Optimizing nitrogen fertilizer recommendations for field corn grown in Florida sandy soils

Nitrogen (N) is essential to maximize corn ( Zea mays L.) yield; however, over‐ and underapplication can cause environmental concerns or yield losses. Optimizing N management is critical to balance productivity and sustainability. This study was conducted during 2022–2024 in Florida to determine corn N response. The experiment included six N rates (0–392 kg N ha −1 by 78.5 increments) over 3 years, with an additional rate (471 kg N ha −1 ) in the third year, using a randomized complete block design with four replications. Results showed that 314–471 kg N ha −1 produced the highest and statistically similar aboveground biomass (21,598–23,166 kg ha −1 ), grain yield (12,479–13,588 kg ha −1 ), and N uptake (227–250 kg ha −1 ). For grain N removal, (144–162 kg ha −1 ), 392 and 471 kg N ha −1 were statistically similar, while 314 kg N ha −1 was significantly lower than 392 kg N ha −1 , indicating a threshold response beyond 314 kg N ha −1 . Agronomic N use efficiency and partial factor productivity were highest at 157 (58.8 kg kg −1 ) and 78.5 (57.9 kg kg −1 ) kg N ha −1 , respectively. Results suggest no agronomic advantage above the 314 kg N ha −1 rate, and yield decreased at 471 kg N ha −1 . Response analysis indicated that 23.2 g N was required per kg of corn grain under irrigation system. The nitrogen nutrition index confirmed that moderate applications (235–314 kg N ha −1 ) sustained crop N status, while higher rates (>392 kg N ha −1 ) offered little to no benefit. Collectively, these results support refining N recommendations to optimize agronomic production in Florida.