Integrated Application of Organic (PLBC and Biochar) and Inorganic Fertilizers for Sustainable Onion (Allium cepa L.) Production

Excessive use of inorganic fertilizers degrades soil health by disrupting the microbiota, reducing organic matter, and leading to compaction, acidity, and nutrient imbalance. This study aimed at the combined application of organic and inorganic fertilizers as an environmentally friendly approach increasing soil organic matter and crop yields. From January to April 2022, a field experiment was carried out at the Crop Physiology & Ecology Department of Hajee Mohammad Danesh Science and Technology University in Dinajpur to assess the effects of integrated fertilization on onion (Allium cepa L.). Three replications employing a two-factorial Randomized Complete Block Design (RCBD) were performed to set up the experiment. Factor A contained three onion varieties (V1: Taherpuri, V2: BARI Piaz 4, and V3: BARI Piaz 6) while Factor B comprised four fertilization treatments: T1 (RDF + Cowdung @ 5 t ha⁻¹), T2 (RDF + PLBC @ 5 t ha⁻¹), T3 (PLBC @ 15 t ha⁻¹), and T4 (Biochar @ 10 t ha⁻¹). Measurements were made concerning growth traits such as plant height, leaf number, SPAD value, bulb diameter, neck diameter, average bulb weight, and total yield. The findings showed that variety and fertilization provided a significant effect on growth performance, yield and yield traits. Taherpuri (V1), performed better than V2 and V3. The majority of growth and yield traits were most effectively performed by fertilization treatment T2 (RDF + PLBC), which was followed by T1, T3, and T4. Performance appeared lowest for the V3T4 interaction and got maximum for the V1T2 interaction. These results demonstrate that the combination of organic and synthetic fertilizers leads to sustainable onion production.