Effect of regulated deficit irrigation, partial root drying and N-fertilizer levels on sugar beet crop (Beta vulgaris L.)

The study was conducted in the West of Iran, on the Karafs plain, in the Hamedan province in order to investigate the effects of water stress and nitrogen levels on quantitative and qualitative yields of sugar beet in a semiarid region with limited water resources. The experiments were carried out over two consecutive seasons in 2013 and 2014 respectively using split plots in randomized blocks with three replications. The main blocks included: Full irrigation (FI), three levels of partial root drying: 85 (PRD₈₅), 75 (PRD₇₅), 65 percent (PRD₆₅) and regulated deficit irrigation at three levels: 85 (RDI₈₅), 75 (RDI₇₅) and 65 percent of the crop water requirement (RDI₆₅). The sub blocks encompassed two levels of 100 (f₁₀₀) and 75 percent (f₇₅) of N-fertilizer requirements. Sugar beet of the Canaria variety was utilized in the study. The effect of the irrigation treatments was significant on all quantitative and qualitative characteristics of the sugar beet. By increasing the amount of irrigation water, root and white sugar yields increased and sugar content decreased. The highest root and white sugar yields obtained were through FI treatment with a mean root and white sugar yields of 54,235 and 7803kgha⁻¹, respectively; however, its difference with PRD₈₅ treatment yield was non-significant (with a mean root and white sugar yields of 51,113 and 7644kgha⁻¹, respectively). The effect of fertilizer treatments on sugar content, white sugar content and all of the quantitative attributes of sugar beet were significant. With the increase in the application of N-fertilizer, root and white sugar yields increased and sugar content decreased. Therefore, under such experimental conditions, applying the PRD₈₅ treatment is recommended to prevent yield loss while saving 15% of irrigation water. Whatsmore, the study showed that among the various fertilizer treatments applied in the study, f₁₀₀ treatment shows the best results.