Evaluation of leaf analysis as a guide to nitrogen and phosphorus fertilization of potato (Solanum tuberosum L.)

Summary

‘Recently matured’ leaf samples were collected, at 45, 60 and 75 days after planting, from potato (Solanum tuberosum L.) plants of cultivar ‘Kufri sindhuri’ grown with varying levels of nitrogen (0, 60, 120, 180 and 240 kg N/ha) and phosphorus (0, 60, 120 and 180 kg P₂O₅/ha) on loam soil at Pantnagar. They were separated into petiole, midrib and leaf-lets and analysed for NO₃-N content. Petiole samples were also analysed for PO₄-P content. Nitrogen application increased the NO₃-N content of all the leaf components. P application increased the PO₄-P content in petiole. NO₃-N content and PO₄-P content in leaf tissues were positively correlated with final tuber yield. The association of NO₃-N content of petiole with the final tuber yield was very consistant. Hence this proved to be the best indicator tissue for reflecting the nitrogen status of the plant, particularly at 45 days after planting. NO₃-N content of midrib, at this stage, was also a good indication of nitrogen nutrition status of the plant. PO₄-P content of petiole at 45 days after planting was a good indication of nutritional status of plant with respect to phosphorus. The critical concentration of NO₃-N in petioles of 45 days old plants was in the range of 9100–9600 ppm. The corresponding range for midrib was 3000 to 3900 ppm. The critical concentration of PO₄-P for petioles of 45 days old plants was 2250 ppm.