UPDATED ACTUAL Questions and
CORRECT Answers
Aeration - CORRECT ANSWER - the ventilation of soil
Oxygen availability in soils is affected by - CORRECT ANSWER - soil macroporosity,
soil water content, O2 consumption by respiring roots and aerobic microbes, redox potential
Poor aeration results when ____________% of pores are filled with water. - CORRECT
ANSWER - 80-90%
Mass flow - CORRECT ANSWER - due to differences in pressure
Diffusion - CORRECT ANSWER - due to concentration differences
What is the main gas exchange process in soils? - CORRECT ANSWER - diffusion
Redox potential (Eh) - CORRECT ANSWER - tendency to give or accept electrons
Oxidation - CORRECT ANSWER - removal of an electron from an element
Reduction - CORRECT ANSWER - addition of an electron to an element
Denitrification - CORRECT ANSWER - causes 30% of the total loss of N from
agricultural soils
, Factors affecting Soil Aeration - CORRECT ANSWER - drainage of excess of water, rates
of respiration in soil, subsoil vs topsoil, soil heterogeneity
What percentage of ice-free land do wetlands cover? - CORRECT ANSWER - 14%
Three basic indicators of a wetland - CORRECT ANSWER - hydrophytic vegetation,
water-saturated conditions, hydric soils
Hydric soils - CORRECT ANSWER - saturated long enough during periods of enough
biological activity to cause anaerobic conditions to occur
Benefits of wetlands - CORRECT ANSWER - species habitat, water filtration, flooding
reduction, shoreline protection, commercial and recreational activities, nature products
Why is soil temperature important? - CORRECT ANSWER - affects rates of physical,
chemical, and biological reactions
Factors influencing soil temperature - CORRECT ANSWER - solar radiation, specific heat
capacity of the soil, heat of vaporization of water
Aspect (slope) - CORRECT ANSWER - direction the slope faces with respect to the sun
Subsoil temperatures - CORRECT ANSWER - less fluctuating
General properties of soil colloids - CORRECT ANSWER - size: very small
surface area: large
surface charges: most negative
Soil Minerals - CORRECT ANSWER - O2 46%