Flow Duty:
Flow duty is a term used in the field of irrigation engineering. It refers to the amount of water required to be delivered to a specific area of land through direct irrigation. The name "flow duty" is used to describe this particular aspect of irrigation.

Direct Irrigation:
Direct irrigation is a method of supplying water directly to the plants' root zone, either through surface or subsurface methods. It involves supplying water in a controlled manner to meet the water requirements of the crops. This method ensures that water is efficiently utilized and reduces wastage.

Types of Duty:
In irrigation engineering, there are different types of duty that are considered when designing an irrigation system. These include:

1. Duty:
Duty is the term used to describe the amount of water required per unit area of land for a specific crop. It is usually expressed in terms of volume per unit area or depth of water per unit area. Duty takes into account the water requirements of the crop, the climate conditions, and the soil characteristics.

2. Flow Duty:
Flow duty specifically refers to the amount of water delivered to a specific area of land through direct irrigation. It is the rate of flow of water required to meet the crop's water requirements. Flow duty is influenced by factors such as the type of crop, soil type, and climate conditions.

3. Quantity Duty:
Quantity duty is another term used in irrigation engineering. It refers to the total volume of water required to irrigate a given area of land. It takes into account the irrigation system's efficiency and the water losses that occur during the irrigation process.

Conclusion:
In conclusion, the correct name for the duty called in direct irrigation is "Flow Duty." This term specifically refers to the amount of water required to be delivered to a specific area of land through direct irrigation. It is important to consider factors such as the crop's water requirements, soil characteristics, and climate conditions when determining the flow duty for efficient irrigation.