Shifts in regional precipitation patterns and rising temperatures due to climate change have increased uncertainty surrounding optimal planting windows and nitrogen (N) management strategies for broccoli production in North Carolina (NC). In particular, growers face challenges in aligning planting schedules with ideal environmental conditions and adjusting N application rates to match crop demands under variable temperature regimes. Given that both air and soil temperatures directly influence crop nutrient uptake and development, this study aimed to evaluate the combined effects of planting date, nitrogen rate, and application timing on the growth and productivity of two commercially important broccoli cultivars: 'Eastern Crown' and 'Emerald Crown.' Field experiments were conducted at the Horticultural Crops Research Station of North Carolina State University in Clinton, NC. The first trial included four planting dates—early March, late March, early April, and late April—combined with three fertigation N rates of 120, 100, and 80 lb/acre. The second trial focused on two planting dates, late March and late April, combined with four pre-plant N application rates: 0%, 20%, 40%, and 60% of total recommended N. Across both trials, plant performance was assessed through measurements of canopy volume, aboveground biomass, leaf greenness via Normalized Difference Vegetation Index (NDVI), tissue nutrient content, and marketable yield. Results show that early planting dates were associated with lower accumulation of Growing Degree Days (GDD), which may have limited early crop development. In contrast, later planting dates generally experienced higher GDD accumulation, improving crop rate of growth. Higher N application rates were positively correlated with increased NDVI values, biomass, and yield. Reduced NDVI readings under lower N rates indicate a possible decline in plant vigor and photosynthetic activity. Additionally, strategic pre-plant N applications showed potential benefits in improving early plant establishment and nutrient status, particularly under later planting dates. Overall, our findings show the importance of optimizing both planting timing and N management strategies to improve broccoli productivity in NC. Tailoring N rates based on planting date and anticipated thermal conditions may contribute to more resilient production systems under changing climate conditions.
