Raytraced shadow for foliage

Hi guys , wanna know how to change the distance culling of raytraced shadow , cast by foliage.
What I noticed is objects are far away camera will cast no raytraced shadow.

Also is there a way to just simply shutdown distance culling of dynamic shadow for foliage?
I knew about the cascaded shadow maps , but it seems u can only get good result in a range like 0-20000 units.
When I raise up the value , the shadow seems to be become lower res at far distance.

Raytraced shadow not supported on Foliage right now,i think they will fixed it on future updates