Effect of row spacing and nitrogen levels on the growth and yield of tomato under walk-in polythene tunnel condition

To estimate the “Effect of row spacing and nitrogen levels on the growth and yield of tomato under walk-in polythene tunnel condition” an experiment was conducted at Sakhakot in collaboration with Agriculture Extension Department Dargai Malakand Agency, Khyber Pakhtunkhwa Pakistan in the year 2011-12 to find out optimum row spacing for obtaining maximum yield of tomato under walk-in polythene tunnel condition and optimize the nitrogen level for higher tomato production. Randomized Complete Block Design (RCBD) with split plot arrangement was used in the experiment, treatments were replicated three times. There were two factors i.e. different row spacing (60, 90, 120 cm) and nitrogen levels (0, 60, 100, 140 kg ha). Tomato cultivar “Sahil” was used for the experiment. More days to flowering (62.93), days to fruiting (85.44), plant height (264.73cm) and number of branches (58.89) was obtained when nitrogen was applied at 140 kg ha, while maximum number of fruits kg (12.89) was recorded in control plots. The maximum number of fruits plant (61.56), average fruit weight plant (3.19 kg), fruit weight picking plot (17.78 kg) and yield (28.33 tones ha) were obtained when nitrogen was applied at 100 kg ha .Similarly in case of row spacing, higher days to flowering (52.03), days to fruiting (81.08), plant height (261.23cm) and number of branches (58.10) was obtained when plants were row spaced at 120 cm. More number of fruits kg (11.58) was recorded from the plot, having 60 cm row spacing. The maximum number of fruits plant (58.03), average fruit weight per plant (2.92 kg), fruit weight picking plot (16.89 kg) and yield (27.96 tones ha) were produced by the plots having 90 cm row spacing. Thus, it is concluded that Sahil cultivar treated with 100 kg N ha row spaced at 90 cm must be used in Malakand for best tomato production.


Introduction
The botanical name of tomato is (Lycopersicon esculentum), belongs to the family Solanaceae.The Lycoperesicum genus an annual and short lived perennial herbaceous plant.Tomato is a warm season crop which is resistant to heat and drought and grown on many type of soil and climatic conditions [1].Tomato is native to Peru and Mexico and the indians grown it about 500 B.C. [2] Tomato is an important vegetable crop in Pakistan and grown an area of 28,880 ha which produced 3,13072 metric tons of tomato.Tomato is rich in vitamin A, B, C, minerals, iron, lime and phosphorous.This fruit vegetable is popular for its nutritional value and diversified use like salad, juice, sauce etc.It contains 1.98g protein, 320 IU vitamin-A, 1.8 mg iron and 31 mg vitamin-C in 100 g edible tomato [3].Tomato ranks second among vegetables next only to potato in area andproduction.It occupies a distinct place in the realm of vegetables because of its high nutritivevalue and large scale utilization.The arrays of processed products include juice, ketchup,sauce, paste, puree and whole canned fruits are the main constituents of 'Pizzas'.Tomato is being grown worldwide with USA, Italy, China, India, Spain, Brazil, Egypt, Mexico, Turkey and Iran as leading countries [4].Every year tomato is grown on an area of 24,144 hectares in Pakistan, with the production of 275241 tons.In Khyber Pakhtunkhwa it is grown on area of 4230 hectares and it's per annum production is 51,062 tons.In Peshawar, tomato is cultivated on 944 acres area which produces 2.978 tons of tomato.In the last 17 years its area has been increased up to 56% in Pakistan [4].Studies revealed that a vegetable lowers many chronicle diseases due to high level of phytochemicals.
Fraser&Gester [5]found increasing intake of tomatoes decreased cancer risk.Tomato has naturally occurring antioxidant such as 'Lycopene' a major carotenoid which plays an important role in scavenging free radicals and protect from heart diseases, arthritis and aging process [6][7][8] in the years (2000) and (1996) respectively, evaluated NP fertilizers rates highly influenced the fruit yield in tomato.Sharma et al. [9] also found that amount of NP fertilizers rates applied affect the average fruit weight of tomato.Thus, higher fruit yields of tomato can be obtained by applying optimum amount of NP fertilizers [10].Tomato crop requires balance fertilizer and water for high yields.Nitrogen is the most responsible element for limiting crop growth, especially on low organic matter and coarse-textured soil.The tomato yield is directly or indirectly affected by the fruit weight, the number of fruits per plant, weight of fruits per plant and vigor as well as the size of the fruits and these are the most important morphological and quantitative traits of the tomato fruit.The genetic factors that influence not only the mentioned traits but also other quantitative traits in tomato fruits which are also under the influence of environmental factors, crop density, growing practices, mineral nutrition, soil properties, and their interaction also [10 -13] Optimum plant spacing is very important for higher productivity of tomato.Plant spacing significantly affected fruit yield in both processing and fresh market tomatoes.Similarly, Aggrey et al [14] also stated that spacing influenced tomato yield parameters.A walk-in polythene tunnel has been defined as "a portable walk-in, greenhouse like structure without a permanent electrically powered heating or ventilation system, covered with one layer of plastic, and sited on field soil.Walk-in polythene tunnel is a permanent greenhouse like structure having the height of 7-9 feet.Walk-in tunnel cannot protect crops from temperature to the same degree as heat equipped green houses, however they are much less expensive to build and operate.Walk-in tunnels mostly used throughout the Asia, Southern Europe and Middle East for vegetable production [15].Several researchers have reported the use of row covers and plastic tunnels over the crop row for temperature enhancement, greater moisture retention, elimination of insects, and reduction in plant desiccation [16 &17].With the passage of time and development of new technologies enhanced fabric characteristics and designs, polypropylene and polyester fabrics used in agriculture flourished plant growth due to high moisture and temperature, exclusion of harmful insects feeding on the vegetable crop and reduction in water stress from wind.In Northern and Eastern United States use of high polythene tunnels (a moveable walk-in, structure like greenhouse with no electrically powered ventilation or heating, which is covered with 6-mil single layer polyethylene) has increased production time between 3 to 12 weeks of vegetables [15].Keeping in view the importance of tomato the research was conducting with the objective to investigate an optimum row spacing for obtaining maximum yield of tomato under walk-in polythene tunnel condition and to explore an optimum nitrogen level for higher tomato production.

Materials and methods
An experiment entitled "effect of row spacing and Nitrogen levels on the growth & yield of tomato under walk-in polythene tunnel condition" was conducted at Sakhakot in collaboration with Agriculture Extension Department Dargai Malakand Agency, Pakistan during 2011-12.RCBD (split plot arrangement) was used for the experiment.Row spacing and different levels of nitrogen were the two factors, Row spacing was assigned to main plots and sub plots were allotted to Nitrogen levels.There were three replications of total twelve treatments.

Soil preparation
Soil inside the tunnel was thoroughly ploughed and leveled.Soil was mixed up with well rotten FYM.Proper height of ridges was managed manually.According to the field layout the plots were provided with four different doses of nitrogen and three different row spacing.Before transplantation of seedling recommended dose of P and K was applied to soil.Source of nitrogen used in the experiment was Urea (containing 46% nitrogen).Whereas nitrogen was applied to the soil in split doses.First dose was supplied at transplantation time and other before flowering at ten days interval after transplantation.
Potassium sulphate (containing 50% of potash) was used as a source of potassium while single super phosphate (containing 18% of phosphorous) was used for phosphorus.Before the application of other fertilizer, at depth of 15 cm to 30 cm, the soil samples were randomly collected from the experimental field and analyzed and analysis is shown in Table1.The data was recorded for the following parameters during the experiment.Plant Height (cm),The data regarding plant height was measured in centimeter by common tape from ground to terminal end of main stem.Number of branches per plant.Stems that were originated from the main stem were counted from selected plants and their mean was calculated.Days to first flowering.Data for days to flowering was collected as number of days from transplantation till the appearance of first flower.Days to first fruiting.Data for days to fruiting was collected as number of days from transplantation till fruit setting.Fruits per plant.Data for fruits per plant were collected from five randomly selected plants in sub plots and then average them.Number of fruits kg -1 .Fruits kg -1 was calculated by weighing randomly selected one kg fruits in each treatment and then the number of fruits was counted.Weight picking -1 plot -1 .Weight picking -1 was determined with the help of the formula: Weight picking -1 plot -1 = Total fruit weight in each plot Total number of picking in each plot Average fruit weight (g).Data was recorded at plant maturity by weighing all the fruits present on a five randomly chosen plants in sub-plot and average was calculated.Yield (tones ha -1 ) Yield ha -1 was calculated using the following formula: Yield ha -1 (tones) = Yield plot -1 (tones) × 10000 m 2 Plot area (m 2 )

Statistical procedure
The data collected on different parameters was subjected to analysis of variance (ANOVA) technology to observe the difference, between different treatments as well as their interactions.In case where the difference was significant the mean was further assist for differences through least significant difference (LSD) test.

Number of branches Plant -1
The data regarding No of branches per plant is presented in Table-3.The statistical analysis of the data revealed that row spacing, nitrogen levels and their interaction significantly influenced number of branches (Table -3).Application of 140 kg N ha - 1 produced more number of branches (60.00), followed by 100 kg N ha -1 (55.86) and 60 kg N ha -1 (55.22) which were at par with each other, while control plants produced less number of branches (48.63).More branches (57.77) were produced by plot having 120 cm row spacing, which was at par with row spacing at 90 cm whereas, less number of branches were recorded (51.10) for 60 cm row spacing plot.Thus, high row spacing plots have high potential for more number of branches as compare to the other plots.Interaction between row spacing and nitrogen levels was also highly significant.More number of branches plant -1 (62.00) was observed in plants at 140 kg N ha -1 and row spaced at 120 cm while less number of branches plant -1 (37.89) was observed in plants at row spacing 60 cm in control plots.More number of branches were at 120 cm row spacing and higher nitrogen application might be due to the reason that there was less competition among plants for nutrients

Number of fruits Kg -1
The data regarding row spacing and nitrogen levels for number of fruits Kg 1 is given in Table -7.The statistical analysis of the data revealed that row spacing, nitrogen levels and their interaction significantly influenced number of fruits kg -1 .Maximum number of fruitskg -1 (11.58) was produced by plots having 60 cm row spacing whereas; minimum number of fruits kg -1 (9.86) was produced by plots having 90 cm row spacing which was statistically indifferent with 120 cm row spacing (10.22).Nitrogen control treatment gave highest number of fruits plant - 1 (12.89), which was statistically different from other treatments, followed by plants fertilized with 140 kg N ha -1 (10.33).The lowest fruits kg -1 (9.11) was produced by 100 kg N ha -1 .Maximum number of fruits kg - 1 (15.33) were recorded in plants untreated with nitrogen and at row spacing 60 cm while the less number of fruits kg -1 (8.67) were observed in plants fertilized with 100 kg N ha -1 at row spacing 90 cm.More number of fruits kg -1 recorded at minimum row spacing (60 cm) might be due to the minimum uptake of nutrients as there was more competition among plants and hence small size of tomato fruits were formed.Increasing nitrogen application rate increased fruit size (length, girth and weight) was recorded bySubramanianet al [32].Stunted growth and less number of fruits and size in tomato can cause by nitrogen deficiency [29].Less nitrogen concentration reduced plant growth by decreasing photosynthetic activity which ultimately decreased fruit size in tomato [26].Dod et al [33]investigated that 100-125 kg N ha -1 significantly increased fruit length in tomato.

Average fruit weight plant -1
The data regarding row spacing and nitrogen levels for average fruit weight plant -1 is given in Table -8.Data revealed that nitrogen levels and row spacing significantly influenced fruit weight plant -1 .Interaction was recorded nonsignificantly.Maximum fruit weight plant -1 (2.92 kg) was produced by plots having 90 cm row spacing closely followed by plants row spaced at 120 cm (2.70 kg) whereas; minimum fruit weight plant -1 (2.27 kg) was produced by plants row spaced at 60 cm.Application of 100 kg N ha -1 gave the highest fruit weight plant -1 (3.19), followed by plants treated with 140 and 60 kg N ha -1 (2.71 and 2.48 kg respectively).The lowest fruit weight plant -1 (2.13 kg) was produced by the control treatment.
More number of fruit weight plant -1 recorded at 90 cm row spacing might be due to the maximum uptake of nutrients as there was less competition among plants, these maximum nutrients positively influenced vegetative growth and high photosynthetic activity production ultimately resulting increased store food.These stored foods in turn increase fruit weight of the plant.Average fruit weight plant -1 was highly influenced by nitrogen levels and row spacing.Application of higher NP fertilizers rates gave greater average tomato fruit weight reported by Sharma et

Fruit weight picking -1 plot -1
The data regarding row spacing and nitrogen levels for fruit weight picking -1 plant -1 is given in Table -9.The statistical analysis of the data revealed that row spacing and nitrogen levels significantly influenced fruit weight picking -1 plant -1 but the interaction was non-significant.Maximum fruit weight picking -1 plot -1 (16.89) was produced by plots having 90 cm row spacing closely followed by row spacing at 120 cm (15.17) whereas; minimum fruit weight picking -1 plot -1 (14.40) was produced by plots having 60 cm row spacing.Maximum fruit weight picking -1 plot -1 (17.78) was obtained by 100 kg N ha -1 .Minimum fruit weight picking -1 plot -1 (13.50) was produced by the control treatment.Maximum fruit weight picking -1 plot -1 recorded at 90 cm row spacing might be due to the maximum uptake of nutrients as there was less competition among plants, these maximum nutrients positively influenced vegetative growth and photosynthates production ultimately resulting increased store food.These stored foods in turn increase fruit weight of the plant.Fruit weight per picking plot -1 was highly influenced by nitrogen levels and row spacing.Balemi [35]reported that, the highest number of fruits picking -1 plot -1 was influenced by high nitrogen and phosphorus rate.

Fruit yield (ton ha -1 )
The data regarding row spacing and nitrogen levels for fruit yield is given in Table-10.The nitrogen and row spacing significantly influenced fruit yield.Interaction was recorded non-significantly.Maximum fruit yield ha -1 (27.96 tons ha -1 ) was produced by the plots having 90 cm row spacing whereas; minimum yield ha -1 (25.13 tons) was produced by the plots having 120 cm row spacing.Highest yield (28.33 tons ha -1 ) was given by100 kg N ha -1 while, the lowest (23.17 tons ha -1 ) was recorded in control plot.Maximum fruit yield recorded at 90 cm row spacing might be due to the maximum uptake of nutrients (nitrogen) as there was less competition among plants, these maximum nutrients (nitrogen) positively influenced vegetative growth and photosynthates production ultimately resulting increased store food.These stored foods in turn increase fruit yield.In addition, the application of high level of nitrogen enhance plant vigor by increasing photosynthetic activity in plant which ultimately results in healthy fruit formation and maximize fruit yield.Row spacing disturbs production and yield of the tomato up to the greater extent.Rashid [37] concluded that row spacing of the plant greatly affected the quality and production of the tomato.Tomato marketable yield was increased by the application of 120 kg N ha -1 [38].Application of 120 to 125 kg N ha -1 resulted maximum tomato yield [30]. Pandey et al. [7]found that application of 80 kg N ha -1 increased fruit yield in tomato.Nitrogen is the most responsible component for the overall yield in tomato were reported by Badr& El-Yazied [39].Table 9. Impact of row spacing and nitrogen (N) on fruit weight picking -1 plot -1 of tomato

Conclusion
During the study it was observed that plant density and nitrogen levels had significant effect on growth and yield of tomato crop under walk-in polythene tunnel condition.In case of planting density, the 90 cm row spacing showed best results for most of the studied parameters including tomato yield followed by 120 cm row spacing.While 100kg N ha -1 gave best results for most of the studied parameters including tomato yield.Best results were observed regarding growth and yield parameters of tomato cv Sahil with the application of 100 kg N ha -1 and 90 cm row spacing under walk-in polythene tunnel condition and hence recommended for better growth and high yield of tomato in the off season (winter season) at Malakand valley.Authors' contributions Conceived and designed the experiments: A Rab, Performed the experiments: A Rashid, H Mohammad, J Ali, M Shahab & A Jamal, Analyzed the data: A Rashid & A Rehman, Contributed reagents /materials/ analysis tools: J Ali & M Ali, Wrote the paper: A Rashid.

Table 2 . Impact of row spacing and nitrogen (N) on tomato plant height (cm)
The data regarding plant height is presented in Table-2.The statistical analysis clearly showed that plant height was significantly influenced by nitrogen levels and the interaction between row spacing and nitrogen levels, while row spacing had no significant effect on plant height of tomato.The tallest (261.23 cm) plants were observed in the plots having 120 cm row spacing, while the shortest plants (253.28 cm) were observed by the plots having 90 cm row spacing.The

Table 3 .Impact of row spacing and nitrogen (N) on number of branches of tomato N (kg ha -1 )
[21]rogen), light, water and space which enhanced vegetative growth of the plants and hence showed good performance regarding more number of branches[21].Prabhakar &  Naik et al. [22]also recorded these findings" which observed more number of branches plant -1 with the increasing nitrogen levels.

Table 8 . Impact of row spacing and nitrogen (N) on average fruit weight plant -1 of tomato
Means followed by the same letter(s) do not differ significantly from one another at 5% probability level, using LSD test.

Table 10 . Impact of row spacing and nitrogen (N) on fruit yield (tons ha -1 ) of tomato N (kg ha -1 )
Means followed by the same letter(s) do not differ significantly from one another at 5% probability level, using LSD test.