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Journal of Biological Sciences
Year: 2008  |  Volume: 8  |  Issue: 5  |  Page No.: 954 - 957

Row Spacing Effects on Light Extinction Coefficients, Leaf Area Index, Leaf Area Index Affecting in Photosynthesis and Grain Yield of Corn (Zea mays L.) and Sunflower (Helianthus annuus L.)

Shahram Riahinia and Sayed Mehdi Dehdashti    

Abstract: In many crop models, light intercepted by a canopy (IPAR) is calculated from a Beer`s Law equation: IPAR = PAR x [1 - exp (-k x LAI)], where k is the extinction coefficient, PAR the photosynthetically active radiation and LAI the leaf area index. The objectives of this research were to determine the effect of row spacing on light extinction coefficient (k), grain yield, LAI, LAIP for different row spacing of corn (Zea mays L.) and sunflower (Helianthus annuus L.). Seeds of the species were sown in rows 0.35, 0.50, 0.65, 0.80 and 1.00 m apart. Measurements of canopy light interception were taken near solar noon. The extinction coefficient showed a linear decrease as row spacing increased. For each crop, the effect of row spacing on k was described by one linear regression. Grain yield decreased for corn and sunflower as row spacing increased from 0.35 to 1 m. Leaf Area Index (LAI) and leaf area index affecting in photosynthesis (LAIp) was significantly increased by decreasing row spacing.

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