Page 168 - Enzymes in Tropical Soils

156 Enzymes In Tropical Soils

Several other researchers also reported some supporting findings. Speir et
al. (1980) observed that the degradation of sulfatase in planted soils were slower
than those in fallowed soils. They argued that this phenomenon was related to the
enzyme temperature-dependent denaturation in the fallow soils. Acosta-Martinez
et al. (2008) also reported that the activities of some soil enzymes (i.e. -
glucoaminidase, -glucosidase, alkaline phosphatase, and arylsulfatase) were
higher (up to 4-fold) in soil under pasture and under trees compared to the soils for
vegetable production, related to the higher soil organic C in parture (2-3-fold) and
mango (Mangifera indica) tree (1.6-fold) compared to soil under vegetable
-1 -1
production (15.8 g kg ) and quenepas (Melico bijugatus) trees (15.9 g kg ).
Other observation indicates that soil pH in the root zones of alang-alang
(Imperata cylindrica) was higher that those of pigweed (Amaranthus spinosus),
Amaranth (Amaranthus trocolor), and green kylinga (Cyperus kyllingia). The
solubilities of Fe, Cu, and P were in general lower in the root zones of alang-alang
that those in the root zones of the other plants (Salam et al., 1997a). Grasslands
showed higher humus contents and, thereby, grasslands showed higher CEC and
base saturation and generally more fertile. Soils of grasslands also showed higher
pH (Harpstead et al., 1988). The leaves of grasses were more alkaline, contained
more Ca and Mg and, thereby, caused higher pH than did the needle leaf plants.
The leaves of broad leaf plants showed higher pH than did neddle leaf plants, but
showed lower pH than grasses (Harpstead et al., 1988).
The introduction of some external substances such as fertilizers,
conditioners, and pesticides may also change the soil chemical properties. For
example, the use of P sources such as P-fertilizers and P-rocks in the sugarcane and
pineapple plantations in Central Lampung, Indonesia, significantly increased the
availability of P in soils, as shown in Table 10.5. The massive inputs of P caused the
available P in both plantations were significantly higher.
Among the soil physical properties greatly affected by land-use conversion is
air and soil temperature. Change from natural ecosystems to modern agriculture,
village, and town ecosystems causes increases in soil and air temperature (Savva et
al., 2010). Of course, these changes may induce a chain effect. For example, these
changes may also induce the changes in the populations and activities of soil
microorganisms, enzyme production, organic matter content, and finally the cycles
of C, N, and S. Because soil water content is determined by organic matter
content, this soil physical property and other factors related to soil water will be
affected.
Along with the increase in the soil organic matter, the soil organic C and
total N also increase. Both C and N are needed by soil microorganisms to grow and

Abdul Kadir Salam - 2014