Potential of different enriched organic manures and bio-stimulants on growth, yield and quality of organic carrot

Introduction

Carrot (Daucus carota L.) is a popular umbelliferous winter season root vegetable, largely consumed as salad, cooked into stews, parathas, pickles and roasted vegetable. The root is excellent source of essential vitamins, several minerals and dietary fibres. Carrot gets its characteristic bright orange colour from β-carotene pigment which partly metabolized into Vitamin A in the digestive system. It also possesses trace amounts of α-carotene, γ-carotene, lutein, and zeaxanthin. For early and higher production, farmers use traditional production practices. But vegetables and fruits grown on chemically overfertilized soils are more prone to attack by insects and diseases (Karungi et al.,) [4] . Moreover, it also reduces the protein and carbohydrate content of crops (Marzouk and Kassem,) [5] . High potassium containing soil decreases carotene, vitamin C and antioxidant compounds in vegetables (Toor et al.,) [18] . Carrot is consumed as salad in raw form. Therefore, demand for contamination free carrot is increasing day by day both in international and domestic market. Traditional organic production consists of sole use of farmyard manure and occasional use of biofertilizer. Thus, the system suffers from adequate supply of essential plant nutrients which results marginal yield and economic return. Influence of Azotobacter-enriched organic manures increase nitrogen fixation and productivity of lettuce and turnip (Rodrigues et al.,) [11] . In the present experiment, apart from farmyard manure, vermicompost and poultry manure were also included as sources of organic manure. To increase the amount of nutrient availability, the organic manures were enriched by incorporating Azotobacter and phosphate solubilizing bacteria. Apart from basal use of enriched organic manures, foliar application of different bio stimulants namely panchagavya, jiwamrita, vermiwash, liquid mustard cake, seaweed extract and humic acid were incorporated in the standing crops to enhance further root yield.

Materials and Methods

The field experiment was conducted at the Instructional Farm of UBKV, Pundibari, Cooch acid] were laid in split plot design with 3 replications. 'Early Nantes' variety of carrot was sown during first fortnight on November for both the years in the plot size of 2 m × 1.5 m with a spacing of 20cm × 10 cm. The seeds for the experiment were collected from local market. Well decomposed organic manures (FYM, Vermicompost, Poultry manure) were mixed with the microbial inoculants Azophos containing Azotobacter chroococcum and Phosphate Solubilizing Bacteria (Acinetobacter sp.) with standard microbial population (5x 10 8 ) at the rate of 10 g biofertilizer per kg of organic manure. The treated organic manures were kept in shade for 20 days and then applied as basal dose as per the treatment combination. The different bio-stimulants were applied as foliar spray at 45, 60 and 75 DAS. A pre sowing irrigation was given for better germination of seeds. There after irrigation was given as and when required depending upon the soil moisture condition. Weeding, hoeing and other operations were conducted as and when required. Observation on different growth, yield and quality characters of carrot were recorded following standard procedure. Vitamin C (Ranganna) [10] , total soluble solids (ERMA hand refractometer (0 to 32ºBrix), total sugar content (Anthrone method (Dubois et al.) [2] of root were analysed. Total chlorophyll content of leaves was also estimated (Sadasivam and Manickam,) [12] . Among different soil parameters organic carbon of soil samples expressed in percentage (%), available N (kg ha -1 ), available P (kg ha -1 ) and potassium (kg ha -1 ) content were determined using the standard protocols.

Results and Discussion

The result showed that enriched organic manures had significant effect on growth, yield, physiological attributes and root quality of carrot (Table 1). Among different organic manures used, enriched farmyard manure (20 t ha -1 ) recorded the highest plant height (34.96 cm), numbers of leaves (13.57), total chlorophyll content of leaves (225.25 mg 100 g -1 ), crop growth rate (3.77 g m 2-1 days -1 at 75-120 DAS), root length (15.02 cm), root diameter (3.27 cm), individual root weight (88.35 g), total root yield (22.97 t ha -1 ) and harvest index (78.06%). Result also showed that enriched FYM showed 11.073% and 36.64% higher root yield over the enriched vermicompost and enriched poultry manure. The same treatment not only improved the growth and yield attributes but also enhanced the quality attributes and recorded the highest root TSS (5.74 o B), beta-carotene content in roots (10738 IU/100 g), root total sugar (6.46%) and root ascorbic acid content (7.25 g 100 g -1 ). The result showed a significant interaction between combined application of enriched organic manure and bio-stimulants through foliar application for the different growth, root yield and quality attributes of carrot (Table 2). Application of enriched farmyard manure (20 t ha -1 ) as basal along with vermiwash through foliar application (3%) at 45, 60 and 75 DAS (A 1 B 3 ) recorded the maximum plant height (38.40 cm) and the highest crop growth rate of carrot (4.54 g m 2-1 days -1 at 75-100 DAS). This might be attributed to enhanced vegetative growth in presence of beneficial microorganisms and growth promoting substances released by vermiwash (Tomati and Galli, 1995; Edwards, 1998) [17,3] . However, combined use of enriched farmyard manure (20 t ha -1 ) as basal and jiwamrita bio-stimulant through foliar application (3%) at 45, 60 and 75 DAS recorded the highest root length (15.00 cm), root diameter (3.27 cm), root weight (87.33 g), root yield (22.70 t ha -1 ) and harvest index (78.27%). Jiwamrita is a fermented microbial culture which acts as a catalytic agent and promotes the activity of soil microorganisms as well as increases the activity of earthworm in the soil that subsequently sustain the availability and uptake of applied as well as inherent soil nutrients. The combined application of enriched FYM and jiwamrita might have enhanced the decomposition of organic substances and increased the slow and steady supply of essential nutrients which ultimately resulted in better root yield in carrot.

The quality attributes of carrot root were also influenced significantly in presence of enriched organic manure and biostimulants. The maximum root TSS (5.75 0 B), ascorbic acid content (7.24 g 100 g -1 ) and root total sugar (6.63%) were recorded for the plants received enriched farmyard manure (20 t ha -1 ) as basal and panchagavya bio-stimulant as foliar application (3%) at 45, 60 and 75 DAS. However, the highest beta-carotene content in roots (10735 IU 100 g -1 ) was registered for the treatment comprised of enriched farmyard manure (20 t ha -1 ) as basal and sea weed extract bio-stimulant as foliar spray (3%) at 45, 60 and 75 DAS. The increase level of root TSS and ascorbic acid content in the enriched farmyard manure and panchagavya bio-stimulants may have attributed to increased availability of nutrients in the soil that might lead to biosynthesis of ascorbic acid. Seaweed extract contains auxins, cytokinins and or other hormone-like substances that enhances the photosynthetic activity and improve the quality of produce. Improvement in ascorbic acid content with the application of higher amount of organic manures was reported earlier by Bahadur in broccoli and Wang in chinese cabbage. The status of soil nutrients at the end of two consecutive years of experiment revealed that among the different organic manures, application of enriched farmyard manure (20 t ha-1) recorded the highest soil available nitrogen (124.47 kg ha -1 ), whereas application of enriched vermicompost (5 t ha -1 ) recorded the highest soil available phosphorous (28.10 kg ha -1 ). Among the different bio-stimulants, the highest soil available nitrogen (122.27 kg ha -1 ) as well as soil available phosphorous (26.76 kg ha -1 ) were recorded in jiwamrita application (3%). The interaction effect showed that the combined application of enriched farmyard manure (20 t ha -1 ) as basal and jiwamrita through foliar application (3%) recorded the highest soil available nitrogen (125.91 kg ha -1 ), whereas combination of enriched vermicompost (5 t ha -1 ) as basal and jiwamrita through foliar application (3%) showed the highest available phosphorous (28.97 kg ha -1 ) in soil. The economics of organic production of carrot (Table 4) revealed that the gross return and net return of carrot was influenced to a great extent by the combination of different nutrient sources. The combined use of enriched farmyard manure (20 t ha -1 ) as basal and jiwamrita bio-stimulant as as topdressing (3%) recorded the maximum gross return (Rs.397878.00 ha -1 ) and net return (Rs.292018.00 ha -1 ). However, the treatment comprising of enriched farmyard manure (20 t ha -1 ) and foliar spray of Panchagavya (3%) recorded the maximum benefit cost ratio (2.96) owing to reduction in variable cost of production. The experimental findings established that depending on duration of crops, the organic manures should be selected. Organic carrot produces root around 110-120 days, enriched farmyard manure will be the best option over enriched vermicompost and poultry manure due to slow decomposition and steady mineralization of nutrients. Use of bio-stimulants impart positive impact on carrot growth, root yield and quality. The nutrient schedule comprised of basal application of Azophos containing Azotobacter and Phosphate Solubilizing Bacteria enriched farmyard manure (20 t ha -1 ) along with foliar application of Jiwamrita (3%) at 45, 60 and 75 DAS may be adopted for large scale organic carrot production.

Conclusion

The present investigation clearly demonstrated that the combined application of enriched farmyard manure (FYM) with Azotobacter and PSB, along with foliar application of Jiwamrita at 45, 60 and 75 days after sowing, significantly enhanced growth, yield, quality attributes, and nutrient uptake in organic carrot production. Among the various treatments, the integration of Enriched FYM + Azotobacter + PSB with Jiwamrita foliar spray proved most effective, recording the highest root yield (22.70 t/ha), superior quality (total soluble solids, sugars, carotene), and improved nutrient uptake and soil fertility. Therefore, the use of enriched organic manures in conjunction with bio-stimulants like Jiwamrita offers a promising, sustainable, and eco-friendly approach to boost productivity and quality in organic carrot cultivation.

Acknowledgement

AcknowledgementsAuthors are highly thankful to Department of Vegetable and Spice Crops, Uttar Banga Krishi Viswavidyalay, West Bengal, India for giving the opportunity to cunduct the reasearch work.

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