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Bahan Kajian MK. Dasar Ilmu Tanah

Bahan Kajian MK. Dasar Ilmu Tanah. REAKSI PERTUKARAN ION & KETERSEDIAAN HARA. Smno.agroekotek.fpub.okt2013. Muatan listrik pd Komponen Tanah. Humus » 200 cmol c /kg Smectite /Vermiculite » 100 cmol c /kg Illite » 25 cmol c /kg Kaolinite » 10 cmol c /kg

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Bahan Kajian MK. Dasar Ilmu Tanah

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  1. BahanKajian MK. DasarIlmu Tanah REAKSI PERTUKARAN ION & KETERSEDIAAN HARA Smno.agroekotek.fpub.okt2013

  2. Muatanlistrik pd Komponen Tanah • Humus » 200 cmolc/kg • Smectite/Vermiculite » 100 cmolc /kg • Illite» 25 cmolc /kg • Kaolinite» 10 cmolc /kg • Fe and Al oxides » 5 cmolc /kg

  3. AsalnyaMuatanListrik cmol / Kg

  4. Penjerapan Ion - - - - - - - - - - - + + + Muatannegatifpadapartikeltanahdinetralkanoleh anion darilarutantanah + + + + + +

  5. Kation Yang Dijerap (Kation-Tukar) (a) arid region soils = "basic" cations Ca2+, Mg2+, K+, Na+ (b) humid region soils = “acidic” cations as well Ca2+, Mg2+, H+ and Al3+ (c) KekuatanJerapan Al3+> Ca2+ = Mg2+ > K+ = NH4+ > Na+

  6. PertukaranKation Exchange process Ca2+-colloid + 2 Na+¬¾® 2 Na+-colloid + Ca2+ = Na+ replaces Ca+2 adsorbed to soil colloids Ca-x + 2 Na+¬¾® 2 Na-X + Ca2+ X = the soil solid phase Dispersion

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

  8. poor water infiltration Sodic Soils (ESP > 15) dispersion flocculation

  9. Sodium Ion Effect flocculation dispersion è attraction ç ç repulsion è Na+ Ca2+& Mg2+

  10. SAR Parameter Predict sodium effect from saturated soil extract or irrigation water 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

  11. Sources of Acidity áWater: H2O ¬® H+ + OH- áCO2 from soil respiration CO2 + H2O ¬® H2CO3¬® H+ + HCO3- carbonic acid áOrganic acids from O.M. decomposition RH ¬® R- + H+ áOxidation of S and N S ¾® H2SO4¾® 2 H+ + SO42- NH3¾® HNO3¾® H+ + NO3-

  12. Human-Induced Acidity * Chemical fertilizers üammonium-based N materials NH4+¾(O2)® HNO3 üFerrous-Fe materials Fe2+® Fe3+¬(+ 3 H2O)® Fe(OH)3 + 3 H+ üElemental Sulfur 2 So + 3 O2 + 2 H2O ¾® 4 H+ + 2 SO42-

  13. Human-Induced Acidity • ü Acid Rain: N and S gases emitted from combustion processes • SO2¾(O2, H2O)® H2SO4 • NOx¾(O2, H2O)® HNO3 • mining wastes, wetland drainage • oxidation of sulfide (S2-) mineral • S2-¾(O2, H2O)® H2SO4 http://www.physicalgeography.net/fundamentals/8h.html

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

  15. Acid Soils: Role of Aluminum Al3+¬® Al(OH)2+¬® Al(OH)2+¬® Al(OH)3 |¬strongly ¾®|¬ moderately ¾¾¾®|¬ alkaline acid soils acid soils soils

  16. Acid Soils: Role of Aluminum Al3+ + H2O  Al(OH)2+ + H+ K = 10-4.93 Al(OH)2++ H2O  Al(OH)2++ H+ K = 10-4.97 Al(OH)2++ H2O  Al(OH)3o+ H+ K = 10-5.7 Al(OH)3o + H2O  Al(OH)4-+ H+ K = 10-7.4 http://www.landfood.ubc.ca/soil200/interaction/acidity.htm

  17. Changes in Al Speciation Why [Al3+] ~ [H+] in Acid Soils Clay Interlayer Soil Solution H+ - - - - - - Al+3¨ Al(OH)+2¨ Al(OH)2+¨ Al(OH)3 - - - - - - H+ pH 4 pH 6

  18. Why Not Iron? Fe3+ + H2O <--> Fe(OH)2+ + H+ K = 10-2.19 Fe(OH)2+ + H2O <--> Fe(OH)2+ + H+ K = 10-3.5 Fe(OH)2+ + H2O <--> Fe(OH)3o + H+ K = 10-7.4 Fe(OH)3o + H2O <--> Fe(OH)4- + H+ K = 10-8.5

  19. Liming Materials Carbonate forms (a) "limestone" deposits and industrial byproducts (b) calcite = (CaCO3) = calcium carbonate and dolomite = CaMg(CO3)2 (c) dolomitic limestone maintains Ca:Mg balance

  20. Liming Materials Oxide and Hydroxide forms (a) oxides formed by heating limestones CaCO3¾(heat)®CaO + CO2 calcitegas burned lime or quicklime (b) add water to oxides to form hydroxides CaO + H2O ¾® Ca(OH)2 hydrated lime

  21. ReaksiKapurdalam Tanah 1. Neutralize acidity 2 H-X + CaCO3¾® Ca-X + H2CO3 + H2O • Base Saturation increases BS = (CEC – [Al3+][H+]) / (CEC) * 100 BS = {[Na]+[K]+[Ca]+[Mg]}/CEC *100 3. Soil pH increases 4. Al solubility decreases Al+3 + 3 OH-¾® Al(OH)3 soluble insoluble (toxic) (not toxic)

  22. Ciri-ciri Tanah Masam

  23. Wetland (Hydric) Soils and Redox Conditions

  24. Energy Yields *pH 7 Acceptor Eh (mV)* Condition Donor CH2O O2 700 CO2 H2O CH2O NO3- oxic CO2 N2 CH2O MnO2 400 CO2 Mn2+ CH2O Fe(OH)3 suboxic CO2 Fe2+ 100 CH2O SO42- anoxic CO2 H2S

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

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

  27. Plant Effects on Redox Conditions

  28. Pembentukan Plaque padaAkarTanaman O2(g) FeIII(OH)3 deposit Fe2+ O2 Fe(OH)3 H2O

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