Interactive Effects of Sowing Dates and Nitrogen Splits Applications on Cotton (Gossypium hirsutum L.) Variety Aleppo124 Performance under Field Conditions

Abstract

A field study was conducted to evaluate the interaction effects of sowing dates and nitrogen (N) split applications on the yield of cotton cultivar Upland Aleppo 124 under field conditions of northeastern Syria. The experiment used a split-plot design with three sowing dates (April 30, May 15, and May 30) and four nitrogen application schedules (single dose to four split doses of 250 kg N ha⁻¹). All data were subjected to statistical analysis using Genstat software (Version 12.1). Means were compared using the Least Significant Difference (LSD) test at P≤0.05, and the coefficient of variation (C.V.%) was determined. The April 30 sowing date significantly improved reproductive growth and key yield components, such as the reproductive-to-vegetative branch ratio (92.11%), boll weight (2.555 g), cotton seed yield (3425 kg ha⁻¹), fiber yield (2475 kg ha⁻¹), and cotton ginning rate (42.59%). The most effective N strategy was to divide the dose into three equal applications (at sowing, at the 5–6 true leaf stage, and at first flowering), which further increased boll growth and fiber productivity. The interaction between early sowing and triple N splits (D1 × T3) resulted in the highest fiber production (2969 kg ha⁻¹), indication the agronomic advantage of synchronizing fertilizer with key growth stages. The results of this study highlight the efficacy of integrated nutrient timing in optimizing cotton yield, improving nitrogen use efficiency, and mitigating environmental impact, thereby demonstrating a sustainable approach for semi-arid cotton production.