Chapter 7 - Soil Aeration

Air filled porosity slide (macroporosity)

Below 20% air plant growth and microbial activity become severely inhibited

Other gases that become more prevalent under waterlogged (saturated) conditions Why do these become more present?

Methane, hydrogen sulfide, ethylene. they are microbe byproducts that arise from microbes using electron acceptors other than O2

Typical ratios of atmospheric air ====================== Nitrogen ratio in soil Oxygen ratio in soil CO2 ratio in soil ====================== What ratios of O2/CO2 become problematic ===================== Why is there more CO2 the deeper in profile?

O2: 21% CO2: 0.035% N2: 78% ================ N2: same as air O2: <= 20% CO2: ~0.35% ================= as O2decreases, CO2increases ================ CO2: >= 10% becomes toxic to some plants O2: <= 10% becomes a problem (by volume) Anarobic means all O2 has been exhausted, there is none. ================ compaction causes CO2 toget stuck lower down, so there's more of it. ================