Page 43 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 31

The presence of soil microorganims may enable the accumulation of organic
matter in the field to be alleuviated. This will provide opportunity for the organic
compounds to decompose releasing all or most of the nutrients packed in the
organic compounds. The release of inorganic nutrients may provide some
elements needed by plants for their growth and development.
However, organic matter decomposition in soils progresses relatively slowly
and is affected by several factors such as the nature of organic matter, soil
moisture content, soil temperature, the presence of microorganisms, the presence
of catalysator, the concentrations of catalysators, etc. The nature of organic
matters such as C/N ratios is of great importance as will be shown later on in the
folowing chapters. The presence of enough water, heat, and also microorganisms
is also very important. The more important is the presence and concentrations of
catalysators that may enhance the rates of organic matter decomposition.

3.4 Roles of Soil Enzymes

As discussed previously, soil enzymes are biocatalysator. As catalysators,
soil enzymes may work to increase the rates of decomposition of organic matters.
The decomposition of organic P is speeded up by the presence of phosphatases,
that of organic S is by arylsulfatase, and that of Urea is by urease. However, soil
enzymes do not participate in the decomposition processes. After the reaction, the
enzyme molecules are preserved as before the reaction. Soil enzymes in soils may
be by some reasons denatured, however, this process is not due to the enzyme
reaction during the decomposition. Most of the time it is due to enzyme protein
denaturation. Some soil enzymes may live for several hours, but some others may
live for several weeks.
Therefore, the presence of soil enzymes are, by no means, of great
importance to speed up the organic matter decomposition in soils. By adjusting
the soil environment properties such as soil water, soil temperature, soil pH, soil
microorganisms, etc. we can accelerate the decomposition of organic matters. As
will be shown in the following chapters, the activities of soil enzymes in general
increase with the increase in soil water contents (Klein and Koths, 1980; Tabatabai,
1982; Balligar et al., 1988; Salam, 1998a; Yusnaini et al., 2002), soil temperature

Abdul Kadir Salam - 2014