Tier 4 is a death trap. I have no problem with emissions control equipment on vehicles that are constantly in use. Such as trucks, construction equipment, etc.
But if you take into consideration the time that a average compact tractor owner uses their machines for annually (hour wise), this is where the emissions equipment takes it toll. In order for it to be most effective it needs to be regularly cycled. EGR can not be given time to have soot harden, same with the DPF filter. I think Kubota cycles every 8 hours, so say you are working your tractor 7 hours after your last regen, and you don't force a regen and completely forget about it until a month down the road when you got to use the tractor again....