Page 127 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 115

The pattern of increasing activity of soil enzymes with soil pH was also
reported by Reddy et al. (1991). The activities of dehydrogenase and acid
phosphatase increase with the increase in soil pH. The relationship between the
activity of dehydrogenase with soil pH is given in Fig. 7.6.
In accordance with the above phenomenon, Salam et al. (1997a) also
reported the effect of the changes in soil pH by liming or alkalination on the
phosphatase activity in the root-zones of several weeds including Alang-Alang
(Imperata cylindrica), Green Kyllinga (Cyperus kyllingia), Pigweed (Amaranthus
spinosus), and Amaranth (Amaranthus tircolor) (Table 7.5). The observation
consistently showed that the activities of acid phosphatase were lower in lower pH
(unlimed soils) than those in higher pH (limed soils). This phenomenon strengthen
the above conclusion (Salam et al., 1997c) that acidification lowers the soil acid
phosphatase activity. These data also shows that, based on the increasing trend of
phosphatase activity with soil pH, acid phosphatase dominates both soils for the
experiments.

6

5

Activity (mg Formazan g -1 d -1 ) 4
3

2

1

0
3.3 4.3 5.3
Soil pH

Fig. 7.6. The effect of soil pH on the activity of dehydrogenase
(Redrawn from Redy et al. (1991)

Abdul Kadir Salam - 2014