Turn off yang drop

[MaStErIaKo]

Hi guys,
i need some help with my problem.

I have edited Demon tower on my server with mobs lvl 100+ but there is a lot of mobs and therefore there is a lot of yangs on the ground and so many people are complaining about it. They say its laggy and such stuff.
Any idea how to turn off yang drop on ground only in this one zone? Or whole server, both would be great.

Thanks for any ideas,
Masteriako