This same
relationship between Cu and Zn is deducible from the
other Tables (4 - 6). It is noteworthy that the effect of
Zn was not significant on the activities of the soil
microbes all through the work; but in combination with
Cu, it engenders a more toxicological effect than even
Cu itself. Cu has long been reported to be very toxic to
microorganisms in the free ionic form (Zevenhvizen et
al., 1979; Baker and Senft,1995).