Page 104 - Enzymes in Tropical Soils

92 Enzymes In Tropical Soils

of soil microorganisms and macroorganisms were higher with the increase in water
content (Jha et al., 1992; Salam, 1998a; Yusnaini et al., 2002). For example,
Yusnaini et al. (2002) found that earthworms were found more in the rainy season
than those in the dry season. Observation in coffee plantation of Sumber Jaya,
West Lampung, Sumatra, Indonesia, showed that the populations of earhworms
were lower between July and November and began to increase in December and
the highest was between February and April in the rainy season. It was also
reported that the populations and activities of soil microorganisms were related to
the soil moisture content (Yusnaini et al., 2002). Salam (1998a) also found that the
increase in water content below 40% increased the rate of soil organic P
decomposition. Other workers also reported that forest conversion changes the
soil water contents (Klein and Koths, 1980; Baligar et al., 1988) and also the types
of vegetation, plant roots, and soil microorganisms (Duxbury and Tate III,1981;
Frankenberger and Dick, 1983; Jha et al., 1992). Jha et al. (1992) reported that in
the regions of Northeast India, the activities of soil enzymes such as
dehydrogenase, urease, and phosphatase were higher in the regions that have not
been degraded than those in the degraded regions. This phenomenon was related
to the lower populations of fungi and bacteria in the degraded regions.

180
Activity (mg p-NPP g -1 h -1 ) 120
160
140

100
80
60
40
20
0
0 2 6 10 14
Time (days)

Fig. 6.6. The time dependence of soil phosphatase activity in
a japanese soil (Adapted from Salam, 1998a)

Abdul Kadir Salam - 2014