Page 56 - Enzymes in Tropical Soils

44 Enzymes In Tropical Soils

from soils. Therefore, the presence of phosphatase in soils is very important to
utilyze these accumulated nutrients. The released P in soils will then eventually re-
absorbed by plant roots and re-ultilyzed to produce new organic matters. The
chain of transformation from Organic P to inorganic P by decomposition process
and absorption of inorganic P through its re-synthesis in plants to produce new
organic matters and back to the decomposition of organic matters to produce
inorganic P is called Phosphorus Cycle or P-Cycle. The P-Cycle is shown in Fig. 4.6.

-
H 2 PO 4
2-
HPO 4
NUTRIENTS
SOIL MICROORGANISMS PLANTS
(DECOMPOSERS) (PRODUCERS)

PHOSPHATASE

ANIMALS
ORGANIC P
(CONSUMER I)

ANIMALS
(CONSUMER II)

Fig. 4.6. The cycle of P in the soil – plant system.

Fig. 4.6 clearly shows that the presence of phosphatase is of utmost
importance related to P in soils, since the rate of P release is determined by its
2-
presence. The results of its role are alcohol and orthophosphates (HPO 4 ). The role
of phosphatase is shown in Eq. 4.1 as follows (Tabatabai, 1982). The action of
phosphatase on the organic P molecules must, however, be in the presence of
enough water molecule. Therefore, the decomposition of organic P will be
inhibited in dry soils. Water must be added to allow the accelerated rates of
organic P decays catalyzed by phosphatase occur in soils.

2-
2-
RO—PO 3 + H 2 O  R—OH + HO-PO 3 ....... Eq. 4.1

Abdul Kadir Salam - 2014