Submitted to: International Evapotranspiration Irrigation Scheduling Conference
Publication Type: Abstract Only
Publication Acceptance Date: November 7, 1996
Publication Date: N/A
Technical Abstract: Developing and verifying irrigation scheduling methods requires accurate tools for quantifying evapotranspiration (ET) in the field. Closed chamber measurements provide one tool for measuring crop water use. A Mobile Research Gas Exchange Machine (MRGEM) has provided closed-chamber measurements of ET and Carbon Dioxide Exchange Rate (CER) on the crop- canopy level through the past 15 growing seasons. As new technology become available,the onboard instrumentation is updated. We describe the current state of the art for the MRGEM measurement system, providing a detailed description of the tractor, closed-chamber with mixing fans, pumps and plumbing, instrumentation, data acquisition system, computer, software, and flux calculation methods. This portable tool provides ET measurements at the crop canopy level in remote locations within one minute. These measurements can be used to verify predictive ET models, compare water use efficiencies of various production techniques, and compare measured ET wit non-direct or remotely sensed irrigation scheduling criteria such as leaf water potential and canopy temperatures.