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.
