Soil Atmosphere
The atmosphere of soil is radically different from the atmosphere above. The consumption of oxygen by microbes and plant roots and their release of carbon dioxide decrease oxygen and increase carbon dioxide concentration. Atmospheric CO2 concentration is 0.03%, but in the soil pore space it may range from 10 to 100 times that level. At extreme levels CO2 is toxic. In addition, the soil voids are saturated with water vapour. Adequate porosity is necessary not just to allow the penetration of water but also to allow gases to diffuse in and out. Movement of gases is by diffusion from high concentrations to lower. Oxygen diffuses in and is consumed and excess levels of carbon dioxide, which can become toxic, diffuse out with other gases as well as water. Soil texture and structure strongly affect soil porosity and gas diffusion. Platy and compacted soils impede gas flow, and a deficiency of oxygen may encourage anaerobic bacteria to reduce nitrate to N2, N2O, and NO, which is then lost to the atmosphere. Aerated soil is also a net sink of methane CH4 but a net producer of greenhouse gases when soils are depleted of oxygen and subject to elevated temperatures.
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Famous quotes containing the words soil and/or atmosphere:
“If the accumulated wealth of the past generations is thus tainted,—no matter how much of it is offered to us,—we must begin to consider if it were not the nobler part to renounce it, and to put ourselves in primary relations with the soil and nature, and abstaining from whatever is dishonest and unclean, to take each of us bravely his part, with his own hands, in the manual labor of the world.”
—Ralph Waldo Emerson (1803–1882)
“And so I look on those sentiments which make the glory of the human being, love, humility, faith, as being also the intimacy of Divinity in the atoms; and, that, as soon as the man is right, assurances and previsions emanate from the interior of his body and his mind; as, when flowers reach their ripeness, incence exhales from them, and, as a beautiful atmosphere is generated from the planet by the averaged emanations from all its rocks and soils.”
—Ralph Waldo Emerson (1803–1882)