Role of boron, potassium, and iron in improving productivity and fruit characteristics of squash (Cucurbita pepo L.)

Balanced mineral nutrition, especially macronutrients and micronutrients involved in plant physiological and biochemical activities, is a key factor in improving the productivity and fruit quality of squash (Cucurbita pepo L.). The study was conducted at the Zakho Technical Institute, Kurdistan Region, Iraq, under greenhouse conditions during the 2025–2026 growing season to examine the effects of boron (B), potassium (K), and iron (Fe) on the growth and fruit characteristics of squash. The experiment was laid out as a split-split plot, Randomized Complete Block Design (RCBD) with three replications. Two levels of iron fertigation (0 and 2 g L⁻¹), two levels of potassium fertilizer (0 and 2 g L⁻¹), and two levels of boron foliar (0 and 2 mL L⁻¹) were applied. The results indicated that plant fertigation with an Iron concentration of 2 g L-1 improved the number of fruits to 8.250 fruit plant-1. However, foliar application of potassium at a concentration of 2 g L-1 increased the number of fruits to 8.583 fruit plant-1, fruit length to 12.900 cm, plant height to 81.500 cm, fruit weight to 100.588 g, and fruit diameter to 3.850 cm. Furthermore, spraying Boron at a concentration of 2 mL L-1 increased the number of fruits to 8.417 fruits plant-1 and plant height to 80.124 cm. The study emphasized the need to properly manage nutrients in greenhouse squash production and the possibility for balanced potassium fertilization to greatly increase fruit quality and yield.