Journal of Food, Agriculture and Environment

Determination of economical yield loss threshold of Chenopodium album at interference with rapeseed (Brassica napus)

Author(s):

Negar Valizadeh, Bahram Mirshekari ^*

Recieved Date: 2010-12-06, Accepted Date: 2011-04-16

Abstract:

In order to study of economical yield loss threshold of lambsquater (Chenopodium album) at interference with rapeseed (Brassica napus) an experiment was conducted on rapeseed cv. Sarigol in Tabriz Research Field of Islamic Azad University. Studied factors were lambsquater density at three levels (d₁= 4, d₂= 8 and d₃= 12 plants per metre of crop row) and weed relative emergence time (simultaneously with crop (e₁), 15 (e₂) and 30 (e₃) days after crop emergence) and weed free (d₀) as control. As lambsquaters emerged simultaneously with rapeseed and received maximum density, its stem height was 15 cm more than in most weak weed competition treatments. Rapeseed leaf area index was affected by weed density and decreased from 3.1 in control to 2.3 in d₃ (27% reduction). Chlorophyll content index changed from 78.9 in control to 576.6 in full season interference of 12 weeds with crop. Greatest seed yield was 4450 kg ha^-1 in weed-free treatment. Seed yield decreased 45% in d₃e₁ in comparison to control. On the base of regression analysis rapeseed green coverage percent (GCP), 1000-seed weight and plant silique number could explain 98% of seed yield changes, and high R² showed that these attributes had high effects on seed yield which can be advantageous for breeders in rapeseed yield development. Oil yield in weed full season competition in d₃ was 42% less than in control. Considerable yield decrease was expectable by early emergence of Chenopodium rather than rapeseed. It is concluded that the weed economic yield loss threshold in the field of studied rapeseed cultivar was in d₁ in its third emergence time.

Keywords:

Breeder, lambsquater, relative emergence time, yield loss

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Journal: Journal of Food, Agriculture and Environment
Year: 2011
Volume: 9
Issue: 2
Category: Agriculture
Pages: 409-412

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