Yield Comparison and Determining the Best Harvesting Time of Different Rapeseed (Brassica napus L.) Lines as the Second Crop in Rotation after Rice in Guilan Region

The pod drop and seed losses in rapeseed is one of the most important problems in the cultivation of this plant and determining the most appropriate harvesting time can greatly prevent this problem and subsequently reduce the grain yield reduction. Thus, the present research was conducted as a split-plot in time in the form of a randomized complete block design with three replications during the crop year of 2019-2020 in the Research Station of the Rice Research Institute of Iran in Rasht. The main factor was rapeseed genotypes at 22 levels and the subfactor was harvesting time at three levels (including the amount of moisture between 30-40, 20-30, and 10-20% in the third grade of the lower stage of the original stem). The results of analysis of variance showed that in addition to the significance of yield-related traits in rapeseed lines, the interaction of lines in time was also significant, which shows the effect of harvesting time on rapeseed lines is different. In most of the lines, the highest and lowest grain yields were related to the first and second harvesting time, respectively. The highest grain yield was found for SRL-98-17 with a mean of 3662 kg ha-1. Number of siliques per line due to loss of pods decreased from the first to the third harvesting time. However, SRL98-9, SR-98-19, SRL-98-1 and SRL-98-11 had the lowest loss of grains. According to these results, it seems that the first harvesting time results in the highest grain yield, hastens the harvest of rapeseed by one week, and potentiates it as a suitable choice for inclusion in the rotation after a rice crop.