Needs review
Source: Sandstorm

Description: When you knock your foes into the sand, they have a hard time regaining their feet.

Prerequisites: Combat Expertise, Improved Trip

If you successfully trip an opponent in any area of ash, dust, loose earth, or sand that is at least 1 inch deep, that opponent must take a full round action to stand during the round after being tripped. Following that round, the target can get to his feet with a move action (as normal). The opponent still provokes attacks of opportunity while attempting to stand, as normal.