Page 213 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 201

tissues and microorganisms, and then their ultimate decomposition back to
-
+
form inorganic N (NH 4 and NO 3 ) available to plants.
Non-Humic Substance is plant residue that has not been decomposed; is easy to
indentify and consists of polysaccharides, lignin, and polypeptides.
Optimum pH is a pH value at which the activity of soil enzymes is highest.
Permanent Wilting Point or PWP is the water hold by soil matrix at water potential
of about 1,520 kPa.
Phosphorus Cycle or P-Cycle is 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

Phosphatase is an organic substance produced by microorganisms, earthworms, or
plant roots acting as a biocatalyst functioning to accelerate the detachment
- 2-
of P from organic P to form inorganic orthophosphates (H 2 PO 4 and HPO 4 )
available for plan root absortion.
Phytoextraction is a method of soil remediation to extract heavy metal
contaminants in contaminated soils, sediments, and muds using some
species of vegetations called metallophyte as a hyperaccumulator such as
Thlaspi caerulescens that can grow well in a medium with concentrations of
-1 -1
up to 25,000 mg Zn kg and 1,000 mg Cd kg ; this plant is tolerant to and
may absorb extremely high heavy metals.
Porosity of soil is a soil physical property that indicates the part of soil volume not
occupied by soil solids. Total porosity of soils can be calculated by the

following equation: or , where is Total Porosity,

V p volume of pores, V t total volume of soil, V a volume of soil air, and V s
volume of soil solid. Total porosity of soils can also be calculated by the
following equation: = 1 - v/s, where is the total porosty of soils,  v
is the soil bulk density, and  s is the soil particle density.
Precipitate is a chemical compound resulted by precipitation process that occur at
saturated concentrations of all the related species controlled by the reaction
solubility constant.

Precipitation is a chemical process resulting in precipitate that occur at saturated
concentrations of all the related species controlled by the reaction solubility
constant.

Abdul Kadir Salam - 2014