Page 24 - Ilmu Tanah

The Chemistry and Fertility of Soils under Tropical Weeds 11

2-
2-
RO—PO 3 + H 2 O  R—OH + HO-PO 3 ....... Eq. 1.4

As shown by Eq. 1.4, this reaction depends on the availability of organic P and
water. Phosphatase accelerates this reaction but does not react with any of the
substances in the reaction.
The presence of soil enzymes is of utmost importance related to the cycles of
nutrient elements absorbed from soils and accumulated in organic matter. The
presence of soil enzymes may accelerate the cycling of nutrient elements such as P,
S, and N, which are very important for plant growth. Some of the nutrient cycles
are shown in Fig. 1.7, Fig. 1.8, and Fig. 1.9 for P, S, and N, respectively.

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

PHOSPHATASE

ANIMALS
ORGANIC P
(CONSUMER I)

ANIMALS
(CONSUMER II)

Fig. 1.7. The cycle of P in the soil – plant system
(Salam, 2014).

Abdul Kadir Salam and Nanik Sriyani – 2019