Effect of sowing date, planting density and cultivar on solar radiation interception indices in sugar beet I. Radiation interception and extinction coefficient

Sadeghzadeh Hemayati, S.; Kashani, A.; Taleghani, D.; Nour- Mohammadi, G.; Siadat, S.A.

doi:10.22092/jsb.2008.1035

Effect of sowing date, planting density and cultivar on solar radiation interception indices in sugar beet I. Radiation interception and extinction coefficient

Document Type : Scientific - Research

Authors

¹ Ph. D. graduated in Islamic Azad University , Science and Research Branch

² Professor of Chamran University , Ahwaz, Iran

³ Assistant Professor of Sugar Beet Seed Institute (SBSI) - Agricultural Research Education and Extension Organization (AREEO), Karaj, Iran.

⁴ Professor of Islamic Azad University , Science and Research Branch ,Tehran, Iran

10.22092/jsb.2008.1035

Abstract

In order to evaluate the effects of sugar beet sowing date, planting density and cultivar on solar radiation interception, the present study was conducted in Kamal-Abad Agricultural Research Station of Sugar Beet Seed Institute (SBSI) in 2005 and 2006. The experiment arranged was in split-split plots based on Randomized Complete Block Design (RCBD) with three replications. The sowing date, planting density and cultivar were assigned to main, sub and sub-sub-plots, respectively. Results showed that the photosynthetically active radiation (PAR) rised from 8 MJ.m^-2.day^-1 during late April and after reaching the maximum amount (17.61-17.75 MJ.m^-2.day^-1) during June started to gradually decrease through growing season. Total intercepted PAR (iPAR) had significance differed significantly (P<0.01) between studied years and iPAR in 2005 (1817.04 MJ.m^-2) was about 8.15% greater than that in 2004 (1680.22 MJ.m^-2). The relationship between radiation interception (fi) and leaf area index (LAI) was significant in 2005 (r²=0.82^**) and 2006 (r²=0.64^**) indicating that increase in LAI caused the increase in iPAR. The highest fi was observed in mid-October and LAI equaled to 2.5-3.5 in Karaj. Sowing date had a significant effect (P<0.01) on fi and sowing the sugar beet in the earliest possible date increased the iPAR by 29.67%. The effect of planting density on fi was non-significant and linear correlation coefficient was positive and non-significant. Average radiation extinction coefficient (K) was estimated to be 0.605. The effect of sowng date on K was not significant. The increase in planting density from 6.0 plants.m^-2 (K=0.717) to 7.5, 9.0 and 10.5 plants.m^-2 reduced the K by 11.2, 18.6 and 32.9%, respectively. The significant effect of cultivar on K in 2006 showed that the K of cultivar 428 (0.373) was less than that of cultivars Jolgeh and DS4027 by 54.1 and 72.9%, respectively.

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