Page 119 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 107

involving ionization and deionization of acidic and basic groups in the active center
of enzyme proteins (Frankenberger and Johanson, 1982).

Table 7.3. Estimated lime requirement for
soils of different textures.

Lime
Soil Texture -1
(ton ha )

1 Sand 1
2 Sandy Loam 2
3 Clay Loam 4
4 Organic Soils (Peat) 8
*Singer and Munns (1987),
**To raise pH from 4.5 to 5.5

The direct effect of pH on the main enzyme producers such as bacteria and
fungi is probable (Fernandez-Calvino et al., 2012). As has been suggested by
several workers (Singer and Munns, 1987; Harpstead et al., 1988; Garbuio et al.,
2011) bacteria may live better in neutral and alkaline soils, while fungi may live
better in acidic soils. Therefore, the decrease in soil pH may lower the populations
and activities of bacteria and increase those of fungi. It has been reported recently
that liming at 0-5 cm top-layer of Typic Hapludox in Brazil increased not only the
soil pH but also the population, activity, and bacteria/fungi ratio (Garbuio et al.,
2011).

7.1 Relationship between Soil pH and Enzymatic

Activities

Soil biochemists suggest that soil pH may considerably affect the soil
enzymatic activities. This is particularly more important for phosphatases, because
it determines the magnitude of their activities and types in soils (Malcolm, 1983;
Nakas et al., 1987; Rojo et al., 1990; Reddy et al., 1991; Trasar-Cepeda et al., 1991;

Abdul Kadir Salam - 2014