How much to irrigate | Netafim

Summary

This video script explains the concept of precision irrigation and how to calculate the water consumption of crops to maintain optimal water balance. It introduces key concepts like evapotranspiration (ET), which includes both plant transpiration and soil evaporation, and how to adjust for crop-specific factors using a crop factor (KC). Through a step-by-step example, viewers learn how to calculate the actual water consumption of a crop using ET and KC values. The importance of dynamic irrigation schedules, adjusted daily based on weather and crop growth stages, is emphasized to maintain healthy, stress-free plants.

Takeaways

• 😀 Drip irrigation is a smart choice for managing water usage effectively in agriculture.
• 😀 Irrigation is about balancing the amount of water available in the soil with the plants' consumption.
• 😀 The goal is to replace the water plants have consumed to avoid drying out and stress.
• 😀 Evapotranspiration (ET) is the total water consumed by plants through transpiration and evaporation from the soil.
• 😀 ET is calculated using meteorological data such as temperature, humidity, wind speed, and radiation.
• 😀 Every plant has a unique water consumption rate, which is called the crop's specific evapotranspiration (ETc).
• 😀 The measured reference ET value (ETo) is based on evapotranspiration from a standardized grass surface.
• 😀 You can get the ETo values from a weather station on the farm or from applications like NetPhim ETo.
• 😀 The crop factor (Kc) adjusts the reference ETo for each crop type and growth stage.
• 😀 To calculate the crop’s actual water consumption (ETc), multiply the ETo by the crop’s Kc value.
• 😀 For instance, if ETo is 6.5mm and Kc is 0.2, the cotton field's water consumption for that day is 1.3mm or 13 cubic meters per hectare.
• 😀 The values for ETc are dynamic, changing daily based on weather conditions and periodically according to the crop's growth stage.
• 😀 If irrigation is not daily, you should sum the ETc for the days since the last irrigation to determine the total amount of water to apply.

Q & A

What is the primary goal of irrigation scheduling?

The primary goal of irrigation scheduling is to balance the water availability in the soil with the water consumption by plants, ensuring the plants do not dry out or suffer from stress.

What does ET stand for, and what does it measure?

ET stands for evapotranspiration, which is the total amount of water that plants consume through transpiration, along with evaporation from the soil.

How is ET calculated?

ET is calculated based on meteorological data, which includes temperature, humidity, wind speed, and radiation.

What is the difference between ET and ETc?

ET is the general measure of evapotranspiration for a standard vegetated surface of grass, while ETc refers to the actual water consumption of a specific crop in a specific field at a given growth stage.

How can you calculate the water consumption of a specific crop?

To calculate the water consumption of a specific crop, you multiply the ETo (reference evapotranspiration) by the crop’s crop factor (Kc), which reflects the crop's water requirements at its growth stage.

Where can you obtain the ETo values needed for calculations?

ETo values can be obtained from a weather station located on your farm or from an online source such as the NetPhim ETo application.

What is the crop factor (Kc), and why is it important?

The crop factor (Kc) represents the specific water needs of a crop at different growth stages. It is crucial for adjusting the reference evapotranspiration (ETo) to match the actual water consumption of the crop.

How do you determine the crop factor (Kc) for a specific crop?

The crop factor (Kc) can be determined by doing a quick internet search, consulting crop literature, or asking an irrigation specialist.

What does the example of the cotton field illustrate in the script?

The example illustrates how to calculate the actual water consumption (ETc) of a cotton field. Given an ETo of 6.5 mm and a crop factor (Kc) of 0.2, the cotton field's water consumption for the day is calculated as 1.3 mm.

What happens if irrigation is not done daily?

If irrigation is not done daily, you need to sum the ETc values of the days since the last irrigation event to determine how much water needs to be applied.