Question

The relationship between irrigation period (IP) and irrigation frequency (IF) for a well designed irrigation system will be

• A. IP $<$ IF
• B. IP $>$ IF
• C. IP = IF
• D. IP $\leq$ IF

Hint:

To prevent crop wilting in any part of the command area, you must finish irrigating the entire field before the next scheduled irrigation interval begins:
\[ \text{Irrigation Period (IP)} \leq \text{Irrigation Frequency (IF)} \]

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
In the design of irrigation systems, two operational time intervals are defined:
1. Irrigation Frequency (IF): The time interval (in days) between two consecutive water applications required to prevent crop stress.
2. Irrigation Period (IP): The actual time (in days) required to complete one round of irrigation over the entire command area of the system.

Step 2: Detailed Explanation:
To ensure that crops are irrigated adequately, we must establish the relationship between these two parameters:
- Let us assume a field has an irrigation frequency of \( IF = 10 \text{ days} \).
This means the soil moisture in any part of the field will be depleted to the critical limit every 10 days, requiring replenishment.
- Case 1 (\( IP > IF \)): If the irrigation period is \( 12 \text{ days} \), it takes 12 days to irrigate the entire field once.
The plants in the last section of the field will have to wait 12 days for water, exceeding their critical limit of 10 days, which will cause water stress and yield loss.
This represents a poorly designed system.
- Case 2 (\( IP \leq IF \)): If the irrigation period is less than or equal to 10 days (e.g., \( 8 \text{ days} \)), the entire field can be irrigated before any section exceeds its critical moisture depletion limit.
Therefore, for a well-designed irrigation system, the irrigation period must be less than or equal to the irrigation frequency:
\[ IP \leq IF \]

Step 3: Final Answer:
The correct relationship is IP $\leq$ IF.