Comparative assessment on effect of seaweed extracts and levels of RDF on growth, yield and economics of tomato (Solanum lycopersicum L.) var. Saaho

Introduction

Tomato (Solanum lycopersicum L.) is one of the most significant horticultural crops bearing chromosome number of 2n=2X=24 (Fedorov, 1969) [5] , with a global production exceeding 138 million metric tonnes. Taxonomically, it belongs to the Solanaceae family, with Solanum pimpinellifolium recognized as its closest wild relative (Preedy and Watson, 2008) [12] . Tomato is a globally significant vegetable, ranking second in both production and consumption. In the United States, it is the second most consumed fresh vegetable, with an annual per capita intake of 6-7 kg (FAOSTAT, 2020) [4] . Tomatoes are renowned for their rich nutritional profile, offering an abundant source of essential vitamins, minerals, and bioactive compounds. They provide significant amounts of vitamin C, pro-vitamin A, βcarotene, and folate, along with vital minerals such as potassium. Additionally, they are rich in secondary metabolites, including lycopene, flavonoids, phytosterols, and polyphenols, which contribute to their health-promoting properties (Luthria et al. 2006) [11] . Excessive fertilizer use contributes to water pollution through surface runoff, as rainfall erodes chemically treated soils, carrying nitrogen and phosphorus into water bodies. This non-point source pollution leads to eutrophication and the formation of "dead zones" in rivers, lakes, and oceans, depleting oxygen levels and threatening aquatic ecosystems (Singh et al. 2017) [15] . Furthermore, chemical pesticides not only target harmful pests but also pose risks to nontarget plant and animal species, including humans. Concerns over pesticide residues in food, groundwater contamination, and biodiversity loss have amplified the need for safer agricultural practices. To mitigate these detrimental effects, recent agricultural practices are increasingly incorporating natural plant-based fertilizers. Among these, seaweed-based biofertilizers have gained significant attention for their eco-friendly properties. Seaweed extracts, rich in essential nutrients, bioactive compounds, and growth-promoting hormones, offer a sustainable alternative to synthetic fertilizers (Hong et al. 2007) [8] . Unlike chemical inputs, seaweed fertilizers are biodegradable, non-toxic, and environmentally benign, posing no threat to humans, animals, or birds (Begum et al. 2018) [1] . Thus, the adoption of natural bio-fertilizers is a promising step towards sustainable agriculture, promoting soil health and reducing chemical dependency. Therefore, evaluating growth and yield of tomatoes using seaweed extracts becomes crucial, as it offers a potential solution to overcome nutrient deficiencies, reduce chemical dependency, and promote sustainable agricultural practices, ultimately ensuring food security and environmental sustainability.

Materials and Methods

The present investigation was meticulously carried out at the Horticultural Research Farm of the Department of Horticulture, Naini Agricultural Institute, Sam Higginbottom University of Agriculture, Technology and Sciences (SHUATS), Prayagraj, Uttar Pradesh, during the Rabi seasons of 2023-24 and 2024-25. The distinguished university is strategically situated approximately 5 kilometres from Prayagraj City, along the Prayagraj-Rewa National Highway, offering convenient accessibility. In the present investigation the design used for analysis of variables was Randomized Block Design (RBD) comprising 3 replications comprising of foliar application of micronutrients total treatment combinations being fifteen. The treatments comprised T 0 (Control); T 1 (50% RDF + Water Spray); T 2 (100% RDF + Water Spray); T 3 (50% RDF + 2% K SAP); T 4 (50% RDF + 4% K SAP); T 5 (50% RDF + 6% K SAP); T 6 (50% RDF + 2% S SAP); T 7 (50% RDF + 4% S SAP); T 8 (50% RDF + 6% S SAP); T 9 (100% RDF + 2% K SAP); T 10 (100% RDF + 4% K SAP); T 11 (100% RDF + 6% K SAP); T 12 (100% RDF + 2% S SAP); T 13 (100% RDF + 4% S SAP) and T 14 (100% RDF + 6% S SAP). Characters like Plant height (cm) [90 and 120 DAT]; number of branches per plant [90 and 120 DAT], days to 50% flowering, number of fruits per plant, days to first harvest and average fruit weight (gm), fruit diameter (cm), number of fruit per plant and Yield per plant (kg/plant) were observed. Analysis of Variance was worked out using Fisher and Yates (1967) [6] .

Results and Discussion

Plant height and Number of branches per plant Among the different treatments applied, T 14 (100% RDF + 6% S SAP) showed maximum height of plant [Table 1] at 90 DAT (105.95, 106.92 and 106.43 cm) followed by T 11 (100% RDF + 6% K SAP) having 99.54, 99.37 and 99.46 cm for both year 2023-24, 2024-25 and pooled mean respectively. However, minimum height of plant (64.88, 68.06 and 66.47 cm) at 90 DAT was observed in T 0 (Control). Among the different treatments applied, T 14 (100% RDF + 6% S SAP) showed maximum number of branches per plant [Table 1] at 90 DAT (11.90, 10.35 and 11.13 branches) followed by T 11 (100% RDF + 6% K SAP) having 11.00, 10.08 and 10.54 branches for both year 2023-24, 2024-25 and pooled mean respectively. However, minimum number of branches per plant (5.65, 4.48 and 5.06 branches) at 90 DAT was observed in T 0 (Control). Evaluation of the interaction effect over the two years revealed that its magnitude was relatively low, indicating minimal variation in treatment performance between the years. This small interaction effect also suggests that the treatment rankings remained largely consistent across both years. Consequently, the interaction can be regarded as nonsignificant and negligible, implying that the treatment effects derived from the pooled analysis are generally stable and dependable. The findings for plant height and number of branches per plant in tomato demonstrated superior performance under treatment T 14 (100% RDF + 6% S SAP), followed by T 11 (100% RDF + 6% K SAP), indicating the positive influence of liquid seaweed extract. The enhanced growth in T 14 may be attributed to the presence of essential micronutrients, plant growth hormones, and bioactive compounds in S SAP, which likely promoted cell elongation and division. Similarly, K SAP also contributed to improved vegetative growth in T 11 . Both treatments provided a synergistic effect with RDF, enhancing nutrient uptake and physiological processes, thereby outperforming all other treatments in terms of plant height. Hernandez-Herrera et al. (2013) [7] working with seaweed extracts application on tomatoes revealed SLF to be effective biostimulants to improve tomato growth, highlighting the potential of Mexican seaweed resources for sustainable agricultural practices. Similarly, Selvakumari et al. (2013) [13] reported improved tomatoes growth through the combined RDF with seaweed extracts, highlighting the significant role of secondary and micronutrients in optimizing crop productivity across different cropping systems.

Days to 50% flowering and days to first harvest

Among the various treatments applied, T 14 (100% RDF + 6% S SAP) exhibited the earliest flowering [Table 2], recording 58.95, 55.27, and 57.11 days to 50% flowering during the years 2023-24, 2024-25, and in the pooled mean, respectively. This was closely followed by T 11 (100% RDF + 6% K SAP), which took 59.74, 55.75, and 57.75 days across the same periods. Among all treatments, T 14 (100% RDF + 6% S SAP) resulted in the earliest harvest [Table 2], recording 98.57 days in 2023-24, 94.80 days in 2024-25, and a pooled mean of 96.69 days. This was followed closely by T 11 (100% RDF + 6% K SAP), which achieved harvest at 99.36, 95.59, and 97.48 days, respectively. The observed earliness in these treatments is likely due to the presence of bioactive constituents such as auxins, cytokinins, and micronutrients in the seaweed extracts, which stimulate growth, accelerate flowering, and enhance overall physiological development. The combined application with RDF likely ensured optimal nutrient availability and uptake, further promoting earlier maturity. In contrast, the control treatment T 0 showed the latest harvest (113.42, 111.10, and 112.26 days), reflecting delayed growth due to the absence of nutritional supplementation. These results clearly highlight the positive impact of seaweed liquid SAPespecially when integrated with recommended fertilizer doses-on reducing the time to marketable harvest, thereby improving the productivity and profitability of tomato cultivation. Hussain et al. (2021) [9] investigated the effects of seaweed extract (SWE) derived from brown algae Durvillaeapotatorum and Ascophyllum nodosum on tomato plants and reported earliness in maturity in fruits.

Number of fruits per plant

Among the treatments assessed, T 14 (100% RDF + 6% S SAP) emerged as the most effective, recording the highest number of fruits per plant-67.29 in 2023-24, 86.10 in 2024-25, and a pooled average of 76.70 fruits [Table 2]. This remarkable enhancement in fruit set is largely attributed to the presence of bioactive compounds in the S SAP-based liquid seaweed extract, such as auxins, cytokinins, gibberellins, amino acids, and essential micronutrients. These constituents are known to stimulate reproductive development by promoting floral differentiation, enhancing flower viability, improving pollen germination, and facilitating successful fertilization. The synergistic interaction between the seaweed extract and the recommended dose of fertilizers (RDF) likely enhanced nutrient assimilation and hormonal equilibrium, thereby boosting fruit-setting potential. T 11 (100% RDF + 6% K SAP) also demonstrated commendable results, yielding 56.80, 79.15, and 67.97 fruits per plant during the respective years. The potassium-enriched SAP was instrumental in supporting flower retention, optimizing energy transfer, and enhancing carbohydrate metabolism-all critical processes for robust fruit development. Conversely, the control treatment (T 0 ) registered the lowest fruit count-19.14, 18.98, and 19.06 fruits-highlighting the pivotal role of integrated nutrient management, particularly the application of liquid seaweed extracts, in significantly improving the reproductive efficiency and productivity of tomato plants. Youssif and Tawfeeq (2021) [9] in cauliflower and Vijayanand et al. (2023) [18] in cluster bean put forward the effectiveness of Seaweed extract application for enhancement of fruiting in crops.

Fruit diameter, fruit weight and fruit yield per plant and per hectare Among the various treatments administered, T 14 (100% RDF + 6% S SAP) recorded the largest fruit diameter, with values of 7.30 cm in 2023-24, 7.91 cm in 2024-25, and a pooled mean of 7.60 cm. This was closely followed by T 11 (100% RDF + 6% K SAP), which achieved fruit diameters of 6.82, 7.45, and 7.13 cm, respectively [Table 3], over the same periods. In contrast, the smallest fruit diameter was observed in the control treatment (T 0 ), which registered 4.91 cm, 5.20 cm, and a pooled average of 5.06 cm. Among the various treatments administered, T 14 (100% RDF + 6% S SAP) recorded the largest fruit weight, with values of 79.65 grams in 2023-24, 76.16 grams in 2024-25, and a pooled mean of 77.91 grams [Table 3]. This was closely followed by T 11 (100% RDF + 6% K SAP), which achieved fruit weights of 74.90, 70.79 and 72.84 grams, respectively, over the same periods. In contrast, the smallest fruit weight was observed in the control treatment (T 0 ), which registered 45.73 grams, 43.10 grams, and a pooled average of 44.41 grams. Among the treatments evaluated, T 14 (100% RDF + 6% S SAP) demonstrated the highest fruit yield per plant [Table 3], recording 5.35 kg/plant in 2023-24, 6.55 kg/plant in 2024-25, and an average of 5.95 kg/plant. T 11 (100% RDF + 6% K SAP) followed closely, yielding 4.26, 5.60, and 4.93 kg/plant during the same periods. Conversely, the control treatment (T 0 ) exhibited the lowest yields, with figures of 0.89 kg/plant, 0.82 kg/plant, and an average of 0.85 kg/plant. Among the treatments evaluated, T 14 (100% RDF + 6% S SAP) demonstrated the highest fruit yield per hectare [Table 3], recording 1154.88 q/ha in 2023-24, 1190.14 q/ha in 2024-25, and an average of 1172.51 q/ha. T 11 (100% RDF + 6% K SAP) followed closely, yielding 986.78, 1154.01 and 1070.39 q/ha during the same periods. Conversely, the control treatment (T 0 ) exhibited the lowest yields, with figures of 141.93 q/ha, 164.04 q/ha, and an average of 152.98 q/ha. An analysis of the interaction effect over the two years revealed a relatively low magnitude, indicating minimal variation in treatment responses from year to year. This limited interaction effect suggests that the performance rankings of the treatments were largely consistent across both seasons, leading to the conclusion that the interaction effect is statistically non-significant and practically negligible, thereby reinforcing the reliability and stability of the pooled analysis results. The exceptional fruit yield observed in T 14 (100% RDF + 6% S SAP) can be credited to the collaborative effects of vital nutrients and bioactive substances found in S SAP, including auxins, cytokinins, and amino acids. These components significantly improve flowering, fruit set, and nutrient absorption. When paired with RDF, they enhance plant growth and reproductive success, resulting in higher yields. Similarly, T 11 (100% RDF + 6% K SAP) exhibited remarkable results, largely due to potassium's contribution to carbohydrate metabolism, water management, and flower retention. Both treatments surpassed all others by promoting superior physiological functions and nutrient uptake, highlighting the advantages of combining seaweed extracts with RDF to optimize tomato yield. Kharbyngar and Singh (2019) [10] in cauliflower demonstrated the cost-effective enhancement of fruit yields using a mixture seaweed extracts along with recommended fertilizer dose applied as foliar spray.

Economics Parameter

Maximum gross returns were recorded in treatment T 14 (100% RDF + 6% S SAP) with (Rs 5,77,438; Rs 5,95,072 and Rs 5,86,255 ha -1 ) for year 2024, 2025 and mean respectively [table 4] followed by T 11 (100% RDF + 6% K SAP) with (Rs 4,93,390; Rs 5,77,003 and Rs 5,35,196 ha -1 ) for year 2024, 2025 and mean respectively and the minimum (Rs70, 966; Rs 82,018 and Rs 76,492 ha -1 ) was recorded in treatment T 0 (Control) for year 2024, 2025 and mean respectively. Maximum net returns were recorded in treatment T 14 (100% RDF + 6% S SAP) with (Rs 4,94,101; Rs 5,11,735 and Rs 5,02,918 ha -1 ) for year 2024, 2025 and mean respectively followed by T 11 (100% RDF + 6% K SAP) with (Rs 4,10,101; Rs 4,93,714 and Rs 4,51,907 ha -1 ) for year 2024, 2025 and mean respectively and the minimum (loss of Rs9,107 in year 2024; Rs 1,945 in year 2025 and overall loss of Rs 3,581 ha -1 ) was recorded in treatment T 0 (Control). Maximum benefit cost ratio was recorded in treatment T 14 (100% RDF + 6% S SAP) with (6.93, 7.14 and 7.03ha -1 ) for year 2024, 2025 and mean respectively followed by T 11 (100% RDF + 6% KSAP) with (5.92, 6.93 and 6.43ha -1 ) for year 2024, 2025 and mean respectively and the minimum (0.89, 1.02 and 0.96ha -1 ) was recorded in treatment T 0 (Control) for year 2024, 2025 and pooled mean respectively.

Conclusions

The study clearly demonstrated that the combined application of 100% Recommended Dose of Fertilizers (RDF) with seaweed-based biostimulants, particularly 6% S SAP (T 14 ), significantly enhanced the vegetative and reproductive growth parameters of tomato plants across two consecutive years. T 14 consistently outperformed all other treatments in plant height, number of branches per plant, earliness to flowering and harvesting, number of fruits per plant, fruit size, weight, and ultimately fruit yield per plant. The superiority of T 14 is attributed to the presence of growth-promoting compounds such as auxins, cytokinins, gibberellins, amino acids, and essential micronutrients in the S SAP, which synergistically improved nutrient uptake, physiological processes, and hormonal balance when applied alongside RDF. T 11 (100% RDF + 6% K SAP) also demonstrated considerable improvement in growth and yield attributes, largely due to potassium's role in enhancing energy transfer and metabolic activities. Economically, T 14 proved the most profitable, with the highest net returns (₹ 5,02,918 ha⁻¹) and benefit-cost ratio (7.03), reinforcing its viability for commercial adoption. The findings strongly support integrating seaweed extracts, particularly S SAP, with RDF as a sustainable, cost-effective approach to improving tomato productivity and profitability.

Acknowledgement

AcknowledgementThe author expresses sincere gratitude to the Head of the Department of Horticulture SHUATS, Prayagraj for their invaluable support and assistance.

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