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Computational Approach to Assess Actual Transpiration from Aerodynamic and Canopy Resistance
Author(s) -
BenAsher J.,
Meek D. W.,
Hutmacher R. B.,
Phene C. J.
Publication year - 1989
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1989.00021962008100050016x
Subject(s) - transpiration , canopy , loam , irrigation , mathematics , environmental science , hydrology (agriculture) , atmospheric sciences , soil water , soil science , agronomy , chemistry , botany , physics , biochemistry , photosynthesis , geotechnical engineering , biology , engineering
A simple method for estimating actual transpiration may help to control precise irrigation. The Penman‐Monteith equation can be a useful method, provided data on canopy resistance ( r c ) and aerodynamic resistance ( r av are available. These parameters are complex and hard to obtain. The objective of this study was to estimate r c and r av with infrared thermometers (IRT). Tomato ( Lycopersicon esculentum Mill. cv. UC‐82B) grown under various irrigation regimes on a Panoche clay loam soil (fine‐loamy, mixed, thermic Typic Torriorthents) were used to obtain differential values of canopy and air temperatures. With standard climatological data, they were used for the determination of r c and r av . Calculated values of r c and r av were used to estimate actual transpiration rates. A basic assumption is that both r c and r av are crop‐specific coefficients of proportionalities rather than physically measurable parameters. While r c varies according to water availability, r av is not directly affected by soil water status, but is a factor of crop and climatic conditions. Thus, r av determined under conditions approximating potential transpiration ( T p ) was also used to evaluate r c under water deficit conditions. Calculated values of r c and transpiration agreed with values measured with a steady state diffusion porometer. A computational link exists between measurements of canopy, air temperature, r c , and r av . Infrared thermometers can be effectively used in irrigation management.