Effect of Nitrogen and Phosphorous Application on the Efficiency of Nitrogen Uptake and Consumption in Sugar Beet (Beta vulgaris L.)

In order to evaluate efficiency of nitrogen fertilizers consumption in a sugar beet monogerm hybrid variety of Zarghan, a field experiment was conducted in a loamy soil during 2007 in the research farm of Sugar Beet Seed Institute located in Karaj. Five levels of nitrogen fertilizers including 0 (check), 120, 160, 200 and 240 Kg/ha of net nitrogen from urea fertilizer (46 percent of pure nitrogen) and three levels of phosphor including 0 (check), 50 and 100 Kg of P2O5 per hectare from the triple super phosphate were arranged in a factorial experiment (5×3) in a randomized complete block design with four replications. The results showed that the effect of nitrogen application was significant for nitrogen uptake of both top and root parts of sugar beet, and also for nitrogen uptake efficiency of whole crop. However, nitrogen uptake of sugar beet was not affected by phosphor fertilizer and by the interaction of nitrogen × phosphor application. The highest nitrogen uptake by whole crop in this experiment was equal to 447 Kg ha-1 from the treatment of 240 Kg ha-1 nitrogen application. In the check treatment, nitrogen uptake by whole crop was 250 Kg ha-1. In Zarghan sugar beet variety, for one t ha-1 beet root production about 4 Kg nitrogen was used and from the total nitrogen uptake by whole crop, 44% was allocated in the top part and 56% in the storage root of sugar beet. There was no significant difference between the treatments for nitrogen uptake efficiency, whereas nitrogen utilization efficiency for sugar yield in the treatment of N0P0 was 35% greater than that in the treatment of 240 Kg ha-1 nitrogen application. On average, nitrogen utilization efficiency was equal to 40 Kg sugar for each Kg of N uptake by the crop. Thus, for the production of sugar beet close to actual yield potential it is necessary to consider 5 Kg of N for each t of beet root. Consequently, in order to prevent the environmental pollution, improve nitrogen efficiency, and taking into account the best quality and quantity of sugar beet yield, nitrogen application must be recommended based on the soil analysis and expected root yield and quality of sugar beet.