Univrsity of Tehran Press Iranian Journal of Field Crop Science 2008-4811 45 4 2014 12 22 Yield and quality of potato seed and edible tubers in response to different phosphorus levels and nitrogen application times Yield and quality of potato seed and edible tubers in response to different phosphorus levels and nitrogen application times 489 498 53559 10.22059/ijfcs.2014.53559 FA Amir Mohammad Jamshidi Former Graduate Student, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran Ali Ahmadi Professor, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran 0000-0003-0044-2645 Babak Darvishi 0000-0003-0955-2525 Journal Article 2014 07 14 To investigate the appropriate distribution of nitrogen fertilizer application and optimum amount of phosphorus fertilizer to achieve high quality and quantitative yield in edible and seed potato (<em>Solanum tuberosum </em>L.) tubers, this experiment was conducted in Research Farm of the College of Agriculture and Natural Resources, University of Tehran in 2012. The experiment was performed a strip split blocks based on randomized complete block design (RCBD) with three replications. The effects of two factor of phosphorus fertilizer diammonium phosphate (DAP) at four rates of 0 (control), 175, 350 and 525 kg.ha^-1) and supplemental nitrogen (N) fertilization (Urea) was studied on three application times includes: N1 (15% planting time, nonuse in tuberization stage and 85% at three times of tubers bulking stage), N2 (35% planting time, nonuse in tuberization stage and 65% at once in tubers bulking stage) and N3 (35% planting time, 30% in tuberization stage and 35% in tubers bulking stage) on potato plant. Results showed that third method of supplemental nitrogen fertilization reduced effectively the rate of nitrate percentage in tubers.Tuber yield significantly increased in this treatment. Although, the different levels of phosphorus fertilization had no effect on tubers yield, but rising of phosphorus fertilization up to the third level (350 kg DAP.ha^-1) caused to enhance the number of tubers and excess application of this rate reduced the number of tubers significantly. Moreover fourth level of P fertilizer (525 kg DAP.ha^-1) significantly increased specific gravity of tubers, compared to the other levels. Therefore results indicated that addition of phosphorus fertilizer effectively stimulated tuberization of potato plants. To investigate the appropriate distribution of nitrogen fertilizer application and optimum amount of phosphorus fertilizer to achieve high quality and quantitative yield in edible and seed potato (<em>Solanum tuberosum </em>L.) tubers, this experiment was conducted in Research Farm of the College of Agriculture and Natural Resources, University of Tehran in 2012. The experiment was performed a strip split blocks based on randomized complete block design (RCBD) with three replications. The effects of two factor of phosphorus fertilizer diammonium phosphate (DAP) at four rates of 0 (control), 175, 350 and 525 kg.ha^-1) and supplemental nitrogen (N) fertilization (Urea) was studied on three application times includes: N1 (15% planting time, nonuse in tuberization stage and 85% at three times of tubers bulking stage), N2 (35% planting time, nonuse in tuberization stage and 65% at once in tubers bulking stage) and N3 (35% planting time, 30% in tuberization stage and 35% in tubers bulking stage) on potato plant. Results showed that third method of supplemental nitrogen fertilization reduced effectively the rate of nitrate percentage in tubers.Tuber yield significantly increased in this treatment. Although, the different levels of phosphorus fertilization had no effect on tubers yield, but rising of phosphorus fertilization up to the third level (350 kg DAP.ha^-1) caused to enhance the number of tubers and excess application of this rate reduced the number of tubers significantly. Moreover fourth level of P fertilizer (525 kg DAP.ha^-1) significantly increased specific gravity of tubers, compared to the other levels. Therefore results indicated that addition of phosphorus fertilizer effectively stimulated tuberization of potato plants. https://ijfcs.ut.ac.ir/article_53559_bdee2ae1619a7f65e8f3321caaee6ec3.pdf