Response of potato cultivars to varying levels of nitrogen and phosphorus

Response of potato cultivars to nitrogen and phosphotic fertilizers was carried out at Vegetable Experimental Farm of Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Shalimar, Srinagar during 2002 −03 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 × 20cm, while combinations of three levels of each nitrogen (120, 160 and 200 kg/ha) and phosphorus (80, 100 and 120 kg/ha) were tried in the sub plots. Analysis of variance revealed that main effects due to cultivars, nitrogen and phosphorus were significant for morphological characters, yield and yield attributing traits and dry matter content except on the 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 was also non significant. The interaction effects of cultivar × nitrogen were found significant for plant height, tuber number/plant average tuber weight, tuber weight/plant, tuber yield q/ha and production of “A” and “B” grade tubers while as interaction effects of nitrogen × phosphorus were found significant for tuber number/plant, average tuber weight, tuber weight/plant and tuber yield (q/ha). Significant increase in the tuber yield 264.86 q/ha to 314.26 q/ha was observed when nitrogen level increased from 120 to160 kg/ha and further increase in the level of nitrogen up to 200 kg/ha significantly decreased the tuber yield to 269.78 q/ha. Similarly a significant increase in tuber yields from 280.81 q/ha to 290.78 q/ha was observed when the level of phosphorus was increased from 80 to100 kg/ha and at the higher dose of 120 kg P₂ O₅/ha the tuber yield significantly decreased to 274.93 q/ha. 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 treatment combination of 160 kg N and 100 kg P₂ O₅/ha with constant dose of 100 kg K₂O/ha recorded the highest benefit-cost ratio of 1.39 with PP-48, 1.23 with PP-2500 and 1.03 with Kufri Jyoti. From the present investigation, it is concluded that a fertilizer combination of 160 kg N, 100 kg P₂ O₅ and 100 kg K₂O/ha was found optimum for obtaining higher yield and net returns from the potato cultivars under Kashmir conditions.