Hi Toleman. Getting a parrot to poo on command is not an easy task. They will learn to repond fairly quickly to rewards so do not feed it any sunflower seeds in the mixture, keep that as treats. Repetition is the key. Try rubbing its bottom with a soft wipe, that often stimulates them and when it does pass (even if you see that it only tries) praise and give it one sunflower seed. You need to do this every half hour when it is out of the cage as they poop fairly often. If it does have an 'accident' wipe its botty anyway so that it comes to associate a wipe with passing a dropping.
You can teach it most things with the sunflower seed reward as long as you never hand-give it those seeds for not doing anything.
The pooping when placed/landing somewhere is a nervous thing and will go away eventually.
As with most animals, parrots also respond a lot better to positive reaction than negative. Putting it back in the cage will not have any effect as it regards it as its safe space, it will never learn not to poo, it can only learn to poo on command, if you know what I mean.
Hope this is of some help.