how to apply ACL on a nfs filesyste.

root@xxrtxx01xxxx:~ # setfacl -m u:ahoover:rwx /facl_portfolios/cs/dart_rental
setfacl: /facl_portfolios/cs/dart_rental: Operation not supported

Why you want to setup acl on NFS exported share? NFS share permissions are governed from NFS server side. From what you mentioned it appears that you want to setup acl on exported NFS share on client side. And yes the error message that you are getting is expected that is "Operation not supported" because it is mounted as nfs share with default options on NFS client. As far as I am aware I haven't heard of anyone using acl option for NFS exported share. I doubt that any such option even exist.

Acl works on system native partitions because you mount them with acl option either via /etc/fstab or by specifying in command line while mounting.

NFS does have some support for ACLs - how much depends on the server, and its implementation of NFS.

v2 and v3 of NFS may not be compatible, as NFS controls are provided by an external protocol. NFSv4 has them built in, but it still requires the server to support ACLs.

http://wiki.linux-nfs.org/wiki/index.php/ACLs

How to enable it will depend on your distribution, at a minimum it requires the exported filesystem to be mounted with ACLs enabled and exported, and the client will need them enabled on the mount (see man page on "exports" and "mount", as well as man pages on the filesystems used).