EE FROM TRUCKING COMPANY WAS PICKING UP AG LIME IN A EXTENDED OPEN DUMP BODY TRUCK. HE WAS STANDING ON A LADDER AT THE FRONT OF THE DUMP BODY. AS HE WAS DIRECTING THE LOADER OPERATOR WHERE TO DUMP THE THIRD OF 4 BUCKETS IN THE MIDDLE OF THETRUCK, THE BUCKET CAME IN CONTACT WITH THE SIDE RAIL AND ROCKED THE DUMP BODY. THE EE ROCKED BACK THEN JUMPED OFF. HE INJURED HIS SHOULDER.