Irrigation scheduling | Netafim

Summary

This video guides viewers on how to schedule irrigation for a field by calculating the optimal time interval between irrigation events. The focus is on maintaining soil water content within the readily available water range by using calculations based on soil type, effective root zone, and evapotranspiration (ETC) rates. The video covers how to determine total available water (TAW), adjust for the wetted area, and apply a depletion threshold to calculate irrigation intervals. Viewers learn how to fine-tune the irrigation process for precision, improving water use efficiency and crop health.

Takeaways

• 😀 Irrigation scheduling helps determine when to irrigate by maintaining soil water content within the readily available water range.
• 😀 To set the irrigation event, the soil water content is raised to field capacity, and irrigation occurs when it reaches the depletion threshold.
• 😀 Different soil types have varying depletion thresholds and water dynamics, which influence irrigation timing.
• 😀 The time interval between irrigation events can be calculated using the equation: raw / etc, where raw is a calculated value and etc changes daily.
• 😀 Total Available Water (TAW) is the difference between field capacity and wilting point, and it’s essential for calculating irrigation needs.
• 😀 The effective root zone, where 85% of plant roots are located, is the primary area irrigated, not the full soil profile.
• 😀 To calculate the wetted area, use specific values for width and depth, or consult an agronomy advisor for more accurate measurements.
• 😀 The depletion threshold (within TAW) indicates when irrigation is needed and is customized for each field and crop.
• 😀 Irrigation intervals can be calculated more precisely by considering the daily max or average ETC of the crop’s current stage.
• 😀 If the calculated irrigation interval results in a fraction (e.g., 3.3 days), it should be rounded to the nearest whole day for practical application.
• 😀 While irrigation scheduling is affected by multiple factors, the soil's water-holding capacity remains the leading factor for optimal scheduling.

Q & A

What is the primary goal of irrigation scheduling?

The primary goal is to maintain the soil water content within the readily available water range, ensuring that irrigation occurs at the right intervals to prevent water depletion below the threshold.

How do you determine when to schedule the next irrigation event?

You schedule the next irrigation event when the soil water content reaches the depletion threshold, which is the lowest acceptable level of available water in the soil.

What is the method used to calculate the irrigation interval?

The irrigation interval is calculated using the equation: raw (required available water) divided by the evapotranspiration (etc) value.

What is the role of the depletion threshold in irrigation scheduling?

The depletion threshold represents the lowest point of water content in the soil that triggers the need for irrigation. It helps to determine when irrigation should occur.

What does the term 'total available water' (TAW) refer to?

Total available water (TAW) is the difference between the field capacity and wilting point of the soil, representing the amount of water available for plant use.

Why is it important to focus on the effective root zone for irrigation?

Irrigation should focus on the effective root zone, where 85% of the roots are located, ensuring that water is available to the plants where it matters most.

How is the percentage of wetted area calculated in this method?

The percentage of wetted area is calculated by dividing 100% by the distance between dripper lines and multiplying it by the width and depth of the wetted area.

What are the default values for wetted area width and depth used in the example?

In the example, the default values for wetted area width and depth are 30 cm and 50 cm, respectively.

How does the evapotranspiration (ETC) value impact irrigation scheduling?

The evapotranspiration (ETC) value impacts the amount of water needed for irrigation. It changes daily based on weather and plant development, and it influences the irrigation interval.

What should be done if the irrigation interval results in a fractional day?

If the irrigation interval results in a fractional day, it should be rounded down to the nearest whole day, ensuring practical application.

What other factors can affect irrigation scheduling besides soil type?

Other factors that can affect irrigation scheduling include plant traits, salinity, soil permeability, operational constraints, and agronomical decisions such as applied stress or profile filling.