BRAE 340 Exam2 questions and
answers graded A+ updated
Field Capacity (FC) - correct answer ✔✔Soil moisture status corresponding to about 10 cb
tension.
"By Feel" Method - correct answer ✔✔Only soil moisture measurement to give SMD (in/ft)
directly.
Gypsum Block - correct answer ✔✔Can measure soil moisture content up to about 10 bars.
Soil moisture characteristic curve - correct answer ✔✔Graph relating soil moisture tension to
soil moisture content.
PWP - correct answer ✔✔Soil moisture status corresponding to about 15 bars tension.
Troxler (FDR) device - correct answer ✔✔Can determine SMD indirectly, if FC is known.
AWHC - correct answer ✔✔The difference between FC and PWP
Saturation - correct answer ✔✔Soil moisture condition corresponding to zero tension.
SMD - correct answer ✔✔Irrigate when this reaches threshold determined by MAD
Tensiometer - correct answer ✔✔Directly measures soil moisture tension, often in centibars
,MAD - correct answer ✔✔When SMD is the indicator, this sets the threshold.
Leaf Bomb - correct answer ✔✔Measures plant rather than soil status.
Between irrigations, the moisture content of the surface layers of soil can not be drier than
PWP. - correct answer ✔✔F
Plants respond directly to the moisture tension in the soil. - correct answer ✔✔T
If spatial variability of soil properties is sufficiently high, commercial irrigation schedulers will
install and use many sampling sites to characterize the moisture status of the soil. - correct
answer ✔✔F
Which soil moisture probe test identifies and measures deep percolation? - correct answer
✔✔E) none of these: neutron probe, FDR probe, resistance meter, tensiometer
The FDR prob measures & moisture by volume: That is, the difference between FC and _______.
- correct answer ✔✔SMD
Hand-move sprinkler set systems: - correct answer ✔✔Large MAD
Corn during the pollination stage of growth: - correct answer ✔✔Small MAD
Strawberries: - correct answer ✔✔Small MAD
Microirrigation with saline water: - correct answer ✔✔Small MAD
Root crops like carrot, onion, potato: - correct answer ✔✔Small MAD
,Cotton: - correct answer ✔✔Large MAD
Circumstances when less frequent irrigations are required or desired: - correct answer ✔✔Large
MAD
Permanent set sprinkler irrigation systems: - correct answer ✔✔Small MAD
Tomato or citrus, just prior to bud formation: - correct answer ✔✔Large MAD
Situations calling for more frequent irrigations: - correct answer ✔✔Small MAD
Wine grapes prior to harvest: - correct answer ✔✔Large MAD
Surface irrigation systems with long runs and sandy soils: - correct answer ✔✔Large MAD
During an irrigation event, most of the soil above the wetting front will be unsaturated. - correct
answer ✔✔T
It is impossible for an irrigation event to increase the moisture content at the top and bottom of
the root zone without bringing intermediate depths to FC. - correct answer ✔✔T
Plants generally tend to take more water from the upper than the lower portions of the root
zone. - correct answer ✔✔T
Pre-irrigation is the practice of watering a field before the crop is planted. - correct answer ✔✔T
, Weather influences the ET of a well watered, full cover crop, but the irrigation system does not.
- correct answer ✔✔T
Which of these are reduced when a plant undergoes moisture stress?
a) stomatal opening
b) vegetative growth
c) relative transpiration
d) photosynthesis
E) all are reduced - correct answer ✔✔E) all are reduced.
(The response to stress is to close stomata, which reduces the transpiration. Since the CO2 can't
enter the leaves, photosynthesis stops, reducing vegetative growth.)
Consider sandy loam and clay soils. The moisture tension at which crop relative transpiration
begins to decline:
a) depends on the MAD
b) is the same for both soils
c) is greater on the clay soil
d) is greater on the sandy loam soil
e) depends on the AWHC - correct answer ✔✔B) is the same for both soils
Under drip irrigation, roots do not seek out the locations where water is being applied. - correct
answer ✔✔T
Too much moisture in the root zone can cause Aeration problems because insufficient carbon
dioxide is available to the roots. - correct answer ✔✔F ("aeration problems" are the result of
insufficient oxygen available to the roots)
answers graded A+ updated
Field Capacity (FC) - correct answer ✔✔Soil moisture status corresponding to about 10 cb
tension.
"By Feel" Method - correct answer ✔✔Only soil moisture measurement to give SMD (in/ft)
directly.
Gypsum Block - correct answer ✔✔Can measure soil moisture content up to about 10 bars.
Soil moisture characteristic curve - correct answer ✔✔Graph relating soil moisture tension to
soil moisture content.
PWP - correct answer ✔✔Soil moisture status corresponding to about 15 bars tension.
Troxler (FDR) device - correct answer ✔✔Can determine SMD indirectly, if FC is known.
AWHC - correct answer ✔✔The difference between FC and PWP
Saturation - correct answer ✔✔Soil moisture condition corresponding to zero tension.
SMD - correct answer ✔✔Irrigate when this reaches threshold determined by MAD
Tensiometer - correct answer ✔✔Directly measures soil moisture tension, often in centibars
,MAD - correct answer ✔✔When SMD is the indicator, this sets the threshold.
Leaf Bomb - correct answer ✔✔Measures plant rather than soil status.
Between irrigations, the moisture content of the surface layers of soil can not be drier than
PWP. - correct answer ✔✔F
Plants respond directly to the moisture tension in the soil. - correct answer ✔✔T
If spatial variability of soil properties is sufficiently high, commercial irrigation schedulers will
install and use many sampling sites to characterize the moisture status of the soil. - correct
answer ✔✔F
Which soil moisture probe test identifies and measures deep percolation? - correct answer
✔✔E) none of these: neutron probe, FDR probe, resistance meter, tensiometer
The FDR prob measures & moisture by volume: That is, the difference between FC and _______.
- correct answer ✔✔SMD
Hand-move sprinkler set systems: - correct answer ✔✔Large MAD
Corn during the pollination stage of growth: - correct answer ✔✔Small MAD
Strawberries: - correct answer ✔✔Small MAD
Microirrigation with saline water: - correct answer ✔✔Small MAD
Root crops like carrot, onion, potato: - correct answer ✔✔Small MAD
,Cotton: - correct answer ✔✔Large MAD
Circumstances when less frequent irrigations are required or desired: - correct answer ✔✔Large
MAD
Permanent set sprinkler irrigation systems: - correct answer ✔✔Small MAD
Tomato or citrus, just prior to bud formation: - correct answer ✔✔Large MAD
Situations calling for more frequent irrigations: - correct answer ✔✔Small MAD
Wine grapes prior to harvest: - correct answer ✔✔Large MAD
Surface irrigation systems with long runs and sandy soils: - correct answer ✔✔Large MAD
During an irrigation event, most of the soil above the wetting front will be unsaturated. - correct
answer ✔✔T
It is impossible for an irrigation event to increase the moisture content at the top and bottom of
the root zone without bringing intermediate depths to FC. - correct answer ✔✔T
Plants generally tend to take more water from the upper than the lower portions of the root
zone. - correct answer ✔✔T
Pre-irrigation is the practice of watering a field before the crop is planted. - correct answer ✔✔T
, Weather influences the ET of a well watered, full cover crop, but the irrigation system does not.
- correct answer ✔✔T
Which of these are reduced when a plant undergoes moisture stress?
a) stomatal opening
b) vegetative growth
c) relative transpiration
d) photosynthesis
E) all are reduced - correct answer ✔✔E) all are reduced.
(The response to stress is to close stomata, which reduces the transpiration. Since the CO2 can't
enter the leaves, photosynthesis stops, reducing vegetative growth.)
Consider sandy loam and clay soils. The moisture tension at which crop relative transpiration
begins to decline:
a) depends on the MAD
b) is the same for both soils
c) is greater on the clay soil
d) is greater on the sandy loam soil
e) depends on the AWHC - correct answer ✔✔B) is the same for both soils
Under drip irrigation, roots do not seek out the locations where water is being applied. - correct
answer ✔✔T
Too much moisture in the root zone can cause Aeration problems because insufficient carbon
dioxide is available to the roots. - correct answer ✔✔F ("aeration problems" are the result of
insufficient oxygen available to the roots)
