1 Introduction

Tomato (Solanum lycopersicum) is recognized as one of the most extensively cultivated vegetable crops worldwide, ranking second after potatoes in terms of consumption and leading among processed vegetable crops (Sharma et al., 2015; Atif et al., 2016). In addition to its culinary value, tomatoes serve important roles in medicine, cosmetics, and the food industry (Dahliani and Darmayanti, 2023). They are rich sources of potassium, fiber, and essential vitamins such as A, C, and K (Ramasami, 2023). In Nepal, tomatoes hold the position of the third most important vegetable crop; however, their productivity has slightly decreased from 19.14 tons per hectare in 2021 to 18.45 tons per hectare in 2023 (MoALD, 2023).

One of the primary causes of the decline in output is the inferior seedling quality, which is a direct consequence of the selection of proper growing media during the nursery phase. Traditional soil-based media generally do not meet the optimal physical and chemical requirements needed for vigorous seedling growth (Ati et al., 2016). Even though various alternative substrates have been studied globally, research specific to Nepal's midhill conditions remains limited.

Growing media, which provide structural support and nutrients, are generally classified into organic (e.g., vermicompost, cocopeat, farmyard manure) and inorganic (e.g., perlite, sand) types (TM et al., 2020). Cocopeat, a byproduct of coconut fiber processing, is favored for its excellent water retention and aeration properties (Krishnapillai et al., 2020). Vermicompost, which results from the decomposition of organic matter by earthworms, improves nutrient availability and soil structure (Adhikary, 2012), whereas farmyard manure enhances soil fertility and microbial balance (Gama et al., 2015). Besides that, perlite, a thermally expanded volcanic glass, improves aeration and drainage.

An ideal growing medium should have an adequate water-air ratio, adequate drainage, good aeration, low soluble salt concentration, and stronger cation exchange capacity (Bagci et al., 2011; Hazarika et al., 2022). These properties greatly influence root development, germination rates, and overall seedling vigor (Abad et al., 2002; Bilderback et al., 2005; Periasamy and Duraisamy, 2017). Furthermore, the use of well-formulated growing media reduces the risk of soil-borne diseases, promoting healthier seedling emergence (Mathowa et al., 2016).

Since this topic has minimal research in individual regions, particularly in Nepal’s midhill areas, such as Kaski District. This study aimed to identify the most effective growing media for tomato seedling production under the mid-hill conditions of Nepal by evaluating seed germination traits and seedling vigor across seven substrate combinations. By determining the optimal substrate formulation, the study seeks to enhance nursery management practices, promote the production of healthy and vigorous seedlings, and ultimately contribute to improved tomato yield and productivity in the region.

2 Materials and Methods

2.1 Experimental site and conditions

The experiment was conducted at Birauta-17, Pokhara, Kaski, in a naturally ventilated plastic greenhouse. The site's geographical location was 28° 12' 47.693'' N latitude and 83° 58' 16.596'' E longitude with an elevation of 800 m above sea level (Figure 1). The average temperature and relative humidity inside the greenhouse during the study period were approximately 28 °C to 35 °C and 70% to 80%, respectively.

Figure 1 Map of the study area

2.2 Experimental design and treatments

The experiment was laid out in a Completely Randomized Design (CRD), with three replications. Seven treatments of growing media i.e., T₁ - soil (control), T₂ - cocopeat + vermicompost (1:1), T₃ - cocopeat + perlite (1:1), T₄ - soil + vermicompost (1:1), T₅ - soil + FYM (1:1), T₆ - soil + cocopeat (1:1), and T₇ - conventional growing medium (soil, sand, and FYM in 1:1:1) were tested (Table 1).

Srijana, a popular hybrid variety, was selected for the study due to its widespread adoption by farmers in Kaski District. The treated seeds of the Srijana variety were brought from a certified source. The required manures and other inputs were obtained from the local sources and agrovets. The N% was determined by Kjeldhal’s method, available P by Modified Olsen’s method, available K by Flame photometer, and pH by Digital pH meter.

2.3 Nursery management practices

Seeds were sown directly in a plastic seedling tray placed inside a greenhouse. For the first few days, the trays were covered by soaked newspaper to create a dark condition for germination. Seedlings were periodically and equally irrigated using a spray bottle with a nozzle, but no additional nutrient elements were supplied.

2.4 Data collection and measurements

Data on germination and seedling growth parameters were recorded during the seedling stage. Germination percentage was calculated using the formula:

This value indicated the proportion of seeds that successfully germinated in each replication.

Germination speed was calculated according to the formula described by Mangure (1962), which considers the number of seeds germinated over time:

Where X1, X2...Xn are the cumulative numbers of seeds germinated on days Y1, Y2...Yn after sowing. This parameter reflects the rapidity of germination.

Seedling vigor I was determined using the formula given by (Abdul-Baki, 1973):

This index provides insight into the early growth potential of seedlings under each treatment.

For seedling growth parameters, ten seedlings per replication (30 per treatment) were randomly selected for measurement. Shoot length and root length (in cm) were measured after 24 days of sowing using a standard ruler. From these values, the shoot-to-root length ratio was calculated using the formula:

Total seedling length was calculated by summing the shoot and root lengths for each seedling:

The number of leaves per seedling was recorded by counting the true leaves (excluding cotyledons) on each of the selected seedlings, and the average was computed.

Seedling fresh weight was determined by weighing seedlings using an electronic balance after removing surface moisture with butter paper. The mean fresh weight per seedling was then calculated.

Seedling dry weight was measured after oven-drying the sampled seedlings (including roots) at 105 °C for approximately 17 hours. Dry weights were recorded using a digital weighing balance.

The shoot-to-root fresh weight ratio was computed using the formula:

Likewise, the shoot-to-root dry weight ratio was determined using oven-dried values, calculated as:

Finally, the plant stand percentage was calculated by observing the number of seedlings that remained viable 24 days after sowing. The percentage was derived using the formula:

2.5 Statistical analysis

The observations were recorded on various seed germination and seedling growth parameters. Data were subjected to analysis of variance (ANOVA) to compare media effects. The differences between the means were compared using the least significant difference (LSD) test at a 5% significance level. All analyses were performed using R-studio version 4.4.1.

3 Results and Analysis

3.1 Germination performance

Significant differences were observed in germination percentage, speed, and seedling vigor index among the seven tested growing media treatments (Table 2). The highest germination percentage (94.67%) was recorded in T₃ (cocopeat + perlite), which was statistically at par with T₂ (cocopeat + vermicompost, 90.00%), T₆ (soil + cocopeat, 86.67%), T₄ (soil + vermicompost, 86.00%), T₅ (soil + FYM, 86.00%), and T₇ (conventional medium, 84.00%). The lowest germination percentage was observed in the control (T₁, 62.00%). Similarly, germination speed and seedling vigor index I followed the same trend, with T₆ and T₂ showing significantly higher values. The F-test showed highly significant effects (p < 0.001) for all three parameters.

3.2 Seedling morphological traits

Different growing media treatments had a significant effect on seedling shoot length, root length, shoot-to-root length ratio, and total seedling length (Figure 2; Figure 3; Figure 4; Figure 5). The highest shoot length (12.99 cm) was observed in T₂ (cocopeat + vermicompost), while the shortest (3.29 cm) was recorded in the control (T₁). For root length, T₆ (soil + cocopeat, 8.73 cm) and T₂ (7.44 cm) performed best. The highest shoot-to-root ratio (1.40) was also recorded in T₂, statistically at par with T₄ (1.39). T₂ exhibited the maximum seedling length (20.44 cm), whereas T₃ (cocopeat + perlite) and T₁ had the lowest values.

Figure 2 Shoot length as influenced by different growing media on tomato in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences

Figure 3 Root length as influenced by different growing media on tomato in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences

Figure 4 Seedling length as influenced by different growing media on tomato in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences

Figure 5 Shoot-to-root length ratio as influenced by different growing media on tomato in Kaski district, 2024 Note: Error bars represent LSD (0.05); Letters indicate significant differences

3.3 Biomass characteristics

Fresh and dry weights of seedlings were significantly affected by the growing media (Table 3). The highest fresh weight (1.56 g) and dry weight (0.192 g) were observed in T₂. Other notable treatments were T₄ (soil + vermicompost) and T₆ (soil + cocopeat), while T₃ (cocopeat + perlite) showed the lowest biomass accumulation. Significant differences were also noted in shoot-to-root fresh weight and dry weight ratios. The control (T₁) showed the highest shoot-to-root fresh weight ratio (5.86), followed closely by T₂ and T₄. T₂ also recorded the highest shoot-to-root dry weight ratio (5.34).

3.4 Plant stand and leaf development

The number of leaves per seedling and plant stand percentage varied significantly among the treatments (Table 4; Figure 6). T₂ (cocopeat + vermicompost) produced the highest number of leaves (13.8), followed by T₄ (soil + vermicompost, 10.4). The fewest leaves were observed in T₃ (3.23). Regarding plant stand percentage, T₂ again ranked highest (98.58%), while T₁ (control) showed the lowest stand (84.49%).

4 Discussion

The findings of this study demonstrate that the choice of growing media significantly affects seed germination and seedling growth characteristics in tomatoes. Among the treatments, T₂ (cocopeat + vermicompost) consistently outperformed the others across various growth parameters.

The enhanced performance of T₂ can be attributed to physiological and substrate-related mechanisms. Seed germination requires adequate water, oxygen, and temperature. Water softens the seed coat (Kumar et al., 2016), oxygen supports aerobic respiration to fuel early growth, and warm temperatures accelerate enzymatic activity in seeds (Hazarika et al., 2022). Cocopeat and vermicompost possess favorable physical properties, such as high porosity and moisture retention, which ensure adequate oxygen diffusion and water availability for seedling emergence (Alam et al., 2014).

Vermicompost further contributes to seedling development due to its balanced nutrient composition, particularly the availability of phosphorus and potassium, and bioactive substances that stimulate root and shoot growth (Mahala and Sharma, 2020; Ramasami, 2023). These characteristics result in vigorous germination and growth compared to inert media such as perlite. In the case of T₃ (cocopeat + perlite), although high porosity supports aeration, the lack of nutrients limits shoot development, as perlite contains negligible amounts of essential macronutrients (Hazarika et al., 2022).

The improved root and shoot lengths in cocopeat + vermicompost media may be due to the enhanced mobilization of nutrients and moisture, facilitating better root development and increased photosynthate accumulation. This supports greater biomass production, as indicated by the highest fresh and dry weight in T₂ (Anjanawe et al., 2013). In contrast, the control and cocopeat + perlite media provided suboptimal nutrition, resulting in lower biomass. The compactness of the control medium likely hindered root elongation, while cocopeat + perlite lacked key nutrients despite sufficient moisture availability.

Biomass partitioning, as shown by the shoot-to-root biomass ratio, also favored T₂, indicating that nutrient-enriched organic media encouraged both below- and above-ground growth. Organic amendments like vermicompost enhance porosity and water retention, thereby improving nutrient uptake and translocation to shoots (Gogoi and Sarma, 2015). This is consistent with Zhang et al. (2011) and Anjanawe et al. (2013), who reported a similar trend in nutrient-enriched substrates.

The number of leaves per seedling, another important indicator of seedling vigor, was also highest in T₂, followed by T₅ (soil + vermicompost). This trend is likely due to the contribution of vermicompost’s nutrients, which support vegetative growth. Adiloğlu et al. (2018) and Lohani (2023) observed that vermicompost application increases leaf number, area, and biomass. These results align with Mahala and Sharma (2022), Periasamy and Duraisamy (2017), and Panthi et al. (2023), who reported significant increases in leaf production with vermicompost-based growing media.

The superior performance of the cocopeat + vermicompost mixture aligns with studies conducted in various crops. Periasamy and Duraisamy (2017) and Atif et al. (2016) observed better seedling emergence and growth in tomatoes under vermicompost-based media. Cocopeat’s beneficial pH and electrical conductivity also support early root development, as observed in nutmeg seedlings by Abirami et al. (2010). Kalaivani and Jawaharlal (2019) noted similar effects in tomato root development due to better nutrient and water retention in cocopeat.

Hazarika et al. (2022), Mathowa et al. (2016), and Panthi et al. (2023) also found positive effects of cocopeat and vermicompost on seedling development. The nutrient-rich environment promotes cell division and elongation, thereby contributing to greater seedling mass and vigor. Mualchin and Verma (2022) and Mahala and Sharma (2022) also documented reduced disease incidence and improved potassium uptake in cocopeat + vermicompost media, supporting the current findings.

5 Conclusion

The findings of this study support that the choice of growing medium has a significant influence on the germination and early growth of tomato (Solanum lycopersicum cv. Srijana) seedlings. Among the tested media, the combination of cocopeat and vermicompost (1:1) consistently outperformed others in promoting both germination efficiency and seedling vigor. Despite the fact that cocopeat mixed with perlite improved germination percentage, it did not support seedling development as effectively, likely due to its lower nutrient level.

In conclusion, it is recommended that the cocopeat-vermicompost mix is the most suitable growing medium for tomato seedling production in Kaski district's environmental conditions. Its use can lead to the development of stronger, healthier seedlings, higher transplanting success rates, and ultimately increased tomato yields. Future studies should examine the economic practicality and potential application of this mix across different agro-ecological zones in Nepal.

Authors’ contributions

MT conceived and designed the study, performed the experiments, collected the data. Interpreted the results, and wrote the manuscript. BSi assisted with data analysis, statistical interpretation, and the preparation of figures and tables. PG contributed to the literature review and helped gather relevant resources for manuscript development. BS supervised the study, provided critical feedback, and helped enhance the manuscript through suggestions and revisions. All authors read and approved the final manuscript.

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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