Enrichment of vermicompost by using biofertilizer and its effect in Calendula (Calendula officinalis L.)

Introduction

Floriculture is an important branch of horticulture dealing with the production and management of flowering and ornamental crops. Calendula (Calendula officinalis L.) is one of the cultivated seasonal flowers and belongs to the Asteraceae family. It is a tetraploid plant with 32 chromosomes (2𝑛 = 4𝑥 = 32) (Golestani et.al., 2013) [1] . is an important seasonal flowering crop grown under winter conditions. The crop has ornamental, medicinal and commercial importance and is valued for its attractive flowers and multiple uses. Calendula has become well established as a winter-season flower in India. The flowers contain important bioactive compounds such as flavonoids, carotenoids, volatile oils, and vitamin A, and are used in pharmaceutical, cosmetic, and food industries (Ehsan et al., 2012) [2] . Vermicompost contains essential macro-and micronutrients, humic substances and beneficial microorganisms. The nutrient concentration varies according to the type of organic substrate, earthworm species and vermicomposting conditions. Generally, well-rotted vermicompost contains about 1.2-2.5% nitrogen (N), 0.9-1.7% phosphorus (P) and 1.5-2.5% potassium (K). Application of vermicompost improves soil structure, aeration, porosity, water-holding capacity and nutrient availability, and stimulates microbial activity in the soil. Biofertilizers contain beneficial microorganisms capable of improving nutrient availability. Azotobacter and Azospirillum are associated with biological nitrogen fixation and plant growth promotion, while phosphate-solubilizing bacteria can improve phosphorus availability. The combined use of these microorganisms with vermicompost may provide complementary effects on nutrient availability and plant growth. Biofertilizers represent an important strategy for sustaining soil fertility and crop yield over the years. Utilizing fertilizers, manure, and bio-fertilizers together not only improves soil health but also enhances crop growth and output (Sowmya et al., 2017) [3] . the present investigation was undertaken to evaluate different combinations of biofertilizer-enriched vermicompost for improving growth, flowering and root development in calendula under the agro-climatic conditions of Raipur, Chhattisgarh.

Materials and methods

The field experiment was conducted during the Rabi season of 2025-26 at the Horticultural Research cum Instructional Farm, Department of Floriculture and Landscaping, College of Agriculture, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh. The experimental site is situated at an elevation of approxi mately 289.56 m above mean sea level and falls under the dry sub-humid agro-climatic zone. The experiment was laid out in a Randomized Block Design (RBD) with three replications and eight treatments, comprising T 0: Control; T 1: vermicompost enriched with Azotobacter @ 5%; T 2: vermicompost enriched with Azospirillum @ 5%; T 3: vermicompost enriched with PSB @ 5%; T 4: vermicompost enriched with Azotobacter @ 5% + Azospirillum @ 5%; T 5: vermicompost enriched with Azotobacter @ 5% + PSB @ 5%; T 6: vermicompost enriched with Azospirillum @ 5% + PSB @ 5%; and T 7: vermicompost enriched with Azotobacter @ 5% + Azospirillum @ 5% + PSB @ 5%. For preparation of enriched vermicompost, welldecomposed vermicompost was weighed at 720 g per experimental plot and spread uniformly on a clean polyethylene sheet. Biofertilizer cultures were applied according to the respective treatment combinations at the rate of 1 L per 100 kg vermicompost. The cultures were diluted with water and sprinkled uniformly over the vermicompost, followed by thorough mixing. The material was then covered with a moist jute bag for approximately 1-1.5 weeks under suitable moisture conditions. The enriched vermicompost was subsequently applied uniformly to the respective plots at the time of transplanting. The experimental field was brought to fine tilth through repeated ploughing and leveling. Urea @ 174 kg ha -1 , muriate of potash @ 50 kg ha -1 and single super phosphate @ 188 kg ha

Result and discussion

Vegetative parameter

Plant height :-Plant height increased progressively with crop age. T 7 recorded 18.73, 39.10 and 49.93 cm at 30, 60 and 90 DAT, respectively, whereas T 0 recorded 12.20, 25.86 and 31.50 cm. The higher growth observed under T 7 may be attributed to the combined effects of Azotobacter, Azospirillum and PSB on nutrient availability and uptake. The application of biofertilizers along with organic growing media improved plant height in calendula, which may be attributed to better nutrient availability and enhanced plant growth. The present findings are in close agreement with Jogi et al. (2022) [4] (Kaushik et al.) [5] , (Verma et al.) [6] , Thakur et al. (2016) [7] Number of leaves :-The number of leaves increased with crop age. T 7 recorded 40.00, 145.43 and 192.00 leaves plant -1 at 30, 60 and 90 DAT, respectively. The control recorded 31.10, 115.50 and 131.66 leaves plant -1 . The observed response may be associated with improved nutrient availability particularly nitrogen and phosphorus, and enhanced microbial activity. The application of biofertilizers along with organic growing media increased the number of leaves in calendula. This improvement may be attributed to better nutrient availability and enhanced vegetative growth due to the combined application of Azotobacter, Azospirillum and PSB. The present findings are in close agreement with Thakur et al. (2016) [7] , Jogi et al. (2022) [4] , (Kaushik et al.) [5] , Plant spread :-At 90 DAT, T 7 recorded 39.30 cm N-S spread, 39.86 cm E-W spread. The application of biofertilizers and organic growing media resulted in greater plant spread in calendula, indicating better vegetative development under improved nutrient conditions. The present findings are in close agreement with Jogi et al. (2022) [4] , Thakur et al. (2016) [7] , (Verma et al.) [6] . Stem diameter :-Stem diameter showed an increasing trend with treatment application, and the maximum stem diameter (16.33 mm) was recorded under T 7 at 90 DAT. The application of biofertilizers along with organic growing media improved stem diameter in calendula, which may be attributed to better nutrient availability and plant growth promotion. Lower stem diameter under less effective treatments may be due to comparatively poor nutrient availability. The present findings are in close agreement with Thakur et al. (2016) [7] , Jogi et al. (2022) [4] . Fresh weight of shoot ;-T 7 recorded the maximum fresh shoot weight (300.40 g) compared with 231.66 under T 0 . Higher shoot biomass under T 7 may be attributed to improved nutrient availability and enhanced plant growth due to the application of biofertilizers. The application of biofertilizers along with organic growing media increased fresh shoot weight in calendula, indicating improved vegetative growth and biomass accumulation. The present findings are in close agreement with Thakur et al. (2016) [7] , Hoseini-Mazinani and Hadipour (2014) [8] , and Mehdi et al. (2022) [9] . Dry weight of shoot ;-The maximum dry shoot weight (99.00 g) was recorded under T 7 , whereas the minimum (78.33 g) was observed under T 0 . The higher dry biomass under T 7 may be due to better nutrient availability and enhanced plant growth resulting from biofertilizer application. The present findings are in close agreement with Mehar et al. (2022) [10] , Thakur et al. (2016) [7] , Mehar et al. (2022) [10] , and Shaabani et al. (2022) [11] .

Flowering parameter

50% flower appearance:-The earliest 50% flowering was recorded under T 7 (51.66 days). Suitable nutrient management and biofertilizer application influenced the time required to attain 50% flowering in calendula. The present findings are in close agreement with Thakur et al. (2016) [7] , Jogi et al. (2022) [5] , Kumar and Singh (2013) [12] and Pushparaj and Tamrakar (2025) [13] . Flower diameter :-T 7 recorded the maximum flower diameter (6.63 cm), whereas T 0 recorded the minimum flower diameter (3.76 cm). The greater flower diameter under T 7 may be associated with better root development, as increased root length can enhance nutrient and water uptake, thereby promoting flower development and diameter. The present findings are in close agreement with Hoseini-Mazinani and Hadipour (2014) [8] , while similar findings were reported by Jogi et al. (2022) [4] , Mehdi et al. (2022) [9] , and Pushparaj and Tamrakar (2025) [13] . Average flower weight:-T 7 recorded the maximum average flower weight (3.66 g) compared with 1.90 g under T 0 . The use of biofertilizers and suitable nutrient management increased flower weight in calendula, which may be attributed to improved nutrient availability and better flower development. The present findings are in close agreement with Hoseini-Mazinani and Hadipour (2014) [8] , while similar findings were reported by Jogi et al. (2022) [4] , Mehdi et al. (2022) [9] and Pushparaj and Tamrakar (2025) [13] .

Number of flowers plant -1

:-T 7 recorded the maximum number of flowers (98.33 flowers plant -1 ) compared with 68.66 flowers plant -1 under T 0 . The application of biofertilizers and organic nutrient sources increased the number of flowers in calendula, indicating improved flowering performance under favourable growing conditions. The present findings are in close agreement with Hoseini-Mazinani and Hadipour (2014) [8] , while similar results were reported by Jogi et al. (2022) [4] , Mehdi et al. (2022) [9] , Parveen et al. (2022) [14] and Pushparaj and Tamrakar (2025) [13] . Shelf life :-T 7 recorded the highest shelf life (4.33 days) compared with 2.00 days under T 0 . the application of biofertilizers improves nutrient availability and promotes the development of stronger and healthier flower tissues. These stronger tissues help delay flower deterioration and maintain flower quality for a longer period, thereby improving the shelf life of calendula flowers. The present findings are in close agreement with Hoseini-Mazinani and Hadipour (2014) [8] , while similar findings were reported by Harish et al. (2018) [15] and Jogi et al. (2022) [4] .

Root parameter

Root length :-The maximum root length (20.10 cm) was recorded in T 7 (Vermicompost enriched with Azotobacter @ 5% + Azospirillum @ 5% + PSB @ 5%), whereas the minimum (12.90 cm) was recorded in T 0 . The combination of Azotobacter and PSB creates a beneficial environment for root growth. These findings were in close agreement with Pushparaj and Tamrakar (2025) [13] in calendula, Verma et al. (2025) [6] in marigold. Fresh weight of root :-The maximum root fresh weight (15.36 g) was recorded in T 7 whereas the minimum (11.23 g) was recorded in T 0 . The better root growth in biofertilizer-inoculated plants might be attributed to easy uptake of nutrients and the production of growthpromoting substances such as auxins, which stimulated root initiation, cell division and elongation. These findings were in close agreement with Sardoei (2014) [16] . Dry weight of root :-The maximum root dry weight (5.63 g) was recorded in T 7 whereas the minimum (3.73 g) was recorded in T 0 . The increase in dry weight of root under T 7 might be attributed to the combined beneficial effects of Azotobacter, Azospirillum and PSB, which enhanced nutrient availability and promoted root development. These findings were in close agreement with Sardoei (2014) [16] , Pansuriya & Chauhan (2015) [17] . revealed that the application of T 7 (Vermicompost enriched with Azotobacter @ 5% + Azospirillum @ 5% + PSB @ 5%) was found effective for improving various growth, flowering and root parameters of calendula. Treatment T 7 recorded superior performance in terms of plant height (18.73, 39.10 and 49.93 cm at 30, 60 and 90 DAT, respectively), number of leaves (40.00, 145.43 and 192.00 plant -1 at 30, 60 and 90 DAT, respectively), plant spread (39.30 cm N-S and 39.86 cm E-W), stem diameter (16.33 mm), fresh weight of shoot (300.40 g), dry weight of shoot (99.00 g), 50% flowering (51.66 days), flower diameter (6.63 cm), average flower weight (3.66 g), number of flowers (98.33 plant -1 ), shelf life (4.33 days), root length (20.10 cm), fresh weight of root (15.36 g) and dry weight of root (5.63 g). T 5 (Vermicompost enriched with Azotobacter @ 5% + PSB @ 5%) ranked second whereas T 0 (Control) recorded the lowest performance for most growth, flowering and root parameters. Thus biofertilizer enriched could be adopted by the Calendula producers which need higher price for beautifully fresh flower and ecofriendly way.

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