Integrated effects of vermicompost and town refuse on growth and nutritional status of onion cultivated in calcareous soil

This study investigates the influence of organic amendments vermicompost and town refuse on the growth parameters, nutrient uptake, and biochemical quality of onion (Allium cepa L) grown in calcareous soils. A pot experiment was carried out at Burg El-Arab City, Alex, Egypt. By using three levels (10, 15, and 20 ton fed-1) of both amendments compared to a non-treated control. Results indicated that the application of vermicompost, particularly at 20 ton fed-1 significantly enhanced chlorophyll a, b and carotene levels (0.086, 0.036 and 0.131mg g-1 FW) as well as growth indicators such as plant height, bulb diameter, and total leaf area (44.58 cm, 4.268 cm and 2.894 cm2. Both fresh and dry weights of bulbs and leaves increased notably with organic treatments. Macronutrient (N, P, K) and micronutrient (Fe, Zn, Cu) concentrations and uptake were significantly elevated by increasing amendment levels, with vermicompost showing superior results over town refuse. Additionally, the oil content (9.83%), total soluble sugars (TSS) (15.25%), and protein percentage (28.95%) in onion (Allium cepa L) bulbs improved remarkably under organic treatments. Strong positive correlations were found among most growth and nutrient parameters, indicating that enhanced nutrient availability translates directly to improve physiological and yield responses. The findings suggest that vermicompost is an effective and sustainable amendment for improving onion (Allium cepa L) productivity and nutritional quality under nutrient-poor calcareous soil conditions.