Rainfed cotton response to polymer-coated and conventional urea under different placement methods

Surface broadcasting of conventional urea is a common method of supplying nitrogen (N) to cotton, but this practice can increase the risk of N losses through volatilization and leaching, especially under a rainfed production system. A 2-year (2023–2024) field study was conducted at the West Florida Research and Education Center in Jay, FL, to evaluate the effects of N source and placement method on cotton growth, plant N status, lint yield, fiber quality, and partial factor productivity of applied N (PFP). Treatments consisted of conventional urea (46-0-0) and polymer-coated urea (PCU; 41-0-0), applied through surface broadcasting and subsurface banding at 100 kg N ha−1. Growing season conditions differed substantially between years, with hotter and drier conditions in 2023 and greater, more evenly distributed rainfall in 2024. Surface-applied conventional urea resulted in 29–31% higher chlorophyll index (CHL) and 51–57% higher nitrogen balance index (NBI) than other treatment combinations at early square stage in 2023 compared to 2024. N source significantly affected leaf area index (LAI), with conventional urea producing ∼11.2% higher LAI in 2023 and ∼19.4% higher LAI in 2024, on average, compared to PCU-treated plots. Subsurface banded urea generally resulted in the highest petiole nitrate-N (PNN) concentrations across both seasons. Under specific rainfed conditions and N rates evaluated in this study, conventional urea provided greater early or in-season N availability for some physiological indicators than PCU, particularly during the drier season. However, these differences did not result in greater lint yield or PFP.