by which Zeolite works is call Cation Exchange. This is the process by which the nutrients are held in the potting medium and released again for the plants use. I believe Zeolite has one of the highest Cation Exchange ratios. Well Rotted Cow manure is another that is well up on the list by the way, but has disadvantages against Zeolite.
100% grit of any kind (& Zeolite is only a mined "grit" afterall) should not be used in
ANY potting medium!!! (Possible exception being pond or aquarium potting mediums). All potting mediums need and must have some form of Buffer. This buffer can be in the form of soil, compost, peat or manure (OK maybe thats just compost, but if I didn't include it someone would have asked
) The reason a buffer is so important is simply to protect the root system. I have been sitting here for quite a while trying to remember, but must be getting old
. There is a temperature at which plant roots cease growing and go into a form of hibernation. That temp isn't that high and is regularly reached inside a pot, not so often in the ground, but we speak Bonsai here. Now, this hibernation wont effect a tree/plant in the normal cycle, but if the temp is reached often enough or for long enough the tree will suffer long term damage and will eventually die. So we take a Bonsai pot, any pot, large or small, fill it with grit and plant our tree into the pot and then take the tree and place it out on the bench where it receives the required sunshine and proceed to cook the root system through. Don't know if any of you have felt a Bonsai pot around lunch time, but they sure can get hot. The soil inside the pot will be even hotter if you were to stick a finger into it. Before you ask Jamie, the pelletised Chook poo used in the fast grow is the buffer
. Zeolite on its own will not harm a plant, if it was kept cool, but then the plant would suffer as it needs the warmth to grow, just add a buffer to the grit component of your potting medium.
Andrew if you have a chat to Pauline (You should know which one she is) about temps in a pot, she will fill you in as she did a fair amount of scientific research on the subject a few years ago. Janet will be the one to speak to about Zeolite, but dont get the two subjects mixed with the wrong person
(Pauline has diffent views on the worth of Zeolite
) While you are talking to them, could you tell them I said hello as well please, haven't spoken to them for a long while.
i might have to get some perlite and use it in a mix with zeolite and just to add to it maybe some coir peat? not gonna hurt hey 
taking the top half of trees of since 2005! 
