2018 ASHS Annual Conference

Plant growth and bulb quality of onion (Allium cepa L.) are responsive to sulphur (S) and nitrogen (N) interaction, but compost and S interaction is understudied. This study was performed to assess the response of onion cv. Safran to stabilized municipal solid waste compost (MSWC) and sulphur (Magnesium sulphate) amendments in a greenhouse container-experiment. The treatments were MSWC at 0, 25, 50 and 75% w/w; and sulphur at 0, 10 and 20 mg pot^-1 mixed in Promix-BX peat moss soilless substrate. An increase in the rate of MSWC increased SPAD value for onion plant leaf greenness, anthocyanin content (up to 50%) and photosynthetic activity. Unlike the MSWC, S application and the interaction between S and MSWC had no significant (P>0.05) effect on onion plant growth and bulb yield components. Consistently, the 25% MSWC treatment significantly (P<0.01) increased plant height, bulb diameter, number of fresh scale leaves and bulb fresh and dry weights. MSWC at ≥50% significantly (P<0.01) reduced these growth and yield parameters. Total soluble solids (TSS) content of the onion bulb was significantly (P<0.01) influenced by the applications of S and MSWC, and their interaction. The 25% MSWC and the 10 mg S pot^-1 treatments gave the highest onion bulb tissue TSS content. The MSWC and the S applications increased the nutrients contents of the onion bulb tissue at harvest. In conclusion, MSWC amendment can be adopted to increase onion plant growth and plant tissue quality. Future studies should increase S rate and evaluate onion bulb flavor indices.

Keywords: onion, organic amendment, compost, sulphur, onion plant growth, onion quality