Nitrogen Rate Effects on Silage Corn Yield and Nitrate Dynamics in Florida Sandy Soils

Nitrogen (N) management in silage corn on sandy soils requires balancing biomass production with nitrate loss. This study evaluated biomass yield, crop N removal, soil, leaf, and pore water N responses to seven N rates (0–470.8 kg N ha−1) at Ona, Florida, in 2025. A randomized complete block design included four replications and 28 plots. Biomass and harvest whole-plant N were measured separately by plot; soil and leaf samples were pooled across four blocks, and pore water from two blocks was pooled by treatment before analysis. Soil nitrate-N (NO3−-N) concentrations were generally greatest at 0–30 cm. Seasonal mean pore water NO3−-N increased from 1.7 mg N L−1 in the control to 46.0 mg N L−1 at the highest N rate. The highest observed mean dry biomass yield was 19.5 Mg ha−1 at 392.4 kg N ha−1, while upper rate means showed limited additional response. Apparent crop N recovery was approximately 71% at 235.4 kg N ha−1 and 36–38% at the two highest rates. Estimated NO3−-N leaching was 9–222 kg N ha−1 using 519 mm of measured drainage; an illustrative ±50% drainage scenario gave 111–333 kg N ha−1 at the highest rate. These descriptive findings indicate increasing nitrate exposure at high N rates under this wet season’s conditions, but do not establish an economic optimum or a transferable N rate threshold.