Impact of bone char and triple superphosphate on yield, fruit quality, and seed characteristics of melon ( Cucumis melo L. )

Phosphorus (P) is an essential macronutrient for crop production. While global P demand continues to rise, finite phosphate rock reserves are being depleted, creating an urgent need for sustainable P alternatives. Bone char (BC), produced by pyrolyzing animal bones, provides a renewable P source with slow-release characteristics. This study evaluated the effectiveness of BC compared with triple superphosphate (TSP) for greenhouse melon (Cucumis melo L.) production, examining yield, fruit quality, and seed characteristics. It was hypothesized that BC would yield comparably to TSP while enhancing fruit quality attributes due to its slow-release P availability. A completely randomized design experiment with three replications was conducted in 2020 at the Sistan Agricultural Research Center greenhouse facility in Zahak, Iran (30°5′N, 60°15′E). Three treatments were compared: control (no P application), TSP (87 kg P ha−1), and BC (87 kg P ha−1). Both P sources significantly enhanced yield compared to the control, with ∼49% increases (BC: 25.4 ± 1.1 kg plot−1; TSP: 25.5 ± 1.1 kg plot−1 vs. control: 17.1 ± 0.6 kg plot−1). BC demonstrated superior fruit quality attributes, including greater flesh thickness (3.23 ± 0.2 vs. 2.4 ± 0.3 cm in TSP) and higher total soluble solids (TSS) content (14.6 ± 0.3 vs. 13.6 ± 0.6°Brix in TSP). Seed quality parameters improved with BC, yielding higher thousand-seed mass (TSM: 51.7 ± 0.07 vs. 51.32 ± 0.14 g in TSP) and a significantly lower empty-seed percentage (ESP: 9.23 ± 0.58 vs. 11.8 ± 0.28% in TSP). These findings demonstrate BC’s potential as an alternative P fertilizer for greenhouse melon production, offering comparable yields with enhanced quality attributes. However, as a single-season study, these results should be considered preliminary.