YIELD AND QUALITY OF ONION BULBS AS AFFECTED BY MANURE APPLICATIONS

Field experiments were conducted over two growing seasons to study the effect of four different pre-plant treatments, consisting of fermented fresh animal manures and olive pomace in the planting row on the productivity and pungency of onions. The main treatments: pre-plant soil-incorporation of organic matter, then soil was covered by black polyethylene (BPE) sheets for six weeks (Non Continuous Mulch-NCM); as in (NCM), but soil surface was covered by BPE mulch for the whole growing season (Continuous Mulch-CM); pre-plant soil-incorporation of organic matters, but soil surface was kept bare during the six week period, and chemical weed were control was applied later in the season (Chemical application-CHA); and the control (C), where fresh organic matter was soil incorporated manually at the time of planting without weed control. Each main treatment included four sub-plots, and each sub-plot received a different source of organic matter; cow, poultry, sheep manure or olive pomace. Plant height, leaf number, Pseudo-stem length and weight, bulb yield, and pungency were measured. Results revealed a varying effect on all parameters tested. Pungency was the highest in the CM and Cow-manure treatments due to the higher temperature and moisture availability. CM treatment was as effective as the CHA treatment in its impact on the parameters tested.