Effect of supplemental Irrigation on Yield, Yield Components and Water Use Efficiency of Two Canola Cultivars (Brassica napus L.)

Supplemental irrigation is considered as a beneficial economic mechanism in the situation of water constraint and increase water use efficiency of canola. The aim of this study was to evaluate the effect of supplemental irrigation on yield, yield components and water use efficiency. This research was carried out at split plots in a randomized complete block design with three replications at Gachsaran Agricultural Research Station in 2017-18 and 2018-19. Irrigation regimes applied in four levels (without irrigation (I1), supplemental irrigation at flowering stage (I2), supplemental irrigation at grain filling stage (I3), supplemental irrigation at flowering stage + grain filling (I4)) in main plot, Hyola and Shirali cultivars were sown in the subplot. The studied traits including number of pods per plant, number of seeds per pod, 1000 seed weight, biological yield, grain yield, harvest index and water use efficiency. Results of ANOVA showed that the number of pods per plant increased from 88 in rainfed conditions to 120 with two supplemental irrigations, which increased by 36%. The supplemental irrigation increased the harvest index from 24.1 to 27.9 percent, which was an increase of 12.4 percent. Increasing the frequency of supplemental irrigation increased the grain yield and biological yield, so that the two supplemental irrigations increased the average grain yield from 782 in rainfed conditions to 2378 and increased biological yield from 3228 to 8350 kg ha-1. The highest water use efficiency (0.73 kg m3) was obtained from treatment I4 and the lowest (0.39 kg m3) was obtained from treatment I1. Overall, the results showed that supplemental irrigation increased grain yield, oil yield, harvest index and water use efficiency 83, 12, 7, and 23 percent, respectively. In case of canola cultivation in rainfed conditions, high yield can be achieved by supplemental irrigation in two stages of flowering and grain filling.