EFFECTS OF SINGLE AND SUCCESSIVE ADDITIONS OF CADMIUM, NICKEL AND ZINC ON CARBON-DIOXIDE EVOLUTION AND DEHYDROGENASE-ACTIVITY IN A SANDY LUVISOL

The effects of single and successive additions of Cd, Ni, and Zn on CO2 evolution and dehydrogenase activity in a sandy luvisol were investigated in batch experiments under laboratory conditions. Successive additions of Cd, Ni, and Zn inhibited soil respiration relatively more than single doses, even before the same amount of metals had been added. In general, split additions of all metals reduced dehydrogenase activities in all soils to a lesser degree until the 28th day. Thereafter both modes of metal addition had the same effects throughout although the last successive addition was added on the 35th day. It is assumed that the relatively greater effect, especially on CO2 evolution, of successive additions during the first period was due to short-term increases metal concentrations in the soil solution after each application.