Effects of nitrogen and phosphorous application on physiological parameters of sugar beet seed bearing plants in Ardabil

In order to study the effects of nitrogen and phosphorous application on yield and physiological parameters of sugar beet polygerm seed (cv. 7233), this study was conductedin 2000-2001 in Ardabil Agricultural Research Station (Alarough). The experiment was carried out with two factors including nitrogen in 4 levels (0 as control, 100, 200 and 300 Kg N/ha) and phosphorous in 3 levels (0 as control, 100 and 200 Kg P2O5/ha) in four replications in a complete randomized block design. Each plot consisted of 8 rows of 10 meters long with row space of 65 cm. The results did not show any significant effects of nitrogen and phosphorous application on raw and marketable seed yield, while increase in nitrogen application to 300 kg/ha had a significant effect on the yield of standard(3.5-4.5mm) seed with kernel and led to a significant decrease in seed yield to 833 kg/ha. Following the natural increase in early growth period, total dry matter began to exponentially increase after gotting 350-400 heat units, but lessened after reaching the maximum total dry weight(453-626 g/m2) in the range of 750-900 heat units which accompanied by leaf fall. On the other hand, nitrogen application increased the total dry weight of plants and accelerated reaching to the maximum TDW. Leaf area index slowly increased to gain 300 heat units thereafter it increased exponentially. The highest leaf area index (1.61-2.67) was achieved with gaining 600-700 heat units. The growth trend of plants was ascending from the early growth season until receiving 550-590 heat units (1.04-1.54 g/m2/gdd) and then, it was descending. Finally, nitrogen and phosphorous application led to an increase in leaf area and biomass duration.