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T7+Slides - Topic #7 Goals Soil Aeration Understand factors...

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1 Topic #7 Goals Soil Aeration Understand factors controlling soil aeration (oxygen – carbon dioxide levels) Understand the consequences and management of soil aeration ____________________________________________ Nitrogen Oxygen Carbon dioxide -------------------------------- % ----------------------------- Atmosphere 78 21 0.039 (390 ppm) Soil Air 78 0-21 0.05-21 ____________________________________________ Comparison of soil and atmospheric gas concentrations C 6 H 12 O 6 + 6O 2 = 6CO 2 + 6H 2 O + energy organic matter + oxygen = carbon dioxide + water Respiration Photosynthesis Soil respiration: Roots, Microbes, Soil Animals Photosynthesis Respiration (Organic matter) Factors affecting soil oxygen concentrations Root and microbial activity respiration consumes O 2 Macropore content macropores most important in gas exchange Soil water content Gases move much faster through air-filled pores than water-filled pores Mechanisms for soil gas exchange Mass flow Diffusion - most important
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2 Mass Flow (due to differences in pressure) Infiltrating water front pressurizes gas in pores until it is forced out Oxygen Carbon dioxide Gas Diffusion
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T7+Slides - Topic #7 Goals Soil Aeration Understand factors...

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