Topband: Ground conductivity

[K1FZ-Bruce]

Done my yearly spring maintenance of my SE single wire Beverage antenna.   With poor soil, It typically is best  with a 350 ohm matching  transformer and a 330 to 350 ohm termination resistor. 
But this year it is best with a 450 ohm matching transformer and 450 ohm termination resistor. 
 
A higher value typically means more conductive soil. I do not have the time, or equipment to make accurate RF ground conductivity measurements now.   
 
But got wondering where Maine gets the WX after it passes over most of the lower 48 states,  With climate change and the highest carbon content in the air.  Could rain be causing my soil to be more conductive ?. 
 
Has anyone else noticed anything like this ?
 
73
Bruce-K1FZ
 
PS:       Delta,Pennant, Flag antenna notes    has a new address   www.qsl.net/k1fz/flag_antennas.html