Effects of planting date, paclobutrazol, and nitrogen fertilizer on bolting percentage and some quantitative and qualitative traits of three autumn sugar beet cultivars

Considering the importance of water in agriculture as well as extending ​​autumn-sown sugar beet cultivation area, this study was conducted to evaluate the effect of growth restriction treatments, planting date and cultivar on bolting and other quantitative and qualitative traits of autumn-sown sugar beet in Karaj, Iran during two years (2018-19). The experiment was performed as a factorial split plot in a randomized complete block design with 3 replications. Studied factors included two planting date (22nd September and 22nd October) as the first factor, the growth restriction with four levels including control (without limit), paclobutrazol (300 pp M), Nitrogen fertilizer restriction (50% of the recommended amount), Paclobutrazole + Nitrogen fertilizer restriction as the second factor, and three cultivars including Giada, Eudoro, and one Iranian genotype resistant to bolting as the third factor. Planting date and growth restriction factors were included in main plots and genotype factor in subplots. The studied traits included bolting percentage, root yield, sugar content, molasses sugar, and white sugar yield. Results showed that the effect of the year on bolting percentage was significant. The lowest bolting percentage (50%) was obtained by Eudoro cultivar on the second year of study planted on 22nd October. The highest root yield (79.91 tha-1) was related to the Eudoro cultivar, planted on 22nd September and treated with paclobutrazol (300 ppm). Giada and Eudoro cultivars planted on the 22nd September had the highest white sugar yield of 8.15 and 8.62 t ha-1, respectively with no significant difference between.