Chapter 7 - Soil Temperature/Aeration

Oxygen in soil is required for:

• Respiration of aerobic organisms

• Photosynthesis by plants and algae

• Hydration of minerals during the weathering process

• Complexation of elements in minerals as part of chemical weathering

• Hydrolysis of water

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NGSS.MS-LS2-1

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Diffusion of gases in a soil is primarily a function of:

• total porosity

• particle density

• air pore volume

• oxygen consumption by microorganisms

• organic matter content

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Under normal aerated conditions, soil air is usually higher in _______ than atmospheric air.

• O₂

• CO₂

• N₂

• H₂

• Hg

Little to no oxygen availability in soils is mostly likely due to _______________

• High macroporosity, low water content, and high microbial activity

• High microporosity, high water content, and high microbial activity

• High microporosity, low water content, and low microbial activity

• High macroporosity, high water content, and low microbial activity

• High total porosity, low water content, and low microbial activity

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NGSS.MS-LS2-4

A well-aerated soil has

• as much O2 as the atmosphere

• a relative humidity < 70%

• enough O2 for aerobic biotic life

• less CO2 than the atmosphere

• macropores filled with water

The aeration of a soil having strong, very fine, granular structure is likely to be:

• Very good due to predominance of micropores

• Very good due to the stability of the structures

• Very poor due to predominance of micropores

• Very poor due to the stability of the structures

Which is true about the specific heat of a soil?

• A soil that is wet will require more energy to warm than a dry one

• A soil that is dry will require more energy to warm than a dry one

• A wet soil will conduct the most heat

• A dry soil will conduct the most heat

• A dry, compacted soil is the best conductor of heat

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At which depth, would you expect temperature fluctuations to be minimal?

• 5 cm

• 10 cm

• 15 cm

• 1 m

• 4 m

Adding organic residues to the soil surface:

• will decrease texture

• will increase texture

• will not affect soil temperature

• will help to buffer extremes in soil temperature

• will decrease soil water

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NGSS.MS-LS2-4

Select the appropriate answer based on the temperature of the soil in July/Aug in Texas at the surface (0-30 cm depth) and subsurface (30-60 cm depth).

• The soil surface and subsurface will reach maximum temperature simultaneously

• The soil surface will reach maximum temperature, but the subsurface will not change

• The soil surface will reach maximum temperature, but the subsurface will reach this temperature a few months earlier

• The soil surface will reach maximum temperature, but the subsurface will reach this temperature a few months later

• None of the above