Effect of plant geometry and NPK combinations on growth, flowering, and seed production of annual phlox (Phlox drummondii Hook.)

The present study was conducted to evaluate the effects of plant geometry and NPK combinations on the growth, flowering, and seed production of Phlox drummondii at the Experimental Field of the Division of Floriculture and Landscape Architecture, SKUAST-K, Shalimar. The experiment was conducted using a split-plot design with three different plant spacings (25×25 cm, 25×35 cm, and 25×45 cm) and four NPK dosages (0, 60:30:30, 90:45:45, and 120:60:60 kg/ha). Each treatment combination was replicated three times, and data were analyzed using OP STAT software. Key findings indicate that closer spacing (25×25 cm) resulted in maximum plant height (52.02 cm) and seed yield per hectare (328.48 kg), while wider spacing (25×45 cm) enhanced vegetative growth, including the number of primary branches (12.75), plant spread (49.97 cm), leaf area (3956.32 cm²), and flowering parameters like floret size (24.74 mm). Among the NPK treatments, the highest dosage (120:60:60 kg/ha) significantly increased plant height (53.38 cm), pod weight per plant (6.84 g), and 1000-seed weight (2.39 g), contributing to the maximum seed yield (328.35 kg/ha). The interaction between spacing and NPK had a notable impact, with the combination of wider spacing and the highest NPK dosage (S3×F4) yielding the best results for most parameters, including pod number (499.88), pod weight (7.51 g), and 1000-seed weight (2.45 g). These findings suggest that optimizing plant density and nutrient application can significantly enhance the growth and yield of Phlox drummondii.