UC Cooperative Extension Horticulture Advisor, Mary Bianchi, said it’s important to be precise with irrigation during times of limited water. Speaking on the topic of avocados, she explains evapotranspiration and why it’s critical to get the right information for your precise growing location. “So evapotranspiration takes into account the amount of water that’s lost from the landscape by evaporation from the soil surface, or any surface, and the water lost from the transportation by the plant. It’s a mathematical estimate of the amount of water the plant loses in a day or an irrigation period,” Bianchi said.
Finding that number specific to your land is the key and Bianchi said statewide systems can be a little general in some areas. “There are various ways to calculate that number. The California Irrigation Management Information Service (CIMIS) has weather stations throughout California that will provide that information but in an area like the Central Coast, where we have micro-climates that can differ widely, it’s important to use a more site-specific weather station and/or a tool like an atmometer,” Bianchi said.
Atmometers are not a new agriculture tool and Bianchi said it’s a very simple tool that has been around for some time. “It uses a column of water that evaporates through a porous cap with a fabric that helps it to mimic the values that you would get from a full-on weather station. It gives an individual who is in a narrow, coastal canyon a better idea of what the evapotranspiration is for his trees as opposed to something that is calculated from a weather station that is 10, 20 or 30 miles away,” Bianchi Said.