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This article in AJ

  1. Vol. 79 No. 1, p. 181-184
     
    Received: Oct 28, 1985


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doi:10.2134/agronj1987.00021962007900010037x

A Portable Chamber for Measuring Canopy Gas Exchange of Crops Subject to Different Root Zone Conditions1

  1. W. S. Meyer2,
  2. D. C. Reicosky3,
  3. H. D. Barrs2 and
  4. G. S. G. Shell2

Abstract

Abstract

The measurement of above ground plant function is an integral part of monitoring crop response to root zone conditions. The objective of this work was to adapt a field gas exchange chamber technique to a lysimeter facility so that apparent photosynthesis (APS) and evapotranspiration (ET) of cotton (Gossypium hirsutum L.) could be studied. A cylindrical chamber covered with clear Teflon film was manipulated with a gantry to enclose plants growing in each of 32 different soil cores within a lysimeter facility. Air was circulated within the chamber and sub-sampled to measure change in CO2 and H2O vapor concentrations with an infra-red gas analyser (IRGA) during a 45-s-measurement period. Measurement timing and data processing were computer controlled. Sensitivity of measurement was ± 0.02 mg CO2 m−2s−1 for APS and ± 4.5 mg H2O m−2s−1 for ET which was about 2 to 3% of values measured in a well-watered, fully developed cotton canopy. Values of ET from IRGA measurements were similar (P>0.05, r2 =0.89) to those calculated from psychrometer measurements. The system permits accurate, rapid, and repetitive measurements over soil cores in which concurrent measurements of root zone conditions can be made.

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