Effect of sowing date, planting density and cultivar on solar radiation interception indices in sugar beet. II. Radiation use efficiency

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

doi:10.22092/jsb.2009.975

Effect of sowing date, planting density and cultivar on solar radiation interception indices in sugar beet. II. Radiation use efficiency

Document Type : Scientific - Research

Authors

¹ Assistant Professor of Sugar Beet Seed Institute (SBSI) - Agricultural Research Education and Extension Organization (AREEO), Karaj, Iran.

² Professor of Chamran University , Ahwaz, Iran.

³ Professor of Ramin Agricutural and Natural Resourses University, Molasani, Ahwaz, Iran.

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

10.22092/jsb.2009.975

Abstract

In order to evaluate the effect of sugar beet sowing date, planting density and cultivar on solar radiation interception, a study was conducted in Kamal-Abad Agricultural Research Station of Sugar Beet Seed Institute (SBSI) in 2005 and 2006. The experimental design was split-split plots based on Randomized Complete Block Design (RCBD) with three replications with two sowing dates as the main plot (the earliest possible date including 04-April and 22-April in 2005 and 2006 and 40 days later including 23-May and 31-May in 2005 and 2006, respectively), four plant densities as the sub-plot (6.0, 7.5, 9.0 and 10.5 plants.m^-2) and three sugar beet monogerm cultivars as the sub-sub-plot (Jolgah, Hybrid 428 and DS 4027). In terms of the effect of sowing date, it was shown that sugar beet sowing in Karadj at the earlist possible date (Mid-March) compared to the sowing date delayed for 40 days only led to an increase in intercepted radiation by 425 MJ.m^-2; while radiation use efficiency (RUE) for producing dry matter which was in the range of 1.43-1.48 g.m^-2 MJ^-1 did not differ between the two sowing dates. The increase in plant density from 6.0 to 10.5 plants.m^-2 led to a non-significant increase in intercepted radiation. RUE did not show a linear response to plant density, too; while the increase in plant density led to a decrease in radiation extinction coefficient and improvement of radiation distribution in canopy. The cultivar DS 4027 had better RUE than the cultivars Jolgah and Hybrid 428 (1.85 and 1.43 g.m^-2.MJ^-1, respectively). The main reason for this difference was the higher RUE of DS 4027 (1.54 g.m^-2.MJ^-1) in producing root system than the other two cultivars (1.10 g.m^-2.MJ^-1). In terms of RUE in producing shoot system, there was no significant difference between Jolgah and Hybrid 428 (0.34 g.m^-2.MJ^-1) and DS 4027 (0.32 g.m^-2.MJ^-1). According to the results, it can be conclude that improving the main drawback of domestic cultivars i.e. low R/S ratio should be given priority.

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