SCSC 301 TAMU Exam 2 Howe –
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
Evaporation losses of water from soils may be reduced by - ANSWERS✔✔ Crop
residue on the surface
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
Evaporation losses of water from soils may be reduced by - ANSWERS✔✔ Crop
residue on the surface
