Page 193 - Ilmu Tanah

180 The Chemistry and Fertility of Soils under Tropical Weeds

Secondary Forest Land-use of forest relatively disturbed by human activities
covered by regrown or replanted vegetation.

Soil The toppest part of earth crust consisting topsoil (Horizon A), subsoil (Horizon
B), and parent materials (Horizon C) being weathered affected by soil parent
materials, climate, topography, living things, and time.

Soil Enzyme A catalyst that accelerates the transformation of elements in organic
matters not available for plant root absorption to inorganic elements easily
absorbed by plant roots.

Soil Minerals Naturally formed inorganic crystallic compounds mostly composed of
Si, Al, and O with small amounts of other complementary elements.

+
Soil Reaction (pH) A mathematical expression of the magnitude of H
concentration in soil solution expressed as minus logarithmic concentration of
+
H in soil solution.
Succession The process of ecosystem recovery through a series of vegetation
composition changes after a major natural or anthropogenic disturbance.

2-
Sulfur Cycle or S-Cycle The chain of all the processes of S transformation from SO 4
in soil solution absorbed by plant roots and its transformation to be structural
and functional substances like proteins in plant tissues and microorganisms,
2-
and then their ultimate decomposition back to form inorganic SO 4 available
to plants.

Urease An organic substance produced by microorganisms, earthworms, or plant
roots acting as a biocatalyst functioning to accelerate the detachment of N
from Urea to form NH 3 .

Urease Inhibitor An organic or inorganic compound that may inhibit the work of
Urease so that the hydrolysis of urea and, hence, the production of NH 3 is
limited.

Water Content The amount of water contained in soils expressed as percent
weight.

Abdul Kadir Salam and Nanik Sriyani – 2019