Effect of urea-intercalated coir dust biochar on growth and yield of onion (Allium cepa)

Abstract

Nitrogen fertilizers are essential for boosting crop yields, but conventional urea often suffers from rapid nutrient loss through leaching and volatilization, resulting in low nitrogen use efficiency and environmental pollution. This study investigates an innovative approach using urea intercalated biochar (UIBC) as a slow-release nitrogen source to improve the performance of onion (Allium cepa). A pot experiment was conducted to evaluate the effectiveness of UIBC, which was produced from coir dust biochar via a simple capillary absorption method. The resulting UIBC had a nitrogen content of 40.13 ± 0.51 %. The experiment included seven treatments: T1 (control), T2–T4 (100 %, 75 % and 50 % urea) and T5–T7 (100 %, 75 %, and 50 % UIBC), arranged in a completely randomized design (P<0.05) with four replicates. Plant height was measured at two-week intervals, the weight of sprinkles at 45 days, and bulb weight at harvest. The results demonstrated that UIBC treatments, particularly at full application (100% UIBC), consistently improved plant growth and yield compared to conventional urea. Notably, 100% UIBC increased fresh bulb weight (26.53 ± 1.57 g) and dry bulb weight (3.25 ± 0.21 g), outperforming conventional urea (21.81 ± 0.21 g fresh and 2.78 ± 0.04 g dry). Meanwhile, 75% UIBC achieved bulb yields compared to 100 % urea (20.63 ± 2.33 g fresh and 2.61 ± 0.05 g dry), indicating higher nitrogen use efficiency and the potential to reduce fertilizer input without compromising productivity. Overall, UIBC treatments improved the growth and yield of Allium cepa, highlighting its potential as an efficient slow-release fertilizer for sustainable farming.