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Kapasitas Tukar Kation (KTK)
Clay Particles dan Humus
1. affect chemical properties of soil2. complex structures with many
negative charge sites3. negative charge sites attract positive
ions called cations
Negative charge sites are referred to as . . .
Cation exchange sites
attract cations from soil solution
Kapasitas Tukar Kation (KTK)
http://www.soils4teachers.org/chemistry
Force of attraction is called:
Adsorption
similar to force of a magnet holding
iron filings.
Kapasitas Tukar Kation (KTK)
http://www.geology.wisc.edu/~sahai/AdsorptionAffinity.html
Cations can move on and off particles . . .
when one leaves, another replaces it
This process is called cation exchange, and cations involved are said to be exchangeable
http://www.une.edu.au/~agronomy/SSCATXCH.dcr
Kapasitas Tukar Kation (KTK)
The number of sites that a colloid (small particle) of
charged clay or humus (micelles)
contains is measured by the:
Cation Exchange Capacity expressed in mEq/100g (older
unit) or cmolc/kg
Kapasitas Tukar Kation (KTK)
http://nelspeterson1.wordpress.com/agrn-2124-chapter-8-notes/
may range from:
2.0 mEq/100g for sandto
> 50 mEq/100g for some claysand
humus 100-300 mEq/100gunder certain soil conditions
Kapasitas Tukar Kation (KTK)
How fertile can a soil be?
Does applying more fertilizer always
provide more nutrients to
plants?
How much of the CEC is actually
filled with cations?
Kapasitas Tukar Kation (KTK)
http://clasfaculty.ucdenver.edu/callen/1202/Soils/Soils.html
The proportion of the CEC occupied by basic (+) nutrients such as Ca, Mg, K, Na, is called:
Percent Base Saturation and is an indication of the potential CEC of a given soil
Kapasitas Tukar Kation (KTK)
Estimations that > 99% of cations in soil solution are adsorbed . . .
does not mean that percent base saturation is 99%
Kapasitas Tukar Kation (KTK)
Exchangeable nutrient cations adsorbed on soil particles exist in equilibrium with cations
in the soil solution. Cations from the particles replenish those taken up from the
soil solution by plants.
Sumber: http://extension.missouri.edu/p/MG4
Contoh:A soil with CEC of 10 mEq/100g has 6 mEq/100g of bases (Ca, Mg, K, Na) occupying exchange sites
What is the percent base saturation of the soil?
Kapasitas Tukar Kation (KTK)
6 mEq/100g bases
10 mEq/100g sites
= 60 % base saturation
Kapasitas Tukar Kation (KTK)
http://www.spectrumanalytic.com/support/library/ff/CEC_BpH_and_percent_sat.htm
Cation Exchange is determined
by:
1) strength of adsorption
2) law of mass
Kapasitas Tukar Kation (KTK)
http://www.swac.umn.edu/classes/soil2125/doc/s12ch2.htm
Strength of adsorption is as
follows:
H+ and Al3+ > Ca2+ > Mg2+ > K+ > NH4+ >
Na+
Kapasitas Tukar Kation (KTK)
http://www2.mcdaniel.edu/Biology/botf99/nutrition/soils.htm
Law of Mass
the more of one ion available,
the greater the chance of adsorption
Kapasitas Tukar Kation (KTK)
http://www2.mcdaniel.edu/Biology/botf99/nutrition/soils.htm
There are at least 17 elements recognized as essential nutrients for plants;
we will recognize 18 elements:
C, H, O, P, K, N, S, Ca, Fe, Mg,
Mn, Mo, Cl, Cu, Zn, B, Co, Ni
Unsur Hara Tanaman
http://www.hydroponicist.com/pages/p52-macronutrients-n-p-k.htm
Nutrients grouped into 2 categories according to the relative amount used by plants:
Macronutrients – major elements; large amounts
Micronutrients – minor elements; small amounts
Both are essential for optimal plant production
Unsur Hara Tanaman