Integrated nutrient management’s impact on Dahlia cultivation (Dahlia variabilis L.) cv. Zail Singh

Kaushik, K., Kumar, M., Kumar, R., Gheware, K. M., Shukla, D., Tomar, R., Vedwan, A., Srivastava, V., Sharma, M., and Chahar, S. (2025). "Integrated nutrient management’s impact on Dahlia cultivation (Dahlia variabilis L.) cv. Zail Singh," BioResources 20(4), 10028–10050.

Abstract

The experiment was conducted during the winter season of 2022–2023 at the Horticultural Research Centre, SVPUA&T, Meerut, to evaluate the impact of Integrated Nutrient Management (INM) on Dahlia variabilis L. cv. Zail Singh using a Randomized Complete Block Design (RCBD) with 19 treatments and three replications. Significant differences (P < 0.05) were observed among treatments for vegetative growth, flowering, and soil parameters. Treatment T₁₂ (50% RDF + poultry manure + Azotobacter + VAM) recorded the maximum number of primary branches (9.75), leaf area (97.75 cm²), leaf area index (0.048), chlorophyll index 55.45 mg/m²), and nitrogen index (26.62 mg/m²), showing approximately 81% improvement over the control (100% RDF). T₁₇ (25% RDF + vermicompost + Azospirillium + VAM) produced the largest stem diameter (14.30 mm), stalk diameter (10.30 mm), and flower diameter (18.00 cm). T₅ enabled early color break (6.58 days), T10 extended vase life (7.10 days), while T₆ and T₇ significantly enhanced soil nutrient availability, and T₁₄–T₁₅ improved soil organic carbon, EC, and pH. In contrast, the control (T₁) consistently recorded the lowest values across traits. These findings demonstrated that integrating organic manures and bio-inoculants with reduced levels of chemical fertilizers significantly enhanced crop performance and soil health, offering a sustainable strategy for ornamental horticulture.

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**Integrated Nutrient Management’s Impact on Dahlia Cultivation (Dahlia variabilis L.) cv. Zail Singh**

Krishna Kaushik, ^a,* Mukesh Kumar ,^a Ravi Kumar ,^aKedar Mahadev Gheware ,^b Devanshu Shukla ,^a Rohan Tomar,^a Abhay Vedwan ,^a Vishal Srivastava,^a Mahima Sharma,^a and Shivani Chahar ^a

DOI: 10.15376/biores.20.4.10028-10050

Keywords: Integrated nutrient management (INM); Vermicompost (VC); Poultry manure (PM); Farm yard manure (FYM); Recommended dose of fertilizer (RDF)

Contact Information: a: Department of Floriculture and Landscaping Architecture, College of Horticulture, Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, 250110, India; b: Division of Floriculture and Landscaping, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu;*Corresponding author: kaushikkaali007@gmail.com

Graphical Abstract

INTRODUCTION

Dahlias, one of the most popular half-hardy tuberous rooted perennials, are valued for their beautiful blooms and landscaping value. Mexico’s national flower is native to the Asteraceae family. According to Darlington (1973), the wild species from which the octoploid (8X) Dahlia variabilis (n = 64) is believed to have arisen are tetraploids with 32 chromosomes. The main producer of tuberous-rooted dahlias is the Netherlands (Bhattacharjee et al. 2019). It is noteworthy that Holland annually exports 50 million dahlia tubers to international markets and the Netherlands floriculture market size is estimated at $4.89 billion US in 2024, growing at a compound annual growth rate (CAGR) of 4.70% during the forecast period 2024 to 2029 (Dutch flower Industry Report 2023, 2024). Dahlias are used as both cut flowers and loose flowers. The trade appreciation of the dahlia crop has been exploited only in certain countries (Milian 2024). The Netherlands is a major producer of tuberous-rooted Dahlias, supplying 50 million tubers annually to international markets (Singh et al. 2023; Kumar et al. 2024). Dahlias are grown for ornamental purposes due to their aesthetic characteristics, which are crucial for the ornamental industry. Improved quality in these aspects requires proper rooting and vegetative growth, ensuring water, gas exchange, nutrient supply, and plant support (Shukla et al. 2023).

Successful cultivation and production of quality dahlia flowers are influenced by various factors, such as rooting media, nutrient management during crop cultivation, and environmental factors. Nutrient management is a major factor, and it plays a vital role in producing quality yield while improving soil health (Wararkar et al. 2020). In modern horticulture, integrated nutrient management (INM) is a comprehensive and advanced approach intended to meet the complex nutritional requirements of crops (Kushwah et al. 2024). INM entails the strategic integration of several nutrition sources, such as crop residues, organic manures, inorganic or chemical fertilizers, and bio-fertilizers. The aim of INM is clear to develop a sustainable and optimal nutrient supply that meets the various needs of crops at their crucial stages of growth and improving soil health (Wu and Ma 2015). Organic manures, such as farm yard manure (FYM), poultry manure (PM), and vermicompost (VC) have been widely known to restore soil health and improve soil structure (Tripathi et al. 2020; Sharma et al. 2024). Inorganic fertilizers can reduce costs for farmers and provide nutrients instantly to the plants in their initial stage (Tiemann and Douxchamps 2023). However, in the comparison of organic fertilizers, which have a longer-lasting effect on soil and plant health, inorganic fertilizers can leach into groundwater, and nutrient runoff can pass into waterways (Tiwari and Pal 2022; Kumar et al. 2024a). Bio-fertilizers, encompassing symbiotic nitrogen-fixing bacteria, phosphorous-solubilizing bacteria, as well as potassium solubilizing bacteria, offer a promising avenue for sustainable nutrient management (Samad et al. 2024).

Application of INM was also reported to be associated with improvement in plant growth (Sudhagar et al. 2019), flowering (Kaushik and Singh 2020), tubers growth (Singh et al. 2024), chlorophyll content (Tian et al. 2024), and photosynthetic rate of plant, as well as nutrient uptake, nutrient availability, and soil structure (Dróżdż et al. 2023). Rajaselvam et al. (2024) showed that the INM is effective when applied in the right combination of organic, inorganic, and bio-fertilizers. They noticed an improvement in the growth, flowering, and photosynthetic rate of tuberose (Polianthes tuberosa L.) cv. Prajwal through applying INM treatments.

Previous researchers have reported positive effects of INM on floricultural crops viz., gladiolus (Maniram et al. 2012; Kumar et al. 2014; Singh et al. 2014; Motla et al. 2022; Kaur et al. 2023), chrysanthemum (Kumar et al. 2015; Aashutosh et al. 2019), marigold (Singh et al. 2015; Garge et al. 2020), and tuberose (Tomar et al. 2024). Unlike previous studies that have mainly focused on cereals, vegetables, and a few ornamentals, research on INM in Dahlia remains very limited. To the best of the authors’ knowledge, this is the first systematic evaluation of combined organic manures, inorganic fertilizers, and bio-inoculants on the growth, flowering, and soil health of Dahlia variabilis L. cv. Zail Singh under subtropical conditions. Building on these findings, the present study was undertaken to assess whether integrating organic manures and bio-inoculants with reduced levels of chemical fertilizers could enhance vegetative growth, floral quality and soil fertility in dahlia.

EXPERIMENTAL

Materials

The present experiment was executed in the HRC, Sardar Vallabhbhai Patel University of Agriculture and Technology (SVPUA&T), Meerut during 2022-2023. D. variabilis L. cv. Zail Singh cuttings were purchased from a local plant nursery in Kolkata in November. Source of macro and micronutrients, such as FYM, VC, PM, Azotobacter, Azospirillium, Vesicular Arbuscular Mycorrhizae (VAM), urea (46% N), Single Super Phosphate (SSP) (18% P), and Muriate of Potash (MOP) (46% K), were used. These prepared inputs were collected from the store of the College of Horticulture, SVPUA&T, Meerut.

Treatment Details

The different combinations of various concentrations of inorganic fertilizers were calculated and applied to dahlia plants at distinct intervals.

Methods

The experiment was laid out within three replications of 19 treatments and a total of 57 plots. Each replication had 19 plots. There were 12 plants in each plot, out of which 5 healthy plants had been selected for measuring qualitative characteristics. There were 6 vegetative parameters, 10 flowering parameters, and 12 soil parameters that were measured from each treatment. In vegetative parameters, the stem diameter (SD) was measured through calculating the average (avg) of three values from each plant by vernier caliper in millimeters (mm); number of primary branches (No. PB) were observed by counting of primary branches present on the plant. Leaf area (LA) was calculated with a leaf area meter in unit mm²; chlorophyll index per leaves (Ch/L) was measured by using a soil plant analysis development (SPAD) meter by measuring five leaves from each plant, in which three readings were taken from each leaf, and the mean value was calculated which represent the chlorophyll content of the plant. Nitrogen content in leaves (N/L) were calculated by chlorophyll content in leaves (SPAD value) multiplied by constant value and expressed in mg/m².

(1)

The total leaf area index (LAI) was calculated through dividing leaf area by the respective ground area from each treatment in cm.

(2)

In the flowering parameter, the number of days taken for the appearance of the first flower bud (DAFFB) was recorded. The days were counted from the date of planting until the first floral bud appeared. For each treatment, the values were then averaged across the selected plants. Days taken to color break (DTCB) were recorded from each plant of all treatments from the appearance of floral buds to color break and then the average was calculated. Days taken to first flower opening (DAFFO) were counted from the planting date of selected plants in each treatment to first flower opening in each treatment. Days taken to flower opening (DAFO) were counted from color break stage to full opening of flower and then the mean value was calculated. Duration of flowering (DOF) values were recorded from the time of the first flower opening until the last flower opening in each treatment and the mean value was calculated. Stalk diameter (StD) values were measured by calculating the average (avg) of three values from each plant by vernier caliper in millimeters (mm); fresh weight of flower (FWF) were taken from each plant by randomly selecting five flowers and the avg weight of the flower was calculated in gram (gm) by digital balancer; dry weight of flower (DWF) were measured in gram through weighing balance machine in gram after full drying of selected flowers for fresh weight at room temperature; flower diameter (FD) values were taken by scale in cm²using the method of the avg of the east to west and north to south length of the selected flowers; vase life (VL) values of selected flowers were counted in days from placing the fully open flower into the vase to the stage when the flowers started to lose their aesthetic value.

Each of the soil parameters was estimated from soil samples collected from a soil depth of 0 to 15 cm prior to the start of the experiment and after the termination of the experiment. Soil samples from furrow slices were collected to evaluate the effect of organic and inorganic inputs on pH, electrical conductivity, organic carbon, and the availability of nitrogen, phosphorus, and potassium. Collected soil samples were air-dried in the shade and ground using a pestle and mortar, passed through a 2-mm sieve, and stored in polythene bags for further analysis as per the method given below.

The pH of soil at planting time (pHP) and pH of soil after harvesting (pHH) were estimated by the 1:2 (soil water suspension) method given by Jackson (1973). The procedure was to measure 20 g of soil in a 50-mL beaker, add 40 mL of distilled water, and stir the mixture at least four times within a period of half an hour. This is required for the soil and water to reach an equilibrium state. After half an hour again, the soil suspension was stirred and the pH was measured with a pH meter.

The EC of soil was estimated by taking a soil sample of 20 g and pouring it into a 50-mL beaker. Then 40 mL of distilled water was added to the beaker followed by stirring four times within a period of half an hour. Again, stirring of soil suspension was done after half an hour. Then electric conductivity was measured on an electric conductivity meter (dS/m).

The available nitrogen in soil was estimated by taken 5 gm soil sample for micro-Kjeldahl’s method given by Subbiah and Asija (1956) and calculated in ppm through given formula. The volume of acid used is equivalent to the amount of ammonia and also amount of nitrogen present in soil sample,

(3)

where V₁ is the volume of acid used for the sample (mL), V₂ is the volume of acid for blank (mL), N is the normality of acid, 14 is the atomic weight of nitrogen, and W is the weight of soil sample (gm).

Then the ppm value of available nitrogen from the sample was converted into kilogram/hectare (Kg/ha) through the following conversion formula:

(4)

Available phosphorus was determined using Olsen’s method (Olsen et al. 1954). The intensity of the color was determined by a visible spectrophotometer at a wavelength of 660 nm using a red filter. The readings were then located in the standard curve and calculated in ppm through the given formula,

(5)

where C is the concentration of P from colorimeter reading (mg/L), V_e is the volume of extractant (mL), and W is the weight of soil (gm). The ppm value of available phosphorus from sample is converting into kg/ha through the conversion formula:

(6)

Available potassium was extracted with neutral normal ammonium acetate as per the procedure given by Merwin and Peech (1951). The sample solution to the atomizer of the flame photometer, and the reading was indicated by the galvanometer needle. Then, with the help of the standard curve, the amount of available potassium in the soil under test was calculated,

(7)

where C is the concentration of K from flame photometer, V_e is the volume of extractant (mL), and W is the weight of soil (gm). The ppm value of available K from sample is then converted into kg/ha through the conversion formula:

(8)

The organic carbon percent was estimated by following the rapid titration method given by Walkely and Black (1934).

Statistical Analysis

The experiment was laid out according to a randomized complete block design (RCBD) with three replications and 19 treatments, making a total population of 285 plants in the experiment. The replications served as the blocking factor, which were arranged to minimize the influence of field heterogeneity, particularly soil fertility gradients across the experimental site. This ensured that treatment effects could be evaluated more accurately and with improved reliability. Collected data for growth, flowering, and soil health traits were taken from five selected plants from each treatment and analyzed using analysis of variance (ANOVA) to check any differences between the means (Gomez and Gomez 1984). Significant means were compared by using Tukey’s honestly significant difference (HSD) test at a 5% probability level (Nanda et al. 2021) using Statistical Package for the Social Sciences (SPSS) software. As the study was not structured as a factorial design but rather as fixed INM treatment packages, main and interaction effects (organic source × fertilizer level) could not be separated; therefore, single-factor ANOVA was used.

RESULTS AND DISCUSSION

Effect of Integrated Nutrient Management on Vegetative Growth Characteristics of Dahlia

Significant variation (P <0.05) was observed among the treatments for all vegetative growth parameters of dahlia (Table 1).

Stem Diameter (SD) mm

The plants treated with treatment T₁₇ (25% RDF + 2.5 ton/ha VC + 6 Kg/ha Azospirillium + 4.50 L/ha VAM) showed the best performance in terms of stem diameter (14.30 mm), followed by T₁₆ > T₄ > T₂, respectively. However, treatment T₇ (75% RDF + 0.41 tons/ha PM + 2 Kg/ha Azospirillium + 4.50 L/ha VAM) showed the lowest stem diameter (5.87 mm). Treatment T₁₇ achieved 25% RDF with the combination of VC, Azospirillium, and VAM, which increased microbial activity in the soil and enhanced macro and micro nutrients in the soil. These nutrients are crucial for overall growth and development, VC and Azospirillium produces many useful substances such as macro and micro nutrients, PGRs, and enzymes like lipases, chitinases, etc. (Arancon et al. 2020). The VAM enhances the ability of plants to absorb phosphorus from soil, also increases phyto-availability of micronutrients, and enhances absorption of trace elements (boron and molybdenum); the VAM is able to mobilize organically bound nitrogen (Abbasi et al. 2015), which enlarged the stem diameter. Similar results were also recorded by Verma et al. (2017), whereas chemical fertilizer with organic manure increases stem diameter in cape gooseberry.

Number of Primary Branches per Plant (No. PB)

The maximum number of primary branches (9.75) was observed in T₁₂ (50% RDF + 0.82 ton/ha PM + 4 Kg/ha Azotobacter + 4.50 L/ha VAM), which was statically superior to most treatments, followed by T₁₃ > T₁₆ > T₁₇. The lowest number of primary branches (2.42) was recorded in the control treatment (T₁). In this study, the number of primary braches per plant were significantly increased with the combination of 50% inorganic fertilizer, 0.82 ton/ha PM, 4 Kg/ha Azotobacter, and 4.50 L/ha VAM, thereby promoting macro, micro nutrients availability (Sumita et al. 2017), which is essential for protein and protoplasm synthesis in the plant (Rajaselvam et al. 2024). Additionally, microbial inoculants such as VAM and Azotobacter enhance cytokinin synthesis, further boosting plant growth (Gangwar et al. 2017; Shaifali et al. 2024). The use of reduced inorganic fertilizers supports cell division and carbohydrate accumulation, improving vegetative growth (Singh 2018). Similar findings have been also reported in other crops by Verma et al. 2017 whereas 50% NPK with 50% organic manure increase the number of branches per plant in cape gooseberry. Chirukuri et al. (2023) also observed similar results in marigold flower.

Leaf area (LA) and Leaf area index (LAI) (mm²)

Treatment T₁₂ with the combination of 50% RDF, 0.82 ton/ha PM, 4 Kg/ha Azotobacter, and 4.50 L/ha VAM was recorded to outperform other treatments in terms of LA (97.75 mm²) and LAI (0.048 mm²), followed by T₁₃ > T₁₈ > T₁₉, respectively. In contrast, the control (T₁) showed poor performance in LA and LAI (75.32 mm² and 0.037mm², respectively).

The combination of T₁₂ had 50% RDF, PM, Azotobacter, and VAM, which has high microbial activity due to presence of fungi, bacteria. These microbes are reported to produce plant growth regulators (PGRs) (Mattos Abreu et al. 2021; Kaur et al. 2023a) and abscisic acid, which affects LA and LAI, which may be due to the cell division caused by cytokinins (Gangwar et al. 2017; Shaifali et al. 2024). Similarly, Verma et al. (2017) also observed optimum leaf width and length in cape gooseberry due to the application of 50% NPK with 50% organic manure. In spinach, Adison et al. (2024) also recorded the best results in leaf area per plant due to the effect of Azotobacter with organic manure.

Chlorophyll index (Ch/L) and Nitrogen Index (N/L) per Leaf (mg/m²)

The plants treated with treatment T₁₂ (50% RDF + 0.82 ton/ha PM + 4 Kg/ha Azotobacter + 4.50 L/ha VAM) showed the best performance in terms of chlorophyll index (55.45 mg/m²) and nitrogen index (26.62 mg/m²) per leaf, followed by T₁₃ > T₉ > T₁₇, respectively. However, treatment T₁ with 100% RDF was found to have the lowest chlorophyll index and nitrogen index in the leaf (45.00 mg/ha and 21.60 mg/ha, respectively).

Treatment T₁₂ reached 50% RDF with the combination of PM, Azotobacter, and VAM, which increases microbial activity in the soil and enhances macro and micro nutrients in the soil. Nitrogen (N) is a constituent of protein (Sumita et al. 2017), while phosphorus is known to promote cell division as well as photosynthetic activity (Rajaselvam et al. 2024), which plays a vital role in enhancing chlorophyll in leaves and as well as nitrogen in leaves. Similar results were also recorded by Iqbal et al. (2021), whereas chemical fertilizer with PM increased chlorophyll content in the leaves of the paddy crop.

Effect of Integrated Nutrient Management on Flowering Characteristics of Dahlia

The application of different combinations of organic, inorganic, and bio-fertilizers significantly (P <0.05) influenced all flowering parameters of dahlia (D. variabilis L.) examined in the present study (Table 2).

Days Taken to Appearance of First Flower Bud (DAFFB)

The earliest bud initiation (52.00 days) was recorded in T₁₂(50% RDF + 0.82 ton/ha PM + 4 kg/ha Azotobacter + 4.50 L/ha VAM), followed closely by T₁₃ > T₈ > T₄, all of which were significantly earlier than the control (T₁). In contrast, treatments, T₁₈ recorded the longest time to bud appearance (82.00 days).

Table 1. Effect of Integrated Nutrient Management on Vegetative Growth of Dahlia

The current study examined treatment T₁₂ with 50% RDF + 0.82 ton/ha PM + 4 Kg/ha Azotobacter + 4.50 L/ha VAM influenced the DAFFB due to balanced the carbon-nitrogen ratio (C: N Ratio) and enhanced nutrient availability to the plant (Indhumathi et al. 2023), which is essential for bud initiation and flower development (Adhikari et al. 2020). Similar results were also observed by Ayoub and Masoodi (2023) on the hyacinth crop, where the minimum number of days taken to bud appearance was found in the treatment that was treated with a combination of RDF, organic manure, and bio-fertilisers. Indhumathi et al. (2023) also reported similar results in the Gaillardia flower crop with the combination of RDF, organic manure, and bio-fertilizer.

Days Taken to Color Break (DTCB)

The maximum reduction in days to color break (5.33 days) was observed in treatment T₅ (75% RDF + 0.83 ton/ha VC + 2 Kg/ha Azospirillium + 4.50 L/ha VAM), followed by treatment T₁ > T₁₂ > T₆, which were statistically superior. However, treatment T₁₇ (25% RDF + 2.5 ton/ha VC + 6 Kg/ha Azospirillium + 4.50 L/ha VAM) was recorded with the lowest reduction in days to color break (6.75 days). From a physiological point of view, balanced N, P, and K is a prerequisite for bud initiation and its development (Adhikari et al. 2020). These elements are crucial for floral primordial production (Choudhary et al. 2021). Phytohormones from Azotobacter and VAM promote cell division and expansion, accelerating blooming (Abdel-Ghany et al. 2019; Ayoub and Masoodi 2023; Paul et al. 2024). These results are in close conformity with the findings of Ayoub and Masoodi 2023 on the hyacinth flower crop.

Days Taken to First Flower Opening (DAFFO) and Days Taken to Flower Opening (DAFO)

Treatments T₁₂ (50% RDF + 0.82 ton/ha PM + 4 Kg/ha Azotobacter + 4.50 L/ha VAM), recorded the earliest first flower opening (62.17 days), followed by treatment T₁₃ > T₈> T₄, which were significantly earlier than T₁ (93.92 days). In contrast, taken maximum days for first flower opening was counted in treatment T₁.

In terms of DAFO, T₁₂ (50% RDF + 0.82 ton/ha PM + 4 Kg/ha Azotobacter + 4.50 L/ha VAM) and T₅ (75% RDF + 0.83 ton/ha VC + 2 Kg/ha Azospirillium + 4.50 L/ha VAM), both treatments taken same days to flower opening (9.00 days), followed by T₁₃ > T₉ > T₆> T₂, while the treatment T₁ (control) required the longest duration for flower opening (12.42 days).

In the present investigation, treatment T₁₂ (50% RDF + 0.82 ton/ha PM + 4 Kg/ha Azotobacter + 4.50 L/ha VAM) significantly reduced the days taken to first flower opening and days taken to flower opening, primarily by optimizing the C:N ratio and enhancing nutrient bioavailability, which is essential for floral development or floral primordia initiation (Singh et al. 2015; Ahmed et al. 2023; Shah et al. 2024), while phytohormones synthesized by Azotobacter and VAM (Singh et al. 2015), such as Auxins, gibberellins and cytokinins, promote cell division and expansion, thereby accelerating flowering (Ahmed et al. 2023; Paul et al. 2024). Similar findings have been reported in hyacinth, where integrated application of RDF, organic manure, and biofertilizers resulted in earlier flower opening (Ayoub and Masoodi 2023), and in Gaillardia under combined nutrient management (Indhumathi et al. 2023)

Duration of Flowering (DOF)

The maximum duration of flowering (74.75 days) was observed in T₁₂ (50% RDF + 0.82 ton/ha PM + 4 Kg/ha Azotobacter + 4.50 L/ha VAM), which was followed by T₁₃ > T₈ > T₄, while the treatment T₁ (control) recorded the minimum days of flowering (43.17 days). Treatment T₁₂ (50% RDF + 0.82 ton/ha PM + 4 Kg/ha Azotobacter + 4.50 L/ha VAM) significantly influenced the duration of flowering. This effect is attributed to the slow mineralization of PM, which serves as a sustainable source of N, P, and K, thereby ensuring continuous nutrient supply and enhanced assimilation (James et al. 2020; Kumar et al. 2024b), which encouraged the long duration of flowering. Similar experiment results were also reported by Indhumathi et al. (2023) in the Gaillardia flower crop. Ayoub and Masoodi (2023) also recorded similar results in the hyacinth crop.

Stalk Diameter (StD) (mm)

T₁₇(25% RDF + 2.5 ton/ha VC + 6 Kg/ha Azospirillium + 4.50 L/ha VAM) recorded the maximum stalk diameter (10.30 mm), followed by T₁₆ > T₄ > T₂, whereas the lowest stem diameter (1.87 mm) was noted in T₇ (75% RDF + 0.41 ton/ha PM + 2 kg/ha Azospirillium + 4.50 L/ha VAM). Vermicompost has high microbial activity due to presence of fungi, bacteria and actinomycetes (Prasad et al. 2018). These microbes are reported to produce plant growth regulators (PGRs) such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid (Dikr and Belete 2017). Similar results were also observed by Ayoub and Masoodi (2023) on the hyacinth crop, where the maximum stalk thickness was found in the treatment that was treated with a combination of RDF, organic manure, and bio-fertilisers.

Fresh and Dry Weight of Flowers (FWF and DWF) (gm)

The highest fresh flower weight was obtained in T₁₂ (34.60 gm), followed by T₁₃ > T₁₀ > T₇, while the T₁ control recorded the lowest (24.70 gm).

Similarly, the maximum dry flower weight was recorded in T₁₂ (3.46 gm), followed by T₁₃ > T₁₀ > T₇, whereas the treatment T₁ (control) had the lowest (2.47 gm).

The observed enhancement may be attributed to the synergistic effects of PM and Azotobacter, wherein improved nutrient availability and microbial activity promoted greater floral expansion, leading to increased flower diameter and corolla length, which consequently contributed to higher individual flower weight (Indhumathi et al. 2023). Similar results were also mentioned by Prasad et al. (2018) on dahlia crop and close conformity with the findings of Kaushik and Singh (2020) in the marigold crop.

Flower Diameter (FD) (cm²)

Maximum flower diameter (18.00 cm²) was observed in T₁₇ (25% RDF + 2.5 ton/ha VC + 6 Kg/ha Azospirillium + 4.50 L/ha VAM), followed by T₁₆ > T₁₅ > T₁₉, which were significantly larger than the T₁ (control) (11.28 cm²). These enhancement may be attributed to the effects of PM and Azotobacter, which improved nutrient availability and microbial activity, thereby promoting floral expansion and resulting in increased flower diameter and corolla length (Kaushik and Singh 2018). The experimental results are in accordance with the findings of Koli and Jayanthi (2018) in marigold crop with organic and inorganic combinations of different treatments. Prasad et al. (2018) also reported similar results in dahlia with integrated nutrient managements. Abhishek et al. (2024) also observed the effect of organic manures in the marigold crop.

Vase Life (VL)

The longest vase life (7.10 days) was observed in T₁₀ (50% RDF + 1.6 ton/ha VC + 4 Kg/ha Azotobacter + 4.50 L/ha VAM), followed by T₁₇ > T₁₁ > T₁₉, while the shortest was recorded in T₁ with 100% RDF (3.8 days).

Table 2. Effect of Integrated Nutrient Management on Flowering of Dahlia

The delay degeneration of water-conducting tissues in dahlia may be attributed to the phytohormonal activities of vermicompost and biofertilizer, which collectively contributed to prolonged floral freshness (Jha et al. 2020; Indhumathi et al. 2023). The application of biofertilizers likely extended vase life due to the higher retention of water in the cells of flowers and lower desiccation (Koli and Jayanthi 2018). These results are in close conformity with the findings of Kumar et al. (2019a) on the dahlia flower crop. Chaudhary et al. (2020) also noticed similar results in dahlia. After that, Sarkar et al. (2024) reported similar findings in chrysanthemum.

Effect of Integrated Nutrient Management on Soil Chemical Properties

Significant differences (P < 0.05) were observed among treatments for all soil chemical properties at both the planting and harvesting stages in dahlia, shown in Tables 3 and 4.

Available Nitrogen at Planting Time (ANP) and after Harvesting Time (ANH) (Kg/ha)

At planting time, the highest available nitrogen (253 kg/ha) was recorded in T₇ (75% RDF + 0.41ton/ha Poultry manure + 2Kg/ha Azospirillium + 4.50 L/ha VAM), which was statistically followed by T₆ > T₄ > T₅. However, the lowest value was found in the control T₁ (220 kg/ha).

After harvesting of the crop, T₇ (75% RDF + 0.41ton/ha Poultry manure + 2Kg/ha Azospirillium + 4.50 L/ha VAM) again showed the maximum nitrogen content (238 kg/ha), followed closely by T₆ > T₅ > T₄, while T₁ recorded the minimum (196 kg/ha) available nitrogen in soil after the harvest.

The improvement in nitrogen availability under INM treatments may be attributed to the synergistic role of organic amendments and biofertilizers, which enhance microbial activity and mineralization processes (Zhang et al. 2023; Neelima et al. 2022). Poultry manure provides a slow and sustained release of nitrogen, reducing leaching losses compared with sole inorganic fertilizers (Tomar and Saikia 2022). Furthermore, Azospirillium improves nitrogen fixation and enhances rhizosphere activity, thereby increasing N availability (Wang et al. 2020). These results are consistent with earlier studies demonstrating that INM improves soil nitrogen dynamics compared with chemical fertilization alone (Madhurya et al. 2022; Al-Shammary et al. 2024).

Available Potassium at Planting Time (AKP) and after Harvesting (AKH) (Kg/ha)

At planting, the highest available potassium (199.36 kg/ha) was observed in T₇ (75% RDF + 0.41ton/ha Poultry manure + 2Kg/ha Azospirillium + 4.50 L/ha VAM), followed by T₆ > T₅ > T₄, which were significantly superior to most other treatments. The lowest potassium value was recorded in T₁₉ (170.67 kg/ha).

After harvest, T₆ (75% RDF + 0.41 ton/ha PM + 2 Kg/ha Azotobacter + 4.50 L/ha VAM) maintained the maximum potassium level (159 kg/ha), which was followed by T₇ > T₁₂ > T₄, while the treatment T₁control recorded the minimum potassium level (133 kg/ha) after harvesting crop. The increase in potassium availability under INM treatments can be explained by the role of organic manures and biofertilizers in mobilizing nutrients, enhancing cation exchange capacity, and reducing nutrient depletion (Neelima et al. 2022; Zhang et al. 2023). This finding corroborates the observations of Tomar and Saikia (2022) and Indhumathi (2023), who reported enhanced soil K availability with integrated approaches.

Table 3. Effect of Integrated Nutrient Management on Soil Chemical Properties in Dahlia

Available Phosphorous at Planting Time (APP) and after Harvesting Time (APH) (Kg/ha)

Phosphorus availability at planting (19.36 kg/ha) was highest in T₆ (75% RDF + 0.41 ton/ha PM + 2 Kg/ha Azotobacter + 4.50 L/ha VAM), which was followed by T₅ > T₇ > T₄, significantly higher than the treatment T₁₈ (15.61 kg/ha).

After harvest, the maximum phosphorus level (15.9 kg/ha) was recorded in the treatment T₆ (75% RDF + 0.41 ton/ha PM + 2 Kg/ha Azotobacter + 4.50 L/ha VAM) and followed by T₇ > T₄> T₅, while the lowest was observed in the treatment T₁ (12.27 kg/ha).

The improvement in phosphorus status under INM treatments is attributed to the role of poultry manure and VAM in solubilizing and mobilizing phosphorus. VAM fungi act as chelating agents and produce organic acids and phosphatases, which release bound phosphorus for plant uptake (Debnath et al. 2023; Indhumathi 2023; Sinha et al. 2024). Similar phosphorus enhancement under INM practices has been documented in multiple studies (Madhurya et al. 2022; Al-Shammary et al. 2024).