THE ACCIDENT AIRPLANE NOSED OVER IN SOFT ROUGH TERRAIN DURING A LANDING ROLL. THE PILOT DESCRIBED HOW HE ELECTED TO LAND ON THE LEFT SIDE OF THE SOD RUNWAY. DURING THE LANDING ROLL THE AIRPLANE ENCOUNTERED WET, SOFT TERRAIN AND THE AIRPLANE SWERVED TO THE LEFT AND NOSED OVER. IN A TELEPHONE INTERVIEW THE PILOT STATED HIGH GRASS ON THE RUNWAY SURFACE OBSCURED THE SOFT TERRAIN. HE ALSO SAID LANDING DIRECTLY INTO THE SETTING SUN RESTRICTED HIS VISION.