This study was carried out at the University of Georgia (UGA) Vidalia Research Center during the 2022/2023 winter season and is being repeated in 2023/2024. The objectives of this experiment were to identify the relationship between planting density, nitrogen fertilizer rates, and the effects on yields and bulb size distribution. The variety “Sweet Magnolia” was tested at three planting densities (116,000; 87,000; and 58,000 plants per acre) and three nitrogen rates (120, 100, and 80 lbs. per acre). Results indicated there is no interaction between planting density and nitrogen rates on onion bulb size distribution or total production. However, the effect of planting density was significant. Higher densities (116,000 plants/acre) yielded a total weight of 1788 40 lbs. bags/acre with a significant proportion of jumbo-sized bulbs 62%, while lower densities (58,000 plants/acre) resulted in larger colossal bulbs 290 40 lbs. bags/acre with a reduced total yield 1370 40 lbs. bags/acre. Nitrogen application also had a significant impact on both yield and size of the bulb. The highest nitrogen rate (120 lbs./acre) produced a higher total yield (1670 40 lbs. bag/acre), with a significant portion of jumbo at 50% and colossal bulbs at 15%. There was no significant difference between the nitrogen rates of 100 and 120 lbs./acre, but the lowest nitrogen rate (80 lbs./acre) had the worst yield with 1434 40 lbs. bags/acre resulting in a 15% decreased yield compared with the higher rate. These results suggest that optimal planting density and nitrogen application are decisive for reaching the desired bulb size distribution and maximizing yield.
