Response of Cotton to Mineral Nitrogen-Phosphorus Fertilization and Nano-Fertilizers of Zinc and Copper

Two field experiments were conducted at Sakha Agricultural Research Station, Egypt, during the 2023 and 2024 seasons to evaluate the effects of three nitrogen-phosphorus (NP) fertilizer rates—75%, 100% (recommended rate, control), and 125%—combined with foliar applications of Nano-zinc (200 ppm) and/or Nano-copper (20 ppm) three times on the productivity and quality of the cotton cultivar Super Giza 97. A strip plot design with three replicates was used. The data indicated that ncreasing NP rate, foliar spraying with Nano zinc and Nano copper in combination and their interaction significantly increased TWC, RWC, N, P, photosynthesis pigments and total carbohydrate concentrations in cotton leaves, growth traits, earliness attributes (except boll shedding % which was decreased), seed cotton yield/fed and its components in both seasons and significantly decreased LWD, OP, PMI, and proline concentrations. Zn and Cu concentrations in leaves were significantly decreased under high NP rate and significantly increased with nano fertilizers. Applying 125% NP rate improved fiber length and uniformity index in both seasons, and fiber strength and micronaire reading in one season. Fiber length and uniformity index were significantly increased by spraying Nano zinc and Nano copper in combination in one season, while their combination with 125% NP rate significantly improved fiber length and strength in both seasons and uniformity index in one season. It could be recommended that the application of 125% NP rate and sprayed with Nano zinc and Nano copper in combination led to an increase in the cotton productivity and quality under Sakha region.