Application of different levels of nitrogen fertilizer and foliar application of zinc sulfate on quantitative and qualitative characteristics of two sugar beet cultivars (autumn sowing)

The aim of this study was to evaluate the effect of reducing nitrogen fertilizer application as well as foliar spray of zinc sulfat on the quality characteristics of two sugar beet cultivars in autumn cultivation. The study was conducted in a factorial design based on randomized complete block design with three replications at the Faculty of Agriculture in Lorestan University during two crop seasons (2017-19). The Experimental treatments included two autumn-sown sugar beet cultivars (Chimene and Rosagold) and four fertilizer levels including F1: 138 kg ha-1 nitrogen (control), F2: 124 kg ha-1 nitrogen and foliar spray of zinc sulfate, F3: application of 110 kg ha-1 nitrogen and foliar spray of zinc sulfate, F4: 96.6 kg ha-1 nitrogen and foliar spray of zinc sulfate at a rate of 5/1000. The highest root yield (90.15 t ha-1) belonged to Rosagold cultivar and among the treatments, the highest root yield was related to F2 treatment. The highest sugar content (16.15%) was obtained in 20% reduction in nitrogen application and foliar spray of zinc sulfate. Also, the highest white sugar content (15.57%) was obtained from Rosagold cultivar in 20% reduction in N fertilizer application and foliar spray of zinc sulfate, which showed 26.17% increase compared with control treatment (F1). The highest molasses sugar and Na, K and α- N as 2.7, 2.61, 7.90 and 2.90 meq 100 gr beet-1, respectively was observed in Chimene. Also, the highest bolting percentage was obtained in Chimene and the application of 300 kg ha-1 nitrogen. According to the results of this study, it can be concluded that autumn cultivation of sugar beet using Rosagold cultivar is possible in Khorramabad region and foliar spray of zinc sulfate can compensate the reduction of nitrogen consumption by 20% without reducing the quantity and quality of autumn sugar beet.