Effect of Plant Density and Weed Controlling on Yield and Yield Components of Rapeseed (Brassica napus L.)

IntroductionOil as a major source of food and energy has an important role in human nutrition. A great deal of Oil produced in Iran is originated in vegetable Oils. Oil-producing crops such as Canola play a significant role in oil production industry, and as a sole source of saturated fatty acids, has an important role in public health. . Rapeseed (Brassica napus), also known as oilseed rape and Canola, is a bright yellow flowering member of the family Brassicaceae, and is grown for the production of edible vegetable oils, biodiesel and animal feed, globally. The harvested area of Canola in Iran has had an increasing trend in the recent years and requires more agronomic researches to achieve the optimum yield of the oil-seed crop and meet the oil demands via increasing its oil yield and production. Optimum plant density per unit area is an important agronomic factor, which maximizes plant access to environmental growth sources during the growing season. This is an essential factor, which contributes to maximum plant yield. This factor varies in terms of region and depends on plant variety. Proper weed control and optimal weed management are another important factors in yield improvement. Weeds damage products both quantitatively and qualitatively. Qualitative damage reduces product's quality, nutritional value and toxicity (if weeds mix with the product excessively). Quantitative damage slightly reduces production per unit area. Laansite et al.(2008) reported that grain yield was significantly affected by increased plant density in Canola. They also showed that increased plant density reduced the number of tributaries per plant. The number of pods per unit area was the most important indicator that increased as plant density increased. The goal of this study is to investigate different agronomic and physiologic characteristics of Canola under different density and weed management levels in Zabol, Iran.
Materials and MethodsThe study is conducted in Dawlat Abad village located in south of Zabol (61° 29 E and 31° 2 N and 487 m above sea level) in 2012-2013 growing season. Two levels of weed managements as the main-plot factors and four levels of plant density as the sub-plot factors was performed based on a RCBD as split plot arrangement. The treatments were applied as: W1: weed control and W2: no weed control; D1: 50 plants per square meter, D2: 75 plants per square meter, D3: 100 plants per square meter and D4: 125 plants per square. In order to evaluate the effects of the treatments on the Canola, some agronomic indices like: plant height, number of tributaries per plant, number of pods per plant, thousand grain weights, dry matter yield, grain yield, weed biomass, oil content and yield, were measured at the end of the experiment.
Results and DiscussionThe results of this research showed that weed control had a significant effect on grain yield and oil yield of Canola. In addition, the density of 75 plants per square meter not only improved yield components, but also significantly increased grain yield and oil yield (oil content). However, the lowest weed biomass and the highest dry forage of canola were obtained at a density of 125 plants per square meter. This result recommended that properly weed control and cultivating 75 plants per square meter of canola can be the optimum treatment to obtain the highest grain yield and oil content in Zabol region. This is while densities with more than 75 plants per m2 are proper to control weeds and produce forage in Canola.
ConclusionOur result showed that increasing plant density increased canola yield and yield components and resulted in better weed control, allowing for the use of reduced herbicide rates in way to reach sustainable agriculture. In fact, the result revealed that manipulating plant density in canola production has potential to affect weeding and finally these two methods improved quantitative and qualitative characteristics of canola.