Introduction

Cauliflower (Brassica oleracea var. botrytis L.) is the most popular vegetable crop among cole crops belong to the family cruciferae having chromosome no. 2n = 14. The word cauliflower is derived from the Latin words “Caulis” meaning stalk and “floris” meaning flower. (Gocher et al., 2017) reported that cauliflower is being grown round the year for its white and tender curd. The success or failure of cauliflower production is largely depends upon climate, especially temperature (Hossain et al., 2015). The life cycle of cauliflower is divided into three stages based on the effect of temperature; they are vegetative growth stage, curd initiation stage and reproductive stage. (Farzana et al., 2016)  suggested that cauliflower requires a period of cold not only for curd formation but also for flowering. Cauliflower is used as fried vegetable, dried vegetable, making soups and pickles (Bashyal, 2011). The popularity and consumption of Cauliflower is increasing because of their nutritional value. It is a high-value crop and contains substantial amount of protein, carbohydrates, phosphorus, calcium, iron and ascorbic acid (Devi et al., 2018). It is low in fat but high in dietary fiber, folate, water, vitamin C and possessing a high nutritional density. Cauliflower contains several phytochemicals that may be beneficial to human health (Madumathi et al., 2017). Its Leaves are also rich source of iron and beta-carotene, due to these properties it is utilized in various value-added products. Consumption of cauliflower also helps in detoxification of body fats, boosting healthy heart, improved digestion and helpful in treating scurvy as a blood purifier.  Nitrogen is essentially required nutrient for plant growth and fruit development. Nitrogen is associated with vigorous vegetative growth. It is helpful in large curd compact size. Proper use of nitrogen improves the nutritional value of cauliflower as reported. Nitrogen is involved in physiological processes and enzymatic activities. (Yeshiwas, 2017) reported that nitrogen is a major fertilizer which is constituent of protein and protoplasm of chlorophyll and enzymes. It is required in much large quantities than other nutrients (Singh et al., 2015). Lack of nitrogen causes stunted growth or leaves discoloration in cauliflower. Its deficiency also causes interveinal yellowing, rolling of leaves, chlorosis and necrosis and it also checks the growth, reduces the yield (Rani et al., 2015). Farmers use excessive urea as a nitrogen fertilizer, to enhance flowering, curd set and increase curd size in cauliflower as reported by (Kodithuwakku and Kirthisinghe, 2009). (Islam et al., 2018) reported that excessive application of nitrogen on the other hand is not only uneconomical but also induces physiological disorder and pollutes the environment. Plant spacing is an important criterion for attaining maximum vegetative growth and for maximizing the yield (Ullah et al., 2013). Optimum spacing ensures judicious use of natural resources and makes the intercultural operation easier as suggested by (Hasan et al., 2017). The spacing of crop varied according to climatic condition, soil fertility and cultivar adaption to particular region. (Bairwa et al., 2017) reported that under the wider spacing, the plant was more vigorous in terms of growth of plants, which may be due to less competition for light, nutrients and moisture as compared to closer spacing. On the other hand, densely planted crop obstruct the proper growth and development  as reported (Sani et al., 2018). Considering the above facts, the present experiment was planned and undertaken with the objective to study the response of different levels of nitrogen and spacing on growth and yield of cauliflower grown under central region of Punjab.

Materials and Methods

The present experiment was carried in the Experimental Farm, Department of Agriculture, Mata Gujri College, Fatehgarh Sahib, Punjab, India situated between 30°41’ 51.93”N latitudes and 76° 24’36.1”E longitudes and at a mean height of 279 meter above sea level from October 2018 to February 2019. The experimental soil was sandy loam having pH 7.3, EC 0.40 dS m^-1, 366.71 kg ha^-1 available nitrogen, 28.64 kg ha^-1 available phosphorus and 129.03 kg ha^-1 available potash. The experiment was laid out in Factorial Randomized Block Design (FRBD) with three replications. The experiment consisted of two factors such as Factor A: Nitrogen levels, N₀: 0 % ha^-1, N₁: 50 % ha^-1, N₂: 75 % ha^-1 and N₃: 100 % ha^-1 and Factor B: Spacing, S₁: 45×30 cm², S₂: 45×45 cm² and S₃: 60×45 cm². There were 12 treatment combinations such as N₀S₁, N₀S₂, N₀S₃, N₁S₁, N₁S₂, N₁S₃, N₂S₁, N₂S₂, N₂S₃, N₃S₁, N₃S₂ and N₃S₃. The seeds of cauliflower cultivar ‘Golden-75’ were sown on well prepared raised nursery beds on October 3^rd, 2018. The experimental Farm was ploughed followed by clod breaking, hoeing and levelling. Vigorous seedlings were transplanted into field on October 27^th, 2018. The field was divided into three blocks and each block was divided into 12 plots. There were 36 unit plots and the size of the each unit plot was 3×2.4 m². All appropriate cultural practices including weeding, watering, hoeing and insect-pest control were timely performed. Urea was used as source of nitrogen fertilizer.

Obsevations on different growth and yield attributing characters were recorded from six randomly selected plants from each replication to find out the significance difference of nitrogen fertilization and spacing on growth and yield contributing characters of cauliflower. Plant height, plant spread, leaf length and width was measured with the help of meter scale. The experimental data for various observations were analysed by fisher’s method of analysis of variance (ANOVA) as per outlined by (Panse and Sukhatme, 1967). The data were analysed and are presented at the 5% level of significance.

Results and Discussion

The effect of different levels of nitrogen and spacing at harvest presented in Table 1. The result revealed that at harvest maximum plant height (53.56 cm) was obtained with N₃ (100% N ha^-1) while minimum plant height (47.19 cm) was recorded in the N₀ (control). It might due to the fact that nitrogen being an important component of chlorophyll imparts green colour to the plants and improves photosynthesis which results into more production of photosynthates and ultimately increased plant height. Statistically significant variation due to spacing on plant height was recorded from the present study. At harvest maximum plant height (51.97 cm) was obtained with S₃ (60×45cm²) because higher doses of nitrogen and wider spacing increase the availability of nutrients and show the positive effect on plant height. However, minimum plant height (49.49 cm) was recorded in the S₁ (45×30 cm²). Similar results were observed by (Kaur and Sharma, 2018) and (Rashid et al., 2016). Interaction effect of nitrogen and spacing showed significant difference among the treatments in terms of plant height of cauliflower. Maximum plant height (54.27 cm) was found from N₃S₃ while, the lowest plant height (43.20 cm) was found from N₀S₁.

Table 1: Effect of different levels of nitrogen and spacing on growth characteristics of cauliflower

The data pertaining to plant spread have been presented in Table 1. Maximum plant spread (69.00 cm) was obtained with N₃ (100% N ha^-1) because Nitrogen enhances the cytokinin production in the roots of the plants and more cytokinin carried to the leaves, resulted in more cell division. So, plant spread increases with higher doses of nitrogen. While, Minimum plant spread (59.44 cm) was recorded in the N₀ (control). In spacing, maximum plant spread (66.67 cm) was obtained with S₃ (60×45 cm²) which was statistically at par with S₂ (45×45cm²) with the value of 65.14 cm. whereas, minimum plant spread (63.69 cm) was recorded in the S₁ (45×30 cm²). This is due to the fact that closer spacing cause competition of nutrients, moisture and light among the plants therefore wider spacing increased the plant spread of cauliflower. Statistically significant variation was recorded due to interaction effect of different levels of nitrogen and spacing in terms of plant spread of cauliflower. The highest plant spread (69.53 cm) was found from N₃S₃ while, minimum plant spread (55.27 cm) was found from N₀S₁. Similar findings were also reported by (Easmin et al., 2009) in chinese cabbage.

The maximum number of leaves plant^-1 (16.88) was reported under N₃ (100% N ha^-1). However, minimum number of leaves plant^-1 (14.79) was reported under control (N₀). In spacing, maximum number of leaves plant^-1 (16.28) was obtained with S₃ (60×45 cm²). While, Minimum number of leaves plant^-1 (15.51) was srecorded in the S₁ (45×30 cm²). This is due to the reason that nitrogen promotes vegetative growth and increase in spacing promotes number of leaves in cauliflower. Interaction effect of nitrogen and spacing showed significant difference among the treatments in terms number of leaves plant^-1 of cauliflower. The highest number of leaves plant^-1 (17.00) was found from N₃S_3. While, lowest number of leaves plant^-1 (13.27) was found from N₀S₁. These findings were obtained by (Sohail et al., 2018) in cauliflower.

It was observed that different levels of nitrogen and spacing showed significant variation on leaf length. The data revealed that maximum leaf length (45.84 cm) was obtained with N₃ (100% N ha^-1) Nitrogen is essential component of metabolically active compounds like protein, nucleic acids, chlorophyll and shows positive effect on leaf length of plant. However, Minimum leaf length (39.23 cm) was recorded in the N₀ (control). In spacing, maximum leaf length (44.28 cm) was obtained with S₃ (60×45 cm²) Minimum leaf length (41.97 cm) was recorded in the S₁ (45×30 cm²). It was revealed that with the increase in spacing leaf length showed increasing trend. This is due to the fact that in case of closer spacing plant compete for light and with the time being leaf length decreases. Similar results were observed by (Shrestha and Thapa, 2018), (Moniruzzaman, 2006). Statistically significant variation was recorded due to interaction effect of different levels of nitrogen and spacing in terms of leaf length of cauliflower. The highest leaf length (46.60 cm) was found from N₃S₃. While, the lowest leaf length (36.23 cm) was found from N₀S₁.

Data pertaining to leaf width have been presented in Table 1. The data revealed that maximum leaf width (24.64 cm) was reported under N₃ (100% N ha^-1). While, minimum leaf width (21.13 cm) was reported under N₀ (control) because nitrogen is essential component of metabolically active compounds like protein, nucleic acids, chlorophyll and shows positive effect on leaf length of plant In spacing, maximum leaf width (23.83 cm) was obtained with S₃ (60×45cm²). However, minimum leaf width (22.46 cm) was recorded in the S₁ (45×30cm²). In case of spacing, it was revealed that with the increase in spacing leaf width showed increasing trend. This is due to the fact that in case of closer spacing plant compete for light and with the time being leaf width decreases Similar results were observed by (Shrestha and Thapa, 2018) and (Farzana et al., 2016).  Statistically significant variation was recorded due to interaction effect of different levels of nitrogen and spacing in terms of leaf width of cauliflower. The highest leaf width (25.03 cm) was found from N₃S₃. The lowest leaf width (19.17 cm) was found from N₀S₁.

3.2.  Yield parameter

The analysis of variance revealed significant differences among all the treatments for fresh weight of curd presented in Table 2. The mean performance of different levels of nitrogen showed that maximum fresh weight of curd (827.02 g) was obtained with N₃ (100% N ha^-1) because nitrogen fertilizers ensure favourable condition for the growth of plant with optimum vegetative growth and ultimately increase the fresh weight of curd. However, minimum fresh weight of curd (681.60 g) was recorded in the N₀ (control). In spacing, maximum fresh weight of curd (788.11 g) was obtained with S₃ (60×45 cm²). However, minimum fresh weight of curd (731.94 g) was recorded in the S₁ (45×30 cm²) because spacing significantly affected fruit size, with the closest spaced plants having the smallest fruits, while the widest spaced plants had the largest fruits. Similar result was also observed by (Boroujerdnia and Ansari, 2007) and (Joshi et al., 2018).  Statistically significant variation was recorded due to interaction effect of different levels of nitrogen and spacing in terms of fresh weight of curd of cauliflower. The highest fresh weight of curd (833.33 g) was found from N₃S₃. While, minimum fresh weight of curd (580.17 g) was found from N₀S₁.

The data recorded on dry weight of curd have been presented in Table 2. It was observed that different levels of nitrogen and spacing showed significant variation on dry weight of curd. The data revealed that maximum dry weight of curd (0.88 g) was obtained with N₃ (100% N ha^-1) because nitrogen is combined with plant constituents of compounds during photosynthesis such as glucose, ascorbic acid, amino acid and protein which increases the dry weight of curd. While, minimum dry weight of curd (0.68 g) was recorded in the N₀ (control). In spacing, maximum dry weight of curd (0.83 g) was obtained with S₃ (60×45 cm²). Due to increase in spacing dry weight of curd shows increasing trend because of less competition for nutrients among the plants during growth stages. Whereas, minimum dry weight of curd (0.75 g) was recorded in the S₁ (45×30 cm²). Similar findings were found by (Fatimah et al., 2019) and (Moniruzzaman, 2006). The interaction effect of different levels of nitrogen and spacing in terms of dry weight of curd was found to be non-significant.

The data pertaining to curd yield plot^-1 have been presented in Table 2. The mean performance of different levels of nitrogen showed that maximum curd yield plot^-1 (29.72 kg) was obtained with N₃ (100% N ha^-1). Due to application of nitrogen at higher rate, the crop traits improved substantially and these traits linearly influenced the yield plot^-1 in positive direction. However, minimum curd yield plot^-1 (18.64 kg) was recorded in the N₀ (control). In spacing, maximum yield plot^-1 (26.14 kg) was obtained from the closest spacing because the increase in number of plants per unit area While, minimum curd yield plot^-1 (24.00 kg) was recorded in the S₃ (60×45 cm²). Similar results have been recorded by (El-Shabrawy et al., 2005) and (Biswas et al., 2015). Statistically significant variation was recorded due to interaction effect of different levels of nitrogen and spacing in terms of curd yield plot^-1 of cauliflower. The highest curd yield plot^-1 (30.03 kg) was found from N₃S₁. Whereas, minimum curd yield plot^-1 (18.65 kg) was found from N₀S₃.

Table 2: Effect of different levels of nitrogen and spacing on yield characteristics of cauliflower

The data recorded on curd yield ha^-1 have been presented in Table 2. It is evident from the data that the curd yield ha^-1 was significantly affected by different treatments. The mean performance of different levels of nitrogen showed that maximum curd yield ha^-1 (325.54 q) was obtained with N₃ (100% N ha^-1) because in increase in nitrogen helps plant for higher vegetative growth. While, minimum curd yield ha^-1 (241.83 q) was recorded in the N₀ (control). In spacing, maximum curd yield ha^-1 (295.69 q) was obtained with S₁ (45×30cm²) because in case of wider spacing, individual plants will yield more but yield ha^-1 may be reduced due to low plant population. Therefore, closer spacing must be worked out at which average yield ha^-1 was found maximum. Whereas, minimum curd yield ha^-1 (281.29 q) was recorded in the S₃ (60×45 cm²). Similar finding was observed by (Baloch et al., 2014) and (Hiwale et al., 2010). Statistically significant variation was recorded due to interaction effect of different levels of nitrogen and spacing in terms of curd yield ha^-1 of cauliflower. The highest curd yield ha^-1 (326.90 q) was found from N₃S₁. However, minimum curd yield ha^-1 (225.97 q) was found from N₀S₃.

Economics

Economics of the treatments was worked out under different levels of nitrogen and spacing. Examination of the data revealed that maximum net return (Rs. 299443) and highest gross return (Rs. 392280) were obtained in T₁₀ (100 % N ha^-1 + 45×30 cm²). Whereas, minimum gross return (Rs. 271164) and net return (Rs. 180652) were obtained in T₃ (0 % N ha^-1 + 60×45 cm²). On the same lines, maximum benefit: cost ratio (3.22) was calculated in T₁₀ (100 % N ha^-1 + 45×30 cm²) and minimum (1.99) was recorded in T₃ (0% N ha^-1 + 60×45 cm²). Economics was calculated by Parmar et al. (2015) and Gessesew et al. (2015) (Table 3).

Table 3: Effect of different levels of nitrogen and spacing on economic parameters of cauliflower

Conclusion

Treatment 100 % Nitrogen  ha^-1+60×45 cm² gave best results in respect to growth and yield of cauliflower and second best treatment is 100 % N ha^-1+45×45 cm². While, maximum yield plot^-1 and yield ha^-1 was obtained from treatemnt 100% N ha^-1+45×30 cm²). However, maximum net return and B: C ratio was found to be maximum with treatemnt (100% N ha^-1+45×30 cm²).

Acknowledgement

We are highly thankful to Mata Gujri College, Fatehgarh Sahib for providing the fields and labs facilities for conducting researc

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