Shiraz University Iran Agricultural Research 1013-9885 45 2 2026 07 01 Foliar nitrogen dynamics and yield responses of sugarcane (CP69-1062) to urea and urea–ammonium nitrate under delayed fertigation in northern Khuzestan, Iran 20 26 8782 10.22099/iar.2026.54369.1714 EN Ali Motamedi Amin Department of Agricultural Research, Karun Agro Industrial, Inc., Shushtar, I. R. Iran Journal Article 2025 09 24 Delayed planting and variable spring rainfall frequently complicate nitrogen (N) management in sugarcane production systems in Iran. Despite the large scale of production, information on foliar N dynamics and crop performance under delayed fertigation with different N sources remains limited. This study evaluated the response of sugarcane cultivar CP69-1062 to nitrogen source (urea vs. urea–ammonium nitrate (UAN)) and fertigation timing (early June, 1‑week delay, and 3‑week delay). Furrow fertigation was applied either as urea (184 kg N ha–1) or UAN (97 kg N ha–1), with both treatments delivered in three monthly split applications. Statistical analysis using a Linear Mixed Model (LMM) showed that foliar N concentration decreased significantly as fertigation was delayed (P ≤ 0.05). However, UAN resulted in a significantly faster recovery of foliar N status compared with urea. Despite these differences in early-season foliar N dynamics, end‑of‑season quantitative and qualitative traits did not differ significantly between fertilizer sources (P > 0.05). In contrast, fertigation timing significantly affected yield‑related traits. Delayed application reduced stalk density and final biomass, indicating that the timing of N availability is more critical than the fertilizer source itself. Overall, these findings provide practical guidance for optimizing N management under delayed planting conditions and are particularly relevant for improving productivity in semi‑arid sugarcane production systems similar to those evaluated in this study.

https://iar.shirazu.ac.ir/article_8782_d419c4666e84f13e47583aa12aa35485.pdf