1. Introduction
Plants are generally seen growing either in terrestrial or aquatic ecosystems depending on their habits. Soil and water function as a natural media for growing plants in terrestrial and aquatic ecosystems, respectively. Soil properties such as nutrient levels, salinity, acidity, microbial load, and particle size differ from one area to another. These soil properties usually to a great extent determine the vigour and nutritional value of cultivated crops. John et al. [1] documented that sufficient application of nitrogen to plants is linked with increased photosynthetic activity, strong asexual growth, and dark green pigmentation of the leaves. Also, according to Pandey and Sinha [2], nitrogen plays a significant part in processes such as nucleic acid activities, chlorophyll, and protein syntheses. Phosphorus is vital for photosynthesis and growth while potassium supports enzyme activities [3]. Potassium does not form any organic compounds in the plant; however, its presence is needed for plant growth due to its function as an enzyme activator that promotes metabolism [4]. Poor soil fertility has steered the introduction of inorganic fertilizer to augment the soil fertility status and its usage has affected adversely on the soil and consequently the plant growth due to an increase in soil acidity, nutrient discharge, decomposition of the soil’s organic material, and physical environments [5].
Furthermore, the accessibility of land for the cultivation of crops has decreased greatly with time due to anthropogenic activities on the terrestrial ecosystem geared towards enhancement and improvement of the human race. This condition is evident in most places like metropolitan areas, where the soil is not accessible for farming crops at all while some areas have a scarcity of fertile soil as a result of unfavourable geographical or topographical conditions [6]. Sardare and Admane [7] reported that as a result of fast development and industrialization, arable lands under cultivation will further decrease with time.
Unfortunately, Farmers are challenged with a shortage of fertile arable land for cultivation coupled with bush fallowing which limits their acquisition of land for cultivation. Irrigation farming for active and maintainable crop production in the Niger Delta is rarely practiced. According to Fubara-Manuel et al. [8], Niger Delta is categorized by separate rainy and dry periods in a year, and agriculturalists grow crops at a subsistence level only during the rainy period. However, Fubara-Manuel [9] earlier noted that even within the rainy period, particularly in May and June, crops may yet be affected by water stress as a result of inadequate soil water available at the root zone. This condition is also worsened by oil pollution which has become a regular occurrence in some areas of the Niger Delta. A scenario that demands an alternative approach to maintaining the food chain. One of the alternatives to growing food without soil is called hydroponics. It has a positive connotation among consumers and producers due to the purported environmental benefits it can offer [10]. The frequent use of this hydroponic technology will help to determine which crop is suitable to be grown in hydroponic systems [11]. Inadequate access to food, especially fresh food and vegetables, is a public health concern because the intake of fruits and vegetables is linked with reduced the danger of certain protracted illnesses [12] [13]. Hence, making vegetables available should be a priority to any government or nation which serves as source of nutrients to human beings. This study is aimed at using NPK 20-10-10 fertilizer in the formulation of locally hydroponic nutrient solutions for growing T. occidentalis.
2 Materials and Methods
Source of materials: The seeds of fluted pumpkin used were sourced from Choba Market and the River-sand was obtained from Choba-River Port Harcourt (4˚54'0"N 6˚54'0"E) while the NPK 20:10:10 fertilizer used was produced by Unique Fertilizer Company Nigeria and obtained from Agricultural Development Programme, Rumuodumaya Port Harcourt.
Formulation of the nutrient solution: The method of Kratky [14] was used with modification in nutrient formulation and container used. NPK 20:10:10 granular fertilizers were weighed (25 g, 50 g, 75 g, 100 g, 125 g, and 150 g, respectively) and transferred into black plastic bowls with the dimensions: 29 cm width, 41 cm length, and 23 cm depth. The same was dissolved with 20 litres of tap water in the plastic bowls leaving space for aeration with the addition of 20 ml micronutrients stock solution (0.6 g H3BO3; 0.4 g MnCl2∙4H2O; 0.05 g ZnSO4; 0.5 g CuSO4∙5H2O; 0.02 g Na2MoO4∙2H2O) and Epsom salt (9.8 g MgSO4). The Control medium (water) was set up without the addition of Urea, micronutrients, and Epsom salt. These formulations were replicated four times. The growth media were M25NPK, M50NPK, M75NPK, M100NPK, M125NPK, M150NPK, and Control (0 g) depending on the amount of NPK 20:10:10 dissolved in water.
Study site and weather condition: The study was conducted in a screen house inside the University of Port Harcourt (Lat. N4˚54'15", Long. E6˚54'35"). The site was free from direct rainfall and was open to sunlight any time of the day. The screen house had a transparent cover that permits light penetration and hinders direct rainfall. During the period of the experiment, the weather condition of the University was relatively wet with the daytime temperature that ranges from 24˚C in the early morning to 32˚C in the middle part of the day.
Planting of T. occidentalis: The seeds of T. occidentalis were planted in nursery bags containing River-sand as a medium for germination to take place. After germination, the two weeks old seedlings (17 - 20 cm) from the River-sand were transferred into the non-circulating hydroponic systems containing different formulations of nutrient solution. The components of the nutrient solutions were sourced locally.
Growth indices measurement: The vine length, petiole length and internode were measured using meter rule while the number of leaves was by direct count. The leaf area was determined following the method of Akoroda [15]. The vine girth was determined with the aid of electronic digital caliper (Carbon Fiber Composites Digital Caliper).
Pigment content: The chlorophyll content was obtained according to the method of Poora [16] while the carotenoid content was determined following the method of Sumanta et al. [17].
Statistical analysis: The data obtained for the morphological characters and pigment contents of fluted pumpkin were subjected to statistical analysis. Statistical Analysis System (SAS) version 9.0 was used to carry out the two-way analysis of variance (ANOVA) of the data to ascertain significant difference at P =0.05 between the treatment means and within each treatment means. Duncan Multiple Range Test (DMRT) was used for mean separation where significant different (P ≤ 0.05) existed.
3. Results
Vine main length of T. occidentalis grown in different growth media: The results of the investigation of different NPK growth media on the vine main length of T. occidentalis are presented in Table 1. There was increase in vine main length (VML) from week 3 - 5 across growth media. The VML value was higher in M50NPK medium compared to other media for the week 3 - 4 and was also significantly different (P =0.05) from other media except the Control and M25NPK medium. After the fourth week, there was exponential increase in VML value for Control and M25NPK media, respectively. The percentage increase in VML values were 99.27%, 54.45%, 0.48%, 3.40%, 12.75%, 0.91% and 1.86% for Control, M25NPK, M50NPK, M75NPK, M100NPK, M125NPK and M150NPK media, respectively. At week 3, the Control medium (57.05 ± 18.018 cm) had the highest VML value, followed by M25NPK medium (45.33 ± 16.224 cm) in that order and this difference in VML was significant. It was also evident that as the NPK concentration in the medium increases the VML value decreases. The lowest VML value was obtained at M150NPK.
Stem girth of T. occidentalis grown in different growth media: The stem girth (mm) of T. occidentalis grown in varying concentration of NPK solutions
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Table 1. Vine main length (cm) of T. occidentalis in different NPK growth media.
Mean ± Standard deviation; Means with the same letter in a column are not significantly different; WAP = weeks after planting.
is shown in Table 2. The rate at which the stem girths increased was minimal across and within growth media from weeks 3 - 5. The ranges within media were: Control (4.55 - 5.35 mm), M25NPK (4.87 - 5.00 mm), M50NPK (4.38 - 5.30 mm), M75NPK (2.90 - 4.23 mm), M100NPK (2.58 - 3.95 mm), M125NPK (4.23 - 5.00 mm) and M150NPK (4.25 - 5.00 mm). Amongst growth media, the percentage increment in stem girth was 17.58%, 3.09%, 21.00%, 45.86%, 58.10%, 18.20% and 17.65% for Control, M25NPK, M50NPK, M75NPK, M100NPK, M125NPK and M150NPK growth media, respectively. M100NPK medium had the highest percentage increase of stem girth from week 3 - 5. However, at week 5, the highest value for stem girth (5.35 ± 0.370 mm) was obtained at Control medium and this was not significantly different (P ≤ 0.05) compared to other growth media except M100NPK medium while the lowest stem girth value was 3.95 ± 0.580 mm at M100NPK growth medium.
Number of leaves of T. occidentalis grown in different growth media: Table 3 shows the number of leaves of T. occidentalis grown in varying NPK growth media. The number of leaves reduced with increased NPK concentrations in the growth media. However, M75NPK medium had higher number of leaves than M100NPK medium. Amongst growth media from weeks 3 - 5, the percentage increase in number of leaves was 34.38%, 23.33%, 17.86%, 7.69%, 11.54%, 4.35% and 4.35% for Control, M25NPK, M50NPK, M75NPK, M100NPK, M125NPK and M150NPK media, respectively. Control medium had the highest percentage increase for number of leaves from weeks 3 - 5, followed by M25NPK growth medium. Hence, the highest mean value for number of leaves (10.75 ± 0.957) was recorded at the Control medium and it was significantly different from other growth media except for M25NPK medium while the lowest (6.00 ± 0.816 and 6.00 ± 1.414) at M150NPK and M125NPK growth media, in that order at
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Table 2. Stem girth (mm) of T. occidentalis in different NPK growth media.
Mean ± Standard deviation; Means with the same letter in a column are not significantly different; WAP = weeks after planting.
week 5.
Leaf petiole length of T. occidentalis grown in different growth media: The leaf petiole length (LPL) of T. occidentalis grown in varying concentrations of NPK growth media varied across growth media (Table 4). The rate at which the petiole lengths increased was minimal across and within growth media from weeks 3 - 5. The ranges within growth media were: Control (3.90 - 4.90 cm), M25NPK (3.18 - 4.70 cm), M50NPK (3.95 - 4.93 cm), M75NPK (4.25 - 4.40 cm), M100NPK (3.10 - 3.83 cm), M125NPK (2.35 - 3.18 cm) and M150NPK (2.95 - 4.30 cm). Amongst growth media, the percentage increase in the petiole lengths was
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Table 3. Number of leaves of T. occidentalis in different NPK growth media.
Mean ± Standard deviation; Means with the same letter in a column are not significantly different; WAP = weeks after planting.
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Table 4. Petiole length (cm) of T. occidentalis leaves in different NPK growth medium.
Mean ± Standard deviation; Means with the same letter in a column are not significantly different; WAP = weeks after planting.
25.64%, 27.72%, 24.81%, 3.53%, 23.55%, 35.32% and 42.37% for the Control, M25NPK, M50NPK, M75NPK, M100NPK, M125NPK and M150NPK media, respectively. Percentage increase in LPL from weeks 3 - 5 was highest in M150NPK medium. However, the highest value for leaf petiole length (4.93 ± 0.150 cm) was recorded at M50NPK medium and it was not significantly different from other growth media except for M125NPK medium while the lowest value for LPL was 3.18 ± 1.021 cm at M125NPK medium at week 5.
Leaf internodes of T. occidentalis grown in different growth media: Table 5 shows the growth performance of T. occidentalis leaf internodes (cm) in different NPK growth media for 5 weeks. There was increase in leaf internodes from weeks 3 - 5 across growth media. The leaf internodes value was higher in the Control medium compared to other media for weeks 3 - 4 after seedlings were transferred into the growth media except in week 4 (M125NPK). After week 2, there was rapid increase in leaf internodes value for M75NPK medium. After week 4, the percentage increase in leaf internodes values was 1.78%, 7.83%, 11.03%, 53.82%, 17.57%, 6.03% and 3.51% for Control, M25NPK, M50NPK, M75NPK, M100NPK, M125NPK and M150NPK growth media, respectively. At week 5, the M75NPK medium (5.23 ± 2.188 cm) had the highest leaf internodes mean value, followed by M50NPK medium (4.83 ± 1.609 cm). The lowest mean value for leaf internodes (3.83 ± 1.228 cm) was recorded at M150NPK.
Leaf area of T. occidentalis grown in different growth media: The results of the evaluation of different NPK growth media on the leaf area of T. occidentalis are shown in Table 6. There was an increase in the leaf area from week 3 - 5 and the growth performance varied across the growth media. The leaf area ranged from 110.28 - 138.00 cm2, 117.00 - 132.68 cm2, 118.31 - 122.28 cm2, 113.94 - 122.80 cm2, 95.18 - 106.75 cm2, 84.96 - 108.77 cm2, and 90.97 - 127.24
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Table 5. Internode (cm) of T. occidentalis leaves in different NPK growth medium.
Mean ± Standard deviation; Means with the same letter in a column are not significantly different; WAP = weeks after planting.
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Table 6. Leaf area (cm2) of T. occidentalis in different NPK growth media.
Mean ± Standard deviation; Means with the same letter in a column are not significantly different; WAP = weeks after planting.
cm2 for Control, M25NPK, M50NPK, M75NPK, M100NPK, M125NPK and M150NPK growth media, respectively. The Control medium had the highest leaf area value (138.00 ± 17.617 cm2) at week 5, followed by M25NPK medium (132.68 ± 48.723 cm2) while the lowest value (106.75 ± 25.275 cm2) was recorded at M100NPK growth media. These points had the percentage leaf area increase from weeks 3 - 5 as follows: 25.14%, 13.40% and 12.16% for Control, M25NPK and M100NPK treatments, in that order. There was no significant difference (P =0.05) amongst growth media from weeks 3 - 5.
Total leaf area of T. occidentalis grown in different growth media: The results of the total leaf area (cm2) of T. occidentalis grown in different NPK growth media for 5 weeks are shown in Table 7. There was increase in the total leaf area from weeks 3 - 5 across growth media. The total leaf area value was higher in the Control medium compared to other growth media for weeks 3 - 5. There was rapid increase in the total leaf area value for all growth media. The percentage increase in total leaf area values for weeks 3 - 5 was 68.58%, 42.26%, 22.09%, 14.15%, 27.57%, 28.33% and 46.74% for Control, M25NPK, M50NPK, M75NPK, M100NPK, M125NPK and M150NPK media, respectively. At week 5, the Control medium (1492.04 ± 298.148 cm2) had the highest total leaf area value, followed by M25NPK medium (1283.37 ± 762.582 cm2) and it was significantly different (P =0.05) from other growth media except M25NPK medium. The lowest mean value for total leaf area (650.58 ± 170.441 cm2) was recorded at M125NPK medium.
Pigments composition of T. occidentalis leaves grown in different NPK growth media: The pigments composition of T. occidentalis leaves grown in different NPK growth media at 5 WAP are as shown in Table 8. The chlorophyll and carotenoid contents of T. occidentalis leaves varied and had significant
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Table 7. Total leaf area (cm2) of T. occidentalis in different NPK growth media.
Mean ± Standard deviation; Means with the same letter in a column are not significantly different; WAP = weeks after planting.
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Table 8. Pigments composition (mg/g) of T. occidentalis leaves in different NPK growth media at 5 WAP.
Mean ± Standard deviation; Means with the same letter in a column are not significantly different; WAP = weeks after planting.
difference (P ≤ 0.05) amongst growth media. Chlorophyll a content of the leaves was higher than chlorophyll b in all the growth media. The leaves grown in the Control medium had the highest chlorophyll content and were not significantly different from M125NPK and M50NPK media but these growth media differed significantly from others (M25NPK, M75NPK, M100NPK, and M150NPK). The lowest chlorophyll content of T. occidentalis leaves was recorded at M150NPK growth medium. The chlorophyll a, chlorophyll b and total chlorophyll contents ranged from 7.09 - 17.31 mg/g, 3.65 - 15.90 mg/g and 10.73 - 33.22 mg/g, respectively. However, the result recorded for carotenoid of the leaves was different. The highest carotenoid content (6.00 mg/g) of the leaves was recorded at M25NPK medium which was significantly different from other growth media while the least carotenoid content (2.82 mg/g) was obtained at the Control medium. The carotenoid contents recorded were lower than the chlorophyll contents.
Root length (cm) of T. occidentalis grown in different growth media at 5 WAP: The root length of T. occidentalis grown in different growth media (Figure 1). The root length varied in different NPK growth media. The root lengths ranged from 13.18 - 20.55 cm. T. occidentalis grown in Control medium had the highest root length compared to other growth media, which was significantly different at P = 0.05. For the NPK growth media, the root length values differed from one another but there was no significant difference at P = 0.05. However, the lowest root length was recorded at M75NPK growth media. From Figure 1, the treatment (bar) that has “a” is significantly different (p ≤ 0.05) compared with other treatments (bars) having “b” while the bars having the same alphabet are not significantly different at p ≤ 0.05.
Root fresh weight (g) of T. occidentalis grown in different growth media at 5 WAP: The fresh weight of T. occidentalis roots varied in the NPK growth media (Figure 2). The root fresh weight values ranged from 2.02 - 8.77 g. The root fresh weight values recorded for NPK growth media were statistically different (P = 0.05) with the Control medium. Among the growth media, the Control medium had the highest (8.77 g) root fresh weight while the lowest value (2.02 g) was recorded at M125NPK medium.
Root dry weight (g) of T. occidentalis grown in different growth media at 5 WAP: The root dry weight of T. occidentalis decreased as the quantity of NPK increased in the growth media (Figure 3). Among the growth media, the Control medium had the highest root dry weight (0.71 g) and was significantly different when compared to other growth media. Although the root dry weight values differed and ranged from 0.24 - 0.38 g (M150NPK to M25NPK medium), there was no significant difference in NPK growth media.
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Figure 1. Root length of T. occidentalis grown in different NPK growth media at 5 WAP.
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Figure 2. Root fresh weight of T. occidentalis grown in different NPK growth media at 5 WAP.
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Figure 3. Root dry weight of T. occidentalis grown in different NPK growth media at 5 WAP.
4. Discussion
Growth of T. occidentalis grown in different growth media
The vine lengths and number of leaves of T. occidentalis recorded in this study were lower compared to works of other researchers [18] - [23]. Ndor and Dauda [18] reported the vine length range of 51.22 - 79.23 cm and number of leaves range 18.53 - 27.46 for 4 - 6 weeks after germination of T. occidentalis while Chukwudi and Agbo [19] reported 40.60 - 220.50 cm and 14.80 - 97.20 ranges, respectively, 3 - 9 weeks after transplanting. This variation could as a result of trellis. Trellis improved the vine length of cucumber and fluted pumpkin over the unstaked [19] [24]. They suggested that the leaves on the staked plants were all exposed to greater light interception leading to a higher accumulation of photosynthates for vegetative growth. According to Akpaniwo et al. [20], the vine length of untreated T. occidentalis was 146 cm while irradiated T. occidentalis with 100 kv reduces vine length to 116 cm. Vine length is a major leave yield component of fluted pumpkin. Also, Akpaniwo etal. [20] suggested higher number of leaves per plant with longer vine length yield. Oke [21] documented that T. occidentalis grown for 3 - 12 weeks after planting had the following growth indices range: vine length (189.61 - 225.17 cm); number of leaves (13.61 - 40.05); vine girth (0.86 - 0.99 cm); leaf area (118.14 - 370.06 cm2); total leaf area (1607.87 - 14820.90 cm2). The stem girth in this study was lower compared to the stem girth range of 5.13 - 9.4 mm as reported by Chukwudi and Agbo [19]. This difference could as a result of frequent leaf cutting of T. occidentalis which provides opportunity for more growth.
Nwonuala and Obiefuna [22] recorded varied growth indices range of different genotype of T. occidentalis at 6WAP: vine length (81.3 - 158.3 cm); number of leaves (58.3 - 93.5); leaf area (31.8 - 79.0 cm2); internode (5.4 - 7.7 cm) and petiole length (5.5 - 7.6 cm) while Uwalaka et al. [21] reported: main vein length (113.24 to 128.65 cm), and stem girth (0.32 to 0.37 cm) range from 6 - 8WAP and number of leaves (8.24 - 26.73) from 2 - 8 WAP. There is the difference among several researchers and these differences in the growth indices could be attributed to genetic differences according to Chukwudi and Agbo [25]. It is also possible that the ecological system will also affect the growth parameters giving rise to varied results. According to Smith and Ayeigbara [26], the quicker release of N, P, and K from high nitrogen fertilizer will make for quick growth but weaker plants that are susceptible to attacks by diseases and pests. The availability of nutrients in the ecosystem will directly or indirectly culminate in the level of photosynthetic pigments present in T. occidentalis. Earlier, Noggle and Fritz [27] documented that dry matter accumulation is a result of nutrient uptake and it is one of the measures of plant growth. According to Ibeawuchi [28], dry matter accumulation reflects the relative growth rate as regards to the net assimilation rate.
5. Conclusion
From the results recorded, the average pH value and sulphate content of the solutions reduced slightly while the electrical conductivity increased after 28 days. The proportion of the minerals varied in the hydroponic solutions. Considering the performance of T. occidentalis grown in different NPK, the Control treatment had the highest vine main length, number of leaves, leaf area, total leaf area, petiole length, and pigment composition of T. occidentalis compared to other treatments. However, among the NPK treatments, M25NPK treatment effectively enhanced some of the growth indices such as vine main length, number of leaves, leaf area, total leaf area, carotenoid content, root length, root fresh weight, and root dry weight. The use of NPK fertilizer in the cultivation of vegetables especially fluted pumpkins in a non-circulatory hydroponic system should be encouraged.