Study on effect of micronutrients(Potassium and Nitrogen) on quantity and quality of drought tolerant sugarbeet.

Nitrogen and potassium are two essential macronutrient. Deficiency of nitrogen in most arable soils of Iran is more pronounced than that of potassium. Optimum application of nitrogenous fertilizers with regard to the soil available nitrogen reduces the environmental pollutions and increases the sugarbeet yield and quality. Estimate of sugarbeet nitrogen and potassium requirement in drought stress conditions has not taken in to consideration very much so far. The objective of this research was to determine the influence of nitrogen and potassium fertilizers on quantity and quality of drought tolerant sugarbeet. Two sugarbeet genotypes, Mashhad BP and Karaj BP, were evaluated for 3 years (2004-2009) in Karaj and Mashhad as a split plot experiment (split plot factorial) in randomized complete block design. Water treatments were considered as mainplots and nitrogen and potassium levels as subplots. Water treatment included: 1- normal irrigation or non stress ( irrigation after 80-85 mm evaporation from class A pan), 2- irrigation with early season water stress or moderate stress, and 3- sever stress (irrigation after 160-170 mm evaporation from class A pan). Net potassium levels included: ٠(control), 100 and 200 kg/ha, and net nitrogen levels included: ٠(control), 50, 100, and 150 kg/ha. After harvesting, the yield and quality characters of sugarbeet were determined the data were analyzed using SAS and MSTAT-C software. The results indicated that the effect of year on root yield, sugar content, sodium, potassium, amino nitrogen and white sugar content was significant both in Karaj and Mashhad. The effect of water treatments on root yield, sugar yield and white sugar yield was significant in Karaj and Mashhad. In Karaj, The highest root root yield (49,43 t/ha) belonged to the normal irrigation treatment followed by 39,84 t/ha( irrigation with early season water stress) and 34,85 t/ha (sever stress). The highest sugar yield and white sugar yield belonged also to the normal irrigation, while the yields were reduced in irrigation with early water stress and sever stress treatments. Nitrogen had a significant effect on sugar content and the highest sugar content (15,24٪) belonged to the control plots. The effect of potassium on root yield and quality characters of sugarbeet in Karaj was not significant. In Mashhad, the highest root yield (45,08 t/ha) was obtained in the normal irrigation, and was classified with the other two water treatment in the same group. Drought stress along with the higher application of nitrogen increased the root sodium content and decreased sugar content. Any factor that increased nitrogen uptake also increased the potassium uptake. In general, less fertilizer was needed in drought stress conditions. Also, the best nitrogen fertilizer treatment in Karaj and Mashhad for obtaining the highest white sugar yield was the application of 50 kg/ha net nitrogen. On the other hand, when the soil available potassium content is low, non irrigation at the early season (irrigation with early season water stress ) causes reduced uptake of this element which finally affects the sugar cntent.