Effect of Different Levels of Urea on Growth, Yield, and Yield Attributes of Mustard under Kabul Agro-Climatic Conditions

Nitrogen is a key macronutrient that plays an essential role in plant growth, development, and yield formation in oilseed crops such as mustard (Brassica juncea L.). Proper nitrogen management is important for improving productivity while ensuring economic efficiency and environmental sustainability, particularly in low-input farming systems like those in Afghanistan. This study was conducted to assess the effect of different urea (nitrogen) levels on the growth, yield attributes, phenology, and grain yield of mustard under Kabul agro-climatic conditions. A field experiment was arranged with four treatments: T₁ (0 kg urea ha⁻¹), T₂ (60 kg urea ha⁻¹), T₃ (80 kg urea ha⁻¹), and T₄ (100 kg urea ha⁻¹) using a randomized design. Data were collected on plant height, number of branches per plant, number of pods per plant, phenological traits (flowering and maturity), and grain yield. The results showed that nitrogen application significantly improved vegetative growth and yield components of mustard. Increasing nitrogen levels enhanced plant height, number of branches, and pods per plant. Grain yield responded positively to nitrogen application, with the highest yield consistently obtained at 80 kg urea ha⁻¹. However, further increase in nitrogen above this level did not result in proportional yield improvement, indicating diminishing returns. Phenological traits such as days to flowering and maturity were not significantly affected by nitrogen levels. Overall, the study concludes that moderate nitrogen application optimizes growth and yield of mustard without affecting its growth duration. The application of 80 kg urea ha⁻¹ is recommended as the optimal rate for mustard production under Kabul conditions, as it improves productivity, enhances nitrogen use efficiency, reduces production costs, and supports sustainable agriculture.