Analysis of Effect of Different Fertilizers on Onion Crop

Onion (Allium cepa L.) is an important vegetable crop with considerable economic and nutritional significance, and its productivity is strongly influenced by the availability and balanced application of essential plant nutrients. Among the major nutrients required for crop development, nitrogen (N), phosphorus (P), potassium (K), and sulphur (S) play important roles in vegetative growth, bulb development, yield formation, and quality characteristics. However, the response of onion plants to individual nutrients and their combinations may vary depending on the interaction among fertilizer components. Therefore, the present study was undertaken to investigate the effects of four major fertilizers, namely Nitrogen, Phosphorus, Potassium, and Sulphur, on onion yield and selected quality characteristics. A 2⁴ full factorial experimental design was employed to evaluate the individual and interaction effects of the four fertilizer factors. Each factor was considered at two levels, namely presence and absence, resulting in 16 different treatment combinations. Each treatment combination was replicated twice, giving a total of 32 experimental plots. The major response variables considered in the study were bulb weight, neck size, leaf height, and bulb colour. Statistical analysis was carried out using analysis of variance (ANOVA), regression analysis, and correlation analysis to identify significant fertilizer effects and relationships among the measured characteristics. The results indicated that fertilizer combinations containing phosphorus, particularly PK and PKS, had important effects on onion yield. The regression analysis further indicated a positive contribution of phosphorus to yield, while certain interaction effects involving potassium and sulphur were also important. For neck size, the NPK and NPKS combinations showed statistically significant effects. Sulphur-containing treatments also demonstrated significant effects on leaf height, indicating their possible contribution to vegetative development. In addition, treatments containing phosphorus and sulphur were associated with improved colour intensity and visual uniformity of onion bulbs. The correlation analysis showed a strong positive relationship between leaf height and neck size (r = 0.81), while yield showed a moderate positive correlation with leaf height (r = 0.58). The findings suggest that balanced fertilizer combinations, particularly those involving phosphorus and sulphur, can contribute to improved onion yield and selected physical quality characteristics. The factorial design approach also provides a useful statistical framework for evaluating individual and interaction effects of multiple fertilizer factors in crop production experiments.