Evaluation of Rapeseed Yield and Growth Indices as Affected by Nitrogen Fertilizer and Planting Density
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Abstract
Nitrogen fertilizer application and optimal density are important factors in increasing the quantitative and qualitative yield of rapeseed. This study was carried out in order to investigate the effects of nitrogen fertilizers and plant density on physiological characteristics, yield and yield components of Canola, as a factorial experiment in a randomized complete blocks design with three replications at Sheshdeh region of Fasa, Iran (57°28′09″ E, 53°58′06″ N) in 2018-2019 and 2019-2020 years. Nitrogen fertilizer factor in 12 levels including a1: urea (recommended) before planting and stem elongation, a2: urea (recommended) before planting, stem elongation and heading, a3: urea (recommended) in stem elongation and heading, a4: urea ( under recommended) before planting and stem elongation a5: urea (under recommended) before planting, stem elongation and heading, a6: urea (under recommended) in stem elongation and heading, a7: ammonium sulfate (recommended) before planting and stem elongation, a8: ammonium sulfate (recommended) before planting, stem elongation and heading, a9: ammonium sulfate (recommended) in stem elongation and heading, a10: ammonium sulfate ( under recommended) before planting and stem elongation a11: ammonium sulfate (under recommended) before planting, in stem elongation and heading, a12: ammonium sulfate (under recommended) stemming and heading and density factor in three levels 50, 70 and 90 plants m-2. Results indicated that The highest leaf area index (4.1) was obtained at a density of 50 plant.m-2 in 160 days after planting. The increasing slope of rapeseed growth rate at densities of 50 and 70 plants.m-2was much higher than of 90 plants.m-2density. Application of urea as recommended ( F2: 120kg ha-1 or120g plot-1) in three stages as 40 g before planting, 40 g in stem elongation and 40 g in heading stages and the density of 90 plants m-2 caused the lowest number of racemes in main branches (15.83 racemes mainbranches-1). The highest 1000-seed weight was recorded in ammonium sulfate as recommended (264 kgha-1 or 264g plot-1) in before planting and heading stages with 50 and 70 plant m-2 density in both experimental years (4.40,4.40,4.36 and 4.44g respectively). with increasing density, seed yield and oil yield decreased considerably and this decreasing was more in the first year than in the second year. 1000-seed weight was the most important component affecting seed yield (r = 0.65). According to the results of this study, to achieve the highest yield using ammonium sulfate as recommended (264 kg ha-1 or 264g plot-1) in before planting and heading stages and density of 70 plants m-2 is recommended.