Efficiency of vermicompost and chemical fertilizers in sustainable onion cultivation on western zone of Uttar Pradesh, India

Introduction

Onion (Allium cepa L.) is one of the oldest cultivated vegetable crops and belongs to the family Alliaceae. For centuries, it has been valued not only as a food ingredient but also for its nutritional and medicinal qualities (Singh &Khar, 2022) [17] . Among the numerous members of the Allium genus, onion stands out because of its versatility, wide adaptability, and economic relevance. Globally, it ranks second only to tomato in terms of importance, reflecting its role as a vital crop in agriculture and trade (Ochar, & Kim, 2023) [13] . In India, onions are a part of almost every meal and are grown across diverse agro-climatic zones, with major production concentrated in states such as Uttar Pradesh, Odisha, Karnataka, and Rajasthan (Baba, 2024) [4] . This broad adaptability, combined with high demand in fresh and processed forms, makes onion a cornerstone of the agricultural economy. Like most crops, onion production is closely tied to soil health and nutrient management. For a long time, farmers have depended heavily on chemical fertilizers to achieve higher yields. However, the overuse of inorganic fertilizers has caused problems like soil degradation, nutrient imbalance, and environmental concerns. This has increased the focus on organic farming practices and sustainable alternatives. Organic manures, especially compost and vermicompost, are increasingly recognized for their ability to improve soil fertility, texture, and microbial activity. Vermicompost, produced through the breakdown of organic matter by earthworms, is particularly effective in enriching the soil. It provides macroand micronutrients, enhances aeration, improves water retention, and stimulates beneficial microbial populations (Mulatu, & Bayata, 2024) [12] . When combined with balanced chemical fertilizers, vermicompost supports a steady supply of nutrients, ensuring better crop growth, healthier bulb formation, and higher yields. Such integrated nutrient management practices are not only productive but also environmentally friendly, securing long-term soil sustainability. From a nutritional standpoint, onions contribute significantly to human health. They are rich in carbohydrates, which act as an energy source, and contain moderate amounts of proteins, vitamins, and essential minerals. Vitamin C is abundant in onions, serving as a powerful antioxidant and boosting immunity. Minerals like phosphorus and calcium further add to their nutritional profile, aiding in bone health and metabolic functions (Akram et al., 2020) [1] . Beyond basic nutrition, onions are valued for their medicinal qualities. Traditional medicine systems have long recognized their healing potential, and modern research continues to confirm these benefits. One of the reasons onions are so significant is their dual role as both a food and a natural remedy. In culinary practices, they enhance flavor and aroma while also improving the taste of other ingredients. On the medicinal side, onions contain bioactive compounds such as flavonoids and sulfur compounds, which have been linked to reduced risks of lifestyle-related diseases (Chakraborty et al. 2022) [5] . Quercetin, a flavonoid present in high amounts, has strong antioxidant effects, protecting cells from oxidative stress. Sulfur compounds, on the other hand, support cardiovascular health by lowering cholesterol, reducing blood pressure, and preventing excessive blood clotting. In the context of public health, onions are particularly beneficial in addressing modern lifestyle challenges. Their high fiber content and low-calorie value make them suitable for weight management. Fiber promotes satiety, improves digestion, and regulates appetite, making onions a supportive food for individuals battling obesity (Kim et al, 2023) [7] . They also contribute to blood sugar regulation by improving insulin sensitivity and slowing sugar absorption in the intestines, which is beneficial for people with diabetes. Additionally, several studies suggest that regular onion consumption reduces the risk of certain cancers, particularly stomach and colorectal cancers. Organosulfur compounds in onions are believed to suppress tumor growth, induce cell death in cancerous cells, and limit cancer spread. Their antioxidant activity further reduces free radical damage, which is a known contributor to cancer and other chronic diseases. Despite their importance, onion cultivation faces challenges. Productivity is often hindered by declining soil fertility, pest infestations, diseases, and erratic weather patterns. To tackle these issues, sustainable practices are necessary. Integrating organic amendments like vermicompost with chemical fertilizers is an effective way forward. This method not only improves yield and bulb quality but also minimizes environmental risks and reduces dependence on costly external inputs. By utilizing locally available organic resources, farmers can lower production costs while maintaining soil health and long-term productivity.

Materials and Methods

The present experiment was carried out at the experimental site of the School of Agriculture and Environmental Sciences, Shobhit University, Gangoh, Saharanpur, Uttar Pradesh (India). The site is geographically located at 29°58′ N latitude and 77°32′ E longitude, with an altitude of 284 meters above mean sea level. This region falls under the north-western plains subregion of the Upper Gangetic Plains, which is known for its fertile soils and favorable climatic conditions for vegetable cultivation, particularly onion. The soil of the experimental field was sandy loam in texture with a slightly acidic reaction, recording a pH of 6.0, which provides a suitable medium for bulb development and nutrient availability. The field experiment was laid out in a randomized block design (RBD) with three replications to ensure precision and minimize experimental error. A total of nine treatments were imposed, consisting of both organic and inorganic nutrient sources applied either individually or in combinations. The treatments included: T 1 -Vermicompost @ 10 t/ha, T 2 -Vermicompost @ 10 t/ha + N @ 100 kg/ha, T 3 -Vermicompost @ 10 t/ha + P @ 100 kg/ha, T 4 -Vermicompost @ 10 t/ha + K @ 120 kg/ha, T 5 -N @ 100 kg/ha, T 6 -P @ 100 kg/ha, T 7 -K @ 120 kg/ha, T 8 -Vermicompost @ 10 t/ha + N @ 100 kg/ha + P @ 100 kg/ha + K @ 120 kg/ha, and T 9 -Control (without any manure or fertilizer application). These treatments were selected to study the individual and combined effects of organic manure and chemical fertilizers on the growth and yield performance of onion. The onion variety Pusa red was chosen for the study due to its popularity, adaptability, and consumer preference in the region. Healthy seedlings were transplanted into the well-prepared field with a spacing of 20 cm between rows and 10 cm between plants, which ensured optimum plant population and proper aeration. All recommended agronomic practices such as irrigation, weeding, and plant protection measures were followed uniformly across all treatments to maintain crop health and minimize biotic and abiotic stress. During the course of experimentation, regular observations were recorded on plant growth parameters, bulb development, and yield attributes to assess the performance of each treatment. This approach not only provides insights into improving yield but also emphasizes sustainable agriculture by reducing excessive dependence on chemical fertilizers.

Results and Discussion

Growth parameters

The data presented in Table 1 and Fig. 1 clearly demonstrate the significant influence of different levels of NPK and vermicompost on the growth attributes of onion. Among the treatments, T 8 recorded the maximum values for all the studied growth parameters, including plant height (49.83 cm), number of leaves (8.90), stem girth (2.15 cm), fresh weight (129.11 g), and dry weight (11.91 g). This superior performance may be attributed to the synergistic effect of inorganic nutrients with vermicompost, which improves nutrient availability, enhances microbial activity, and promotes root proliferation, ultimately supporting better vegetative growth. Similar findings were reported by Singh et al. (2019), who observed improved growth and yield of onion under integrated nutrient management. The lowest growth was recorded in T 9 (control), which exhibited reduced plant height (28.55 cm), leaf number (4.55), stem girth (1.19 cm), and fresh (71.48 g) and dry weight (7.56 g). This clearly indicates the poor growth performance of onion under nutrient deficiency. The significant differences observed with respect to C.D. at 5% confirm the positive impact of integrated nutrient application compared to control treatments. In terms of plant height, treatments T 2 -T 4 and T 8 showed statistically superior performance compared to T 1 , T 5 , and T 6 , reflecting the importance of balanced nutrient application. Likewise, the number of leaves and stem girth were significantly higher in treatments receiving combined application of NPK and vermicompost, which is consistent with the findings of Kumar et al. (2021) [8] , who highlighted that organic-inorganic nutrient integration enhances physiological processes and biomass accumulation in bulb crops. The fresh and dry weight of plants followed a similar trend, where T 8 recorded the highest biomass accumulation. This may be due to improved photosynthetic efficiency and carbohydrate partitioning towards the bulb, facilitated by optimum nutrient availability. On the other hand, treatments with only NPK or vermicompost (T 1 , T 5 , T 6 , T 7 ) showed moderate improvements compared to the control, suggesting partial but not sufficient contribution when applied alone.

Yield parameters

The data presented in Table 2 &Fig. 2 reveal that the application of NPK in combination with vermicompost significantly influenced yield parameters of onion. The maximum fresh bulb weight (97.41 g), dry weight (12.18 g), bulb diameter (4.54 cm), and bulb yield (28.65 t/ha) were recorded under treatment T 8 , which consisted of the integrated application of NPK + vermicompost. This treatment was statistically superior to all other treatments, indicating a synergistic effect of chemical fertilizers and organic amendments. On the other hand, the lowest performance was observed in T 9 (control), where fresh bulb weight (52.12 g), dry weight (9.22 g), bulb diameter (2.75 cm), and bulb yield (15.24 t/ha) were significantly reduced. This reduction may be attributed to inadequate nutrient availability in the absence of external inputs. Intermediate treatments such as T 2 , T 3 , and T 4 showed moderate improvement in bulb yield (26.78-27.56 t/ha), highlighting the beneficial role of balanced NPK fertilization. Treatments involving vermicompost alone (T 5 -T 7 ) also enhanced growth over control, but the combined application (T 8 ) proved most effective, emphasizing the importance of integrated nutrient management.

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