eds said:
I'm sure I remember on APC someone talking about getting ferts with a percentage purity quoted on them as their ferts were agricutural in origin and not as pure. If you have got that then all you have to do is work out the percentage and up the amount used appropriately. E.g. if they were 80% pure you'd need to add an extra 20% to get the same level.
Most ferts are way more pure than this and to be honest, like Andy said, they are usually just one or two percent and this doesn't really matter for our purposes.
The purity is above 99% in most all cases, these are high temp salts and easy to separate out. You can weigh and make reference standards and they come out as predicted
So the purity has to be extremely high.
Since folks eat the ferts that plants use, the purity needs to be rather high and not have other things in them.
If it's good enough for you and your food, it's good enough for your plants.
One troll was running around trying to spread fear and bad mouth Greg Watsomn, who had already sold the business to Alan, that we should all be using Lab grade pure chemicals(at about 10X or more the cost).
A mod mentioned the ISP number matched another member who had a history of trolling
Go figure.
Regards,
Tom Barr