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 soil 2.complex structures with many negative charge sites 3.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)

Force of attraction is called: Adsorption similar to force of a magnet holding iron filings. Kapasitas Tukar Kation (KTK) tml

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 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 cmol c /kg Kapasitas Tukar Kation (KTK)

may range from: 2.0 mEq/100g for sand to > 50 mEq/100g for some clays and humus mEq/100g under 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)

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:

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)

Cation Exchange is determined by: 1) strength of adsorption 2) law of mass Kapasitas Tukar Kation (KTK)

Strength of adsorption is as follows: H + and Al 3+ > Ca 2+ > Mg 2+ > K + > NH 4+ > Na + Kapasitas Tukar Kation (KTK)

Law of Mass the more of one ion available, the greater the chance of adsorption Kapasitas Tukar Kation (KTK)

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 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

Pertukaran Hara Kation

Except for C, H, O... - Nitrogen (N) is present in greatest concentrations; - Plants respond readily to Nitrogen (N) Unsur Hara Tanaman