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ARS Home Plains Area Lubbock, Texas Cropping Systems Research Laboratory Wind Erosion and Water Conservation Research Research Publications at this Location





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Title:   Author  item
                                            Baker, Jeffreyitem
                                            LASCANO, ROBERT - TAESitem
                                            Gitz, Dennisitem
                                            Payton, Paxtonitem
                                            Van Pelt, Robert

                                                         - *Scott*item
                                            GARCIA, RICK - LICOR
  Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 11/4/2007
                                    Publication  Date: 11/8/2007
                                    Citation: Baker, J.T., Lascano, R., Gitz, D.C., Payton, P.R., Van Pelt, R.S., Garcia, R. 2007. An open system for measuring canopy gas exchange[abstract]. ASA-CSSA-SSSA Joint  Annual Meeting. New Orleans, Lousiana. November 4-8, 2007. Abstract No. 239-7.Interpretive Summary:
                                Technical Abstract: Three portable, CETA (Canopy Evapo-Transpiration and Assimilation) chamber systems were built and evaluated in 2006.  This chamber system is an open or flow-through system that, once deployed in the field, can operate unattended for extended periods (e.g. overnight for example). The CETA chamber consists of an aluminum framework, 1 m x 0.75 m in cross-section and 1 m tall covered with transparent film.  Differentials between incoming and outgoing atmospheric water vapor and carbon dioxide concentrations are used to calculate evapotranspiration and canopy photosynthesis at 10 s intervals using solenoid valve actuated sample lines connected to an infrared gas analyzer. A programmable data logger controls fan speed and air flow rate in order to control chamber air temperature to within 0.5 oC of ambient air temperature using a feedback control algorithm.  In order to validate the mass balance equations used to calculate canopy evapotranspiration, the CETA chamber was placed over potted plants sitting atop a mini-lysimeter. A wide variety of crop canopies and soil water content were created with greenhouse-grown plants.  Preliminary data analysis indicates good agreement between CETA evapotranspiration measurements and the mini-lysimeter over wide ranges of soil moisture contents and canopy leaf area.  However, these tests also indicate a physical limitation of the system to resolve very small gas concentration differentials caused by the combination of very low soil moisture content and low canopy leaf area.


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