Effect of planting date and bulb vernalization on flowering, seed yield and quality of shallot

Shallot (Allium cepa L. ascalonicum) can either be propagated by bulb or seed. The availability of shallot seed at present is relatively small. It was an objective of this study to determine the effect of planting date and bulb vernalization on flowering, seed yield and seed quality of shallot. There were 2 planting dates: the first one was on 28 October 1998 and the second one was on 15 November 1998. Shallot bulbs were stored at 10 deg C for 10,20,30 and 40 days before planting. A Split Plot Design with 3 replicates was used. This was carried out at the Vegetable Experimental Farm, Faculty of Agriculture, Khon Kaen University. It was found that planting date and cold storage of bulb before planting had a significant effect on shallot bulb diameter, flowering date, number of inflorescence per plant and seed yield per unit area. The second planting date gave a significantly higher bulb diameter (2.86 cm) compared with the bulb diameter of 2.62 cm obtained from the first planting date. Number of inflorescence per plant (2.29) and seed yield (35 kg per rai( from second planting date were significantly higher than those obtained from the first planting date of 2.11 inflorescence per plant and 35 kg per rai respectively. Shallot bulb stored under 10 deg C for 30 and 40 days resulted in significantly higher size of bulb diameter and shorter period to first blooming than that of control (without cold storage). The shortest period for the first blooming of 54 days after planting was found from storing the shallot bulb under 10 deg C for 30 and 40 days compared with 70 days from the control plot. Seed yield of 34 and 35 kg per rai were recorded from storing the shallot bulb at 10 deg C for 30 and 40 days respectively while the control plot (without cold storage before planting) gave only 32 kg per rai. Therefore a required duration of cold treatment (10 deg C) for shallot bulb before planting should be at least for 30 days in order to obtain bigger diameter of shallot, early flowering and ultimately high seed yield.