Blog: Field-Level Actual Evapotranspiration, a New Way to Maximize Performance and Minimize Water Use

by Tom Shapland, PhD, CEO of Tule, a part of CropX

Every farmer of irrigated crops has to decide how much and how often to irrigate. A key factor for this decision is how much water the crop has used since the last irrigation. For most, this is an educated guess that considers weather, soil, crop type and maturity and regional ag advice. You can go a long way with this, but irrigating in times of scarcity and competition requires a higher degree of precision – you want to give your crop just what it needs, no more, no less. For decades, knowledge of crop water use at the field-level has been used by scientists but has remained inaccessible to farms due to cost and complexity. Now new solutions are revolutionizing precision irrigation with unmatched accuracy in real-time field water use measurement. 

What is Evapotranspiration (ET)? 

Evapotranspiration (ET) is the combined effects of water evaporating from soil and plant surfaces and transpiration from within plant tissues. This natural phenomenon plays a pivotal role in determining the water requirements of crops, influencing irrigation practices and water management strategies. Evapotranspiration is affected by various factors including weather conditions, plant size, and water availability, making accurate and hyper-local measurements of ET essential for optimizing agricultural productivity and ensuring sustainable water use. 

There are several types of ET, each providing different insights into water dynamics within agricultural systems. Reference Evapotranspiration (ETo) is a measure of the water demand of a well-watered grass field. Farmers are familiar with ETo from weather reports. Reference ET serves as a baseline to understand the influence of the weather on plant water use. Crop Evapotranspiration (ETc) adjusts ETo with a crop-specific crop coefficient (Kc) to estimate the water use of a crop field under ideal, well-watered conditions. However, the most relevant measure for farmers is Actual Evapotranspiration (ETa), which represents the real water use of a field, taking into account the environmental conditions, the plant canopy size, and water stress. ETa provides a direct measure of the water consumed by a crop, making it indispensable for precise irrigation management. 

Actual ET: Now Available for Farms 

While ETa sensors have traditionally only been accessible to scientists and researchers, this year two new solutions have become available for use on farms around the globe: CropX Actual ET, and Reinke Direct ET™ by CropX. CropX Actual ET is a combined software and hardware solution that includes a field mounted ET sensor and feeds data to the CropX agronomic farm management platform. Reinke Direct ET™ by CropX, a pivot mounted ETa sensor available exclusively for Reinke pivots, also feeds data to the CropX platform. Both solutions make it easy for farmers to activate field-level ETa measurements for precise water management and improved crop performance. 

Powered by Affordable, Easy-to-install, and Accurate Hardware 

The ETa sensors from CropX and Reinke stand out as revolutionary tools in the agricultural sector. Unlike traditional methods for agriculture that estimate water use based on weather conditions or generic crop coefficients, the sensors provide precise, field-specific data on how much water is being utilized by a specific crop field. By accurately quantifying the water lost to the atmosphere, ETa data enables growers to replace precisely the amount of water consumed, ensuring optimal irrigation that supports robust crop yields, maximizes water efficiency, and contributes to sustainable agricultural practices.  

Converting Data into Impactful Insights 

The CropX Actual ET and Reinke Direct ET™ by CropX solutions operate on a sophisticated principle, utilizing a combination of hardware installed directly in the field, cutting-edge atmospheric science research developed at the University of California, Davis, and powerful software for generating agronomic insights. The ETa sensor is installed above the plant canopy and measures the amount of water the wind carries away from the crop field. But you don’t need to be a researcher to analyze the data. The sensor reports the amount of water the field has used to the CropX web and mobile app based agronomic farm management system. CropX empowers farmers with actionable insights to make informed decisions on irrigation timing and quantity, ultimately driving efficient water use and supporting sustainable agricultural practices. 

Learn more about Reinke Direct ET™ by CropX and contact a Reinke dealer here

About the Author 

Tom Shapland, PhD, developed a novel technology for crop water use measurement during his doctorate work at the University of California, Davis. In 2014, he cofounded Tule Technologies to make this technology commercially available to California farmers. In 2023, he sold Tule to CropX Technologies, a global digital agronomic solutions developer, in order to expand the reach to farms worldwide and combine the powerful Actual ET sensor of Tule with CropX’s comprehensive agronomic farm management platform.