Efficacy of GA3 Primer and Foliar Application of Nano-NPK Fertilizer on Growth, Flowering, Bulbs and Bulblets Yield of Four Narcissus Cultivars

Abstract

This study was designed to evaluate the effectiveness of gibberellin (GA3) priming and nano-NPK fertilizer application on the growth, flowering, and bulb production of four Narcissus cultivars. The experiment was conducted in Pirmam, Erbil Province, from October 15, 2024, to May 22, 2025. Treatments included four cultivars Little Princess, Golden Delicious, The Bride, and the local Aqra were used, bulb soaking with GA3 at concentrations of 0 and 100 mg L ⁻ ¹ for 24 hours, combined with foliar spraying of nano-NPK fertilizer at concentrations of 0, 50, and 100 mg L ⁻ ¹. Plants were grown in PVC pots (20 cm diameter) filled with a 1:1 mixture of loamy soil and peat moss. The experimental design comprised 24 treatment combinations with three replicates each, and each replicate consisted of a single bulb planted per pot. Our findings demonstrated that the cultivars had a significant effect the highest values of 48.99 cm, 5.97 g and 40.68 cm for plant height, leaves dry weight and flower stalk lenghth, respectively, were recorded for Golden delicious cultivar, and the highest average of 17.83 days and 2.06 were recorded for flower coordination date and bulbest produce, respectively, of Local Aqre cultivar. Moreover, GA ₃ at 100 mg L ⁻ ¹ resulted in a significant increase in plant height, chlorophyll, flower coordination date, bulb volume and bulbest produce 48.99 cm, 64.83, 16.81 days, 45.27 cm3 and 1.69, respectively. Moreover, nano-NPK fertilizer at 100 mg L ⁻ ¹ resulted in a significant increase in leaf area, flower coordination date, bulb volume and bulbest produce 73.27 cm2, 64.83, 16.71 days, 46.81 cm3 and 1.88, respectively. The interaction among Narcissus cultivars, GA ₃ priming concentrations, and nano-NPK fertilizer levels exerted significant effects on flowering and yield-related traits, including leaf area, flowering date, flowering synchronization, flower stalk length, bulb volume, and bulblet number. For leaf area, the highest values were recorded in The Bride cultivar, reaching 88.01 cm² and 87.93 cm² under treatments of 0 and 100 mg·L ⁻ ¹ GA ₃ combined with 100 mg·L ⁻ ¹ nano-fertilizer, respectively. The earliest flowering was observed in the local Aqra cultivar, particularly under 100 mg·L ⁻ ¹ GA ₃ with 100 mg·L ⁻ ¹ nano-fertilizer, achieving a minimum of 137.33 days to flowering. Flowering coordination date was markedly enhanced in The Bride cultivar with higher GA ₃ and nano-fertilizer doses, extending up to 20.00 days. Maximum flower stalk length (44.33 cm) was obtained in Golden Delicious when treated with 100 mg·L ⁻ ¹ GA ₃ and 100 mg·L ⁻ ¹ nano-fertilizer. Similarly, bulb volume peaked at 55.00 cm³ in Golden Delicious under the same treatment conditions. Bulblet production increased significantly with combined treatments, with the local Aqra cultivar producing up to 2.33 bulblets under 100 mg·L ⁻ ¹ GA ₃ and 50–100 mg·L ⁻ ¹ nano-fertilizer.