Nitrogen and Sulfur Fertilizer Application on Subsequent Storage Potential and Quality of Onion (Allium cepa) Bulb in the Central Rift Valley of Ethiopia

Agronomic practices related to post-harvest losses pose a serious threat to onion cultivation, especially in the area of nutrient management in Ethiopia. A study was conducted to evaluate the effect of nitrogen (N) and sulfur (S) fertilizer levels on the storage potential and quality of onion bulbs during 2021 and 2022 growing seasons. Two sets of experiments were carried out. The first experiment was used to produce onion bulbs with different levels of N and S fertilizers. The second one was designed on the first experiment using a completely randomized design (CRD) with three replications. Total weight loss, weight loss causal factors, and total soluble solids (TSSs) were recorded for different durations. The application rate of nitrogen fertilizer increased during bulb production, resulting in a significant increase in the mean stored bulb weight loss after 30 to 90 days of storage. On the other hand, using S fertilizer during the dry-hot season lowers the post-harvest loss of onion bulbs by approximately 5.89% compared to not applying it. In both seasons of storage, bulb TSS was increased by the combination of S and N fertilizer applications. Overall results revealed that applying 92 kg of N and 20 kg of S per hectare extended storage life, maintained quality, and was economical for storing onion bulbs for up to 60 days following harvest in the study area and similar environments.