Page 188 - Ilmu Tanah

The Chemistry and Fertility of Soils under Tropical Weeds 175

Base Saturation The quantity of base cations (Ca, Mg, K, and Na) adsorbed on the
soil exchange sites expressed as percent of base over the soil cation exchange
capacity (CEC).

Bioassay A method to measure response of a particular living organism to
determine the existence or concentration of a chemical in a substrate
(Satelmann, 1987).

Biocatalyst A catalyst produced by living things that accelerate the decomposition
of organic matters and transform the organic forms into the inorganic forms of
nutrients available to plant roots.

Biological Invasion The entry of a progressive foreign plant species into a particular
habitat that is new to the species.

Biological Weed Control The method to control weed population by employing
natural enemies of weeds.

Carbon Cycle or C-Cycle The chain of all the processes of C transformation from CO 2
in the atmosphere to CH 2 O (sugars, proteins, and fats) as structural and
functional substances in plant tissues and microorganisms, and then their
ultimate decomposition back to form inorganic C as CO 2 available to plants.

Catalyst A substance that may accelerate the rate of a reaction to a magnitude of
several orders without itself participates in the reaction. Examples of catalysts
are phosphatases and ureases.

Cation Exchange The exchange of adsorbed cations on the soil exchange-sites with
2
other cations in soil solution controlled by the coulombic law F = q 1 q 2 /r where
F is the attraction force between the soil exchange-sites and cations, q 1 is the
amount of soil exchange-site charges, q 2 the cation charge, and r the distance
of cations from the soil exchange-sites.

Cation Exchange Capacity The maximum quantity of all free ionic metals that can
-1
be adsorbed by the surfaces of a quantity of soil solids, expressed in cmol c kg .

Chelation A chemical process by which a cation is hold by multidentate organic
agent forming a soluble complex.

Abdul Kadir Salam and Nanik Sriyani – 2019