1. Agriculture and Forestry University, Nepal; gautamdhanraj029@gmail.com

*             Correspondence: gautamdhanraj029@gmail.com

Keywords: Allium cepa. L, nitrogen, urea, Nepal

1. INTRODUCTION

The diverse topographic features and climatic conditions in Nepal permit the successful production of a large number of vegetables. Vegetables shared about 9.71% to total agricultural gross domestic product [1]. Allium is one of the 57 genera of the Angiosperms have more than 500 species. Majority of the Allium species are the native of Northern hemisphere mainly Asia, Allium cepa  which have cylindrical to ovoid or rounded bulbs covered with white, brownish or reddish papery coats [2]. Onion contains plenty of beneficial nutrients such as it is the rich source of Vitamins B1, C and E and certain other trace elements. If onion consumed in small amounts for their pungency, they can be considered as condiments. The annual average world production of onion is estimated at around 72 million metric tones [3]. Worldwide, onion (Allium cepa L.) is a vegetable crop of commercial importance and has been the most used flavoring vegetable for centuries. Onion (Allium cepa L.) is one of the world’s most important spice crops, which is cultivated from tropical to the temperate regions. It consumed as raw or a component of meals in many different cultures around the world [4]. Onion is an extensively grown biennial bulb crop, with world production of 74,250,809 tones from an area of 4,364,000hectares. China and India are the primary onion growing countries, followed by the USA, Egypt, Iran, Turkey, Pakistan, Brazil, the Russian Federation, and the Republic of Korea [5]. The area, production and productivity of onion in Chitwan were1364 hectares, 1364 t and 13.6 t ha-1 respectively. The average productivity of onion bulb production is quite low in Nepal as compared to the Asian countries. The average yield of onion is very low as compared to other countries. Production of onion is carried from the tropical conditions regions to the temperate regions of Nepal [6]. It has been reported that the  growth, yield and bulb quality of onion are largely dependent on number of interacting factors as  onion is a long duration crop with high yield which removes large quantities of nutrients from the soil, demands for onion is increasing rapidly among the vegetable consumers in view of its better bulb size, and quality only one source of nutrients like chemical fertilizers, organic manures and bio-fertilizers cannot improve the production or maintain the production sustainability and soil health [7]. The decline in productivity is due to unbalanced use of inorganic nitrogen fertilizers and continuous use of inorganic fertilizers alone which causes low yield per unit with poor quality produce [8]. It has been described that poultry manure is a promising source of organic nitrogen which is cost effective and easily available to the farmers in low cost than inorganic nitrogen sources and has nutritive value for plant growth and development and a cheaper source of both macro and micronutrients. Among the various factors responsible for lower productivity of onion, declining soil productivity due to excess and continuous use of chemical fertilizers and lack of adequate supply of organic manures are the major factors. A consequence of this trend is a deeply unbalanced soil nutrient composition that ultimately leads to a reduction in crop yield potential [9]. The escalating costs of chemical fertilizers also reduce the return per rupee of investment. Its application with inorganic nitrogen sources can insure the sustainable production through reduction of production cost and environment friendly. Hence, the present investigation was under taken with a view to study the effect of different sources of Nitrogen and varietal effect on onion yield and in different yield attributes [10]. This study aimed at comparing the four varieties of onion viz., N53, Agri Found Dark Red, Agri Found Light Red and Red Creole at different sources of nitrogen so that the effect of nitrogen sources on bulb size could be assessed and the appropriate bulb yield and plant growth for achieving the higher total yield could be identified under Chitwan, Nepal condition.

2. LITERATURE REVIEW

The Liliaceae family’s onion (Allium cepa L.) is a major vegetable crop worldwide. Diploids Allium cepa, Allium aggregattum, and Allium prolilum make up its three groupings [11]. Afghanistan, Iran, and Pakistan grow the biennial herb abroad. The origin of Allium cepa is unknown. Allium cepa’s domestication occurred independently in numerous sites and covered a large area of western Asia from Palestine to India. The wild existence of Allium cepa is uncertain. Most botanists believed it originated in Iran, Pakistan, and a northern mountainous country [12]. Onion originated in Central Asia, then the Near East and Mediterranean, onion is a member of the Amaryllidaceae family, Allium genus, and cepa species [13]. The temperate and tropical climates grow onion (Allium cepa L.), one of the world’s most significant vegetables. Nepalese people grow onions more than any other bulb. Nepal also grows garlic, leek, and chive bulbs (Allium sativa, Allium porrum, Allium schenoprasum) [14]. Egyptians honored them and fed them to pyramid builders for strength, many high peaks in Nepal are genetically rich for Jimbu jhar (Allium wallichii), a native herb [15]. It reported that onion’s wild relative Nepal has dundu onion (Allium tuberosum Rottler ex Spreng). Scientists have also found native onion landraces in Nepal, including Mallajh native, Nuwakote Local, and Kathmandu Local. As a condiment and vegetable, onion is essential in every kitchen. Thus, its internal market is large. Green leaves and immature and mature bulbs are eaten raw or to make vegetables. Its pungency makes it valuable. Crispness, juiciness, pungency, and bulb preservation are considered, small bulbs and shallots are vinegar or brine-pickled [16]. Dehydrated bulb or onion power is popular because it cuts transit and storage costs. Onion has several therapeutic benefits. Bruises, boils, and wounds benefit from onion diuretics. It relieves heat. Bulb juice smells fainting spells. It helps prevent heart disease and other illnesses. Besides fresh consumption as a peppery vegetable, onions are used as green leaves and bulbs for processing. Bulb size is a key quality characteristic for direct-consumption bulbs. Genetics determine many of these traits, which determine variation. Artificial culture alters several traits, particularly size [17]. The onion is a popular vegetable that prevents heart disease and other illnesses. One of the richest sources of flavonoids in the diet, it reduces the risk of cancer, diabetes, and heart disease. As a preservation and therapeutic plant, it may have anti-allergenic, anti-bacterial, antiviral, and anti-inflammatory components. It stated that onions are a common and rich source of dietary flavonoids and contain three diverse and highly valuable phyto chemicals in perfect proportion: flavonoids, fructans, and organo sulfur compounds, which are powerful antioxidants and believed to benefit human health [18]. The average bulb weight in Punjab Selection, Pusa Red, Arka Niketan, and Arka Kalyan was 50-70, 70-90, 100-170, and 100-190g. It Total bulb production, dry matter percentage, and plant height rose following nitrogen administration. A study examined the impact of essential nutrients (NPK) on onion growth and yield. Results revealed significant effects of NPK doses on plant height, bulb diameter, single bulb weight, and total marketable yield. Among the treatments, NPK dose 90-60-80 kg ha-1 produced the most marketable bulbs [19]. Ridge-grown onions yielded more than flat-grown ones. For optimal onion (cv. Phulkara) bulb yield, plant on ridges and fertilize with 90-60-80 kg NPK fertilizers ha-1. Intake of minerals is high in onion, qrganic fertilizers improve root rizosphere conditions (structure, humidity, etc.) and plant growth by increasing microorganisms. Organic acids that decompose organic fertilizer increase nutrient benefits. A 35 t/ha crop eliminates 120kg N, 50kg P2O5, and 160kg K2O. FYM adds macro and micro nutrients and enhances soil physical, chemical, and biological qualities [20]. FYM contains urine, faces, and decaying plant straw. It improves soil gas exchange, water retention, and erosion stability. Approximately 1.5 million tons of nutrients come from farms. In addition, chicken litter is a cheap supply of macronutrients (N, P, K, Ca, Mg, S) and micronutrients [21]. It boosts soil microbiology, carbon, nitrogen, and porosity, poultry manure and vermicompost are high in nutrients, thus adding enough can meet crop nutritional needs. A field experiment during the rainy season to study the response of onion (cv. N-53) with integrated application of N (0, 60, 90, 120, and 150 kg ha-1) and FYM (0, 5, 10, and 15 t ha-1). The average bulb yield increased significantly up to 120 kg N ha-1 and FYM at 10 t ha-1 [22]. The influence of Azospirillum brasilense and lopoferum inoculation under different nitrogen levels and found that different poultry manure and inorganic-N fertilizer combinations at different growth stages affected onion total dry matter (leaf + bulb + root). The (50% inorganic N with 10 t ha-1poultry) manures treatment generated the most dry matter (1.61 g plant-1) at all growth stages, while the control treatment produced the least [23]. A study observed that N and variety interaction affected neck size in season two, with the Red Creole variety having the largest neck diameter of 11 cm at 78 and 104 kg N ha-1. Use of N considerably (P<0.001) influenced the production of thick-necked bulbs. Neck diameters increased with higher N rates, with an 18% increase in season 1 and 32% in season 2. Late N application resulted in a significant decrease (P<0.001), but there was no significant difference between the two varieties [24]

3. MATERIALS AND METHODS

The experiment was conducted at Agriculture and Forestry University’s vegetable production farm in Rampur. The initial soil physicochemical properties of the experimental site were recorded by obtaining the composite soil samples, taken from different spots from 0-15 cm depth using bucket auger. The soil sample was air dried, grounded and sieved through 2 mm and 0.2 mm sieve and tested for their properties.

Table 01: Physico-chemical properties of the soil of the experimental site at Rampur, Chitwan, Nepal

Properties	Average content	Rating	Methods
Physical properties
Sand (%)	61.1
Silt (%)	25.2
Clay (%)	13.7
Texture/rating	Sandy loam
Chemical properties	0-15cm
Soil pH	6.2	Acidic	Beckman Glass Electrode pH meter
Soil organic matter (%)	2.36	Low	Walkey and Black method
Total nitrogen (%)	0.12	Low	Kjeldhal distillation method
Available phosphorous (kg  ha-1)	132.59	High	Modified Olsen’s method
Available potassium (kg ha-1)	235.56	High	Ammonium acetate method

The total nitrogen was determined by Kjeldhal distillation unit, available phosphorous by modified Olsen’s method by using a spectrophotometer and available potassium by Ammonium acetate method. Organic matter was determined by Walkey and Black method, pH by Beckman Glass Electrode pH meter (1:1 soil: water suspensions) and soil texture by hydrometer method. Physico-chemical properties of the soil of the experimental site are presented in table above. From the analysis, sand was found to be dominated in the physical property than silt and clay, possessing the sandy loam texture. The average soil pH was found slightly acidic (6.2) in the experimental field. The total nitrogen (0.12%), available phosphorous (132.59 kg ha^-1) high, and available potassium (235.56 kg ha^-1) were high in range. The experiment was led out in two factor Factorial Randomized completely Blocked design with three replications. There were twelve treatments constricting of four varieties as Nasik-53, Red Creole, Agri Found Dark Red and Agri Found Light Red and three different sources of nitrogen, full dose of N by urea,50%N by urea +50% N by PM and full dose of N by PM. There were total 12 treatments in each replication which were replicated 3 times having total 36 plots. Each individual plot had 1.35 m length, 1.2m width and 1.62square meter area. There was 0.5 m spacing between plots and each replication was separated by 1 m space. There were total 108 plants in each plot. Outer most two rows of both sides of each plot were used as border rows. Total 70 plants excluding as the border plants and 10 plants were randomly sampled used for data recording.The treatment combinations comprised of four varieties and the three different sources of nitrogen from urea and poultry manure. The experiment was laid out in two factorial completely randomized designs and replicated three times. There were twelve treatments of both variety and nitrogen from different sources.

Table 02: Treatments details of the field experiment at Rampur, Chitwan, Nepal.

Treatments	Symbols
Factor A: Variety
N-53	V1
Red Creole	V2
Agri Found Dark Red	V3
Agri Found Light Red	V4
Factor B: Nitrogen Sources
Urea	100% N by Urea
PM	50% N Urea + 50% N PM
PM	100% N by PM

 

The combination of the varieties and different sources of Nitrogen were the treatments of the experiment. The following were the treatments combinations.

Table 03:  Treatment combinations used for the field experiments at Rampur, Chitwan, Nepal

Treatments	Combinations	Symbols
T1	N-53 + 100%N by Urea	V1CF
T2	N- 53  + 50% by N Urea +50%N by PM	V150% CF+50%PM
T3	N- 53 +  100%N by PM	V1100%PM
T4	Red Creole + 100%N by Urea	V2CF
T5	RedCreole+50%N by Urea +50%PM	V250% CF +50%PM
T6	Red Creole +  100%N by PM	V2100%PM
T7	AFDR + 100%N by Urea	V3CF
T8	AFDR  + 50% N by Urea +50%N by PM	V350% CF+50%PM
T9	AFDR +  100%N by PM	V3100%PM
T10	AF L R + 100%N by Urea	V4CF
T11	AFLR +50%by Urea +50%N by PM	V4 50%CF  +50%PM
T12	AFLR + 100%N by  PM	V4 100% PM

Figure 01: Field layout of the experimental site at Rampur, Chitwan, Nepal.

All the recorded data was arranged systematically treatment-wise under three replications on the basis of various observed parameters. The data recorded were statistically analyzed by using technique of analysis of variance and significance was determined for Two Factorial completely randomized block design. All the recorded data were subjected to analysis of variance and Duncan’s Multiple Range Test (DMRT) for mean separations from the reference of Gomez and Gomez (1984). For simple statistical analysis R stat were used for carrying out. The standard error of mean (S.E.±) was worked out and ANOVA was done to test the significance difference for each parameter. Calculation was done at 5% significance level.

4. RESULT & DISCUSSION

4.1 Growth parameters

The mean plant height was 18.84 cm at 25 DAT and increased to 76.39 cm at 100 DAT. There was found non-significant difference among the varieties in plant height of onion at 25 (DAT), 50 DAT, 75 DAT and 100 DAT as mention in table below.

Table 04: Plant height of onion at different dates after transplanting as influenced by different varieties and sources of nitrogen at Rampur, Chitwan, Nepal.

Treatments	Plant height(cm)
	25DAT	50DAT	75DAT	100 DAT
Factor A (Varieties)
N-53	19.37	33.86	68.24	76.18
Red Creole	18.32	35.58	68.67	77.61
AFDR AFLR	18.83 18.84	34.19 34.46	66.85 68.81	75.50 76.30
SEm (±)	0.94	2.39	1.65	2.23
Lsd(=0.05) CV%	ns 10.65	ns 14.7	ns 5.16	ns 6.21
Factor B (Nitrogen sources)
Full dose of N by Urea	17.26c	28.70c	65.37c	71.99c
50% N by Urea+ 50% N by PM	20.90a	38.02a	72.03a	81.45a
100% N by PM	18.35b	36.85b	67.02b	75.75b
SEm (±)	0.58	1.22	0.93	1.15
Lsd(=0.05)	1.02**	2.15**	1.64**	2.03**
CV%	6.54	7.5	2.9	3.2
Grand mean	18.84	34.52	68.14	76.39
Interaction(A×B) SEm(±) CV%	0.60 6.98	1.3 8.04	0.83 2.6	1.12 3.13

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance and DAT = Days after transplanting.

The effect of nitrogen through organic and inorganic sources on plant height was highly significant in all observations. The significantly taller plant height was observed from (50% N by Urea +50%N by PM) and the shortest plant height was observed from full dose of nitrogen by urea at 25 DAT, 50 DAT, 75 DAT and 100 DAT. The effect of interaction between varieties and different sources of nitrogen was unable to influence significantly the height of the crop. Result of statistical analysis showed that the varieties had non-significant difference in number of leaves plant^-1 but the different sources of nitrogen had significant effect on number of leaves plant^-1 at different stages of plant growth table below.

Table 05: Number of leaves plant^-1of onion at different dates after transplanting as influenced by different varieties and sources of nitrogen at Rampur, Chitwan, Nepal.

Treatments	Number of leaves plant-1
	25DAT	50DAT	75DAT	100 DAT
Factor A (Varieties)
N-53	3.13	4.76	5.83	6.88
Red Creole	3.23	4.74	5.82	6.85
AFDR AFLR	3.20 3.17	4.91 4.82	6.0 5.97	6.82 6.92
SEm (±)	0.36	0.23	0.381	0.31
Lsd(=0.05) CV %	ns 24	ns 10.56	ns 10.45	ns 9.62
Factor B (Nitrogen sources)
Full dose of N by Urea	2.40c	4.37 b	5.35c	6.22c
50% N by Urea+ 50% N by PM	4.0a	5.12a	6.56a	7.68a
100% N by PM	3.15b	4.93b	5.80b	6.70b
SEm (±)	0.15	0.17	0.15	0.07
Lsd(=0.05)	0.26**	0.31**	0.26**	0.13**
CV %	10.05	7.9	5.49	2.28
Grand mean	3.18	4.81	5.9	6.87
Interaction(A×B) SEm (± ) CV%	0.15 10.30	0.18 8.22	0.15 5.53	0.07 2.21

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance and DAT = Days after transplanting.

Significantly higher number of leaves plant^-1was recorded at all stages of growth in the treatment (50% N by Urea + 50% N by PM). The sources of nitrogen (50% N by Urea + 50% N from PM) had significantly higher number of leaves per plant than (Full dose of N by PM) and the lower number of leaves per plant was found (Full dose of N by Urea) at 25, 50, 75 and 100 DAT. There was no significant effect of varieties on number of leaves per plant at different growth stages of the plant. Similarly, the effect of interaction between varieties and different sources of nitrogen was found non-significant.

4.2 Yield attributing parameters and yield

The polar height of onion bulb was highly significantly influenced due to varieties and different sources of nitrogen.  Results of statistical analysis showed that the polar height of the treatment (50% N by Urea + 50% N by PM) was significantly higher (3.36cm) than full dose of N by Urea (2.90 cm).          Among varieties, N-53 had significantly higher (3.23 cm) polar height than Agri Found Light Red (2.97 cm). However polar height of Red Creole (3.11 cm) was at par with Agri Found Dark Red (3.07 cm) as shown in table below. The effect of interaction between variety and different sources of nitrogen was non-significant. The mean bulb diameter in the experiment was 4.89 cm. The bulb diameter was significantly influenced by varieties and different sources of nitrogen and interaction among treatments on bulb diameter was found non-significant. The bulb diameter of onion was significantly higher (5.41 cm) at (50% N by urea + 50% N by PM) which was followed by (Full dose N by PM) and (Full dose of N by Urea.). Bulb diameter at Full dose of N by PM and full dose of N by urea was statistically similar. Similarly, in case of varieties relatively higher bulb diameter (5.10 cm) was recorded in N-53 and lower diameter (4.68 cm) was in Agri Found Light Red. However bulb diameter of Red Creole (4.95 cm) was at par with Agri Found Dark Red (4.83 cm) (Table 6 and Appendix 5).The effect of interaction between variety and different sources of nitrogen was non-significant. There was highly significant effect of different sources of nitrogen on neck diameter. The interaction effect of varieties and different sources of nitrogen was non-significant on neck diameter of the onion bulb as mention in table. The neck diameter of onion was significantly higher (2.15 cm) at (Full dose of N by Urea) which was followed by (Full dose of N by PM) while smaller diameter obtained (1.41 cm) from (50%N from Urea + 50%N from PM). There was highly significant effect of varieties on neck diameter of the bulbs. The highest neck diameter (2.067 cm) was recorded from Agri. Found Light Red followed by Red Creole (1.84cm), Agri Found Dark Red(1.70cm) and the smaller neck diameter was found  in N-53 (1.61cm). The mean bulb weight of onion in the experiment was 40.38 g. it has been shown that the bulb of onion was significantly influenced by different sources of nitrogen as well as varieties but not due to their interaction. The bulb weight of onion was significantly higher (44.61 g) at (50% N by urea + 50%N by PM) followed by (Full dose of N by PM (39.62 g) and the lowest was obtained from (Full dose of N by Urea) (36 g).

Table 06: Bulb size characters influenced by different varieties and sources of nitrogen at Rampur, Chitwan, Nepal.

Treatments	Bulb size characters
	Polar height (cm)	Neck diameter (cm)	Bulb diameter (cm)	Bulb weight (g)
Factor A (Varieties)
N-53	3.23a	1.61b	5.10a	42.61a
Red Creole	3.11ab	1.84ab	4.95ab	40.82ab
AFDR AFLR	3.07ab 2.97b	1.70b 2.067a	4.83ab 4.68b	40.04ab 38.04b
SEm (±)	0.1	0.155	0.21	1.71
Lsd(=0.05) CV%	0.22** 7.51	0.31** 18.27	0.44** 9.47	3.49 ** 9
Factor B (Nitrogen sources)
Full dose N by Urea	2.90c	2.15a	4.46c	36.89c
50% N by Urea +50% N by PM	3.36a	1.41c	5.41a	44.61a
Full dose of N by PM	3.03b	1.85b	4.79b	39.62b
SEm (±)	0.06	0.09	0.12	1.01
Lsd(=0.05)	0.11 **	0.16**	0.21**	1.78
CV%	4.63	10.85	5.26	5.31
Grand mean	3.09	1.8	4.89	40.38
Interaction(A×B) SEm(±) CV%	0.05 3.80	0.03 4.05	0.1 4.67	0.48 3.6

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance.

The mean bulb weight of single center bulb of onion in the experiment was 2.79 kg. Mean table shows that the mean single center bulb of onion was significantly influenced by different sources of nitrogen as well as varieties but not due to their interaction. The single center bulb weight of onion was significantly higher (3.37 kg) at (50% N by urea + 50%N by PM) and the lowest was obtained from (Full dose of N by Urea) (2.45 kg). Similarly, in case of varieties significantly the highest single center bulb weight was recorded from variety N-53 (3.06 kg) and lowest single center bulb weight was recorded from variety Agri Found Light Red (2.53kg). But the single center bulb weight of Red Creole and Agri Found Dark Red were statistically at par. The mean marketable bulb yield of onion in the net plot was 3.57 kg. Table below shows that the mean marketable bulb weight of onion was significantly influenced by different sources of nitrogen as well as varieties but not due to their interaction. Similarly, in case of varieties highly significant effect was found and the highest marketable bulb yield was recorded from variety N-53 (3.98 kg) and lowest marketable bulb yield was recorded from variety Agri Found Light Red (3.1 kg). But the marketable bulb yield of Red Creole and Agri Found Dark Red were statistically at par.

Table 07: Single center and marketable bulb yield influenced by different varieties and sources of nitrogen at Rampur, Chitwan, Nepal

Treatments
	Single center bulb yieldkgnetplot-1	Marketable bulb yieldkgnetplot-1
Factor A (Varieties)
N-53	3.06a	3.98a
Red Creole	2.83ab	3.73ab
AFDR AFLR	2.75ab 2.53b	3.48ab 3.1b
SEm (±)	0.22	0.3
Lsd CV%	0.46** 17.42	0.8** 23.46
Factor B (Nitrogen sources)
Full dose N by Urea	2.45b	3.06 b
50% N by Urea + 50% N by PM	3.37a	4.41a
Full dose of N by PM	2.56b	3.25b
SEm (±)	0.14	0.3
Lsd(=0.05)	0.247**	0.52**
CV%	10.65	17.81
Grand mean	2.79	3.57
Interaction(A×B) SEm(±) CV%	0.1 8.24	0.29 17.52

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance.

4.3 Qualitative characters

The different sources of nitrogen on TSS was found highly significant but their interaction effect was found non-significant. Highest TSS (11^oBrix) was recorded from (50% N by Urea + 50%N by PM) and the least (9.25^o Brix) was from (Full dose of N by Urea). Similarly, in case of varieties significant effect was found. The highest TSS (11^oBrix) was recorded from Agri Found Light Red and the lowest TSS was found in Agri Found Dark Red. But the TSS of N-53 and Red Creole were statistically at par. Result of statistical analysis showed that there was highly significant effect on different sources of nitrogen on dry matter percentage of onion bulb. The dry matter of bulb was found highly significant and the highest (12.25%) at (50%N by Urea + 50%N by PM) followed by (Full dose of N by PM) (9.75%) and was statistically par at (Full dose of N by Urea) (9.75%). Similarly, in case of varieties significant effect was found and the highest (11%) dry matter percentage of bulb recorded from variety N-53 and the variety Red Creole was statistically at par with Agri Found Dark Red and the lowest was recorded from variety Agri Found Light Red (9.83%) Interaction effect of varieties and different sources of nitrogen was non-significant on dry matter percent of onion bulbs.

Table 08: TSS and dry matter percent of bulb influenced by different varieties and sources of nitrogen at Rampur, Chitwan , Nepal

Treatments	Bulb quality
	TSS (0 Brix)	Dry matter percent (%)
Factor A (Varieties)
N-53	10ab	11a
Red Creole	10ab	10.83ab
AFDR AFLR	9.55b 11a	10.83ab 9.83b
SEm (±)	0.47	1.08
Lsd CV%	0.96* 10.06	1.2** 11.81
Factor B (Nitrogen sources)
Full dose of N by Urea	9.25b	9.75b
50% N by Urea+50% N by PM	11.0a	12.25a
Full dose of N by PM	9.66b	9.75b
SEm (±)	0.33	0.21
Lsd(=0.05)	0.59**	0.37**
CV%	7.17	4.27
Grand mean	9.97	10.58
Interaction(A×B) SEm(±) CV%	0.32 6.89	1.08 2.16

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance.

The effect of different sources of nitrogen and their interaction was non-significant. The varietal effect was found highly significant. The highest bolting percentage (5.01 %) was found in Agri Found Dark Red variety which was  followed by Agri Found light Red (4.84%), N-53 (3.74%) and the minimum bolting percentage was recorded with the variety Red Creole (2%).Non-significant effect was found from different sources of nitrogen.

Table 09: Bolting of onion as influenced by different varieties and sources of nitrogen at Rampur, Chitwan, Nepal

Treatments	Bolting (%)
Factor A (Varieties)
N-53	3.74b
Red Creole	2.0c
AFDR AFLR	5.01a 4.84a
SEm (±)	0.43
Lsd	0.88**
Factor B (Nitrogen sources)
Full dose of N by  Urea	3.97
50%N by Urea + 50%N by PM	3.67
Full dose of N by PM	4.05
SEm (±)	0.726
Lsd	ns
CV %	39.5
Grand mean	3.9
Interaction(A×B) SEm(±) CV %	0.41 22.67

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance.

4.4 Harvest index

The mean harvest index of onion in the experiment was 79.8%. The difference among the treatments was found highly significant. It was significantly influenced by varieties as well as different sources of nitrogen but not due to their interaction. The harvest index of onion was significantly higher at (50%N by Urea +50%N by PM) (81.46%) followed by (Full dose of N by PM) (79.56%) and the lowest was recorded from (Full dose of N by Urea) (78.37%). Harvest index on (Full dose of N by Urea) and (Full dose of N by PM) were statistically at par. Similarly, in case of varieties significantly the highest harvest index was recorded from N-53 (81.42%) followed by Red Creole (80.04%) and Agri Found DarkRed (78.95%) which was recorded statistically at par with Agri Found Light Red (78.79%).

Table 10: Harvest index of onion as influenced by different varieties and sources of nitrogen at Rampur, Chitwan ,Nepal

Treatment	Harvest index
Factor A (Varieties)
N-53	81.42a
Red Creole	80.04ab
AFDR AFLR	78.95b 78.79b
SEm	1.02
Lsd CV%	2.07** 2.71
Factor B (Nitrogen sources)
Full dose N by  Urea	78.37b
50%N by Urea +50%N by PM	81.46a
Full dose of N by  PM	79.56b
SEm (±)	0.94
Lsd	1.65**
CV, %	2.5
Grand mean	79.8
Interaction(A×B) SEm CV%	0.76 2.03

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance.

4.5 Biological yield (t ha^-1)

It was significantly influenced by different sources of nitrogen as well as varieties but not due to their interaction. The biological yield of onion was significantly higher at (50%Nby Urea + 50%N by PM) (54.82 t ha^-1) followed by (Full dose of N by PM) (49.84 t ha^-1) and the lowest was recorded at (Full dose of N by Urea) (47.07 t ha^-1). Similarly, in case of varieties significantly the highest biological yield was recorded from N-53 (51.32 t ha^-1) followed by Red Creole (50.20 t ha^-1) and Agri Found Dark Red (48.06 t ha^-1) and Agri Found Light Red (48.06 t ha^-1) both of them had same the same value.

Table 11: Biological yield of onion as influenced by different varieties to sources of nitrogen at Rampur, Chitwan, Nepal

Treatments	Biological yield (t ha-1)
Factor A (Varieties)
N-53	51.32a
Red Creole	50.20ab
AFDR AFLR	48.06b 48.06b
SEm	1.8
Lsd	3.68**
Factor B (Nitrogen sources)
Full dose of N by Urea	47.07c
50%N by Urea + 50%N by PM	54.82a
Full dose of N by PM	49.84b
SEm (±)	1.17
Lsd	2.06**
CV %	4.92
Grand mean	50.57
Interaction(A×B) SEm CV%	0.83 3.48

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance.

4.6 Economic yield (t ha^-1)

The mean economic yield of onion in the experiment was 26.92t ha^-1. The difference among the treatments was highly significant. It was significantly influenced by different sources of nitrogen as well as varieties but not due to their interaction. The yield of onion was significantly higher at (50%Nby Urea + 50%N by PM) (29.75 t ha^-1) followed by (Full dose of N by PM) (26.43 t ha^-1) and the lowest was recorded at (Full dose of N by urea)(24.59 t ha^-1). Similarly, in case of varieties significantly the highest yield was recorded from N-53 (28.39 t ha^-1) followed by Red Creole (27.21 t ha^-1) and Agri Found Dar Red (26.56 t ha^-1) and the lowest was recorded from Agri Found Light Red (25.52 t ha^-1). Yields from variety Red Creole and Agri Found Dark Red were statistically at par with each other.

Table 12: Economic yield of onion as influenced by different varieties to sources of nitrogen at Rampur, Chitwan, Nepal

Treatments	Economic yield (t ha-1)
Factor A (Varieties)
N-53	28.39a
Red Creole	27.21ab
AFDR AFLR	26.56ab 25.52b
SEm	1.15
Lsd CV%	2.35** 9.1
Factor B (Nitrogen sources)
Full dose of N by Urea	24.59c
50%N by Urea + 50%N by PM	29.75a
Full dose of N by PM	26.43b
SEm (±)	0.67
Lsd	1.18**
CV %	5.29
Grand mean	26.92
Interaction(A×B) SEm(±) CV%	0.48 3.78

Note: Means with same letter in column are not significantly different at p = 0.05 by DMRT. *Significant at 5% (p < 0.05), ** Significant at 1% (p < 0.01) and ns: not significantly different at 5% (p > 0.05). SEM = Standard error of mean, LSD = Least significant difference, CV = Coefficient of variance.

4.7 Correlation among the various growth and yield parameters of onion

Number of leaves/plant, plant height showed highly positive correlation with total weight of bulb, economic yield, polar diameter and equatorial diameter at 0.01% levels of significance (Table 13). Number of leaves/plant, plant height showed highly negative correlation with neck diameter of bulb at harvest stage at 0.01% levels of significance. Economic yield, bulb weight, polar diameter and equatorial diameter showed highly positive correlation with total soluble solids and dry matter percentage of bulb at 0.01 levels of significance.

Table 13: Correlation among the various growth and yield parameters of different onion varieties to sources of nitrogen at Rampur, Chitwan, Nepal

Number of leaves/ plant at 100 DAT	Plant height at 100 DAT	Bulb weight	Economic yield	Equatorial diameter	Polar diameter	Neck diameter	TSS	Dry matter percentage
Number of leaves/ plant at 100 DAT	0.86**	0.80**	0.81**	0.76**	0.77**	-0.81**	0.74**	0.84**
Plant height at 100 DAT	_	0.71**	0.71**	0.71**	0.68**	-0.69**	0.61**	0.74**
Bulb weight		_	0.99**	0.88**	0.92**	-0.88**	0.60**	0.86**
Economic yield			_	0.87**	0.91**	-0.87**	0.62**	0.85**
Equatorial diameter				_	0.89**	-0.83**	0.56**	0.83**
Polar diameter					_	-0.83**	0.62**	0.84**
Neck diameter						_	-0.46**	-0.87**
TSS							_	0.55**

** Correlation is significant at the 0.01 level (2-tailed).

* Correlation is significant at the 0.05 level (2-tailed).

4.8 DISCUSSION

Agri Found Light Red had the lightest bulbs (38.04 g) while N-53 had the most (42.61 g). The bulb weight of Red Creole (40.82 gm) was comparable to Agri Found dark Red (40.04 gm). A study mentioned that N-53 bulbs weigh more than Red Creole bulbs, and Agri Found Light Red had the lowest average bulb weight and genetic variability caused it. [25]. The average plant height was 18.84 cm at 25 DAT and 76.39 cm at 100 DAT, varieties did not differ in plant height however different nitrogen sources significantly affected plant height [26]. It discovered that nitrogen application levels significantly affected plant height at 60 DAT. 120 kg N ha-1 produced the tallest plants (59.81 cm), which was significantly different from the other treatments. The 40 kg (53.67 cm), 80 kg (56.25 cm), and 160 kg (56.81 cm) N ha-1 plants were equal in height [27]. At 60 DAT, AFDR and N-53 plants were similar in height. At 45, 60, and 75 DAT, it discovered no significant differences in plant height amongst types. Similarly, it has been found no height difference between types. Variety and nitrogen sources did not interact significantly [28]. With (50%N by Urea + 50%NbyPM) at 25 DAT, the plant height was 20.90cm, 38.02cm at 50 DAT, 72.03cm at 75 DAT, and 81.45cm at 100 DAT. With (Full dose of N by Urea) at 25DAT, 50DAT, 75DAT, and 100DAT, the plant height. It found that poultry manure and inorganic-N improved onion plant height at different growth phases. Plant height usually rose gradually after transplantation. The control treatment (100%N) generated the shortest plant, while (50%N+10t PM) produced the tallest [29]. The treatments (50%N+10t PM) and (N%75+5tPM) had identical plant heights throughout growth. Balanced nutrients helped shoot apical meristem cell division increase plant height. It found that onion plants might grow taller with the right fertilizer, organic manures+50% N and 100% PK increased onion plant height [30]. Different nitrogen sources significantly affected leavesplant-1 number. The treatment (50%N by Urea + 50% N by PM) had 7.68 more leaves/plant than (Full dose of N by PM) but was comparable on mean data. In the full N by Urea treatment, the minimal leaf/plant was 6.22 [31]. It has been found that 15 and 20 t ha-1PM treatments had 8-21% more leaves per plant than NPK for both onion cultivars [32]. The amended treatments had more leaves per plant than the control due to the significant roles or effects of available essential plant nutrients in the synthesis of protein required for leaf development, photosynthesis, and metabolic processes, promoting rapid growth. Approx. 50% inorganic N and 10t ha^-1 poultry manure produced the most leaves per plant, possibly due to enhanced nitrogen availability [33]. It has found that poultry manure and inorganic fertiliser boosted shallot leaf count on sandy soils. Different nitrogen sources affected onion bulb polar height significantly.  The plant with 50% N by Urea + 50% N by PM had a much greater (3.36 cm) polar height than the treatment (Full dose of N from PM), although the treatment had the lowest (2.90cm) [34]. Texas Grano’s higher growth rate due to more leaves per plant, plant height, total dry biomass accumulation, and dry bulb biomass contributed to its larger mean bulb diameter than Bawku Red [35]. The higher mean bulb diameter in response to PM and NPK application over the control check may be due to increased assimilate production and partitioning to the bulbs, which increases plant height, leaf count, total dry biomass accumulation, and bulb biomass [36]. Bulb diameter correlates favourably with plant height, leaf count, and dry biomass accumulation. Organic manure did not affect bulb length [37]. Multiple nitrogen sources and the four studied types affected neck diameter significantly. The Full dose of N by Urea therapy had the largest neck-diameter (2.15 cm) among nitrogen sources. In therapy (50% N by Urea+ 50% N by PM), the neck diameter was lowest (1.41 cm) [38]. The largest neck diameter (18.05 mm) was 160 kg N ha-1, matching 120 kg N ha-1 (16.74 mm). These treatments ranged greatly. Importantly, the control had the lowest neck diameter (11.3 mm) [39]. Variation significantly affected neck diameter. Agri Found Light Red (2.06cm), Red Creole (1.84 cm), and Dark Red (1.70 cm) had the highest neck diameters, while N-53 (1.61 cm) had the lowest [40]. The variety significantly affected dry matter percentage. The greatest dry matter percentage of bulb was 11.83% in N-53 and the lowest was 9.83% in Agri Found Light Red. Red Creole has TSS comparable to Agri Found Dark Red [41].

5. CONCLUSION

Growth parameters viz., plant height, number of leaves per plant was studied at 25, 50, 75 and 100 days after transplanting and at harvesting stage. Different sources of nitrogen showed remarkable effect on plant height, number of leaves, dry matter percentage of bulb at all the stages. The highest plant height, number of leaves per plant and dry matter percentage were recorded in variety N-53 followed by Red Creole, Agri Found Dark Red. Variety Agri Found Light Red had lowest values for all these growth attributes. Result recorded highly significant effect on bolting percentage. The investigation revealed that there was significant effect of varieties on neck diameter, polar and bulb diameter, average weight and total yield of onion bulb. Different sources of nitrogen revealed significant influence on growth attributes at all the stages. The highest plant height, number of leaves per plant and dry matter percentage of bulb were found at (50% N by Urea + 50% N by PM) followed by (Full dose of N by PM) and the lowest growth attributes were recorded under (Full dose of N by Urea). Different sources of nitrogen had significant influence on neck diameter, polar and bulb diameter of onion bulb, average weight of bulb, total bulb yield and T.S.S. content in bulb and biological yield, harvest index, single center and marketable bulb yield. The result recorded highly significant effect on bolting percentage of variety. Interaction effect of varieties and different sources of nitrogen was non-significant on dry matter percentage of onion bulb. Plant height and number of leaves per plant showed non-significant influence of interaction effect of varieties and different sources of nitrogen. Interaction effect of varieties and different sources of nitrogen did not show any significant effect on neck thickness of bulb, polar as well as bulb diameter, bolting percentage and T.S.S. content of onion bulb. Hence, among the evaluated varieties of onion (Allium cepa. L) N-53variety was found best for response of different sources of nitrogen and the varietal response was more effective to (50% N by Urea + 50% N by PM) than other treatments.

 

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