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Effect of Defoliation on Onion Bulb Production

M.A. Khan
Principal Scientific officer
Regional Spices Research Centre, Bangladesh Agricultural Research Institute, Magura, Bangladesh

M.K. Hasan
Senior Scientific Officer
Spices Research Center, BARI, Bogura, Bangladesh

M.M. Alam
Senior Scientific Officer
Spices Research Center, BARI, Bogura, Bangladesh

M.M. Ahmed
Scientific Officer
Spices Research Sub-Centre, BARI, Lalmonirhat, Bangladesh.

M.A. Islam
Senior Scientific Officer
Spices Research Center, BARI, Bogura, Bangladesh

Abstract/ Executive Summary:

An experiment to study the effect of varying degrees of defoliation viz. 0, 33, 50, 66 and 100 % at different growth stages such as vegetative, bulbing and maturing stages in onion cv. BARl Piaz 1 was carried out at Regional Spices Research Centre, Magura during the year 2004-2005. The results of the trial revealed that onion showed susceptivity to varying degrees of defoliation at different growth stages. Severe yield loss (35.41 %) was obtained from the defoliation at bulbing stage. While yield losses increased up to 49.27 % with the increase in degree of defoliation. The interaction of growth stages x degree of defoliation was also significant except bulb breadth character. Linear regression equation was obtained from the values of yield loss corresponding to the levels of defoliation.

Keywords: Onion, Defoliation, Growth sage, Yield loss, Linear regression

Location: Regional Spices Research Centre, Magura

Start Date: 27-12-2004

End Date: 23-03-2005

Program Area: Crop-Soil-Water Management

Commodity: Onion

Objectives:

Assess the effects of different degrees of defoliation at various growth stages on the yield of onion which is to be applicable in evaluating final crop yield losses due to defoliation from natural hazards.

Methodology:

The study was conducted at the Regional Spices Research Centre, Magura in Rabi season 2004 to 2005 to obtain information about yield losses in onion caused by defoliation. Five levels of defoliation viz. 0, 33, 50, 66 and 100 % were imposed at three growth stages of onion viz. vegetative, bulbing and maturing stages. Seeds of BARl Piaz I were sown on 7 November 2004 and 50-day old seedlings were transplanted on 27 December 2004 using a plant spacing of 15 em x 10 em (Khan et al., 2003). The two-factor experiment was laid out in randomized complete block design with there replications. The unit plot size was 2.5 m x 1.5 m. Well-decomposed cowdung at the rate of K₂0 and 20 kg S/ha in the form of urea, TSP, MP and gypsum, respectively (SRC, 2005). Total amount of TSP, MP, gypsum and half of urea were applied during final land preparation. The remaining urea was applied in two equal splits 25 and 50 days after transplanting. Intercultural operations such as weeding, irrigation, insect-pests and disease control were done as and when needed. Different levels of defoliation were made using shears at various growth stages described. Harvesting of the crop was done on 23 March 2005. Data on bulb diameter, bulb length, individual bulb weight were recorded. Yield and percentage of yield losses were estimated. The collected data were analyzed statistically and the means were compared by LSD method (Gomez and Gomez, 1984)

Source of Information: J. Bangladesh Soc. Agric. Sci. Technol., 4(1 &2): 49-52, 2007

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Crop yield depends on many factors such as climate, soil and management practices. In some season onion yield is severely reduced due to defoliation from different causes such as wind, hailstorms, insect pest and diseases and other type of mechanical damage. The maximum yield loss (35.41%) was found from defoliation at bulbing stage while 100% defoliation gave the highest yield losses (49.27%). The result of the study may be employed for estimation of yield losses in onion crop due to defoliation resulting from natural disasters.

Knowledge Management: Journal