Foliar nutrition of water soluble potassium from banana pseudostem on growth, yield and quality of tomato

Introduction

Tomato (Solanum lycopersicum L.) is one of the most important vegetable crops worldwide due to its nutritional, economic and industrial significance. It is rich in vitamins, minerals, antioxidants and bioactive compounds such as lycopene, making it a vital component of human diets. Globally, tomato occupies a prominent position in area and production. In India, area under tomato reported during 2023-24 was 8.71 lakh ha (21.52 lakh acres), tomato production in 2023-24 is 213.20 lakh tonnes and a productivity of roughly 24.4 metric tonnes per hectare. Potassium (K) is a critical macronutrient in tomato production, influencing photosynthesis, enzyme activation, translocation of assimilates, water relations and stress tolerance. Adequate K supply improves fruit yield, size, firmness, total soluble solids and lycopene content, thereby enhancing both productivity and quality. Crop residues and agro-industrial by products contain appreciable quantities of water-soluble K that can be harnessed through simple extraction methods. Banana pseudostem, in particular, has been reported to release substantial amounts of readily available potassium, making it a promising organic source. Foliar application of such water-extracted K solutions offers the advantage of direct nutrient absorption by leaves, bypassing soil fixation processes, and enabling quick correction of deficiencies. Hence the present investigation was undertaken to evaluate the effect of foliar fertilization of water-extractable potassium from different organic residues on plant growth, fruit yield and fruit quality parameters of tomato under controlled conditions.

Materials and Methods Experimental Site and Crop

The experimental site located at College of Agriculture, Navile, Shivamogga which comes under the Southern Transitional Zone of Karnataka (Agro-climatic Zone -VII). The experiment was conducted under pot culture conditions during rabi 2024-25. Tomato (Saaho hybrid) was used as the test crop.

Organic Residue Collection and Extract Preparation

Banana pseudostem residues wastes were collected from local farm fields. Water extraction method (as described by Reddy and Veeranki, 2013) [17]: To evaluate the impact of extraction variables on waterextractable K, finely ground and dried samples of crop residues were extracted with distilled water employing a range of sampleto-water (w/v) dilution ratios and shaking periods. The treatments consisted of combinations of four sample-to-water (w/v) ratios viz., 1:60, 1:80, 1:100 and 1:120 and three shaking periods viz., 10, 20 and 30 min with three replications. In the present investigation 0.5 g weighed finely ground (<0.5 mm) and dried (60 0 C) plant powder sample was taken into a 250-ml Erlenmeyer flask and distilled water was added to the flask to get the required extraction ratios. The contents of the flask subjected for shaking on a reciprocating shaker and filtered through filter paper (grade 1). The extracted sample preserved for K determination.

Experimental Design and Treatments

The experiment was laid out in a Completely Randomized Design (CRD) with eleven treatments and three replications.

T1

Absolute Control T2 100% RDF T3 100% RD N, P + 75% RDK T4 T2 + 1% water extract K from banana pseudostem as foliar spray T5 T2 + 2% water extract K from banana pseudostem as foliar spray T6 T2 + 3% water extract K from banana pseudostem as foliar spray T7 T2 + 4% water extract K from banana pseudostem as foliar spray T8 T3+ 1% water extract K from banana pseudostem as foliar spray T9 T3 + 2% water extract K from banana pseudostem as foliar spray T10 T3 + 3% water extract K from banana pseudostem as foliar spray T11 T3 + 4% water extract K from banana pseudostem as foliar spray

Planting and Crop Management

The experiment was carried out in an open ventilated polyhouse in pots. The pots are filled with soil of 10 -12 kg in 15 kg capacity pots. The soil sample was collected before imposition of treatments and analyzed for different physical and chemical properties. The result of the analysis is given in Table 1.

One month-old tomato seedling were planted one for all the pots. The recommended dose of nutrients for tomato used was 250 kg N, 250 kg P2O5 and 250 kg K2O kg ha -1 . Nitrogen and phosphorus were applied through urea and DAP, while potash was applied using sulphate of potash (SOP) as per treatments.

The foliar spray of water extracted K from the banana pseudostem was applied to the plants at 30 and 60 days after transplanting with different concentrations as mentioned in treatment details. Standard agronomic practices and plant protection management were followed uniformly across treatments. Fisher's method of analysis of variance was adopted for statistical analysis and interpretation of the data. The treatments were tested at five per cent levels of significance.

Results and Discussion

Growth parameters Plant height

Scrutiny of data indicated that there was no significant variation in plant height of tomato at 30 DAT. At 60 DAT the treatment T7 (100% RDF + 4% We-K from banana pseudostem as foliar spray) recorded the highest plant height (122.33 cm) (Table 2). The maximum plant height (124.67 cm) was recorded in T7 at harvest which was significantly superior to almost all treatments, followed by T6 (119.67 cm). The treatments T2 (110.33 cm), T4 (110.33 cm), T5 (111.67 cm) and T10 (108.67 cm) were on par with each other. Whereas treatment T1 recorded the lowest plant height (98.33 cm). At 30 DAT, no significant differences in plant height were observed among the treatments. However, from 60 DAT onwards, the influence of foliar potassium became statistically significant. The tallest plants at harvest were recorded in T7 (124.67 cm), followed by T6 (119.67 cm). The increase in plant height with foliar application of We-K due to potassium role in promoting cell expansion, osmotic regulation and photosynthate translocation as reported by and Mengel and Kirkby, 2001 [13] .

The significant response at 60 DAT and harvest stages implies that foliar potassium becomes increasingly important during the reproductive phase, when root absorption may be less efficient due to soil moisture or other stress conditions. The increase in plant height may be due to more availability of nutrient in soil and more uptake of nutrients and root growth. (Mercy et al., 2014) [14] .

Number of Branches per plant

There was a significant difference found in the number of branches of tomato at 30 DAT. The maximum number of branches per plant of tomato was recorded in treatment T7 supplied with 100 per cent RDF + 4 per cent We-K from banana pseudostem as foliar spray at all growth stages (12.33, 22.67 and 24.67 at 30, 60 DAT and harvest, respectively). The treatments T6 was on par with T7. At the same time, the treatment received 100 per cent RDF alone (T2) recorded 12.00, 17.33 and 18.67 branches per plant at 30, 60 DAT and harvest, respectively. While, the lowest number of branches per plant was observed in the T1 treatment (8.67, 14.33 and 16.00 at 30, 60 DAT and harvest, respectively) at all the growth stages. The branching pattern in tomato showed a clear positive response to foliar potassium application (Table 2). The maximum number of branches at harvest was recorded in T7

(24.67), followed by T6 (23.00) and T11 (19.33). In contrast, the T2 (100% RDF) had lower branches (18.67) when compared with T7, the control treatment (T1) had the fewest branches (16.00). Potassium influences the synthesis and transport of auxins and cytokinins, which regulate shoot branching and apical dominance (Cakmak, 2005) [4] . Notably, T7 and T6 treatments not only supplied basal potassium viz., RDF but also provided an additional foliar boost, ensuring consistent K availability throughout the crop cycle. These results align with the findings of Subramanian et al. (2005) [20] who observed increased shoot branching in tomato and chilli under foliar potassium treatments. Similar results were observed by Shukla et al. (2021) [18] in which different concentrations at doses foliar spray treatment were used as the tool of application.

Number of leaves per plant

There was a significant difference found in the number of leaves of tomato at 30 DAT. The maximum number of leaves per plant of tomato recorded in the treatment T7 (100% RDF + 4% We-K from banana pseudostem as foliar spray) at all growth stages with the values 75.00, 109.67 and 83.67 at 30, 60 DAT and harvest, respectively. At the same time, the treatment received only 100 per cent RDF (T2) recorded 72.33, 84.00 and 65.00 leaves per plant at 30, 60 DAT and harvest, respectively. While, the lowest number of leaves per plant was observed in the T1 treatment (Absolute control) with values of 63.33, 67.00 and 54.67 at 30, 60 DAT and harvest, respectively as recorded in Table 2. A similar trend was observed in leaf production, with T7 producing the highest number of leaves at harvest (83.67), followed by T6 (78.67) and T11 (74.00). The 100 per cent RDF treatment recorded lesser number of leaf (65.00) compared to the T2 treatment and the control (T1) recorded the lowest leaf count (54.67). The differences were statistically significant from 60 DAT onwards as observed by Mohammad et al. (2014) and Subramanian et al. (2005) [20] . Potassium is essential for stomatal function and chlorophyll maintenance and its sufficiency promotes active leaf growth. A general decline in the number of leaves was observed at harvest in several treatments compared to 60 DAT. This reduction may be attributed to leaf senescence and abscission associated with plant aging and reproductive transition. The extent of leaf loss was less pronounced in potassium-rich treatments (T6 and T7) suggesting that improved K nutrition may delay senescence and help maintain functional leaf area for a longer duration.

Yield and Yield Attributing characters Total number of fruits per plant

The maximum number of fruits per plant of tomato was observed with treatment T7 (100% RDF + 4% We-K from banana pseudostem as foliar spray) (34.33) which was on par with the treatment T6 (33.33 fruits plant -1 ) and significantly superior over the other treatments (Table 3). Treatment with 100 per cent RDF (T2) recorded 31.33 fruits plant -1 which was on par with T4. The lowest total number of fruits per plant (21.00) was recorded in absolute control treatment. Potassium helps maintain the balance of key hytohormones such as cytokinins, auxins and gibberellins, which are involved in flowering and fruit set (Wang et al., 2013) [21] . potassium maintains proper turgor pressure in cells, which prevents flower abortion and enhances retention. The increase in fruit number may be due to more availability of nutrient to the plants during the vegetative period through foliar spray and soil applied nutritents.

The maximum fruit diameter of (5.67 cm) and fruit weight of 70.74 g tomato was recorded in the treatment received 4 per cent We-K from banana pseudostem through foliar fertilization along with 100 per cent mineral fertilizer treatment (T7) which was on par with treatment T6 (5.62 cm and 70.54 g). The Treatment which received only RDF (T2) recorded the fruit diameter of 5.30 cm and 69.87 g fruit weight which was on par with Treatment T11 (5.40 cm), T10 (5.36 cm), T5 (5.34 cm) and T4 (5.31cm). The lowest fruit diameter (4.91 cm) and fruit weight (49.20 g) was observed with the T1 treatment as recorded in Table 3. The increase in fruit size and weight can be primarily attributed to potassium's role in cell division and expansion, which directly contributes to tissue growth. Potassium enhances turgor pressure in fruit cells by maintaining osmotic balance, thus enabling expansion during fruit filling stages (Marschner, 2012) [12] . In potassium-rich environments, sink strength of the fruits is elevated due to enhanced enzymatic activity (starch synthetase, invertase, and sucrose synthase), leading to increased accumulation of carbohydrates and organic acids within fruits (Afzal et al. 2015) [2] . Potassium also increases the efficiency of phloem loading and unloading, ensuring better translocation of photosynthates from source to sink, which results in fruit development and improved size.

Treatment received 4 per cent We-K from banana pseudostem through foliar fertilization and 100 per cent mineral fertilizer treatment (T7) recorded a higher fruit yield of 2.43 kg plant -1 which was on par with T6 (2.35 kg plant -1 ). Whereas treatment T2 (100% RDF) recorded yield of 2.19 kg plant -1 which was on par with treatments T4. The T1 (Absolute control) treatment recorded the lowest total fruit yield per plant with a value of 1.03 kg plant -1 . The maximum fruit yield of 2.43 kg plant -1 was recorded in T7, this treatment outperformed all others (Table 3) and was statistically superior, highlighting the synergistic effect of combining soil-applied K with foliar-applied organic K similar results were obtained in the works of Gopinath et al. (2016) [7] and Abro et al. (2023) [1] . The enhanced yield may be attributed to improved K availability during critical phenological stages such as flowering and fruit setting, ensuring better assimilate partitioning and sink strength of developing fruits (Jiffon and Lester, 2009) [9] . 2.01 0.25 2.48 0.15 FS -foliar spray; We-K -Water extractable Potassium; BPS -Banana pseudostem; RDF -Recommended dose of fertilizers; DATdays after transplanting; RDK -Recommended dose of potassium; RD N, P -Recommended dose of nitrogen and phosphorous; NS -Non significant Fruit Quality Parameters Lycopene content (mg 100g -1 ) The maximum lycopene content was recorded with treatment T7 (100% RDF + 4% We-K from banana pseudostem as foliar spray) with a value of 4.27 mg 100 g -1 , followed by treatment T6 (3.91 mg 100 g -1 ). The treatment T2 (100% RDF) has lycopene content to the tune of 3.33 mg 100 g -1 and the lowest lycopene content of 1.75 mg 100 g -1 in fruit was recorded with treatment T1 (Absolute control) as recorded in Table 4. Lycopene content increased progressively with higher concentrations of We-K. The maximum value of 4.27 mg 100 g⁻¹ was recorded in T7 (100% RDF + 4% We-K), which was significantly higher than all other treatments. The improvement in lycopene content can be attributed to potassium's crucial role in regulating photosynthate translocation to fruits and activating enzymes in the carotenoid biosynthetic pathway, particularly phytoene synthase, which leads to greater pigment accumulation (Dorais et al., 2008). Similar results were obtained by Irfan et al. (2015) who reported that the exogenous application of 0.6 per cent K significantly improved plant height, lycopene content, potassium, fruit weight and diameter.

TSS ( 0 Brix)

Treatment T7 (100 per cent RDF+4 per cent We-K) recorded the value of 4.77 0 Brix, which was on par with treatment T6 with a value of 4.63 0 Brix and T5 (4.5 0 Brix) as presented in Table 4. The treatment T2 (100% RDF) has TSS of 4.20 0 Brix and it was on par with treatment T11. The lowest TSS was obtained in the treatment T1 (Absolute control) to the tune of 3.50 0 Brix. TSS values also showed a significant upward trend with increasing We-K concentration. T7 recorded the highest TSS (4.77 °Brix) and RDF alone (T2) recorded 4.20 °Brix. Potassium plays a vital role in carbohydrate synthesis and translocation. As reported by Nair et al. (1970) [16] it plays an important role in the starch formation and production and translocation of sugar, especially from source leaves to sink tissues like fruits. This finding aligns with Lester et al. (2010) [11] , who reported that foliar K application significantly improved sweetness in tomato due to enhanced sugar metabolism.

Treatment received 100 per cent RDF with 4 per cent We-K from banana pseudostem as foliar spray(T7) 33.68 mg 100g -1 , which was significantly higher than the rest of the other treatments. This was followed by T6 treatment (29.65 mg 100 g - 1 ). The 100 per cent RDF treatment (T2) showed 25.26 mg 100 g - 1 of ascorbic acid content which was on par with treatments T10, T4 and T5. The result further noticed that the lowest ascorbic acid of 17.89 mg 100 g -1 in fruit was recorded in the treatment T1 (Absolute control) as presented in Table 4. Ascorbic acid content was significantly influenced by We-K foliar spray, with T7 showing the highest value of 33.68 mg 100 g⁻¹ which is higher than RDF alone. Potassium enhances the activity of enzymes involved in ascorbic acid biosynthesis (such as L-galactono-1,4-lactone dehydrogenase) and reduces its oxidative degradation, thereby increasing fruit vitamin C levels (Kanai et al., 2007) [10] . Moreover, foliar K ensures nutrient availability at later stages of fruit ripening, when ascorbic acid content typically peaks. Similar observations were reported by Dorais et al. (2001) who found that foliar K sprays enhanced antioxidant content in various horticultural crops.

Fruit shelf life was longest in T7 (19.50 days), significantly higher than the 100 per cent RDF (18.33) and control (15.50 days) (Table 4). Potassium plays a key role in maintaining cell membrane stability, reducing respiration rate and delaying senescence, which collectively improve storability (Cakmak, 2005) [4] . The higher shelf life in T6 and T7 may also be related to the improved firmness from enhanced pectin cross-linking as observed in K-sufficient tomato fruits (Kanai et al., 2007) [10] . Treatments with partial soil K substitution (T8-T11) recorded comparatively lower shelf life, possibly due to insufficient basal K supply affecting overall physiological balance. Subbaiah et al. (2015) [19] reported that foliar application of potassium-rich biomass extract improved the physiological efficiency of tomato plants under organic farming conditions.

Overall Treatment Performance

Treatment ranking clearly indicated the superiority of banana pseudostem extracts foliar spray over the RDF and control. This suggests that water-extractable potassium from banana pseudostem is a readily available, sustainable and effective source of K nutrition when applied as foliar spray. The findings align with earlier reports on the high solubility of K in banana pseudostem and its potential as a fertilizer source (Dayod and Abat, 2016) [5] . The improvements observed can be explained through potassium's multifaceted role in plant metabolism, translocation of assimilates and regulation of enzymatic processes (Jackson and Volk, 1968) [8] that directly affect biochemical quality traits in tomato.

Conclusion

The study demonstrated that foliar application of waterextractable potassium derived from organic residues, particularly banana pseudostem applied as foliar spray at desirable concentration in combination with recommended fertilizer dose NPK will significantly improve growth, yield and fruit quality parameters of tomato. Among the treatments, T7 proved most effective, followed consistently outperforming the recommended dose of fertilizer (RDF) control. With better assimilate translocation and improved biochemical processes contributed to taller plants and more branches and leaves with higher yield and superior quality attributes such as TSS, lycopene, and ascorbic acid. This confirms the vital role of foliar K in enhancing physiological efficiency and ensuring better source-sink balance during reproductive growth and suggest that banana pseudostem extract can serve as a sustainable, low-cost alternative to chemical K fertilizers for tomato cultivation, thereby supporting eco-friendly and resource-efficient horticultural production systems.

Acknowledgement

AcknowledgementThe authors express their gratitude to the Department of Soil Science, College of Agriculture Navile, Keladi Shivappa Nayaka University of Agricultural and Horticultural Sciences, Shivamogga for providing the necessary facilities and support to carry out this study.

References

1. Abro SA, Abro MA, Kapri JH, Ahmed N, Ali H, Parveen S, Khoso A. Extraction and utilization of banana pseudostem sap as organic liquid bio-fertilizer on onion (Allium cepa L.). Pak J Biotechnol. 2023;20(2):275-280.
2. Afzal I, Hussain B, Basra SMA, Ullah SH, Shakeel Q, Kamran M. Foliar application of potassium improves fruit quality and yield of tomato plants. Acta Sci Pol Hortorum Cultus. 2015;14(1):3-13.
3. Amjad M, Akhtar J, Haq MAU, Imran S, Jacobsen SE. Soil and foliar application of potassium enhances fruit yield and quality of tomato under salinity. Turk J Biol. 2014;38(2):208-218.
4. Cakmak I. The role of potassium in alleviating detrimental effects of abiotic stresses in plants. J Plant Nutr Soil Sci. 2005;168(4):521-530.
5. Dayod M, Abat M. The tender core of young banana pseudostem could be nutritionally better than the banana fruit. In: Int Symp Trop Temp Hortic (ISTTH2016). 2016;1205:225-234.
6. Fish WW, Perkins-Veazie P, Collins JK. A quantitative assay for lycopene that utilizes reduced volumes of organic solvents. J Food Compos Anal. 2002;15(3):309-317.
7. Gopinath KA, Sreenivasa MN, Singh PK. Evaluation of organic liquid foliar fertilizers in tomato. Indian J Hortic. 2016;73(3):416-421.
8. Jackson WA, Volk RJ. Role of potassium in photosynthesis and respiration. In: The role of potassium in agriculture. Madison (WI): ASA-CSSA-SSSA; 1968. p. 109-145.
9. Jifon JL, Lester GE. Foliar potassium fertilization improves fruit quality of field-grown muskmelon on calcareous soils in South Texas. J Sci Food Agric. 2009;89(14):2452-2460.
10. Kanai S, Ohkura K, Adu-Gyamfi JJ, Mohapatra PK, Nguyen NT, Saneoka H, Fujita K. Depression of sink activity precedes the inhibition of biomass production in tomato plants subjected to potassium deficiency stress. J Exp Bot. 2007;58(11):2917-2928.
11. Lester GE, Jifon JL, Makus DJ. Impact of potassium nutrition on postharvest fruit quality: melon (Cucumis melo L.) case study. Plant Soil. 2010;335(1):117-131.
12. Marschner H, editor. Marschner's mineral nutrition of higher plants. 3 rd ed. London: Academic Press; 2011.
13. Mengel K, Kirkby EA. Principles of plant nutrition. 5th ed. Dordrecht: Springer Science & Business Media; 2001.
14. Mercy S, Mubsira BS, Jenifer I. Application of different fruit peels formulations as a natural fertilizer for plant growth. Int J Sci Technol Res. 2014;3(1):300-307.
15. Ilyas M, Ayub G, Hussain Z, Ahmad M, Bibi B, Rashid A, et al. Response of tomato to different levels of calcium and magnesium concentration. Pak J Agric Sci. 2014;51(4):987992.
16. Nair KS, Ramaswamy PP, Perumal R. Nutritional factors affecting nitrogen fixation in groundnut. Madras Agric J. 1970;57(8):307-310.
17. Reddy DD, Veeranki K. Simple and inexpensive water extraction method for assaying potassium concentration in tobacco plant tissue. Commun Soil Sci Plant Anal. 2013;44(5):962-970.
18. Shukla P, Jayswal S, Patel R, Maitreya B. Foliar spray application of selected organic fertilizers and their effects on selected plants. Int J Environ Agric Biotechnol. 2021;8(2):647-656.
19. Subbaiah G, Mahalakshmi M, Reddy KS. Effect of liquid potassium from biomass extracts on growth and quality of tomato. Int J Agric Sci Res. 2015;5(4):67-72.
20. Subramanian S, Thamburaj S, Muthulakshmi P. Influence of foliar application of potassium on growth and yield of chilli. Veg Sci. 2005;32(2):188-189
21. Wang M, Zheng Q, Shen Q, Guo S. The critical role of potassium in plant stress response. Int J Mol Sci. 2013;14(4):7370-7390.