Effect of plant density variations at different growth stages on yield and phenological and morphological traits of rapeseed

Abstract

The effect of plant density at different growth stages of rapeseed on yield and phenological and
morphological traits was investigated at Natural Resources Nursery of Bam, Iran during 2010-2011. A
factorial study was devoted to the time of plants removal including seedling emergence, stemming, and
flowering, and the second factor was devoted to the intensity of plants removal at three levels of 25, 50 and
75%. It was found that rapeseed is more sensitive to the intensity of plants removal than to its stage. The
effect of plants removal intensity was significant on seed dry weight, seed yield per plant, total dry weight, oil
yield per unit area at 5% probability level, and on pod dry weight, seed dry weight per unit area and finally,
total yield per unit area at 1% probability level, so that the removal of 25 and 50% of plants was compensated
by greater growth and single-plant yield (by 34.2%), and only the removal of 75% of plants decreased seed
yield per unit area by 30.7 and 19.9% as compared to the removal of 25 and 50% of plants, respectively. The
effect of plants removal time was significant only on stem dry weight per unit area at 5% probability level.
The interactions between the time and intensity of plants removal was significant for stem dry weight and
total dry weight per unit area at 1%, and for pod dry weight, seed dry weight, oil yield, and seed yield at 5%
probability level. The lowest seed yield (2668 kg ha-1) was obtained by the removal of the plants at flowering
and stemming which differed with control by 26.34%. Other evaluated traits were not affected by the
treatments. The evaluation of the response of different seed yield components to the variations of plant
density showed that the removal of plants had the highest effect on pod number per unit area followed by
seed number per plant and single-seed weight. As plants removal was reduced from vegetative growth to
reproductive growth stage, the ability of plants in compensating the loss of plants by increasing pod number
per plant was decreased. It can be recommended that the maximum seed yield can be realized in Bam, Iran
by decreasing plant density by 15% (57 plants m-2).