Evaluation of empirical models and competition indices in ranking canola

Document Type : Research Article

Authors

• A. S Safahani
• R Farhoudi

10.22067/gsc.v9i4.13281

Abstract

In order to evaluate the competitive ability (CA) of canola cultivars against wild mustard, two experiments
were conducted at the Gorgan Institute in Iran during the 2005-2007 cropping seasons. The experimental factors
were canola cultivars (1st year: Zarfam, Option500, Hayola330, Hayola401, Talayh, RGS003 and Sarigol; 2nd
year: Zarfam, Hayola330, RGS003 and Option500) and weed density (1st year: control and 30 plants m-2; 2nd
year: control, 4, 8 and 16 plants m-2). The result of the first year is experiment indicated that the grain yield and
competitive indices differed significantly between the cultivars. Cultivar Zarfam showed a high ability to
withstand competition (AWC = 47 %), high competitive indices (CI=1.79 and CI2 = 1.83) and low grain yield in
the weed- free plots (1729 kg ha-1). The cultivar Option500, a less competitive cultivar had the lowest ability to
withstand competition (AWC = 4 %) and the lowest competitive indices (CI = 0.09 and CI2= 0.11) amongst the
cultivars. However, the cultivar Option500 showed more grain yield in the weed- free plots (2333 kg ha-1) than
cultivar Zarfam. In the second year of the experiment, the result of the yield loss models showed that the lowest
and highest yield loss belonged to cultivars Zarfam and Option500 (50 and 95 % respectively). A comparison of
different empirical models revealed that the empirical yield loss model based on weed relative leaf area was
more reliable for predicting canola yield loss according to a high coefficient of determination (R2=0.99). The
relative damage coefficient (q) of the weed relative leaf area model showed that wild mustard was more
competitive than canola (q>1).

Keywords

• Reciprocal model
• competitive ability, empirical yield loss model
• relative leaf area
• Weed density

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