Does any relationship exist between soil water compounds content (NO3, etc) and EC/pH between Drainage water (taken by lysimeters), soil pore solution through suction cups and soil water extracted from a saturated soil sample (saturated paste)?

I can't really add much more to this then what Chris said. You can probably find some literature out there on this. If you were to use tensiometer controlled extraction you would probably have closer matched data to that of a Lysimeter if it is a controlled tension lysimeter. If it is a drainage lysimeter at zero tension then you are going to introduce a boundary layer which will likely alter the results because of divergence issues and the fact that you are completely changing the way the soil above the lysimeter retains water.