Influence of bulb topping and intra row spacing on yield and yield components of some shallot (Allium cepa var. Aggregatum) varieties at aneded woreda, western Amhara

Lack of improved varieties and production practices have been the major bottlenecks of shallot production and productivity in western Amhara. Practices such as bulb topping have been traditionally practiced among shallot growers in the region though the merits and demerits of the practice remained controversial among producers and agricultural experts worldwide. Moreover, there was no recommended plant spacing for the crop in the study area and farmers used to practice non uniform plant spacing. Thus, a field experiment was conducted to investigate the influence of intra-row spacing, variety, bulb topping and their interactions on yield, yield components, and bulb quality of shallot and thereby to recommend the optimum practices to farmers in the study area. The study was undertaken between December 2009 and May 2010 at Gudalima nursery site, Aneded Woreda. Three different intra-row spacings (10, 15 and 20 cm) and two bulb treatments (whole and topped at onethird of bulb height) were evaluated using four varieties of shallot (‘local’, ‘Negelle’, ‘Huruta’ and ‘Minjar’) using RCBD replicated three times. Data on growth, yield, quality and disease reaction parameters were recorded and subjected to ANOVA using SAS 9.2 software. The results of the study showed significant interaction effects between intra-row spacing and variety on leaf number and diameter, bulb diameter and shape index. As a result, Local and ‘Negelle’ planted at 20 cm intra-row spacing produced the highest leaf number and leaf diameter, respectively. ‘Huruta’ planted at 20 cm intra-row spacing produced the highest bulb diameter and the lowest bulb shape index. Significant interactions were also obtained between variety and bulb topping for plant height, leaf number and length, and bulb dry weight. The combined effect of intra-row spacing and bulb topping were also significant for leaf length and bulb length. In addition, the combined effect of variety, intra-row spacing and bulb topping were significant for shoot number, number of total, marketable and unmarketable bulbs, bulb fresh weight, biological yield and harvest index, total, marketable, and unmarketable yield per ha, total soluble solid and disease incidence. Topped bulbs of ‘Huruta’ planted at 20 cm and ‘Minjar’ planted at 10 cm intra-row spacings produced the highest and the lowest bulb weight per plant respectively. Topped bulbs of Huruta and Negelle planted at 20 cm intra-row spacing produced the highest marketable yield per ha. Using the topped bulbs of ‘Huruta’ and ‘Negelle’ at wider intra-row spacing positively influenced the majority of yield and quality parameters evaluated. Thus, it is advisable to use the wider intra-row spacing (20 cm) and topped bulbs for better production of marketable yield with desirable bulb shape index while Local variety advisable for high dry matter content, total soluble solid and better bulb skin color. However, production of ‘Minjar’ is not advisable in areas having similar conditions with the study area because of its high bolting and the consequent reduction in yield. However, further investigations should be made to come up with complete recommendations.