Impact of Different Dosages of Urea on Nitrogen Distribution, Soil Dynamics, and Seed Yield in Onion Crop

This study examined nitrogen (N) uptake and distribution patterns in onion seed crops (Allium cepa L.) under varying urea application rates, 0, 50, 100, and 150 kg N/ha across two growing seasons. Using a complete randomised block design, the research determined the total nitrogen content in leaves, stems, and bulbs after 30 and 60 days of planting, as well as the soil nitrogen levels before and after harvesting. Results showed that increased levels of nitrogen application highly increase in nitrogen accumulation in all parts of the plant. At 60 days after planting the 150 kg N/ha treatment had the highest nitrogen content in leaf (6.23% and 6.18%), stem (5.70% and 5.61%), and bulb (4.25% and 4.25%) for the years 2020 – 21 and 2021 – 22, respectively. This increased uptake was related to the highest yield of seeds of 774.67 g/plot and 1368.33 g/plot during the years. Post-harvest soil nitrogen levels were also highest at this treatment and were 172.51 and 162.28 kg/ha in 2020–21 and 2021–22, respectively, showing effective nitrogen retention. These results emphasise the need for specific nitrogen management practices, such as split application, to enhance nutrient uptake at crucial growth points. Through matching nitrogen application to the physiological requirement of the crop, this research is useful in increasing onion seed yield and in improving crop productivity and soil health in onion seed production.