Influence of organic manures and inorganic fertilizers on quality attributes of capsicum cultivars under shade-net conditions

Introduction

Capsicum (Capsicum annuum var. grossum, 2n = 2x = 24) is an important high-value vegetable crop belonging to the family Solanaceae and is cultivated under both open-field and protected conditions. It is native to Mexico, with Guatemala considered a secondary centre of origin (Bukasov, 1930) [2] . The crop was introduced into India during the nineteenth century, initially in the Shimla hills (Greenleaf, 1986). Capsicum grows well at a day temperature of 25-30 °C and a night temperature of 18-20 °C with relative humidity of 50-60 percent. Fruit set is adversely affected when the temperature exceeds 35 °C or falls below 12 °C. It is commonly known as bell pepper because of its characteristic bell-shaped fruits and is also referred to as sweet pepper. Capsicum is extensively cultivated in the hill regions of Himachal Pradesh, Uttar Pradesh, the Nilgiri hills and Jammu and Kashmir during summer, while it is grown as an autumn and winter crop in Karnataka, Maharashtra, Tamil Nadu and Telangana. The crop has attained importance as a high-value commercial vegetable owing to its attractive fruits, pleasant flavour and nutritional composition. Capsicum fruits are rich in ascorbic acid, vitamins, minerals, carotenoids and other bioactive compounds (Chassy et al., 2006; Sreedhara et al., 2013) [4,25] . They are consumed fresh and are widely used in salads, stuffing, baking, pizza, burgers and other food preparations. Fruit colour, cultivar and stage of maturity influence the concentration of vitamins and pigments, resulting in considerable variation in the nutritional and biochemical quality of capsicum fruits (Curl, 1962) [8] . Ascorbic acid is an important biochemical constituent of capsicum fruits owing to its nutritional and antioxidant properties. Coloured capsicums are particularly valued for their attractive appearance and nutritional quality and have considerable demand in the hotel and catering industry. Capsicum fruits also contain carotenoid pigments and other secondary metabolites that contribute to fruit colour and antioxidant activity. Oleoresin, which contains concentrated colour and flavour components, is another important quality constituent of pepper with applications in the food industry. The accumulation of these biochemical constituents is influenced by cultivar, environmental conditions, maturity and nutrient availability. Protected cultivation of capsicum, particularly coloured hybrids, is gaining importance as it provides favourable environmental conditions for crop growth and facilitates the production of quality fruits. Shade-net cultivation helps moderate solar radiation and temperature and can reduce the adverse effects of excessive radiation and heat stress. Such modification of the crop microclimate can influence plant growth, fruit development and biochemical composition. Shading has been reported to influence yield and nutritional attributes, including ascorbic acid and carotenoid content, in pepper (Caruso et al., 2020) [3] . However, cultivars may differ in their response to modified environmental conditions. Therefore, identification of suitable cultivars for production under shade-net conditions is important for obtaining quality fruits. Nutrient management plays an important role in determining crop productivity as well as fruit quality. Increasing fertilizer costs and concerns regarding the continuous use of chemical fertilizers have encouraged the adoption of integrated nutrient management practices. The combined application of organic and inorganic nutrient sources can provide nutrients in both readily available and gradually mineralizable forms and may improve nutrient-use efficiency and soil properties (Merentola et al., 2012; Jaggi et al., 2001) [18,14] . Organic manures supply essential macroand micronutrients and improve the physical, chemical and biological properties of soil (Nweke et al., 2013; Chaterjee et al., 2005) [19,5] . Farmyard manure, vermicompost and neem cake are important organic sources used in vegetable production. Vermicompost contains macro-and micronutrients and contributes to improved plant growth and productivity (Hidalgo et al., 1999) [13] . Neem cake supplies nutrients and organic matter and can also contribute to improved soil conditions, while possessing pesticidal and nematicidal properties (Singh et al., 1980) [24] . The integration of organic manures with inorganic fertilizers may therefore provide a balanced nutrient supply and improve soil conditions favourable for crop growth, fruit development and quality. Nutrient management can influence not only yield but also the biochemical composition and nutritional quality of capsicum fruits. Integrated nutrient management involving inorganic fertilizers, farmyard manure and biofertilizers has been reported to improve fruit quality and vitamin C content in capsicum under protected cultivation (Jaipaul et al., 2011; Jat et al., 2022) [15,14] . Similarly, integrated nutrient management practices have been reported to improve ascorbic acid and other quality attributes in pepper (Chouhan et al., 2018) [7] . Shelf life is an important component of fruit quality, particularly in a highly perishable crop such as capsicum. During storage, fruits undergo moisture loss, softening, shrivelling and deterioration in appearance and nutritional quality, which reduce marketability and increase postharvest losses. Crop nutrition can influence fruit development, firmness and biochemical composition and may consequently affect the storage behaviour and keeping quality of harvested fruits. Hence, appropriate nutrient management is important for maintaining fruit quality and improving shelf life.

Organic manures and integrated nutrient management practices have been reported to improve growth, yield and quality of capsicum, although their response may vary with cultivar and growing environment. Therefore, the present study was undertaken to evaluate the effect of organic manures in combination with inorganic fertilizers on the quality and post-harvest behaviour of capsicum cultivars under shade-net conditions.

Materials and Methods

The study was conducted during the Rabi seasons of 2024-25 and 2025-26 at the College of Horticulture, Sri Konda Laxman Telangana Horticultural University, Rajendranagar, Hyderabad. The experiment was conducted under shade net conditions in a Factorial Randomized Block Design (FRBD) with fifteen treatment combinations and two replications.

Experimental Material

The experimental material consisted of three capsicum cultivars, namely Rupali Red, Rupali Green and Rupali Yellow. The nutrient management treatments comprised vermicompost at 5 t/ha and 2.5 t/ha and neem cake at 1 t/ha and 0.5 t/ha, applied 15 days before transplanting. The recommended dose of NPK (100:60:80 kg/ha) was supplied through urea, single super phosphate and muriate of potash. Half of the nitrogen and the entire phosphorus and potassium were applied as basal doses, while the remaining nitrogen was applied in two equal splits at 30 and 60 days after transplanting.

Raising of Seedlings

Protrays measuring 25 × 10 × 5 cm were cleaned and filled with cocopeat, perlite and vermiculite in a 3:1:1 ratio. Seeds were soaked overnight and sown individually in the protray cells. The seedlings were raised under shade net conditions and transplanted at the two-leaf stage.

Crop Management Practices

The experimental field was thoroughly ploughed and brought to a fine tilth. Raised beds measuring 4.00 × 1.00 m were prepared with 40 cm spacing between adjacent beds. Seedlings were transplanted at 45 days after sowing, followed by light irrigation. Drip irrigation was provided based on soil moisture conditions. Weeding and hoeing were carried out at 30 and 60 days after transplanting (DAT). Yellow and blue sticky traps were used for monitoring sucking pests, and standard crop management practices were followed throughout the crop period.

Details of experimental treatments Factor A: Cultivars

Factor B: Inorganic fertilizers and organic manures B 1: 50% RDF + Vermicompost (5 t/ha) B 2: 50% RDF + Neem cake (1 t/ha) B 3: 75% RDF + Vermicompost (2.5 t/ha) B 4 :75% RDF + Neem cake (0.5 t/ha) B 5: Control (100% RDF)

Treatment combinations

A 1 B 1: Rupali Red + 50% RDF + Vermicompost (5 t/ha) A 1 B 2: Rupali Red + 50% RDF + Neem cake (1 t/ha) A 1 B 3: Rupali Red + 75% RDF + Vermicompost (2.5 t/ha) A 1 B 4: Rupali Red + 75% RDF + Neem cake (0.5 t/ha) A 1 B 5: Rupali Red + Control (100% RDF) A 2 B 1: Rupali Green + 50% RDF + Vermicompost (5 t/ha) A 2 B 2: Rupali Green + 50% RDF + Neem cake (1 t/ha) A 2 B 3: Rupali Green + 75% RDF + Vermicompost (2.5 t/ha) A 2 B 4: Rupali Green + 75% RDF + Neem cake (0.5 t/ha) A 2 B 5: Rupali Green + Control (100% RDF) A 3 B 1: Rupali Yellow + 50% RDF + Vermicompost (5 t/ha) A 3 B 2: Rupali Yellow + 50% RDF + Neem cake (1 t/ha) A 3 B 3: Rupali Yellow + 75% RDF + Vermicompost (2.5 t/ha) A 3 B 4: Rupali Yellow + 75% RDF + Neem cake (0.5 t/ha) A 3 B 5: Rupali Yellow + Control (100% RDF)

Observations Recorded

The observations were recorded on quality parameters like ascorbic acid content, shelf life and oleoresin content.

Statistical Analysis

The data collected were analyzed statistically by following the analysis of variance (ANOVA) technique (Panse and Sukhatme 1985) [21] . Statistical significance was tested with 'F' value at 5 percent level of significance and whenever the F value was found significant, critical difference was worked out at five percent level of significance.

Results and Discussion

Quality parameters

The data recorded on growth parameters viz., ascorbic acid content, oleoresin content and shelf life are presented in Table 1-3 Among the cultivars, the maximum ascorbic acid content (142.27 mg/100 g) was recorded in A 3 (Rupali Yellow). Among the nutrient management treatments, B 2 (50% RDF + Neem cake 1 t/ha) recorded the maximum ascorbic acid content (124.02 mg/100 g). The interaction effect between cultivars and nutrient management treatments was significant, with A 3 B 2 (Rupali Yellow + 50% RDF + neem cake 1 t/ha) recording the maximum ascorbic acid content (149.60 mg/100 g). The higher ascorbic acid content in cv. Rupali Yellow may be attributed to its genetic potential and greater accumulation of metabolites during fruit ripening, resulting in enhanced vitamin C synthesis. The integrated application of 50% RDF along with neem cake might have promoted ascorbic acid accumulation through balanced nutrient supply, improved microbial activity and nutrient availability, thereby enhancing physiological and biochemical processes (Premsekhar and Rajashree, 2009) [22] . Similar positive effects of neem-based amendments on crop quality and biochemical characteristics were reported by Gopalakrishnan et al. (2015) [12] . The present findings are also in agreement with Bhattarai et al. (2009) [1] , Jaipaul et al. (2011) [15] , Chetri et al. (2012) [6] and Olowoake et al. (2015) [20] in bell pepper. In addition to quality attributes, significant differences were observed among the cultivars and nutrient management treatments with respect to oleoresin content. Among the cultivars, the maximum oleoresin content (11.08%) was recorded in A₁ (Rupali Red). Among the nutrient management treatments, B 2 (50% RDF + Neem cake 1 t/ha) recorded the maximum oleoresin content (8.80%). The interaction effect between cultivars and nutrient management treatments was significant, with A 1 B 2 (Rupali Red + 50% RDF + Neem cake 1 t/ha) recording the maximum oleoresin content (12.06%) The higher oleoresin content in cv. Rupali Red may be associated with its inherent varietal characteristics and greater capacity to accumulate carotenoids and other pigment-related compounds during fruit maturation. The application of 50% RDF + Neem cake 1 t/ha may have favoured oleoresin accumulation by ensuring a steady nutrient supply and improving soil microbial activity, which enhanced the physiological and biochemical processes involved in pigment and secondary metabolite synthesis. Similar findings were reported in chilli by Dileep et al. (2009) [9] , Sankar et al. (2013) [23] and Gangadhar and Devakumar (2020) [11] . In contrast, A 2 (Rupali Green) exhibited better performance with respect to shelf life. Among the cultivars, the maximum shelf life (7.34 days) was recorded in A 2 (Rupali Green). Among the nutrient management treatments, B 2 (50% RDF + Neem cake 1 t/ha) recorded the maximum shelf life (8.03 days). The interaction effect between cultivars and nutrient management treatments was significant, with A 2 B 2 (Rupali Green + 50% RDF + neem cake 1 t/ha) recording the maximum shelf life (8.67 days). The higher shelf life of cv. Rupali Green may be attributed to its firmer texture, thicker pericarp and lower respiration rate at the green mature stage, resulting in delayed ripening and reduced deterioration during storage. The application of inorganic fertilizers and neem cake may have improved fruit firmness, nutrient availability and membrane stability, thereby reduce moisture loss and extend shelf life (Gopalakrishnan et al., 2015) [12] . Fruits with lower respiration rates and better firmness generally have longer storage life. Similar findings were reported in sweet pepper by Kurubetta and Patil (2009) [17] , Yellava and Patil (2009) [26] and Fawzy et al. (2012) [10] .

Conclusion

Based on the study, it was concluded that different combinations of inorganic fertilizers and organic manures significantly influenced the quality attributes of capsicum under shade net conditions. Among the treatment combinations, treatment A 3 B 2 (Rupali Yellow + 50% RDF + Neem cake 1 t/ha) recorded the highest ascorbic acid content (149.60 mg/100 g), while the highest oleoresin content (12.06%) was recorded in A 1 B 2 (Rupali Red + 50% RDF + Neem cake 1 t/ha), whereas the maximum shelf life (8.67 days) was recorded in A 2 B 2 (Rupali Green + 50% RDF + Neem cake 1 t/ha).

Acknowledgments

At the very outset, I submit the commodious and indefinite thanks to COH, Rajendranagar, Hyderabad for giving me a platform to conduct research work and to ICAR for giving me timely scholarship.

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