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A field study, phosphorus use efficiency ratio of eight sunflower genotypes (Samsung 20, Mehran 2, HO-1, Melabour, Samsung 30, Valugur, Chinika and Sputnik) was determined. The control and treatment plots were fertilized with NP at100-50 kg ha-1 and 100-90 kg ha-1 respectively in randomized completer block design. Results revealed that the overall trend of all genotypes has shown that all agronomic traits and yield parameters were significantly influenced and increased when P level increased. Treatment and genotypes and the interactive effect of increased P level and genotype were also significantly affected seed and leaf P-uptakes (P<0.05). The sunflower crop in treatment and control plots produced plant height 184.39 and 177.69 cm, stem girth 6.45 and 6.22 cm, head diameter 18.85 and 15.72 cm, head weight 1959.8 and 1786.7 g, shoot dry weight 30.13 and 19.11 g, seeds head-1 2048.8 and 1588.5, seed yield kg ha-1 17451 and 1887.9 kg ha-1, leaf P-uptake 0.259 and 0.113%, seed P-uptake 0.252 and 0.109%, respectively. The HO-1 surpassed all the sunflower genotypes for agronomic traits with highest values for seeds head-1 (2153.5), shoot dry weight (29.82 g), plant height (199.97 cm), head diameter (21.10 cm), head weight head weight (2279.1 g), stem girth (7.13 cm) and seed yield (2463 kg ha-1). The HO-1 showed higher P-use efficiency ratio than rest of the genotypes. It was observed that sunflower genotypes responded positively to increase rate of P fertilizer; however, there was significant variation in genotypes for response towards P use efficiency ratio.
Keywords: P level; P-ratio; P-use efficiency; Sunflower genotypes