The present investigation was carried out at vegetable Experimental Farm. Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Shalimar Campus during Kharif 2002 to find out the optimum dose of nitrogen and phosphorus for potato cultivars. The experiment was laid out in split plot design with the three replications. The potato cultivars viz. PP-2500, PP-48 and Kufri Jyoti were planted in the main plots with a spacing of 60 x 20 cm, while combinations of three levels of each, nitrogen (120, 160 and 200 kg ha-1) and phosphorus (80, 100 and 120 kg ha-1) were tried in sub plots. The observations were recorded on percent emergence, plant height, number of shoots plant-1, tuber number plant-1, average tuber weight, tuber weight plant-1, tuber yield q ha-1, tuber yield in grades plant-1, dry matter percentage and benefit-cost ratio. Analysis of variance revealed that main effects of cultivars, nitrogen and phosphorus were significant for morphological, yield and yield attributing traits and dry matter content except the effects on production of “C” grade tubers (<25g), the effect of nitrogen and phosphorus on plant emergence and the effect of phosphorus on number of shoots plant-1. The interaction effects of cultivar x nitrogen were found significant for plant height, tuber number plant-1, average tuber weight, tuber weight plant-1, tuber yield q ha-1 and production of “A” and “B” grade tubers while as interaction effects of nitrogen x phosphorus were found significant for tuber number plant-1, average tuber weight, tuber weight plant-1 and tuber yield q ha-1. Application of nitrogen and phosphorus indicated a linear and significant increase in plant height and number of shoots plant-1 at 120- 200 kg N ha-1 and 80- 120 kg P2O5 ha-1 in all the three cultivars. While a significant increase in tuber number plant-1, average tuber weight, tuber weight plant-1, tuber yield, and dry matter content was observed upto 160 kg N and 100 kg P2O5 ha-1, and thereafter a decrease was observed at 200 kg N and 120 kg P2O5 ha-1, respectively in all the cultivars. Significant increase in the tuber yield from 264.86 q ha-1 to 314.26 q ha-1 was observed when the level of nitrogen was increased from 120- 160 kg ha-1 and further increase in the level of nitrogen upto 200 kg ha-1 significantly decreased the tuber yield to 269.39 q ha-1. Similarly a significant increase in the tuber yield from 280.81 q ha-1 to 290.78 q ha-1 was observed when the level of phosphorus was increased from 80- 100 kg ha-1. But again at the higher dose of 120 kg P2O5 ha-1 the tuber yield significantly decreased to 274.93 q ha-1. Among the cultivars PP-48 proved superior with respect to growth, yield and yield components and quality followed by PP-2500 and Kufri Jyoti. The economic studies indicated that the treatment combination of 160 kg N and 100 kg P2O5 ha-1with constant dose of 100 kg k2o produced the highest benefit-cost ratio which was recorded as 1.39 in PP-48, 1.23 in PP-2500 and 1.03 in Kufri Jyoti. Thus from the present investigation, it is concluded that a fertilizer combination of 160 kg N and 100 kg P2O5 with constant dose of 100kg K2O ha-1 was found optimum for obtaining higher and economic returns of the potato cultivars under Kashmir valley conditions.
M.Sc Thesis submitted to SKUAST Kashmir