Study the effects of relay cropping on yield and yield components, growth length, light interception and solar radiation depreciation of different species of Brassica

The experiment was conducted in 2010-2011 at Isfahan Agricultural Research Station as a split plot layout within a randomized complete block design with three replications. Main plots were two planting dates (27 September was normal cropping and 27 October was relay cropping), subplots were inclusive of species B. napus (Option 500, Hyola 330, Hyola 401, Sargol, Modena, SLM 046, Opera, Zarfam and RGS003), two varieties of B. rapa (Echo and Park land) and one variety of B. juncea (Land race). Planting date had significant effect on LAI, seed yield, a thousand grain weight, biological yield, harvest index, Oil percentage and oil yield. The effect of cultivar was significant on LAI, seed yield, the number of seed per pod, a thousand seed weight, biological yield, harvest index, oil percentage and oil yield. The highest seed yield, biological yield, harvest index and oil yield was obtained by Zarfam and Opera at normal planting date and the maximum seed yield and oil yield was related to Slm046 at relay cropping. Oil yield in Zarfam, Opera and Slm046 was 1662, 1587 and 1578 kg/ha. The interaction between planting date and cultivar had significant effects on the number of days from planting to stem elongation, light interception, light depreciation and LAI. The best cultivar in normal planting date were Zarfam and Opera and in relay cropping was SLM046 that these cultivars with suitable growth length, could provide appropriate conditions to intercept light.