Page 150 - Enzymes in Tropical Soils

138 Enzymes In Tropical Soils

The above indirect mechanisms have been reported by several workers
(Baath, 1989; Landmeyer et al., 1993; Flieach et al., 1994; Hiroki, 1994; Huysman,
1994; Witter et al., 1994; Zhou et al., 2011). Landmeyer et al. (1993) reported that
the microbial biomass drastically decreased in soils treated with Pb. Mathur et al.
(1980) previously reported that the populations and activities of microorganisms in
Histosols with high Cu concentration was lower than those with lower Cu
concentration as indicated by the lower soil respiration rate of peat sample
containing 797 ppm Cu, about half that of the peat sample containing 408 ppm Cu.
Zhou et al. (2011) also reported that the increase in Cu concentration in citrus soils
as a result of soil treatment with Cu containing fungicides lowered the soil
microbial biomass and shifted their biodiversity. The decrease in the populations
and activities of soil microorganisms lowered the activity of soil enzymes due to
lower enzyme production. Flieach et al. (1994) also reported that high heavy
metal contaminations of soils resulted in a substantial decrease in soil microbial
biomass carbon. However, generally low metal concentrations showed beneficial
effects on soil microbial biomass carbon.

7
6
5
Log CFU g -1 4 0 - 30 cm

3
2 50 - 70 cm
90 - 110 cm
1
0
0 2 4 6
Cu (mM)

Fig. 9.6. The relationship between the number of CFU and Cu
concentration in soil from different depths
(Redrawn from Husyman et al., 1994).

Abdul Kadir Salam - 2014