Effect of Row Spacing and Nitrogen Fertilizer Rates on Grain Yield and Agronomic Characteristics of Rapeseed cv. Hayola 308 as Second Crop in Paddy Fields of Guilan in Iran

To determine the suitable row spacing and rate of nitrogen fertilizer for rapeseed cv. Hayola 308, a factorial experiment based on randomized complete block design with three replications was carried out in paddy fields of Rice Research Institute of Iran, Rasht, Iran, in 2003-2004 and 2004-2005 growing seasons. Row spacing at three levels: 20, 25 and 30 cm and four nitrogen fertilizer rates, based on soil testing and Water and Soil Research Institute recommendations, including: 0.7R, 1.0R, 1.3R and 1.6R from urea source. The R factor was determined as 140 Kg urea ha-1. Some important agronomic characteristics such as number of secondary branches per plant, number of siliques per plant, number of seeds per silique, silique length, 1000-seed weight, grain yield, oil content and oil yield were measured and recorded. Combined analysis of variance showed no significant differences between row spacing for grain yield. However, row spacing of 20 cm with an average seed yield of 1947 kgha-1 was relatively superior to other row spacings. Among the nitrogen rates, the highest seed yield was obtained from fertilizer rates of 1.6 R with 2189 kg ha-1. No significant differences were observed among treatments for oil content. Increasing in nitrogen application didn’t decrease the oil content. Results clearly showed that row spacing of 20 cm with average of 887.4 kg ha-1 had the highest oil yield. Nitrogen rate of 1.6R showed maximum number of secondary branches per plant (4.3), number of siliques per plant (89.7), 1000-seed weight (4.719g) and oil yield (1001 kgha-1). Row spacing of 20 cm and nitrogen rate of 1.6R had the highest seed yield, oil content and oil yield. Since there was not significant differences between 1.3R and 1.6R nitrogen rates at 20 cm row spacing for seed and oil yields, the combination of 1.3R nitrogen fertilizer and 20 cm row spacing is recommended. This recommendation package would decrease application and leaching of nitrogen and is more environmental friendly.