Leaf number
Leaf number varied significantly among different dates of planting. Maximum number of leaves (8.5) was recorded in 10
th December planting which was on par with that of 25
th November planting (8.05) (Table 1).
This might be due to the congenial climatic conditions prevailed during the period of November-December. This is in accordance with the findings of
Misra et al., (2014) who reported the highest number of leaves in 25
th November and 10
th December planted crops.
Das (2008) also reported variation in number of leaves of onion varieties among different planting dates. Effect of varieties on number of leaves was also found significant. Agrifound Dark Red recorded the highest number of leaves.
Chandrika and Reddy (2011) also noted a significant varietal effect on number of leaves in onion plant.
Leaf length
Variation in leaf length was significant among different dates of planting. Highest leaf length (46.6 cm) was noted in 25
th November planting which was on par with that of 10
th December planting. Varieties also differed significantly for leaf length. Maximum leaf length was recorded in Arka Kalyan (46.47 cm) which was on par with that of Agrifound Light Red (44.88 cm) (Table 2).
Khan et al., (2001) reported that variation in leaf length among different varieties is due to the difference in adaptability of these cultivars to a particular environment. Interaction effect between dates of planting and varieties on leaf length was also significant. Highest leaf length was recorded in the variety Agrifound Light Red planted on 25
th November. Similar results were reported by
Mohanta and Mondal (2014),
Khurana et al., (2003) and
Misra et al., (2014). They noticed a highest leaf length of 50.50 cm in 25
th November planting which was followed by 10
th December planting (47.85 cm).
Bolting percentage
Bolting is the premature flowering behaviour in onion which is not a desirable trait in bulb yielding crop. Bolting percentage varied significantly among different dates of planting and varieties whereas, the variation was non-significant among the interaction between varieties and planting dates (Table 3).
Goutam et al., (2006) reported a non-significant variation in bolting percentage among varieties, planting time and interaction between the two.
Devulkar (2015) reported a non-significant variation for bolting percentage among different dates of planting (15
th November, 25
th November, 5
th December, 15
th December and 25
th December).
The highest bolting percentage was noticed in 10
th November planting (1.71%). Early planting could be one of the reasons for higher bolting percentage in onion as suggested by
Dong et al., (2013) who also reported that early planting resulted in higher accumulated temperatures which lead to high bolting percentage. The findings are also in line with those of
Singh et al., (1993), Cramer (2003) and
Bijarniya et al., (2015).
Among the varieties, bolting percentage was lowest/absent in Agrifound White (0%) which was on par with Arka Pragati, Agrifound Light Red and Agrifound Dark Red having 0.32%, 0.61% and 0.83% respectively.
Umamaheswarappa et al., (2015) observed a significant variation in bolting percentage when they studied 21 onion varieties including the varieties undertaken in the present study. They observed a bolting percentage of 0.34% in Arka Kalyan, 0.31% in Arka Pragati, 0.29% in Agrifound Dark Red, 0.30% in Agrifound Light Red and 0.37% in Agrifound White.
Dark red
Kharif onion cultivars were observed to be more susceptible for premature bolting than the Light Red
Rabi onion cultivar during late
Kharif season as reported by
Bhonde et al., (1992) and
Warade et al., (1996). The actual mechanism behind different bolting characteristics of the cultivars is yet to be discovered.
Neck thickness
Neck thickness is an important parameter as it determines the storability of onion. Onion having thinner neck store better than those having a thicker neck. Neck thickness showed significant difference among different planting dates and varieties but, the variation was non-significant among the interactions. Lowest value for neck thickness was recorded in 25
th December planting with 3.54 cm which was followed by that in 10
th December planting (Table 4).
Jilani (2004), observed that the thickest onion bulb necks were obtained with early plantings (27
th October) compared to late plantings (26
th December). Formation of thinner neck with later planting can be correlated with small plants caused by earlier bulb initiation for late planted plants than for earlier plantings.
Different onion varieties often differ with respect to neck thickness
(Jilani and Ghaffoor, 2003). This was also observed in the current study, wherein lowest neck thickness was noted in Agrifound White (3.66 cm).
Sharma and Jarial (2017) evaluated different onion varieties and reported a lowest neck thickness in the variety Agrifound Light Red. Similar to the present reports,
Mohanta and Mondal (2014) also reported significantly different variations in neck thickness with respect to varieties, planting time and interaction between both.
Bulb weight
Bulb weight differed significantly with different planting dates. The highest bulb weight was recorded in 25
th November planting (66.2 g) which was followed by 10
th December planting and 10
th November planting with 52.2 g and 48.15 g respectively (Table 5).
Longer day length and cooler temperatures prevailed during this period might be the reason behind production of bulbs having better sizes. The lowest bulb weight was recorded from fourth date of planting, 25
th December (20.45 g).
Mahadeen (2009),
Nandal and Singh (2002), Mohanta and Mondal (2014) also reported a significant variation in average bulb weight with respect to planting dates.
The variation was non-significant among different varieties as well as among the interactions. However a significant variation in bulb weight was noted among varieties by
Tripathy and Lawande (2008). Average bulb weight of varieties ranged from 43.81g to 49.88 g and Arka Pragati and Agrifound Dark Red varieties could produce bubs weighing 71.75 g and 73.5 g respectively when planted on 25
th November, which indicates that the selected varieties can perform better under Kerala conditions.
Yield per plot
Yield per plot varied significantly among different dates of planting, varieties as well as interaction between dates of planting and varieties. The highest yield was recorded in 25
th November planted crop (1.30 kg/m
2) (Fig 1) which was on par with 10
th December and 10
th November planted crops with 1.26 kg/m
2 and 1.02 kg/m
2 per plot respectively (Table 6).
This might be due to the long sun shine hours prevailed during the bulb development stage. These findings are in agreement with the results obtained by
Misra et al., (2014) and are also in line with the findings of
Bijarniya et al., (2015) who reported a highest yield in the crop planted on 15
th November. Similar results were also obtained by
Kumar et al., (1998) and
Hiray et al., (2001).
Yield per plot varied significantly among different varieties also. Highest yield was recorded in Arka Kalyan (1.21 kg/m
2) which was statistically on par with Agrifound Dark Red (1.15 kg/m
2) and Arka Pragati (1.07 kg/m
2). Yield was lowest in Agrifound White (0.86 kg/m
2) which was on par with Agrifound Light Red (0.90 kg/m
2) (Table 6). Differences in yield between varieties indicates that the bulb weight can vary depending on factors affecting plant growth and yield and can be improved through crop management practices
(Menon et al., 2016). Agrifound Dark Red was identified as a promising variety with a bulb yield 5.83 kg/m
2 by
Haldar et al., (2009). Bindu and
Podikunju et al., (2016) also came up with the similar results in Kerala. They evaluated three onion varieties such as Arka Kalyan, Agrifound Dark Red and N 53 and obtained a higher yield from Agrifound Dark Red which was followed by Arka Kalyan.
Khar et al., (2000) and
Yadav et al., (2009) also reported variation in bulb yield among different varieties under same cultural practices.
Menon et al., (2016) reported a highest total bulb yield in the variety Agrifound Light Red which was followed by Arka Kalyan, Agrifound White, Arka Pragati and Agrifound Dark Red.