Response of Oilseed Rape Genotypes to Delayed Planting in Temperate Cold Regions of Kermanshah Province in Iran

Suitable planting date have an important role in winter hardiness of oilseed rape and its grain yield. For many reasons, farmers grow oilseed rape with delayed planting date. To evaluate oilseed rape response to delayed planting, 22 genotypes were studied using split plot arrangement in randomized complete block design with four replications in Islamabad-e-Gharb Agricultural Research Station in three growing seasons (2007-10). September 29 and October 29 were considered as optimum and delayed planting date, respectively. Simple analysis of variance showed that planting date had significant effect (P < 0.01) on grain yield in three growing seasons. Average grain yield (4455 kg ha-1) in normal planting date was higher than that of delayed planting date with 3678 kg ha-1. Growing season effect was significant on all measured traits except plant height.
In 2007-2008, grain yield of oilseed rape genotypes reduced significantly mainly due to severe cold winter. Genotypes significantly differed for all traits except pod number
plant-1. In optimum planting date, ELITE, MHA01/18 and ZARFAM with 5079, 4907 and 4807 kg ha-1 had higher grain yield. In delayed planting date HYOLA 308, ZARFAM and SHIRALEE with 4487, 4474 and 4441 kg ha-1 produced higher grain yield, respectively. Genotype × planting date interaction effect was significant on seed oil content, while effect of growing season × planting date was significant on most of traits. Results showed that response of oilseed rape genotypes to delayed planting depends on weather conditions in autumn. Some oilseed rape genotypes such as HYOLA 401, HYOLA 308, ZARFAM and SHIRALEE had reasonable grain yield because of faster growth rate in autumn.