1. Bahan Kajian MK. Dasar Ilmu Tanah Smno.agroekotek.fpub.okt2013 REAKSI PERTUKARAN ION & KETERSEDIAAN HARA

2. Humus  200 cmol c /kg Smectite/Vermiculite  100 cmol c /kg Illite  25 cmol c /kg Kaolinite  10 cmol c /kg Fe and Al oxides  5 cmol c /kg Muatan listrik pd Komponen Tanah

3. Asalnya Muatan Listrik cmol / Kg

4. ---------------------- + + + + + + + + + Penjerapan Ion Muatan negatif pada partikel tanah dinetralkan oleh anion dari larutan tanah

5. Kation Yang Dijerap (Kation-Tukar) (a) arid region soils = "basic" cations Ca 2+, Mg 2+, K +, Na + (b) humid region soils = “acidic” cations as well Ca 2+, Mg 2+, H + and Al 3+ (c) Kekuatan Jerapan Al 3+ > Ca 2+ = Mg 2+ > K + = NH 4 + > Na +

6. Pertukaran Kation Exchange process Ca 2+ -colloid + 2 Na +  2 Na + -colloid + Ca 2+ = Na + replaces Ca +2 adsorbed to soil colloids Ca-x + 2 Na +  2 Na-X + Ca 2+ X = the soil solid phase Dispersion

7. Saline Soils EC > 4 ds/m = osmotic stress * salt sensitive plants (EC = 2 ds/m) 3 bean, onion, potato, raspberry, carrot, dogwood, larch, linden, peach, rose, tomato 3 bean, onion, potato, raspberry, carrot, dogwood, larch, linden, peach, rose, tomato * salt tolerant plants (EC = 10 ds/m) 3 sugarbeets, barley, cotton, rosemary, 3 sugarbeets, barley, cotton, rosemary, wheat grass, wild rye wheat grass, wild rye (see table 10.2 - 13 th ed. or 10.3 – 12 th ed.) (see table 10.2 - 13 th ed. or 10.3 – 12 th ed.)

8. Sodic Soils (ESP > 15) flocculation poorwaterinfiltration dispersion

9. Sodium Ion Effect flocculation dispersion  attraction  Ca 2+ & Mg 2+  repulsion  Na +

10. SAR Parameter SAR is measured ESP/ESR is estimated in water or extract for soil solids ESR = 0.015(SAR) - 0.01 Good quality irrigation water: 4 for salt hazard = EC < 2 ds/m 4 for Na + hazard = SAR < 15 Predict sodium effect from saturated soil extract or irrigation water

11. Sources of Acidity á Water: H 2 O  H + + OH - á CO 2 from soil respiration CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 - carbonic acid á Organic acids from O.M. decomposition RH  R - + H + á Oxidation of S and N S  H 2 SO 4  2 H + + SO 4 2- NH 3  HNO 3  H + + NO 3 -

12. Human-Induced Acidity * Chemical fertilizers  ammonium-based N materials NH 4 +  (O 2 )  HNO 3  Ferrous-Fe materials Fe 2+  Fe 3+  (+ 3 H 2 O)  Fe(OH) 3 + 3 H +  Elemental Sulfur 2 S o + 3 O 2 + 2 H 2 O  4 H + + 2 SO 4 2-

13. Acid Rain : N and S gases emitted from combustion processes SO 2  (O 2, H 2 O)  H 2 SO 4 NO x  (O 2, H 2 O)  HNO 3 mining wastes, wetland drainage -oxidation of sulfide (S 2- ) mineral S 2-  (O 2, H 2 O)  H 2 SO 4 Human-Induced Acidity http://www.physicalgeography.net/fundame ntals/8h.html

14. Phases of Soil Acidity bound acidity exchangeable acidity soluble acidity As acidity is removed from or added to soil solution maintain equilibrium within system Ø maintain equilibrium within system must change all forms to change pH Ø must change all forms to change pH

15. Acid Soils : Role of Aluminum Al 3+ Al(OH) 2+ Al(OH) 2 + Al(OH) 3 Al 3+  Al(OH) 2+  Al(OH) 2 +  Al(OH) 3 | strongly | moderately | alkaline |  strongly  |  moderately  |  alkaline acid soils acid soils soils acid soils acid soils soils

16. Al 3+ + H 2 O  Al(OH) 2 + + H + K = 10 -4.93 Al(OH) 2 + + H 2 O  Al(OH) 2+ + H + K = 10 -4.97 Al(OH) 2+ + H 2 O  Al(OH) 3 o + H + K = 10 -5.7 Al(OH) 3 o + H 2 O  Al(OH) 4 - + H + K = 10 -7.4 Acid Soils : Role of Aluminum http://www.landfood.ubc.ca/soil200/interaction/acidity.htm

17. Al +3 Al(OH) +2 Al(OH) 2 + Al(OH) 3 Al +3  Al(OH) +2  Al(OH) 2 +  Al(OH) 3 Changes in Al Speciation - - - Clay Interlayer Soil Solution pH 4 pH 6 H+H+ H+H+ Why [Al 3+ ] ~ [H + ] in Acid Soils

18. Fe 3+ + H 2 O Fe(OH) 2 + + H + K = 10 -2.19 Fe(OH) 2 + + H 2 O Fe(OH) 2+ + H + K = 10 -3.5 Fe(OH) 2+ + H 2 O Fe(OH) 3 o + H + K = 10 -7.4 Fe(OH) 3 o + H 2 O Fe(OH) 4 - + H + K = 10 -8.5 Why Not Iron?

19. Liming Materials Carbonate forms (a) "limestone" deposits and industrial byproducts (b) calcite = (CaCO 3 ) = calcium carbonate and dolomite = CaMg(CO 3 ) 2 (c) dolomitic limestone maintains Ca:Mg balance

20. Liming Materials Oxide and Hydroxide forms (a) oxides formed by heating limestones CaCO 3  (heat)  CaO + CO 2 calcite gas burned lime or quicklime (b) add water to oxides to form hydroxides CaO + H 2 O  Ca(OH) 2 hydrated lime

21. Reaksi Kapur dalam Tanah 1. Neutralize acidity 2 H-X + CaCO 3  Ca-X + H 2 CO 3 + H 2 O 2.Base Saturation increases BS = (CEC – [Al 3+ ][H + ]) / (CEC) * 100 BS = {[Na]+[K]+[Ca]+[Mg]}/CEC *100 3. Soil pH increases 4. Al solubility decreases Al +3 + 3 OH -  Al(OH) 3 soluble insoluble (toxic) (not toxic)

22. Ciri-ciri Tanah Masam

23. Wetland (Hydric) Soils and Redox Conditions

24. CH 2 O CO 2 O2O2 H2OH2O NO 3 - CH 2 O CO 2 N2N2 Fe(OH) 3 CH 2 O CO 2 Fe 2+ CH 2 O CO 2 SO 4 2- H2SH2S Energy Yields Donor Acceptor 700 400 100 Eh (mV)*Condition oxic suboxic anoxic *pH 7 MnO 2 CH 2 O CO 2 Mn 2+

25. Soil Colors Yellow -> Orange -> RedFe(III) minerals Black (veneer)Mn(IV) minerals Dark Brown (disseminated)Organic Matter Aerobic Environments Gray -> Green -> BlackFe(II) minerals Dark Brown (disseminated)Organic Matter Anaerobic Environments

26. Iron masses Redox depletions Root linings Mottling Nodules Gleyed colors Redoximorphic Features Histic Horizons “Rotten Eggs”

27. Plant Effects on Redox Conditions

28. Fe III (OH) 3 deposit O 2(g) Pembentukan Plaque pada Akar Tanaman Fe(OH) 3 O2O2 H2OH2O Fe 2+