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Reading Assignment Chapter 7: Soil Aeration and Temperature

Reading Assignment Chapter 7: Soil Aeration and Temperature. Too much water for too long. Aeration relates to: Ventilation of soil with air (moving in and out of soil) The rate of gas exchange with atmosphere Proportion of pore spaces filled with air Composition of soil air

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Reading Assignment Chapter 7: Soil Aeration and Temperature

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  1. Reading Assignment Chapter 7: Soil Aeration and Temperature Too much water for too long

  2. Aeration relates to: • Ventilation of soil with air (moving in and out of soil) • The rate of gas exchange with atmosphere • Proportion of pore spaces filled with air • Composition of soil air • Potential for oxidation and reduction (“redox”) within soil • Moisture status of soil • Temperature of soil • Survival of plants or vegetation

  3. Composition of Air & Soil Atmosphere

  4. GASEOUS EXCHANGE Mass flow (quicker, at shallow depth) Diffusion (concentration gradient, more important)

  5. Soil properties affecting aeration - Structure - Texture - Compaction - Drainage

  6.  Effect of poor aeration on plants and soil properties - As gas exchange is slowed, CO2 produced by organisms cannot escape fast enough and O2 required by organisms cannot enter fast enough - Other gases (H2S, methane, ethylene, etc.) produced by organisms can accumulate and maybe harmful to organisms and change soil chemical properties

  7. If soil contains < 15% O2, plant roots begin to suffer • < 10% O2, toxic substances may be produced

  8. Nutrients Bright Color.................................... Dull Color Fe+3 (oxidized) -------------------- Fe+2 (reduced) Mn+4 (oxidized) --------------------- Mn+2 (reduced) NO3- (oxidized) ---------------------- N2 (reduced) Insufficient oxygen Well Oxidized: sufficient Oxygen

  9.  How to improve Aeration? • Improve drainage • breakup impervious layers • improve aggregation (crumb structure) • prevent crusting

  10. REDOX POTENTIAL Oxidation reduction (REDOX) • Soil REDOX potential is a measure of a soil's ability to lose or gain electrons • Oxidation is the major mechanism of energy generation by organisms • Oxygen is required for respiration by plants and animals • The consumption of oxygen by biota is what reduces the REDOX potential in soil

  11. Oxidation from divalent to trivalent (loses an electron) (2+) (3+) 2 FeO + 2 H2O < = > 2 FeOOH + 2H+ + 2e- Fe(II) Fe(III)

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