Evaluation of a Wide Range of Plant Density on Yield and Yield Components of Rapeseed (Brassica napus L.) Cultivars

Canola (Brassica napus) is a major oilseed crop in the world, and its oil is used not only for salad and frying but also in the processing of margarines, shortenings, and other food products. Canola (Brassica napus L.) is often called a flexible or plastic crop because individual plants can adjust the number and size of branches and pods they produce in response to available moisture, light and nutrients. Therefore, canola naturally compensates for variations in plant population over relatively wide ranges with very little effect on final yield. At plant densities of 70-100 plants per square meter (approximately 7-10 plants per square foot), canola plants normally produce 3-5 secondary branches, in addition to the main stem. At low densities of 20-30 plants per m2, this plant can produce up to four times the number of branches that stands of 70-100 plants per m2 produce. Extension of canola cultivation varieties need effective instruments to follow up characters associated with yield and yield components. Therefore, determination of the response of canola cultivars to plant density is principally important and in general plant density is the most important factor which limit yield production on farmlands.

In order to determine the best planting density for rapeseed cultivars, this experiment was conducted at the agricultural research field of Ferdowsi University of Mashhad, in 2011. A factorial experiment based on RCBD with three replications was used. Factors were cultivars (Hayola401 and Modena) and planting density (40, 70, 100, 130, 160 and 190 plants.m-2). A composite sample of soil from the surface of the ground down to the depth of 30 cm was taken and sent to a laboratory for determining the physical and chemical features of the soil. Results of tests carried out on these samples showed that the available phosphorous, and the available potassium contents of the soil were 31.5 mg.kg-1 and 267 mg.kg-1, respectively. The soil pH was 7.3 with texture containing 40% clay, 41% silt, and 19% sand. Distance between plots was 0.5 meter and between replications 1 meter used as passage way. At crop maturity, five plants were randomly selected from each plot and the seed yield and yield components (including number of seeds per pod, number of pods per plant and the 1000-seed weight) were measured. Analysis of the variance was performed using the SAS statistical software, and comparison of the means was performed on the basis of duncan’s multiple range test at five percent probability level.

Results showed that there were significantly differences between plant density on rapeseed cultivars. Canola crops need 30-40 plants per m2 (approximately 3-4 plants per square foot) to maintain yield potential. Plant populations lower than this is more likely to have yield loss. The average grain yield in Modena cultivar was 13.5% higher than in Hayola401 cultivar. Number of pods per plant in Modena was significantly higher than in the Hayola401.When plant density decreased from 40 to 190 plants.m-2, plant height of rapeseed increased. The greatest number of seeds per pod, biological yield, harvest index and oil percentage were observed in 70 plants.m-2.

Rapeseed cultivars responded strongly to changes in plant density. The average grain yield in Modena cultivar was higher than in Hayola401 cultivar. The maximum seed yield was observed in 70 plants.m-2.
Acknowledgement
This research was funded by Vice Chancellor for Research of Ferdowsi University of Mashhad, which is hereby acknowledged.