THE PIC WAS COMPLETING THE THIRD AND FINAL FLIGHT OF A CERTIFIED FLIGHT INSTRUCTOR'S FLIGHT TEST. BEFORE THE FLT THE FAA INSPECTOR BRIEFED THE APPLICANT THAT THE FLIGHT WOULD ENTAIL A SIMULATED EMERGENCY TOW ROPE BREAK. AT 280 FT AGL THE INSPECTOR DISENGAGED THE TOW ROPE AND THE APPLICANT IMMEDIATELY EXECUTED A LEFT 180 DEG TURN FOLLOWED BY A RIGHT DESCENDING NOSE DOWN TURN. THIS MANEUVER CAUSED THE GLIDER TO LOSE EXCESSIVE ALTITUDE AND THE PIC WAS FORCED TO LAND IN THE OPEN FIELD. DURING THE LANDING ROLL-OUT THE GLIDER STRUCK A LARGE BOULDER, SHRUB TREE AND A BARBED WIRE FENCE. THE APPLICANT STATED THAT HE DIDN'T THINK THE GLIDER'S ALTITUDE WAS SUFFICIENT TO CLEAR SOME WIRES AT THE END OF THE AIRPORT BOUNDARY BUT LATER CALCULATED THAT THE GLIDE RATIO WOULD HAVE BEEN SUFFICIENT TO NEGOTIATE THE AIRPORT. HE ALSO STATED THAT HE WAS UNDER EXTREME SELF-INDUCED PRESSURE DUE TO THE FLIGHT TEST.