Seminar – Colin Campbell

“Two New Discoveries to Address Old Water Problems in Irrigation”

Abstract: When highlighting groundbreaking work in the soil-plant-atmosphere continuum in his 1961 article “Water for Man”, Utah State University Professor Sterling Taylor ended by saying “Each new discovery adds to our basic knowledge of nature…we are bringing light into the darkness of the unknown as we slowly push back the frontiers of knowledge.” Although Dr. Taylor’s untimely death in 1967 and the methodical pace of development may have over-emphasized “slowly”, his passion for “[extracting] true facts from a reluctant nature” ignited a passion for quantifying environmental water through measurement the still burns brightly today. METER Group (once called Decagon Devices) is a direct beneficiary of this as it was he who built an active collaboration with Dr. Walt Gardner at WSU in the early 1960s. Dr. Gaylon Campbell, WSU professor emeritus and founder of METER, moved from Taylor’s USU lab to WSU for a Ph.D. and eventual faculty position here. Now METER, with Gaylon’s continued work, continues to build on Sterling’s ideas to elucidate water’s secrets as it’s shared between soil and plants. Particularly vexing problems then, including how to accurately but inexpensively measure evapotranspiration (ET) from plant canopies and reliably measure the amount and energy state of water and salt in soil, are being solved today.
This presentation will highlight advances in research from METER including a Variance Bowen Ratio approach to measuring ET – a century old concept with a recent twist. Currently, choices for ET data are limited to often expensive flux-based measurements, FAO56 estimates from weather stations, or satellite derived remote sensing values. A recent paper by Wang et al. (2023) proposed measuring the variance in temperature and specific humidity at a single height (not two different heights -Bowen (1926)). We will discuss the theory behind the method, how VBR is performing against other ET approaches and what the possibilities are for using this as a tool to better understand both native and managed ecosystems. We’ll also touch on measuring soil salinity – an arid region challenge, especially when using poor water sources – and the key to effective, autonomous indoor agriculture. New complex dielectric technology (CDX) measures pore water electrical conductivity directly and accurately, opening up a range of options for efficient watering and water savings.