What Does ET Mean to You?
Hopefully, the term “ET” doesn’t make you think of a friendly, homesick extra-terrestrial.
Do you know the importance of ET in your field? Did you know that not all “ET” values are created equal?
What is ET?
Evapotranspiration (ET) is the process of evaporation from plant and soil surfaces and transpiration from within plant tissues. In most modern agricultural systems, ET is the dominant process of water loss from a field.
There are many different platforms and products in the industry that offer growers ET numbers. But what kind of ET is it? Is it reliable?
Are there different types of “ET”?
Based on the source you’re using, the term “ET” can actually mean different things.
ETo is Reference Evapotranspiration. When most people mention “ET” in our industry, they mean Reference ET. This is the type of ET reported by sources like CIMIS. Reference ET is the ET of a well-watered lawn.
ETc refers to Crop Evapotranspiration. ETc incorporates Reference ET and some sort of crop coefficient to guess the water use of your field. ETc assumes your plants never experience water stress. ETc is included in subscriptions to some weather stations and crop models. But every field has a different canopy size and most fields experience some water stress. Simply put, ETc is a shot in the dark.
ETa is Actual Evapotranspiration. This is the real, exact, and measured evapotranspiration rate of a specific field. It’s how much water your field is using. And Tule is the only commercially available technology that measures it.
Why is ETa important?
Consistently irrigating to ETa can improve yields. This ensures your plants get precisely the amount of water they need, exactly when they need it.
Irrigating to crop water needs has many benefits. The most immediate value we see with our growers is that they find they’ve been irrigating too much. Adapting irrigation practices lowers both water and energy bills on the farm. Avoiding over-irrigation can also help reduce disease and improve efficient nutrient uptake by plants. Lower disease risk, better nutrient uptake, and precise irrigation all contribute to better quality and/or higher yields!
In the graph below, you’ll see that Nichols Farms increased their yields by irrigating to ETa year after year. Yields were less than 3,000 pounds in a year when total irrigation was 8 inches off ETa. They grew to nearly 6,000 pounds when irrigation was off by less than an inch.
What makes Tule different?
Unless it comes from Tule, the ET information you’re getting is an estimate, not a measurement. ET estimates can be wildly off for your field because a) your climate is different than the CIMIS station climate, b) your canopy is different than the one-size-fits-all crop coefficient, and c) your crop’s water status may not always be the same as a wet lawn.
Tule sensors offer ETa measurements in real time each day, daily crop water stress reports, irrigation monitoring, and irrigation suggestions.
Knowing ETa means you know the water use of your field – not the water use of a lawn fifty miles from your field.
