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Articles by Sayed Mehdi Dehdashti
Total Records ( 2 ) for Sayed Mehdi Dehdashti
  Shahram Riahinia and Sayed Mehdi Dehdashti
  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.
  Sayed Mehdi Dehdashti and Shahram Riahinia
  We studied the effect of different row spacing and density of corn on Radiation Interception (RI), Total Day Weight (TDW), Leaf Area Index (LAI), Next Assimilation Rate (NAR), Crop Growth Rate (CGR) and grain yield. The experiment was conducted in the field at research station of Isfahan, Iran on loamy clay to compare row spacing and to determine optimum plant density for maize hybrid K704. The experimental design was a randomized complete block in a split-plot arrangement with four replicates. Plot treatments were row spacing (60, 75 and 90 cm). Split-plot treatments were within-row spacing (12, 14, 16 and 18 cm). An increase of PP from 10.5 to 13.9 plants m2 increased LAI, TDW, CGR, RI and grain yield on average by 0.205 m, 48.4 g m1, 1.14 g m2 day1, 0.89% and 222.7 kg ha1 for each 1 plant per m2 added .but decreased NAR by 0.205 g m2 day1 for each 1 plant per m2 added. Moreover, when row spacing was reduced, RI, TDW, LAI, CGR and grain yield increased. But by reducing row spacing, NAR was decreased. The results show that the row spacing 60 cm, within-row spacing 12 cm and density 11.9 plant m2 for conditions of Isfahan is suitable for maize hybrid K704.
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