SCSC 301 Exam 3 tamu – questions and
answers
Which of the following is NOT a carbon-containing compound that is involved in the
cycling of carbon associated with most plant/animal life forms? - ANSWERS✔✔
calcium carbonate
Which organic matter property affects the availability of nutrients to plants? -
ANSWERS✔✔ Cation exchange capacity
**Complete degradation of residues (complete oxidation) results in _______ -
ANSWERS✔✔ CO2
Which of the answers below represents an immobilized form of N? - ANSWERS✔✔
protein in a bacterial cell
Which is true when comparing aerobic vs anaerobic organic matter decomposition?
- ANSWERS✔✔ Anaerobic degradation is much slower than aerobic and results in
compounds that are partially decomposed
Soil organic matter degradation will be greatest when_____________ - ANSWERS✔✔
There is sufficient soil moisture and aeration at neutral pH and relatively warm
temperatures to degrade residue with high levels of N
**Organic matter tends to decrease the ___ of soils. - ANSWERS✔✔ bulk density
**___ is the element in residue that has the greatest effect on the rate of residue
decomposition. - ANSWERS✔✔ nitrogen
**The organic matter content of soils tends to decrease with increasing frequency
of: - ANSWERS✔✔ cultivation
, A soil with C/N ratio of 600:1 could be a material such as_______ - ANSWERS✔✔
sawdust or leaves that have a low N content and a high potential for N
immobilization
**Poorly defined organic substances that are complex, resistant to decay, and
polymeric are ___ - ANSWERS✔✔ humic substances
Which of the following could be used to improve soil organic matter in a cropping
system? - ANSWERS✔✔ Reduce the plant materials that are harvested and return
any residues back to the field
If you had to guess, which environment would likely have the greatest soil organic
matter? - ANSWERS✔✔ northeast US
**Available water in soils is water held between the wilting coefficient and: -
ANSWERS✔✔ field capacity
Water that drains downward in a soil consists of water moving in response to
differences in: - ANSWERS✔✔ primarily gravitational potentials
Water enters a very clayey subsoil from a sandy surface soil: - ANSWERS✔✔ as soon
as the wetting front reaches it
In a soil containing large holes or channels that are closed at the surface, water
enters these large holes_______ - ANSWERS✔✔ only after the surrounding soil is
saturated
Water moves downward in a profile from the B horizon (clay loam) into gravel layer
______. - ANSWERS✔✔ only after the B horizon is saturated
**As water is adsorbed by a dry soil, the soil matric potential of the dry soil ______. -
ANSWERS✔✔ increases
Water moves downward in a profile from the A horizon (sandy loam) to the B horizon
(loam)_____. - ANSWERS✔✔ as soon as the wetting front reaches the B horizon
answers
Which of the following is NOT a carbon-containing compound that is involved in the
cycling of carbon associated with most plant/animal life forms? - ANSWERS✔✔
calcium carbonate
Which organic matter property affects the availability of nutrients to plants? -
ANSWERS✔✔ Cation exchange capacity
**Complete degradation of residues (complete oxidation) results in _______ -
ANSWERS✔✔ CO2
Which of the answers below represents an immobilized form of N? - ANSWERS✔✔
protein in a bacterial cell
Which is true when comparing aerobic vs anaerobic organic matter decomposition?
- ANSWERS✔✔ Anaerobic degradation is much slower than aerobic and results in
compounds that are partially decomposed
Soil organic matter degradation will be greatest when_____________ - ANSWERS✔✔
There is sufficient soil moisture and aeration at neutral pH and relatively warm
temperatures to degrade residue with high levels of N
**Organic matter tends to decrease the ___ of soils. - ANSWERS✔✔ bulk density
**___ is the element in residue that has the greatest effect on the rate of residue
decomposition. - ANSWERS✔✔ nitrogen
**The organic matter content of soils tends to decrease with increasing frequency
of: - ANSWERS✔✔ cultivation
, A soil with C/N ratio of 600:1 could be a material such as_______ - ANSWERS✔✔
sawdust or leaves that have a low N content and a high potential for N
immobilization
**Poorly defined organic substances that are complex, resistant to decay, and
polymeric are ___ - ANSWERS✔✔ humic substances
Which of the following could be used to improve soil organic matter in a cropping
system? - ANSWERS✔✔ Reduce the plant materials that are harvested and return
any residues back to the field
If you had to guess, which environment would likely have the greatest soil organic
matter? - ANSWERS✔✔ northeast US
**Available water in soils is water held between the wilting coefficient and: -
ANSWERS✔✔ field capacity
Water that drains downward in a soil consists of water moving in response to
differences in: - ANSWERS✔✔ primarily gravitational potentials
Water enters a very clayey subsoil from a sandy surface soil: - ANSWERS✔✔ as soon
as the wetting front reaches it
In a soil containing large holes or channels that are closed at the surface, water
enters these large holes_______ - ANSWERS✔✔ only after the surrounding soil is
saturated
Water moves downward in a profile from the B horizon (clay loam) into gravel layer
______. - ANSWERS✔✔ only after the B horizon is saturated
**As water is adsorbed by a dry soil, the soil matric potential of the dry soil ______. -
ANSWERS✔✔ increases
Water moves downward in a profile from the A horizon (sandy loam) to the B horizon
(loam)_____. - ANSWERS✔✔ as soon as the wetting front reaches the B horizon
