Page 55 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 43

utilized in the nutrient cycles. This phenomenon will cause a big problem because,
in addition to the organic matter accumulation, it will also stop the nutrient cycles.
In this situation, the supplies of nutrient elements for plants will be disturbed.
Therefore, soil microorganisms become one of the important factors in soil the
management for agriculture and environment.
Soil microorganisms are small in size and are present in soils in a great
number. The general rule is that the smaller the size of the microorganisms the
greater their numbers (Singer and Munns, 1987). The smaller size also causes the
greater role in the environment. Estimation indicates that in one gram of soil
sample can be found around one million to one billion soil microorganisms.
Therefore, soil microorganisms greatly affect the soil dynamics. Most of the soil
microorganisms are usefull in agriculture. However, some of them are also
patogen, that may give negative effects on plants.
The destruction of organic matters by soil microorganisms is accelerated by
the soil enzymes produced by microorganisms. As dicussed previously, several
workers suggest that soil microorganisms are indeed the main enzyme producers in
the soil system (Duxbury and Tate III, 1981; Ross and Cairns, 1982; Frankenberger,
Jr. and Dick, 1983; Jha et al., 1992; Joner and Jakobsen, 1995; Vinotha et al., 2000).
Some of the soil enzymes also involve directly in the release of important nutrient
elements such as N, P, and S. Some of these soil enzymes are proteases,
phosphatases, and arylsulfatase. These enzymes work on soil organic matter
decomposition to release ions of N, P, and S, respectively, that are available to
plant root absorption.
Carbon is released in the form of CO 2 as organic matters containing N, P, or
S decays accelerated by the presence of their respective enzyme, i.e. proteases,
phosphatases, and arylsulfatase. Carbondioxyde molecules produced in the
reaction are finally consumed by plants, and along with water molecules absorbed
from soils, the CO 2 molecules are transformed into new organic matters. This
means that all the above enzymes participate in the C-cycle.

4.4 Enzymes in the Cycling of Phosphorus

Phosphatases involve in the destruction of organic matters containing P in
their structures called Organic P. Organic P is one of the most important sources of
P in the soil – plant system. The importance is due to the fact that these sources
contain a great amount of P accumulated by plants through plant root absorption

Abdul Kadir Salam - 2014