Soil Air Flashcards
what are 6 factors influencing air content of soil?
- soil texture
- water movement
- water content
- chemistry/biology
- soil structure
- porosity
what are mesophytes?
plants that require O2 for root respiration
what are hydrophytes?
plants that are able to transfer O2 from the atmosphere through leaves and stems to their roots
what is methanogenesis?
carbon dioxide + hydrogen -> methane + water + energy
what are redox reactions?
loss of electron and gain of electron (OIL RIG), ex. respiration and methanogenesis
what is redox potential?
the potential for an electron transfer from one substrate to another, the greater the Eh difference between two redox couples, the greater the energy released in the net reaction
what is the redox potential in well-aerated soils?
0.4-0.7 volts
what is the redox potential when aeration and gaseous O2 is depleted?
0.3-0.35 volts
what is the redox potential when organic-rich soils are flooded under warm conditions?
-0.4 V
what is the redox ladder?
- respiration (O2 -> H2O)
- denitrification (NO3 -> NO2 and N2)
- Manganese reduction (MnO2 -> Mn2+)
- iron reduction (Fe(OH)3->Fe2+
- sulfate reduction (SO4 -> H2S)
- methanogenesis (CO2 -> CH4)
what are 4 reasons for poor plant growth in waterlogged soils?
- no more O2 for respiration
- increased Mn and Fe solubility and toxicity
- loss of NO3 by denitrification: N deficiency
- SO4 reduction to sulphides (H2S) which may be toxic to plant roots
what does redox potential look like in wetland soils?
slow decrease of redox potential with depth due to availability of organic matter (electron donors)
