IA Irrigation Scheduling & Evapotranspiration 2

Question 1

Which weather variable has the greatest influence on reference evapotranspiration (ETo) in humid climates?

Accepted Answer

Net radiation

Answer

Net radiation is typically the dominant driver of ETo in humid climates where vapor pressure deficit is lower.

Question 2

The 'checkbook method' of irrigation scheduling tracks what two primary inputs?

Accepted Answer

Rainfall and ET

Answer

The checkbook method balances rainfall and ET as deposits and withdrawals to maintain soil moisture within an acceptable range.

Question 3

What does the term 'irrigation interval' refer to?

Accepted Answer

The number of days between irrigation events

Answer

Irrigation interval is the number of days between scheduled watering events, determined by depletion rate and MAD.

Question 4

If daily ETo is 0.25 inches and the crop coefficient is 0.8, what is the daily crop water use (ETc)?

Accepted Answer

0.20 inches

Answer

ETc = ETo × Kc = 0.25 × 0.8 = 0.20 inches per day.

Question 5

Which instrument is used to directly measure reference evapotranspiration in the field?

Accepted Answer

Lysimeter

Answer

A lysimeter is a precision device that measures actual water use by plants by weighing or monitoring drainage from an isolated soil-plant system.

IA - Irrigation Association Certification Practice Test