Effect of sustainable nutrient management on growth and flowering of Lisianthus (Eustoma grandiflorum Shinn.) var. Rosita 3 bright blue under protected cultivation

Introduction

Floriculture is a specialized branch of horticulture concerned with the cultivation of flowering and ornamental plants for gardens, landscaping and cut flower production. It contributes significantly to beautification of surroundings and improvement of environmental conditions. In recent years, floriculture has gained importance as a commercially viable sector due to increasing demand for decorative flowers in both domestic and global markets. Lisianthus (Eustoma grandiflorum), commonly called 'Prairie Gentian' and 'Texas Blue Bell' is a member of the family Gentianaceae (2n = 36) (Halevy and Kofranek, 1984) [5] . The genus Eustoma is derived from the Greek words eu, meaning "beautiful," "good," or "well" and stoma, meaning "mouth," referring to the attractive, well-shaped flowers of the plant. It native to warm regions of Northern-South America, Southern-United States, Mexico and the Caribbean islands. It is an annual to short-lived perennial herb growing up to 80 cm in height. It possesses simple, opposite, sessile, bluish-green slightly succulent leaves and attractive bell-shaped flowers borne singly or in terminal panicles on long pedicels. The flowers occur in shades of purple, lavender, pink and white. The plant bears 5-6 stamens with yellow linear anthers, a slender style with a bilobed stigma and produces ellipsoid, two-valved capsules containing numerous minute, reticulate seeds. It grows best under a moderate climate with temperatures ranging from 16-24 °C and a light intensity of 4,000-6,000 foot-candles. It is commercially propagated through seeds and healthy seedlings with four to five pairs of true leaves are transplanted to the main field or protected cultivation structure for optimum establishment and growth. Lisianthus is a heavy-feeding crop requiring relatively high levels of nitrogen and potassium for optimum vegetative growth and flower quality. Fertigation with nitrate-based nitrogen and adequate calcium supplementation is recommended to ensure balanced growth and to prevent physiological disorders such as tip burn, bud abortion and weak stems. Fertilizer application is generally reduced or discontinued after visible bud initiation to improve flower development and quality. Sustainable nutrient management has emerged as an important approach in protected floriculture for enhancing crop productivity while reducing dependence on chemical fertilizers and maintaining soil health. Integration of inorganic fertilizers with beneficial biofertilizers improves nutrient availability, enhances nutrient use efficiency and promotes sustainable flower production. In Lisianthus, appropriate nutrient management plays a vital role in regulating vegetative growth and flowering under protected cultivation. Therefore, the present investigation entitled "Studies on Sustainable Nutrient Management for Growth, Flowering, Yield and Quality of Lisianthus (Eustoma grandiflorum) under Protected Cultivation" was undertaken with the following objectives: 1. To study the effect of sustainable nutrient management for growth of Lisianthus under protected cultivation. 2. To study the effect of sustainable nutrient management for flowering of Lisianthus under protected cultivation.

Materials and Methods

The Seedlings were transplanted at a spacing of 10 × 10 cm, accommodating 100 plants in each plot of 1.0 × 1.0 m² The recommended fertilizer dose for lisianthus was 15 g N, 18 g P₂O₅ and 18 g K₂O m⁻², supplied through urea, single superphosphate (SSP) and muriate of potash (MOP), respectively. The fertilizer quantities for the 70 and 80 percent RDF treatments were adjusted proportionately. During bed preparation, the entire dose of phosphorus and potassium along with half of the recommended nitrogen was applied as a basal application. The remaining half of the nitrogen was top-dressed at 30 days after transplanting (DAT). In addition to the basal fertilizer application, foliar nutrition was provided through water-soluble fertilizers, namely 19:19:19 (4 g L⁻¹), calcium nitrate (3 g L⁻¹) and micronutrients (0.5%), which were sprayed twice a week starting from 30 DAT. Biofertilizers, namely Azotobacter chroococcum, phosphate-solubilizing bacteria (PSB; Bacillus megaterium) and potassium-solubilizing bacteria (KSB; Frateuria aurantia), were applied at 2 g plant⁻¹ as per the treatments at the time of planting. In addition, mycorrhiza and Trichoderma were applied uniformly at 2 kg ha⁻¹ in all treatments except control.

The observations were recorded from five randomly selected and tagged plants at appropriate stages of crop growth and were statistically analysed for growth and flowering parameters like plant height, spread of plant height, plant spread, internodal length, stem girth, leaf area, number of leaves, number of branches at peak growth stage, days taken for flower bud initiation, flower opening, 50 percent flowering, flower stalk harvesting and duration of flowering.

Results and Discussion

Growth parameters

The data presented in [18,12] . This enhanced nitrogen availability promotes chlorophyll synthesis, protein formation and nucleic acid metabolism, resulting in increased plant height and vigorous vegetative growth, as also reported by Kumar et al. (2019) [10] in chrysanthemum, Verma et al. (2023) [17] in Chine aster and Kumari et al.

(2024) [11] in lisianthus. Phosphate-solubilizing bacteria (PSB) convert insoluble phosphorus into plant-available forms through the secretion of organic acids and phosphatase enzymes, thereby improving phosphorus uptake required for ATP synthesis, energy transfer, root development and rapid cell division (Richardson et al., 2009) [12] . Adequate phosphorus availability promotes continuous leaf initiation, cell expansion and canopy development, resulting in increased plant spread, internodal length and leaf area. Similar findings were reported by Singh et al. (2019) [16] in marigold and Kumari et al. (2024) [11] in lisianthus. Potassium-solubilizing bacteria (KSB) increase potassium availability by solubilizing mineral-bound potassium through the production of organic acids (Sheng and He, 2006) [15] . Potassium plays a crucial role in enzyme activation, stomatal regulation, carbohydrate translocation, osmotic adjustment and maintenance of cellular turgor, thereby enhancing stem girth, mechanical strength and overall plant vigour. Improved potassium nutrition also facilitates efficient translocation of photosynthates from source to sink, resulting in greater biomass accumulation and stronger flower-bearing stems, as reported by Sharma et al. (2025) [13] .

The combined action of Azotobacter, PSB and KSB improved root growth, nutrient acquisition and nutrient use efficiency, leading to enhanced chlorophyll synthesis and photosynthetic activity (Vessey, 2003) [18] . Increased leaf area improved light interception and carbon assimilation, resulting in greater dry matter production and overall plant growth. Furthermore, cytokinins produced by Azotobacter promoted axillary bud development and reduced apical dominance, leading to a significantly higher number of branches (Richardson et al., 2009) [18] . Similar improvements in vegetative growth under integrated nutrient management have also been documented by Kumar et al.

(2019) [10] in chrysanthemum, Verma et al. (2023) [17] in Chine aster, Sharma et al. (2021) [14] in alstroemeria and Kumari et al. (2024) [11] in lisianthus. Thus, the integration of 80 percent RDF with Azotobacter, PSB and KSB produced a complementary effect that enhanced vegetative growth while reducing chemical fertilizer application by 20 percent without compromising plant performance. [3] in gladiolus, Akshatha et al. (2019) [1] in gerbera, Ayoub and Masoodi (2023) [2] in hyacinth, Indhumathi et al.

Flowering parameters

(2023) [7] in gaillardia, Hadapad et al. (2024) [4] in alstroemeria, Harshavardhan et al. (2016) in carnation, Krushnaiah et al. (2018) [9] in Italian aster, Sharma et al.

(2021) [14] in alstroemeria and Kaur and Singh (2024) [8] in chrysanthemum.

Conclusion

From the present study, it can be concluded that application of 80 percent RDF along with Azotobacter, PSB and KSB (T₉) significantly improved the growth and flowering of lisianthus under protected cultivation. The integrated use of inorganic fertilizers and biofertilizers enhanced nutrient availability and promoted early flowering with superior vegetative growth. Thus, the application of 80 percent RDF along with Azotobacter, PSB and KSB reduced the requirement for inorganic fertilizer by 20 percent while maintaining superior crop performance, making it a sustainable and efficient nutrient management practice for commercial lisianthus cultivation.

References

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