Adjustment of Phosphorus Concentration to Increase Growth and Yield of Cherry Tomato Using Hydroponic Drip System

The phosphorus element plays an essential role in plant growth both at the vegetative and generative phases, so its concentration modification in the nutrient solution is necessary to stimulate vegetative growth and crop yield. The research aimed to know the influence of different phosphorus concentrations on growth and yield of cherry tomato using a hydroponic drip irrigation system, conducted from February to June 2017 at Green House Research Station of Universitas Padjajaran Jatinangor using Completely Randomized Design with five treatments and five replications. The treatments were: phosphorous concentration of 100 ppm (P/N ratio 0.4), 125 ppm (P/N ratio 0.5), 150 ppm (P/N ratio 0.6), 175 ppm (P/N ratio 0.7), and 200 ppm (P/N ratio 0.8). The results showed that the increasing concentration of phosphorus improved crops height at the end of the vegetative phase, increased the number of flowers from the beginning to the end of the generative period, was able to prevent the flower fall, enhanced harvest index and weight of tomato fruit significantly at harvest time. Application of 200 ppm phosphorus concentration can increase growth and yield of cherry tomato.


INTRODUCTION
Cherry tomato is a horticultural product which is popular among middle up communities in the major cities of Indonesia and only retrieved at the supermarket.The people like this fruit vegetable because of its performance; the red colour and small size, plus the taste is sweeter in comparison with the big tomato.To meet quantity and quality aspects, this crop cultivation can be done in green house with hydroponic systems (Wu & Kubota, 2008).Hydroponic system in a controlled environment makes production of cherry tomato fruit to be maximum, because management of water and nutrient elements correspond with the needs of the plants (Hidayat et al., 2018).A nutrient solution is delivered at the base of the plant with sufficient volume.
Temperature, EC, and nutrients influence the success of cherry tomato plant growth in hydroponic system (Herrero et al., 2014).Phosphorus is the macro nutrient that plays important role in plant metabolism.Phosphorus is part of the essential process of photosynthesis and carbohydrate metabolism functioning as regulator of photosynthate partition between the source and the reproductive organs (Reshma & Sarath, 2017).One of the difficulties in hydroponic cultivation is not yet known concentrations of optimal nutrient elements for plant growth.At too low dosage, it results non-significant effect, whereas at too high dosage it becomes waste and the plant undergoes plasmolysis, the cell fluid is discharged because it is attracted by more concentrated nutrient solution (Wortman, 2015).
The concentration of phosphorus will determine the number of element in a nutrient solution.Research of Wijayani & Widodo (2005), which compared the growth of tomato plants by using two different types of nutrients P/N 0.4 (P=80 ppm; N=180 ppm) and P/N 0.97 (P=321 ppm; N=330 ppm), obtained that the different nutrients ratio P/N influence the tomato fruit yield.Plants with treatment formulations the ratio P/N 0.4 generated more numbers of tomato that is directly proportional to the tomato fruit yield.According to Mason (2014) recommendation P concentration for tomato nutrient between 20-200 ppm; N-total concentration 50-300 ppm and P/N ratio 0.4-0.67.Optimum hydroponic nutrient for tropical and sub tropical differs from one place to another (Resh, 2013).Optimum concentration of P requirement for tomato is not certainly known.Based on the description above concentration of element P offered up from 100 ppm to 200 ppm with the ratio P/N 0.4-0.8.Expected that with increased of element P, the plant growth, the number of flowers, and fruit yield of tomato can be improved.
The aim of the research was to find out the effect of different phosphorus concentrations on growth and yield of cherry tomato cultivar Tropical Ruby using hydroponic drip irrigation system.
Cherry tomato seedlings 14 days were planted on polybag containing a mixture of charcoal and husk (1:1 v/v).Continue and periodic fertigation flew through pipe and emitter to deliver water and fertilizer to the root.Water applied was 25 mm.dec -1 or 900 mL.crop -1 .day - at 0-70 Days After Transplanting (DAT), 40 mm.dec -1 or 1.440 mL.crop -1 .day - at 71 DAT harvest with watering interval was three times a day at 7 am, 11 am and 2 pm.Fertilization used fertilizer A and fertilizer B (Phosporous element concentration adjusment according to the treatment by adjusting KH 2 PO 4 ) which had been dissolved in 5 l of water separately and blended at the time the fertilizer would be given in accordance with a concentration of treatments.EC values were 1.2 mS, at seedling period, 2.0 mS.cm -1 at vegetative phase or 14-50 days after planting (DAT) with pH 6.3 -6.5, and 3.5 mS.cm -1 with 6.0 -6.3 pH at generative phase or when crops started to flowering at 50 DAT (Resh, 2013).Average air temperature was 32 o C, maximum temperature was 38 o C and minimum temperature was 26 o C and RH was 70-90%.
The parameters observed were plant height (cm) measured weekly from 1-8 Weeks After Transplanting (WAT), the number of flower at 10, 11, 12, and 13 WAT, flower fall at 13 WAT, and weight (g) of tomato was calculated at the time of harvest.To analyse the data, F Test at 5% level was used and continued with Duncan Multi Range Test at 5% level.

Climatic Condition at Experimental Sites
The result of observation climatic condition showed that daily average temperature was 31.28 0 C and daily average humidity was 82,69% (Figure 1).According to Aprile & Lorandi (2012)

Plant Height
Application of different phosphorus concentrations gave no significant effect on plant height at initial vegetative phase (1, 2, 3, 4 week after transplanting (WAT) and showed significant effect on plant height at 5, 6, 7 and 8 WAT or at the end of vegetative phase (Table_1).
The data from Table 1 showed that an increasing of phosphorus concentration had no effect on plant height at initial stage of vegetative phase due to the plants were still in adaptation to environment and could not absorb the nutrient maximally (Hidayat et al., 2018).The plant began to respond on different phosphorus concentration starting from 5 WAT.Increasing of phosphorus concentration enhanced plant height until the end of vegetative phase.Application of phosphorus 175 ppm and 200 ppm showed the highest plant height, i.e. 166.6 cm and 164.6 cm where the value were in the range of tomato variety Cherry Ruby height potency i.e. 150-300 cm.The difference of height plant due to application of difference phosphorus concentration is closely related with the role of P in the formation of new cells at the meristematic tissue.Grennan (2008) found that phosphorus required by plants for the formation of cellular compounds so that the treatment with the highest P concentration showed better results in plant height.In accordance with research Aldana (2005) an increasing of phosphorus concentration in chilli plants given in hydroponics significantly increased plant height and stem diameter because it related to the function of P which is fundamental in the process of photosynthate distribution to plant vegetative organs.

Number of Flowers
Application of different phosphorus concentrations significantly increased the number of flowers since the beginning of generative phase.The more phosphorus concentrations, the more the number of flowers_(Table_2).The results showed that increasing the concentration of P until 175 ppm or 200 ppm starting at 12 and 13 WAT have a number of flowers was formed.This data in line with Nowaki et al. (2017) who found that the optimum P can increase some of the reproductive properties of the plants in the form of total mass of flowers, fruit production, and number of seed production of pollen per plant.Phosphorus plays a role in increasing the photosynthetic reaction in plants (Gad & Kandil, 2010).
In conditions of optimum photosynthetic, photosynthate resulted by plants is higher and correlates positively with cell division at the plant as a whole and can therefore stimulate flowering plants and the flowers produced are more in line with the higher P concentrations (Basirat et al., 2011).Optimum P concentration also affect healthy root growth which helps water and nutrient uptake by the plant (Fandi et al., 2010).

Flower Fall
Application of different phosphorus concentrations succeeded to prevent flower fall at 13 WAT.Application of higher phosphorus concentration starting of 175 ppm prevented 86.50 % flower fall comparing with a phosphorus concentration of 100 ppm prevented 60.99 % (Table 3).
Based on Table 3, the highest flower fall occurred in tomato plants treated with low phosphorus concentration of 100 and 125 ppm and decreased in line with increasing of phosphorus concentration.Flower fall correlates with photosynthate availability.Flower fall especially affect by water stress.According to Fandi et al. (2010) high concentration of phosphorus has possitive role in affect root growth.Healthy root in tomato has effect to optimum water uptake by plant.Therefore, optimum water uptake can reduce flower fall of tomato.(Gad & Kandil, 2010) in energy transfer and thus influences the photosynthate.

Harvest Index
Application of different phosphorus concentrations enhanced Harvest Index.Application of phosphorus starting from 175 ppm significantly increased Harvest Index and the concentration of phosphorus 200 ppm showed the highest Harvest Index (Table 4).According to Nowaki et al. (2017) that the lower the concentration of P applied on tomato plants lead to a decrease on plants dry weight in general so that the lower plants dry weight produced mainly fruit, resulting lower harvest index values.
Decreasing of P element on tomato cultivation in hydroponics leads to decrease activity of plant growth and development as well as a reduction in the production of biomass by the roots and shoot plants (Chang & Lee, 2015).

Weight of Tomato Fruit
Application of different phosphorus concentrations influenced weight of tomato fruit per plant at the harvest time.The highest weight of tomato fruit per plant was obtained by application of phosphorus 200 ppm (Table 5).(2016) the influence of fertilizer P in the growth and yield of tomato increased total weight per plant on higher P application.The P concentration of 200 ppm prevented flower fall lower percentage and increased harvest index, so that fruit set on 200 ppm of P concentration has positive role on fresh weight of tomato fruit.Youssef & Eissa (2017) found the same thing, increase the number of P in a nutrient solution which is applied on tomato plants in a hydroponic produced high fresh and dry weight of tomato fruit.This data in line with all data measured such as plant hegiht, number of the flowers, flower fall, and harvest index that showed increasing of P concentration increased all parameters and finally produced highest weight of tomato fruit per plant.A., & Eissa, M. A. (2017).

CONCLUSION
Comparison between organic and inorganic nutrition for tomato.Journal of Plant Nutrition, 40(13), 1900Nutrition, 40(13), -1907. .https://doi.org/10.1080/01904167.2016.1270309 the tropical regions have relatively constant daily temperatures throughout the year.Temperature and humidity fluctuations are determined by solar radiation and rainfall.The optimum temperatures for tomato according to Herrero et al. (2014) is 24-26 o C at the daytime and 18-20 o C at night.

Figure
Figure 1.Average Weekly Temperature and Average Weekly Humidity at Greenhouse

Table 1 .
Effect of Different Phosphorus Concentrations on Plant Height Remarks : Numbers followed by same letter are not significantly different based on Duncan's Multiple Range Test at 5% level

Table 2 .
Effect of Different Phosphorus Concentrations on Number of Flowers

Table 3
Effect of Different Phosphorus Concentrations on Flower Fall

Table 4
Effect of Different Phosphorus Concentrations on Harvest Index

Table 5 .
Effect of Different Phosphorus Concentrations on Weight of Tomato Fruit Remarks : Numbers followed by same letter are not significantly different based on Duncan's Multiple Range Test at 5% level In accordance with research of Cole et al.