Resonating the earth electrode antenna on 136kHz

The 20m spaced earth electrodes "antenna" has about 30m of wire coming back ato low height to the feedpoint upstairs. I wondered if I could increase the current flowing into this structure by tuning out the small inductance presented by the wire. Using a small capacitance switching box I selected the value that gave most current with the 2W beacon TX. It was 100nF although because of the resistance of the ground return path the Q is low and the peak small. This suggests the inductance of the feed wire is only 13.5uH. I also tried matching the loop using a 3C90 transformer with various secondary taps but this made little difference. So, conclusion is that resonating the loop and matching it makes very little difference to the current (and ERP) because of the low Q.