Synergistic impact of vermicompost, biochar and jaggery on antioxidants, phenols and flavonoids in Guava cv. L-49

Abstract

This study was conducted over two growing seasons (2022-2023 and 2023-2024). Using a randomised block design, 16 treatments consisted of combinations of vermicompost, biochar, jaggery, poultry manure, farmyard manure, cow urine, and neem cake, and three replications were used in the study. The objective was to assess how these organic amendments affected the antioxidant, phenolic and flavonoid contents in guava fruit. The treatment T₆(Vermicompost 5 kg/tree + Biochar 7.5 kg/tree + Jaggery 1.25 kg/tree) produced the highest levels of antioxidant, phenolic and flavonoid, according to the results. T₆ in particular showed an increase in antioxidant activity from 46.48% to 48.14%, phenolic content from 29.72 mg TA/g to 30.93 mg TA/g and flavonoid content from 23.88 mg/g FW to 25.14 mg/g FW. This study provides important information for sustainable horticultural practices by highlighting the potential of organic amendments to enhance the nutritional qualities of guava cv. L-49.

Full Article

Synergistic Impact of Vermicompost, Biochar and Jaggery on Antioxidants, Phenols and Flavonoids in Guava cv. L-49

Reetika Sharma, Rakesh Kumar,* Parshant Bakshi, Amit Jasrotia, Bhav Kumar Sinha, Neetu Sharma, Peeyush Sharma, Vijay Kumar, Monika Sood, and Maanik *

This study was conducted over two growing seasons (2022-2023 and 2023-2024). Using a randomised block design, 16 treatments consisted of combinations of vermicompost, biochar, jaggery, poultry manure, farmyard manure, cow urine, and neem cake, and three replications were used in the study. The objective was to assess how these organic amendments affected the antioxidant, phenolic and flavonoid contents in guava fruit. The treatment T₆(Vermicompost 5 kg/tree + Biochar 7.5 kg/tree + Jaggery 1.25 kg/tree) produced the highest levels of antioxidant, phenolic and flavonoid, according to the results. T₆ in particular showed an increase in antioxidant activity from 46.48% to 48.14%, phenolic content from 29.72 mg TA/g to 30.93 mg TA/g and flavonoid content from 23.88 mg/g FW to 25.14 mg/g FW. This study provides important information for sustainable horticultural practices by highlighting the potential of organic amendments to enhance the nutritional qualities of guava cv. L-49.

DOI: 10.15376/biores.19.4.8173-8187

Keywords: Vermicompost; Biochar; Jaggery; Psidium guajava; Nutritional quality

Contact information: Sher-e-Kashmir University of Agricultural Sciences & Technology of Jammu, Chatha, J&K-180009, India; *Corresponding authors:maanikdadheechi@gmail.com, rakeshsangwal21@gmail.com

GRAPHICAL ABSTRACT

INTRODUCTION

Climate change, environmental deterioration, and the pressures of population increase present new challenges for modern agriculture. The increasing demand for agricultural products puts additional strain on crop productivity and makes it necessary for horticultural practices to decrease their adverse impacts on the environment. Thus, increasing sustainable production is essential to satisfying the world food needs in the future while having the fewest negative effects on the environment (Rojas-Downing et al. 2017; Abd-Elmabod et al. 2020). The growing global demand for organic fruit can be attributed to rising consumer awareness of health and diet. Because people believe that organic foods are better than conventional in terms of flavour, nutrition, health benefits, cleanliness, safety, and environmentally friendly manufacturing, consumers are willing to pay premium prices for them (Kamboj et al. 2023). To promote sustainable agriculture, it is essential to emphasize organic farming practices, particularly the use of organic fertilizers. This paper highlights the impact of various organic materials on enhancing soil health, improving crop yields, and fostering environmental sustainability. Organic fertilizers, sourced from compost, manure and green manure, enrich the soil with vital nutrients and improve its structure. Trupiano et al. (2017) found that organic amendments enhance microbial activity and increase soil organic matter, which improves nutrient availability for crops. Additionally, organic fertilizers reduce dependence on chemical inputs, promoting a balanced ecosystem. Ghosh et al. (2014) demonstrated that these practices lead to higher soil fertility, better water retention, and increased resilience against pests and diseases. Emphasizing the integration of organic fertilizers in farming can facilitate a shift towards sustainable agricultural methods, mitigating the negative impacts of conventional practices while ensuring long-term productivity and soil health. Thus, this paper underscores the importance of organic fertilizers in advancing sustainable agriculture. Many researchers have examined the physico-chemical and organoleptic characteristics of conventional and organic fruits and vegetables; however, because cultivation management, soil type, and production size vary, results have occasionally been conflicting (Gamage et al. 2023).

Guava (Psidium guajava L.), which is extensively grown in tropical as well as subtropical areas, is known for its nutritional value. Its abundance of antioxidants, phenols, and flavonoids supports its therapeutic properties, which include anti-inflammatory and anti-cancer effects (Naseer et al. 2018; Shanthirasekaram et al. 2021). It is essential to improve these bioactive chemicals using sustainable farming methods. Because of their potential to strengthen crop quality and promote soil health, biochar and vermicompost have attracted attention (Anand et al. 2020). Plant secondary metabolite improves the soil characteristics and nutrient availability brought about by biochar made from pyrolysed organic sources (Santos et al. 2017).

Earthworms break down organic waste to produce vermicompost, which enriches the soil with vital nutrients, growth hormones, and helpful bacteria that encourage plants to produce more bioactive substances (Mohite et al. 2024). Research has indicated that the utilisation of vermicompost and biochar can considerably raise the antioxidant, phenolic and flavonoid content of guava fruits. For example, when treated with these amendments, organic apples and strawberries have demonstrated increased antioxidant levels, better textural qualities, and greater resilience to deterioration (Hargreaves et al. 2008). In a similar vein, consumers preferred organic tomatoes more because of their superior flavour, texture and rich colour, which is thought to be attributable to increased concentrations of antioxidants like lycopene and anthocyanin (Dumas et al. 2003). Higher concentrations of vitamins and antioxidants are a result of biochar and vermicompost improved soil structure and increased nutrient availability, which are linked to these increases in fruit quality. Because of their distinct ecological advantages, vermicompost and biochar are great soil conditioners. In addition to improving water retention and reducing heavy metal contamination, biochar raises the amount of organic matter in soil (Ennis et al. 2012). Rich in microbes and nutrients, vermicompost enhances soil structure and encourages plant growth. Combining these amendments improves soil health and lowers the demand for synthetic fertilisers, which promotes sustainable agriculture methods while also increasing the nutritional value of guava fruits (Ceritoğlu et al. 2018).

The processed form of sugarcane juice known as jaggery is rich in carbohydrates (sucrose: 72–78 g/100g), (Calcium 40–100 mg; Magnesium 70–90 mg; Phosphorous 20–90 mg; Sodium 19–30 mg; Iron 10–13 mg; Manganese 0.2–0.4 mg; Zinc 0.2–0.4 mg; Chlorine 5.3–0.0 mg; 0.1–0.9 mg) in significant amount (Sharifi‐Rad et al. 2023).

Increased sucrose uptake by the roots enhances the retention of photosynthetic carbon in the plant’s aerial parts, which results in greater biomass accumulation and a reduced root-to-shoot ratio. By transporting sugar molecules, such as sucrose, from the rhizosphere into the root cells, there is less photosynthetic carbon allocated to root growth and development. Consequently, more of the assimilated sugar is distributed to other parts of the plant, such as the fruit (Kazachkova 2023).

This study assessed how biochar and vermicompost affect the concentrations of flavonoids, phenols, and antioxidants in guava fruits. The aim was to provide more information on sustainable methods that improve the nutritional content of guava, to raise consumer awareness, and to support sustainable agricultural practices in guava cultivation by researching how these organic amendments affect the quality of guava fruit.

EXPERIMENTAL

The experiment was formulated to appraise the repercussions of various organic amendments on antioxidants, phenols and flavonoids of guava fruit. The experiment was orchestrated in a randomized block design with sixteen treatments and three replications. Each replication encompassed three plants, totaling 48 guava trees. The experiment was undertaken over two years, 2022 and 2023.

Before administering the treatments, it was essential to analyze the initial status of the orchard soil. The orchard soil utilized for the experiment was characterized as sandy clay loam, with the following nutrient composition: 0.42% organic carbon, 203.24 kg ha⁻¹ of available nitrogen (N), 12.53 kg ha⁻¹ of available phosphorus (P), and 138.65 kg ha⁻¹ of available potassium (K). In Table 1, the experimental treatments for the study feature a range of organic amendments to assess their influence on guava quality. The following treatments were applied: Vermicompost (15 kg/tree) was used for 100% nitrogen replacement (T₁), while other vermicompost treatments included combinations with cow urine and neem cake: 10 kg/tree + 0.5 liter cow urine + 1.0 kg neem cake (T₂), 10 kg/tree + 1.0 liter cow urine + 1.5 kg neem cake (T₃), and 10 kg/tree + 1.5 liter cow urine + 2.0 kg neem cake (T₄). Additionally, vermicompost (5 kg/tree) was combined with biochar and jaggery: 5.0 kg biochar + 1.0 kg jaggery (T₅), 7.5 kg biochar + 1.25 kg jaggery (T₆), and 10 kg biochar + 1.50 kg jaggery (T₇). Poultry manure (5 kg/tree) also served as a 100% nitrogen replacement (T₈), with further combinations including 3 kg/tree + 4.0 kg biochar + 0.5 kg jaggery (T₉), 3 kg/tree + 5.0 kg biochar + 0.75 kg jaggery (T₁₀), and 3 kg/tree + 6.0 kg biochar + 1.0 kg jaggery (T₁₁). Farmyard manure (15 kg/tree) was another 100% nitrogen replacement (T₁₂), combined with cow urine and neem cake: 10 kg/tree + 0.75 liter cow urine + 1.5 kg neem cake (T₁₃), 10 kg/tree + 1.25 liter cow urine + 1.75 kg neem cake (T₁₄), and 10 kg/tree + 1.75 liter cow urine + 2.0 kg neem cake (T₁₅).

The control (T₁₆) treatment in this context refers to following the recommended package of practices without any additional or experimental treatments. This involves strictly adhering to the specified quantities of Urea (700 g), Di-Ammonium Phosphate (275 g), and Muriate of Potash (135 g) according to the tree’s age, along with the recommended timing of application. This standard practice serves as a baseline against which other treatments can be compared. The treatments were applied to evaluate their impact on guava fruit quality and productivity throughout the experimental period.

The incorporation of organic amendments was slated for November. Each treatment was carefully infused into the soil encircling the base of the guava trees to ensure the highest efficacy. Vermicompost, poultry manure, and farmyard manure were uniformly scattered around each tree and lightly plowed into the soil to facilitate proper integration. Biochar was mixed directly into the soil to increase its physical and chemical properties. Jaggery was mixed in water until it was fully dissolved and applied as a liquid fertilizer to increase the capacity of absorption and effectiveness. Cow urine combined with vermicompost and neem cake in specific treatments and was infused directly to the soil to amplify nutrient availability and microbial activity. This thoroughgoing application method was designed to align with the guava growth cycle and maximize nutrient uptake during the winter months.

Table 1. Treatment Combinations of Organic Amendments for Guava Cultivation

Table 2. Chemical Composition of Various Organic Materials Utilized in the Treatments

Sample Preparation

The seeds were removed from ripe guava fruits, which were then chopped into small pieces. The chopped guava pieces were blended with ethanol to make a consistent extract and to ensure that the target chemicals were completely dissolved in the solvent. Once the mixture was homogenised, the extract was strained using filter paper to exclude bigger particles. Alternatively, the mixture was centrifuged for 10 min at 4000 rpm to achieve a clean supernatant. The experiments that follow assessed the guava fruit antioxidants, phenols and flavonoids using this clear supernatant.

Determination of Antioxidant

According to Andrews et al. (2000), free radical scavenging activity was gauged by reduction in the absorbance of the 2,2 diphenyl-1-picrylhydrazyl (DPPH) methanol solution. A0.1 mM DPPH solution was prepared in methanol, and 1 mL of the guava extract was mixed with 3mL of DPPH solution. The mixture was incubated for 30 min at room temperature in the dark. Methanol was used in the control reaction. After incubation, absorbance was determined at 517 nm. DPPH scavenging activity was calculated by Eq. 1,

% Antioxidant activity = (A_control – A_sample)/A_control × 100 (1)

where the control absorbance is 0.329. This formula allows for the determination of the percentage of DPPH radical scavenging activity by the guava extract (Blois 1958).

Determination of Phenolic Content

The phenolic components of guava extract were determined using the Folin-Ciocalteu technique. A 10-fold dilution of the Folin-Ciocalteu reagent (2.5 mL) was combined with 0.5 mL of the guava extract, and 2.0 mL of a 7.5% sodium carbonate solution was added to the mixture. To enable the development of colour, the reaction was incubated for 40 min at 45 °C. The absorbance at 765 nm were determined. The standard curve was prepared using tannic acid as standard (µg/mL), and data was expressed as mg/g dry weight (Agbor et al. 2014).

Determination of Flavonoid Content

With catechin serving as a standard, the total flavonoid content was calculated using the chromogen reagent and the method described by Delcour and Devarebeke (1985). The results were represented in mg of catechin equivalents (CE) 100/g FW, and the absorbance was measured at 640 nm. Total phenols were estimated using the Swain and Hills (1959) approach. In a test tube, 1 mL of the extract was combined with 7.5 ml of distilled water. After thoroughly mixing the material, 0.5 ml of diluted Folin-Ciocalteu reagent was added. Following a 3-min vortex, 1 mL of saturated sodium carbonate and 500 µL of water were added to the samples to make a volume of 10 mL with distilled water. After 1 h of incubation, samples were tested for absorbance at 725 nm, taking distilled water as blank. The standard curve was prepared using tannic acid as standard (µg/mL), and data was expressed as mg/g dry weight. Data were subjected to statistical analysis using SPSS software. A randomized block design was used, and critical difference (CD) was calculated.

RESULTS AND DISCUSSION

As outlined in Table 3, the study evaluated the synergistic impact of various organic amendments on the total antioxidant activity of guava cv. L-49 over two growing seasons (2022-2023 and 2023-2024). Table 3 highlights the substantial variations across treatments.

Fig. 1. An illustration of the pathway of CO₂ entering through stomata, enhancing photosynthetic pathways, and leading to increased production of soluble sugars and soluble proteins in leaves, roots, and fruits. The application of KNP (potassium, nitrogen, and phosphorus) further boosts these soluble components, while starch levels decrease. In fruits, this process enhances antioxidants, flavonoids, phenols, Vitamin C, nitrate levels, and carotenoid biosynthesis. Vermicompost combined with biochar and jaggery, as well as A-K-A-N-A-P (additional nutrients), support this nutrient flow, promoting overall plant health and fruit quality.

Table 3. Total Antioxidant Activity (%) of Guava over Two Years (2022-2023 and 2023-2024)

Note: The treatments were as follows: Vermicompost (15 kg/tree) was used for 100% nitrogen replacement (T₁), while other vermicompost treatments included combinations with cow urine and neem cake: 10 kg/tree + 0.5 liter cow urine + 1.0 kg neem cake (T₂), 10 kg/tree + 1.0 liter cow urine + 1.5 kg neem cake (T₃), and 10 kg/tree + 1.5 liter cow urine + 2.0 kg neem cake (T₄). Additionally, vermicompost (5 kg/tree) was combined with biochar and jaggery: 5.0 kg biochar + 1.0 kg jaggery (T₅), 7.5 kg biochar + 1.25 kg jaggery (T₆), and 10 kg biochar + 1.50 kg jaggery (T₇). Poultry manure (5 kg/tree) also served as a 100% nitrogen replacement (T₈), with further combinations including 3 kg/tree + 4.0 kg biochar + 0.5 kg jaggery (T₉), 3 kg/tree + 5.0 kg biochar + 0.75 kg jaggery (T₁₀), and 3 kg/tree + 6.0 kg biochar + 1.0 kg jaggery (T₁₁). Farmyard manure (15 kg/tree) was another 100% nitrogen replacement (T₁₂), combined with cow urine and neem cake: 10 kg/tree + 0.75 liter cow urine + 1.5 kg neem cake (T₁₃), 10 kg/tree + 1.25 liter cow urine + 1.75 kg neem cake (T₁₄), and 10 kg/tree + 1.75 liter cow urine + 2.0 kg neem cake (T₁₅). The control (T₁₆) followed the recommended package of practices

Among the 16 treatments, T₆ including vermicompost (5 kg/tree) + biochar (7.5 kg/tree) + jaggery (1.25 kg/tree) demonstrated the maximum antioxidant activity. This was immediately preceded by T₅ [vermicompost (5 kg/tree) + biochar (5.0 kg/tree) + jaggery (1.0 kg/tree)]. T₇[Vermicompost (5 kg/tree) + Biochar (10 kg/tree) + Jaggery (1.50 kg/tree)] also showed similar results in respect of antioxidant activity. In contrast, T₁₆ (control, recommended package of practices) had the minimum antioxidant activity. Statistical analysis indicated a very low standard error of mean (S. Em. ± 0.01 to 0.00) and coefficients of variation (C.V. %) ranging from 0.02 to 0.03%, reflecting strong precision and consistency in the results.

Table 4. Total Phenolic Content (mgTA/g) of Guava over Two Years (2022-2023 and 2023-2024)

See notes following Table 4.

Table 5. Total Flavonoid Content (mg/g FW) of Guava over Two Years (2022-2023 and 2023-2024)