Response of Various Nitrogen Levels on the Growth and Yield Performance of Tomato ( Lycopersicon Esculentum Mill . )

Nitrogen (N) fertilization at optimum quantity to cultivated plants is essential for sustainable crop productivity. The experiment was conducted to evaluate the response of nitrogen fertilizers on the growth and yield traits of tomato during 2016, at the experimental field of Orchard, Department of Horticulture, Sindh Agriculture University Tandojam. Six nitrogen treatment doses were tested (T1 =control (untreated), T2 = 30 N kg ha, T3 = 60 N kg ha, T4 = 90 N kg ha, T5 = 120 N kg ha and T6 = 150 N kg ha.). The data were recorded on the number of branches plant, days to flowering, days to fruiting, number of fruits plant, weight of single fruit (g), yield plot and yield ha (tons). The results demonstrated that N fertilization showed significant influence on both vegetative and reproductive traits of tomato. On the contrary, plants which were not fertilized with N displayed minimum values for all investigated traits. The highest N level (150 kg ha) showed maximum number of branches (5.51) plant, minimum day to flowering (42.43) less days to fruiting (46.00), more fruits plant (31.00) maximum weight of single fruit (46.50 g) and highest fruit yield plot (21.01 kg) and per hectare (14008 tons), respectively. It was concluded that the crop growth and productivity was significantly influenced by various levels of nitrogen. However, 150 N kg ha as compared to 120 N and other concentrations considerably displayed better performance in terms of vegetative and reproductive traits of tomato. Hence for optimum growth and economically higher yield, the tomato crop may be fertilized with 150 N kg ha.

, T5 = 120 N kg ha -1 and T6 = 150 N kg ha -1 .).The data were recorded on the number of branches plant -1 , days to flowering, days to fruiting, number of fruits plant -1 , weight of single fruit (g), yield plot -1 and yield ha -1 (tons).The results demonstrated that N fertilization showed significant influence on both vegetative and reproductive traits of tomato.On the contrary, plants which were not fertilized with N displayed minimum values for all investigated traits.The highest N level (150 kg ha -1 ) showed maximum number of branches (5.51) plant -1 , minimum day to flowering (42.43) less days to fruiting (46.00), more fruits plant -1 (31.00) maximum weight of single fruit (46.50 g) and highest fruit yield plot -1 (21.01 kg) and per hectare (14008 tons), respectively.It was concluded that the crop growth and productivity was significantly influenced by various levels of nitrogen.However, 150 N kg ha -1 as compared to 120 N and other concentrations considerably displayed better performance in terms of vegetative and reproductive traits of tomato.Hence for optimum growth and economically higher yield, the tomato crop may be fertilized with 150 N kg ha -1 .

INTRODUCTION
Tomato (Lycopersicon esculentum Mill.) is a popular vegetable and most important ingredient in enhancing the taste and flavor of other vegetables [1].It is referred as "protective food" because of its special nutritive value and widespread production [2].The tomato in ripe state provides potential minerals and vitamins, particularly the carotenoids and vitamin C and they are worldwide consumed as raw and in various processed forms as well [3].Increasing the productivity of horticultural crops with good yield and quality is an important goal of the growers for market and export.The studies carried out worldwide showed that lycopene in fruits helps prevention cancer, but nothing has been conclusively achieved from their research on such health aspects [4].
For successful crop production, N is considered as key element.Due to its immediate availability to crop plants, it guarantees the higher productivity [5].It enhances both vegetative and reproductive growth of crop plants [6].It helps in synthesis of chlorophy which is considered very essential in photosynthesis process.
*Address correspondence to this author at the Department of Plant Breeding and Genetics, Sindh Agriculture University Tandojam, 70060, Pakistan; E-mail: ali.breeder110@gmail.comIt is an important constituent of many essential organic compounds, including nucleic acids and protein.
Nitrogen also affects the uptake and utilization efficiency of phosphorous and potassium and other plant nutrient elements [7].Proper and routinely fertilization with nitrogen gave successful and economical crop production.However, overuse of N in vegetable cultivation leads to excessive accumulation of nitrates beyond its safe limits in various parts of vegetables which caused health risks to humans [8].
To obtain the better yield of tomato, large quantities of nitrogen is generally applied worldwide.Tomato has great demand for N fertilization.Nitrogen is mostly applied to tomato in three splits doses.In the initial stage of tomato, it enhances the vegetative growth of plants.However at later stages it significantly and positively affects the reproductive growth of plants [9].
Although tomato is an important crop of Sindh Province of Pakistan, However, very limited information is available about its optimum and specific N requirement.
Keeping in view the importance of nitrogen for plant growth and development, the current study was designed to evaluate the impact of various nitrogen levels on the growth and yield performance of tomato.

MATERIALS AND METHODS
The present study was carried out to evaluate the response of nitrogen fertilizer on the growth and yield performance of tomato during the year 2016 at the experimental field of Orchard, Department of Horticulture, Sindh Agriculture University Tandojam.The field layout was followed the Randomized Complete Block Design with three replicates.The plot size kept was 5m x 3m (15 m .The Urea which is commonly applied nitrogenous fertilizer to crops was source of N which was applied in three equal split doses (at the time of sowing and at the stage of flowering and fruiting development of crop).The uniform dose of phosphorous and potassium were also applied in the form of single superphosphate and sulphate of potash which were applied at the time of sowing of the crop.The crop was irrigated according to its requirement and all the cultural practices were performed uniformly in all the plots.The data were recorded on Number of branches plant ).

Statistical Analysis
Collected data were subjected for statistical analysis using Statistix version 8. 1 (Statistix, 2006).In order to know the superiority of treatments, the least significant difference (LSD) test at (0.05) probability level was performed.

Number of Branches Plant -1
The results demonstrated that the number of days to flowering of tomato were significantly influenced by different doses of nitrogen fertilizers (P<0.05).The results indicated that nitrogen level of 150 N kg ha -1 produced highest number of branches (5.51) plant -1 on average; followed by the tomato crop supplied with nitrogen fertilizer @120 N kg ha -1 , 90 N kg ha -1 and 60 N kg ha -1 with 5.43, 5.07 and 4.92 average number of branches plant -1 , respectively (Table 1).The crop supplied with nitrogen fertilizer @30 N kg ha -1 produced lower branches number plant -1 (4.52); while lowest branches plant -1 (3.83) was recorded in control (untreated), where no nitrogen fertilizer was applied.In tomato the branching capacity is a trait of primary importance, because more the branches on a plant, greater will be the number of fruits per plant.The branching in tomato may vary variety to variety, but the branching is mainly guided by the environmental factors and quantities of nutrients being supplied to the crop.In present study, lowest branches plant -1 indicated the deficiency of N in the soil.The branches plant -1 significantly increased when synthetic N was supplied to the plants through soil at higher rates.The results are in agreement with those of [1][2][3], who were of the opinion that application of N is essential for proper plant growth of tomato.

Days to Flowering
The results demonstrated that the various doses of N showed significant effect (P<0.05) on number of days to flowering of tomato.The crop fertilized with control (untreated) took minimum days to flowering (42.43) on average; followed by the tomato crop supplied with nitrogen fertilizer @30 N kg ha ) took more days (49.95) to flowering This suggested that the experimental soil was inadequate of nitrogen and responded appreciably to avail proper physiological period for flowering when synthetic nitrogen was supplied to the plants through soil at higher rates.On the other hand, in case of inadequate availability of nitrogen from the soil to the plant resulted in reaching early to the flowering stage without availing the growth period required by the crop naturally.Similar results have also been reported by [10], who reported that higher fertilizer levels delayed the flowering tomato, while [11,12] who reported that increase in the nitrogen and potash proportionately increased the days to flowering.

Days to Fruiting
It is evident from the results presented in Table 3 that tomato crop with nitrogen levels of control (untreated) took more days to fruiting (49.95.00) on average; followed by the tomato crop supplied with nitrogen fertilizer @120 N kg ha -1 , 90 N kg ha -1 and 60 N kg ha -1 taking 53.00, 53.00 and 51.66 days to fruiting, respectively.The number of days to fruiting that the crop supplied with higher nitrogen levels started fruit development later than that given lower nitrogen levels; and with each shortening of nitrogen fertilizer over 150 N kg ha -1 , the crop experienced an earliness in fruit development.This suggested that N was deficit in experimental soil.In tomato the time taken by the plant to fruiting is a physiological parameter that may be influenced by the genetic makeup of parental material of certain varieties; but the influence of soil fertility status and soil amendment by synthetic fertilizers may influence this trait more dominantly.The studies carried out by [9,12,13] also showed similarity with the findings of the present study and reported that higher rates of nitrogen and potash fertilizers delayed the fruiting development in tomatoes.

Number of Fruits Plant -1
The number of fruits plant -1 of tomato was significantly (P<0.05)affected by different nitrogen fertilizer levels.It is obvious from the results that tomato crop supplied with nitrogen fertilizer @ 150 N kg ha -1 and 120 kg ha 1 produced more number of fruits plant -1 (31.00) on average; followed by the crop supplied with nitrogen fertilizers @120 N kg ha -1 , 90 N kg ha -1 and 60 N kg ha -1 producing 31.00,26.66 and 23.00 fruits plant -1 , respectively (Table 4).The crop supplied with nitrogen fertilizers @30 N kg ha -1 produced decreased number of fruits plant -1 (19.33); while the lowest number of fruits plant -1 (13.66) was  recorded in control (untreated), where no nitrogen fertilizer were given to experimental field.The results further showed that the crop supplied with higher nitrogen levels produced more fruits on average plant -1 than that of given lower nitrogen levels; and with each decrease in nitrogen fertilizers rate over 150 N kg ha -1 , the crop experienced reduction in its fruiting capacity.This showed that the experimental soil was inadequate of nitrogen and responded positively to N at higher levels.Moreover, due to soil deficiency of nitrogen lower number of fruits per plant was developed.The results regarding the fruits per plant achieved in the present study are in agreement with those of [14][15][16], who reported that higher fruits number was associated with the higher rates of nitrogen.

Weight of Single Fruit (g)
The results related to weight of single fruit (g) of tomato was significantly (P<0.05)influenced by different nitrogen fertilizer levels (Table 5).The tomato crop supplied with highest level of nitrogen fertilizer (@150 N kg ha -1 resulted in more weight of single fruit on average (46.50 g); followed by the crop supplied with nitrogen fertilizers @120 N kg ha -1 , 90 N kg ha -1 and 60 N kg ha -1 producing 44.57,42.00 and 38.76 g weight of single fruits, respectively.The crop given nitrogen fertilizer @30 N kg ha -1 showed decline in weight of single fruit (35.55 g); while the lowest weight of single fruit (21.22 g) was noted in control (untreated), where no nitrogen fertilizer was given to experimental tomato crop.The weight of single fruit is one of the most influencing traits that contribute to final yield; and this trait in tomato is mainly guided by the genetic makeup of a variety.However, the effect of nutrients compulsorily required for plant growth and fruit development is more dominant.It can be observed from the current study that the crop supplied with higher nitrogen levels produced heavier fruits than that of supplied with lower nitrogen levels; and with each decrease in nitrogen fertilizers rate than 150 N kg ha -1 , the fruits were decreased quantitatively.These results are in accordance with of [17][18][19], who were of the experience that increase in the fertility levels produced heavier fruits.

)
The fruit yield (tons ha -1 ) is calculated on the basis of fruit yield per plot.The results indicated that the fruit yield ha -1 was significantly influenced by varying levels of nitrogen fertilizers (P<0.05).The crop supplied with highest level of nitrogen fertilizer (150 N kg ha -1 ) produced highest fruit yield ha -1 (14008 tons); followed by the crop supplied with nitrogen fertilizer @120 N kg ha , 90 N kg ha -1 and 60 N kg ha -1 producing 13518, 11018 and 9048 tons fruit yield ha -1 , respectively (Table 7).The crop given nitrogen fertilizer @30 N kg ha -1 produced lower fruit yield ha -1 (7125 tons); while the lowest fruit yield ha -1 (3237 tons) was recorded in control (untreated), where no nitrogen fertilizer was given to experimental field (Table 7).The fruit yield is a dependent character that is influenced by plant height, branches per plant, number of fruits per plant and weight of single fruit.The yield is mainly guided by status of the soil for essentially required nutrients; but the genetic makeup of the varieties can also modify this trait.However, the effect of nutrients on fruit yield is more dominant.In the current study, the higher fruit yield per hectare (ha-1 ) in tomato fertilized with higher nitrogen level was mainly associated with more branches per plant, more fruits per plant, higher single fruit weight than that of supplied with lower level.These results are in accordance with those of [20][21][22][23] who were of the opinion that increase in the fertility levels produced heavier fruit yield tons ha -1 .

CONCLUSION
It was concluded that the crop growth and productivity was significantly influenced by various levels of nitrogen.However, 150 N kg ha -1 and 120 kg ha 1 considerably displayed better performance in terms of vegetative and reproductive traits of tomato.Hence for optimum growth and economically higher yield, the tomato crop may be fertilized with 150 N kg ha -1 .