BRAE 340 Final questions & answers
graded A+
Once past the germination stage, plants tend to respond to average root zone salinity. - correct
answer ✔✔True
The equation LR = ECw ÷ [(5 * ECe) - ECw] is for reclamation (not maintenance) leaching. -
correct answer ✔✔False
What are the four major factors that determine the numerical value of the crop coefficient Kc? -
correct answer ✔✔A. Crop, stage of growth, soil surface wetness, and plant moisture stress.
This week in the Central Valley, cotton ETc = 0.35 in/day and ETo = 0.30 in/day. This week in the
low desert ETo = 0.43 in/day. What is the ETc for cotton in the low desert? - correct answer
✔✔A. 0.50 in/day
The correct relationship between the ET for a reference crop and the evapotranspiration for
some other particular crop is: - correct answer ✔✔ETc = Kc * ETo
Which of the following pairs would be MOST likely to generally improve irrigation efficiency? -
correct answer ✔✔Minimize evaporation & spray losses and collect and reuse runoff
California, unlike the USBR, uses a grass reference for determining ETo. - correct answer
✔✔True
A lysimeter is a container filled with soil and a growing crop which is weighed to determine
salinity. - correct answer ✔✔False
, In areas using alfalfa as the reference crop, ET for alfalfa is equal to the reference ET. - correct
answer ✔✔False
Which of these is NOT an ADVANTAGE of improving low on-farm irrigation efficiency? - correct
answer ✔✔More frequenct irrigations
For each condition, determine how Kc relates to Kcb.
Wet soil surface, root zone moisture low enough to cause some stress
Wet soil surface, root zone moisture high enough to cause no stress.
Air dry soil surface, root zone moisture low enough to cause some stress.
Air dry soil surface, root zone moisture high enough to cause no stress - correct answer ✔✔Wet
soil surface, root zone moisture low enough to cause some stress - Impossible to tell, Wet soil
surface, root zone moisture high enough to cause no stress. - Kc is higher than Kcb, Air dry soil
surface, root zone moisture low enough to cause some stress. - Kc is lower than Kcb, Air dry soil
surface, root zone moisture high enough to cause no stress. - Kc is equal to Kcb
Under surface irrigation, soil infiltration rates are not constant over the season. - correct answer
✔✔True
A 127 acre center pivot system, crop peak ETc = 0.26 in/day, DU = 82. Pre-infiltration losses =
5%. With good management, what is the AE? - correct answer ✔✔78
A 95 acre center pivot system, crop peak ETc = 0.34 in/day, DU = 0.80. Pre-infiltration losses =
5%. What is the minimum flow rate the system can have and still meet the net crop ET needs? -
correct answer ✔✔801 gpm
A 107 acre center pivot system, crop peak ETc = 0.32 in/day, DU = 0.85. Pre-infiltration losses =
5%. If the actual system flow rate is 996 GPM, what revolution time applies 1 inch per turn net
to the crop? - correct answer ✔✔60.2 hours
graded A+
Once past the germination stage, plants tend to respond to average root zone salinity. - correct
answer ✔✔True
The equation LR = ECw ÷ [(5 * ECe) - ECw] is for reclamation (not maintenance) leaching. -
correct answer ✔✔False
What are the four major factors that determine the numerical value of the crop coefficient Kc? -
correct answer ✔✔A. Crop, stage of growth, soil surface wetness, and plant moisture stress.
This week in the Central Valley, cotton ETc = 0.35 in/day and ETo = 0.30 in/day. This week in the
low desert ETo = 0.43 in/day. What is the ETc for cotton in the low desert? - correct answer
✔✔A. 0.50 in/day
The correct relationship between the ET for a reference crop and the evapotranspiration for
some other particular crop is: - correct answer ✔✔ETc = Kc * ETo
Which of the following pairs would be MOST likely to generally improve irrigation efficiency? -
correct answer ✔✔Minimize evaporation & spray losses and collect and reuse runoff
California, unlike the USBR, uses a grass reference for determining ETo. - correct answer
✔✔True
A lysimeter is a container filled with soil and a growing crop which is weighed to determine
salinity. - correct answer ✔✔False
, In areas using alfalfa as the reference crop, ET for alfalfa is equal to the reference ET. - correct
answer ✔✔False
Which of these is NOT an ADVANTAGE of improving low on-farm irrigation efficiency? - correct
answer ✔✔More frequenct irrigations
For each condition, determine how Kc relates to Kcb.
Wet soil surface, root zone moisture low enough to cause some stress
Wet soil surface, root zone moisture high enough to cause no stress.
Air dry soil surface, root zone moisture low enough to cause some stress.
Air dry soil surface, root zone moisture high enough to cause no stress - correct answer ✔✔Wet
soil surface, root zone moisture low enough to cause some stress - Impossible to tell, Wet soil
surface, root zone moisture high enough to cause no stress. - Kc is higher than Kcb, Air dry soil
surface, root zone moisture low enough to cause some stress. - Kc is lower than Kcb, Air dry soil
surface, root zone moisture high enough to cause no stress. - Kc is equal to Kcb
Under surface irrigation, soil infiltration rates are not constant over the season. - correct answer
✔✔True
A 127 acre center pivot system, crop peak ETc = 0.26 in/day, DU = 82. Pre-infiltration losses =
5%. With good management, what is the AE? - correct answer ✔✔78
A 95 acre center pivot system, crop peak ETc = 0.34 in/day, DU = 0.80. Pre-infiltration losses =
5%. What is the minimum flow rate the system can have and still meet the net crop ET needs? -
correct answer ✔✔801 gpm
A 107 acre center pivot system, crop peak ETc = 0.32 in/day, DU = 0.85. Pre-infiltration losses =
5%. If the actual system flow rate is 996 GPM, what revolution time applies 1 inch per turn net
to the crop? - correct answer ✔✔60.2 hours
