Bahan Kajian MK. Dasar Ilmu Tanah

Bahan Kajian MK. Dasar Ilmu Tanah

KTK &

KETERSEDIAAN HARA

Smno.agroekotek.fpub.nop2013

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.


http://www.geology.wisc.edu/~sahai/AdsorptionAffinity.html

http://www.geology.wisc.edu/~sahai/FigH.gif

Penjerapan Kation

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




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


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


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?


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


Estimations that > 99% of cations in soil solution are adsorbed . . .

does not mean that percent base saturation is 99%


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?


6 mEq/100g bases

10 mEq/100g sites

= 60 % base saturation


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


http://www.swac.umn.edu/classes/soil2125/doc/s12ch2.htm

Strength of adsorption is as

follows:

H+ and Al3+ > Ca2+ > Mg2+ > K+ > NH4+ >

Na+


http://www2.mcdaniel.edu/Biology/botf99/nutrition/soils.htm

Law of Mass

the more of one ion available,

the greater the chance of adsorption


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

Penyerapan Hara oleh Bulu Akar

http://soilwater.com.au/bettersoils/module3/3_10.htm

Pertukaran Hara Kation

Except for C, H, O . . .

- Nitrogen (N) is present in greatest concentrations;

- Plants respond readily to Nitrogen (N)

Unsur Hara Tanaman

https://nevegetable.org/cultural-practices/nitrogen

Bahan Kajian MK. Dasar Ilmu Tanah

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