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

Reetika Sharma, Kumar, R., Bakshi, P., Amit Jasrotia, Bhav Kumar Sinha, Sharma, N., Sharma, P., Kumar, V., Sood, M., and Dadheechi, M. (2024). "Synergistic impact of vermicompost, biochar and jaggery on antioxidants, phenols and flavonoids in Guava cv. L-49," BioResources 19(4), 8173–8187.

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.

Download PDF

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 *

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, T₆including 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)

See notes following Table 4.

Fig 2. The bar chart compares the total antioxidant activity, phenolic content, and flavonoid content of guava across two years (2022-2023 and 2023-2024) under 16 different treatments.

The significance of the observed differences across treatments was further validated by the critical difference (C.D.) values at the 5% and 1% levels. These results demonstrate how particular organic amendments can improve the antioxidant capacity of guava, with T₆ proving to be the most effective treatment. The antioxidant activity of guava fruits is significantly enhanced by the application of vermicompost, biochar and jaggery as compared to control (T₁₆).

Table 4 presents significant differences between treatments from synergistic impact of various organic amendments on the total phenolic content of guava cv. L-49 over two growing seasons (2022-2023 and 2023-2024). T₆[vermicompost (5 kg/tree) + biochar (7.5 kg/tree) + jaggery (1.25 kg/tree)] showed the greatest phenolic content. T₅[vermicompost (5 kg/tree) + biochar (5.0 kg/tree) + jaggery (1.0 kg/tree)] and T₇[vermicompost (5 kg/tree) + biochar (10 kg/tree) + jaggery (1.50 kg/tree)] also demonstrated a significant improvement. On the other hand, T₁₆(control, recommended package of practices) exhibited the least amount of phenolic content. The findings of the statistical analysis showed a very low coefficient of variation (C.V.%) ranging from 0.02 to 0.06% and a very low standard error of mean (S. Em. ± 0.01 to 0.00), indicating great precision and reliability. The significance of the differences between the treatments was further confirmed by critical difference (C.D.) values at the 5% and 1% levels. These findings highlight the ability of particular organic amendments to increase guava phenolic content; treatment T₆was the most successful. According to Table 5, the study examining the synergistic impact of various organic amendments on the total flavonoid content of guava cv. L-49 over two growing seasons (2022-2023 and 2023-2024) demonstrated significant variations across treatments. T₆[vermicompost (5 kg/tree) + biochar (5.0 kg/tree) + jaggery (1.0 kg/tree)]had the highest total flavonoid content among the 16 treatments. T₅[vermicompost (5 kg/tree) + biochar (5.0 kg/tree) + jaggery (1.0 kg/tree)] and T₇[vermicompost (5 kg/tree) + biochar (10 kg/tree) + jaggery (1.50 kg/tree)] showed a significant increase in flavonoid content as well. On the other hand, T₁₆(control, recommended package of practices) had the lowest level of flavonoid content. The findings of the statistical analysis demonstrated good precision and consistency, with a low standard error of mean (S. Em. ± 0.01) and coefficients of variation (C.V. %) of 0.05 for both years. The significance of the observed differences across treatments was further corroborated by the critical difference (C.D.) values at the 5% and 1% levels. These results demonstrate how adding particular organic amendments can increase the amount of flavonoids in guava, with T₆ being the most successful treatment.

As illustrated in Fig2, the overall antioxidant activity was higher in 2022-2023 for most treatments, with some decline or stability in 2023-2024. Phenolic content generally increased slightly from 2022-2023 to 2023-2024, showing greater stability. Flavonoid content exhibited mixed trends, with some treatments improving and others declining in 2023-2024. Notably, treatments T₅ and T₆ showed significant increases in both antioxidant activity and phenolic content in 2023-2024, while treatments like T₁₄ to T₁₆ demonstrated less pronounced changes

The enhanced antioxidant activity, phenols and flavonoids in guava fruits due to the application of vermicompost, biochar, and jaggery, as well as the corresponding increases in carotenoids, phenolics, and flavonoids, is supported by several studies. A possible explanation is that the biochar, increasing the pH, CEC (Cation exchange capacity), N_tot(Total soil nitrogen), C_tot(Total soil carbon), P_tot (Total soil phosphorous), and water content, could enhance available nutrients for plants and, consequently, biomass accumulation (Scotti et al. 2015). Increase in CEC value could be driven by the presence of cation exchange sites on the biochar surface (Sohi et al. 2010). Vaccari et al. (2015) reported that this could contribute to retaining NH₄⁺, leading to improved N nutrition in biochar-amended soils (Hollister et al. 2013). This would confirm a direct role of biochar in the nutrient supply to plants (Clough et al. 2010). Additionally, the role of biochar in improving soil structure and nutrient retention, as well as its impact on microbial activity and the phenylpropanoid pathway activation during ripening, is corroborated by Lehmann et al. (2011) and Koes et al. (2005).

According to studies published in the literature (Amlinger et al. 2007; Diacono and Montemurro 2011), lettuce plants in compost-added soil demonstrated the highest total biomass accumulation, assimilation rate, and water use efficiency, likely because of the increased soil nutrient availability (soil C_tot, N_tot, P_tot, content). This high soil nutrient status could also have enhanced the activity of enzymes involved in phosphorus and nitrogen cycling (phosphohydrolase, chymotrypsin, and trypsin), which got increased due to soil amendment as compared to those in the unamended soils. Tyrosine and phenylalanine (precursors of phenolic compound) production is enhanced due to the corresponding increase in enzyme activity. Such changes have been reported to be the result of the increased organic matter and the activation of the shikimate pathway (Benhammou et al. 2009). The application of organic manure boosts the synthesis of soluble sugars, amino acids, phenolic volatiles and flavonoids in guava fruits by modulating major metabolic pathways. Specifically, organic manure increases the essential nutrients that activate signaling cascades, contributing to the upregulation of genes culpable for the biosynthesis of these compounds. This reprogramming of the regulatory network of transcripts and metabolites prompts accelerated yields of these valuable components, like flavonoids and phenols, which are antioxidants and contribute to the improved quality of guava fruits (Wu et al. 2024). The effects of vermicompost, which provides organic nitrogen and reduces nitrate accumulation, favoring secondary metabolite synthesis, align with findings from Celikcan et al. (2021).

The introduction of jaggery substantially augmented the microbial population in the soil, thus boosting enzymatic activity. The addition of jaggery makes this change more effective by increasing biochar’s ability to boost microbial activity by making it better at keeping moisture in and letting air flow through. Moreover, biochar amplifies the effects of vermicompost by increasing nutrient concentrations in the soil, hence enhancing antioxidant activity (Gabhane et al. 2012; Waqas et al. 2018). Jaggery’s contribution to the phenolic content further boosts the antioxidant properties (Choudhary et al. 2022).

One hypothesis is that the addition of biochar to vermicompost complexes may cause alterations in the structure, abundance, and activity of the microbial community in soils (Lehmann 2007). The proposed modifications have the potential to enhance the bioavailability of nutrients to plants and may trigger the secretion of plant growth promoting hormones. On the other hand, vermicompost and biochar are generally alkaline in nature with biochar having a high ion exchange capacity and vermicompost has a specific acid-base buffering capacity (Zhao et al. 2015; Li et al. 2018). Hence, both organic additions have the ability to elevate the pH level of the soil. Our investigations have demonstrated that the introduction of organic amendments resulted in a significant increase in soil pH, converting acidic soil to mildly alkaline soil. This finding aligns with prior research outcomes. The material cycle and energy flow within the soil closely interconnect with soil organic carbon, the fundamental component of soil fertility. Dissolved Organic Carbon (DOC) is a highly reactive component of organic carbon that exhibits rapid oxidation, low stability and susceptibility to degradation (Kaiser and Kalbitz 2012; Guillaume et al. 2022; Zhang et al. 2022). Research has demonstrated that applying biochar and vermicompost significantly increases the soil’s organic matter content (Liu et al. 2020; Bi et al. 2021). Although organic matter constitutes less than 10% of the solid phase composition of soil, it plays a crucial role in stimulating microbial activity and facilitating mineral transformation. Furthermore, their composition also serves as an indicator of the nutritional condition and soil quality (Wang et al. 2022). The synergistic effects of these amendments, as noted in studies by Premuzic et al. (2001, 2002), demonstrate the enhancement of antioxidants, phenolic and flavonoid contents in treated guava fruits. The positive correlation between flavonoid content and antioxidant activity during ripening is highlighted by Bhandari and Lee (2016).

As for the results, the consistent and slightly higher values for antioxidant activity in 2023-2024 compared to the previous year may suggest a cumulative or enhanced effect of organic manure over time. The persistent application of organic manure likely improved soil fertility and microbial activity, leading to a more robust nutrient uptake by the plants, which in turn intensified the production of antioxidants. The similar trend observed in phenolic content further supports this hypothesis, indicating that the positive effects of organic manure on guava fruit quality are not only sustained but also amplified over consecutive years. The authors could conclude that the consistent increase in these values over two years underscores the effectiveness of organic manure in enhancing the nutritional quality of guava fruits, likely due to the sustained improvement in soil health and plant metabolic activity.

CONCLUSIONS

During the course of two growing seasons, the application of treatment T₆ including vermicompost (5 kg/tree), biochar (7.5 kg/tree), and jaggery (1.25 kg/tree) considerably increased the antioxidant activity, total phenolic content, and total flavonoid content in guava cv. L-49. The highest results were consistently obtained by treatments T₆ followed by T₅ and T₇, showing their greatest efficacy.
The increased availability of nutrients and improved biosynthetic processes made possible by the organic amendments are responsible for the increase in these beneficial compounds.
These results highlight the possibility of utilising biochar, vermicompost, and jaggery together to increase the antioxidant and nutritional value of guava, providing a sustainable method of enhancing fruit quality.

REFERENCES CITED

Abd-Elmabod, S.K., Muñoz-Rojas, M., Jordán, A., Anaya-Romero, M., Phillips, J.D., Jones, L., Zhang, Z., Pereira, P., Fleskens, L., Van Der Ploeg, M., and De La Rosa, D. (2020). “Climate change impacts on agricultural suitability and yield reduction in a Mediterranean region,” Geoderma 374, 114453. DOI: 10.1016/j.geoderma.2020.114453

Agbor, G.A., Vinson, J.A., and Donnelly, P.E. (2014). “Folin-Ciocalteu reagent for polyphenolic assay,” International Journal of Food Science Nutrition and Dietetics 147-156. DOI: 10.19070/2326-3350-1400028

Anand, A.V., Velayuthaprabhu, S., Rengarajan, R.L., Sampathkumar, P., and Radhakrishnan, R. (2020). “Bioactive compounds of guava (Psidium guajava L.),” in: Reference Series in Phytochemistry, pp. 503-527. DOI: 10.1007/978-3-030-30182-8_37

Andrews, J., Malone, M., Thompson, D.S., Ho, L.C., and Burton, K.S. (2000). “Peroxidase isozyme patterns in the skin of maturing tomato,” Plant, Cell and Environment 23, 415-422.

Benhammou, N., Bekkara, F.A., and Kadifkova Panovska, T. (2009). “Antioxidant activity of methanolic extracts and some bioactive compounds of Atriplex halimus,” ComptesRendus Chimie 12(12), 1259-1266. DOI: 10.1016/j.crci.2009.02.004

Bhandari, S.R., and Lee, J.G. (2016). “Ripening-dependent changes in antioxidants, color attributes, and antioxidant activity of seven tomato (Solanum lycopersicum L.) cultivars,” Journal of Analytical Methods in Chemistry 1-13. DOI: 10.1155/2016/5498618

Bi, Y., Kuzyakov, Y., Cai, S., and Zhao, X. (2021). “Accumulation of organic compounds in paddy soils after biochar application is controlled by iron hydroxides”, Sci. Total Environ 764, 144300. DOI:10.1016/j.scitotenv.2020.144300

Blois, M.S. (1958). “Antioxidant determinations by the use of a stable free radical,” Nature 181(4617), 1199-1200. DOI: 10.1038/1811199a0

Celikcan, F., Kocak, M.Z., and Kulak, M. (2021). “Vermicompost applications on growth, nutrition uptake and secondary metabolites of Ocimum basilicum L. under water stress: A comprehensive analysis,” Industrial Crops and Products 171, article 113973. DOI: 10.1016/j.indcrop.2021.113973

Ceritoğlu, M., Şahin, S., and Erman, M. (2018). “Effects of vermicompost on plant growth and soil structure,” Selcuk Journal of Agricultural and Food Sciences 32(3), 607-615. DOI: 10.15316/sjafs.2018.143

Choudhary, R.C., Bairwa, H.L., Kumar, U., Javed, T., Asad, M., Lal, K., Mahawer, L.N., Sharma, S.K., Singh, P., Hassan, M.M., Abo-Shosha, A.A., Rajagopal, R., and Abdelsalam, N.R. (2022). “Influence of organic manures on soil nutrient content, microbial population, yield and quality parameters of pomegranate (Punica granatum L.) cv. Bhagwa,” PLoS One 17(4), article e0266675. DOI: 10.1371/journal.pone.0266675

Clough, T.J., and Condron, L.M. (2010). “Biochar and the nitrogen cycle: Introduction,” Journal of Environmental Quality 39(4), 1218-1223.

Delcour, J.A., and De Varebeke, J. (1985). “A new colourimetric assay for flavanoids in pilsner beers,” Journal of the Institute of Brewing 91(1), 37-40.

Dumas, Y., Dadomo, M., Di Lucca, G., and Grolier, P. (2003). “Effects of environmental factors and agricultural techniques on antioxidant content of tomatoes,” Journal of the Science of Food and Agriculture 83(5), 369-382. DOI: 10.1002/jsfa.1370

Edwards, C.A., and Arancon, N.Q. (2004). Vermiculture Technology, CRC Press.

Ennis, C.J., Evans, A.G., Islam, M., Ralebitso-Senior, T.K., and Senior, E. (2012). “Biochar: Carbon sequestration, land remediation, and impacts on soil microbiology,” Critical Reviews in Environmental Science and Technology 42(22), 2311-2364. DOI: 10.1080/10643389.2011.574115

Gabhane, J., William, S.P., Bidyadhar, R., Bhilawe, P., Anand, D., Vaidya, A.N., and Wate, S.R. (2012). “Additives aided composting of green waste: Effects on organic matter degradation, compost maturity, and quality of the finished compost,” Bioresource Technology 114, 382-388.

Gamage, A., Gangahagedara, R., Gamage, J., Jayasinghe, N., Kodikara, N., Suraweera, P., and Merah, O. (2023). “Role of organic farming for achieving sustainability in agriculture,” Farming System 1(1), article 100005. DOI: 10.1016/j.farsys.2023.100005

Ghosh, S., Ow, L. F. and Wilson, B. (2014). “Influence of biochar and compost on soil properties and tree growth in a tropical urban environment,” International Journal of Environmental Science and Technology 12(4), 1303-1310. DOI: 10.1007/s13762-014-0508-0

Guillaume, T., Makowski, D., Libohova, Z., Bragazza, L., Sallaku, F., and Sinaj, S. (2022). “Soil organic carbon saturation in cropland-grassland systems: Storage potential and soil quality,” Geoderma 406, 115529. DOI:10.1016/j.geoderma.2021. 115529

Hargreaves, J.C., Adl, M.S., Warman, P.R., and Rupasinghe, H.P.V. (2008). “The effects of organic and conventional nutrient amendments on strawberry cultivation: Fruit yield and quality,” Journal of the Science of Food and Agriculture 88(15), 2669-2675. DOI: 10.1002/jsfa.3388

Hollister, C.C., Bisogni, J. J., and Lehmann, J. (2013). “Ammonium, nitrate, and phosphate sorption to and solute leaching from biochars prepared from corn stover (Zea mays L.) and oak wood (Quercus spp.),” Journal of Environmental Quality 42(1), 137-144.

Kaiser, K., and Kalbitz, K. (2012). “Cycling downwards – dissolved organic matter in soils,” Soil Biol. Biochem 52, 29–32. DOI: 10.1016/j.soilbio.2012.04.002

Kamboj, S., Matharu, M., and Gupta, M. (2023). “Examining consumer purchase intention towards organic food: An empirical study,” Cleaner and Responsible Consumption 9, article 100121. DOI: 10.1016/j.clrc.2023.100121

Kazachkova, Y. (2023) “Give me some sugar: a transporter responsible for sugar uptake from the rhizosphere identified in apple,” Plant Physiology 193(1), 156-158. DOI: 10.1093/plphys/kiad342. PMID: 37313718; PMCID: PMC10469535.

Koes, R., Verweij, W., and Quattrocchio, F. (2005). “Flavonoids: A colorful model for the regulation and evolution of biochemical pathways,” Trends in Plant Science 10(5), 236-242. DOI: 10.1016/j.tplants.2005.03.002

Lehmann, J. (2007). “Bioenergy in the black,” Front. Ecol. Environment 5, 381-387

Lehmann, J., and Joseph, S. (2015). Biochar for Environmental Management, Routledge.

Lehmann, J., Rillig, M.C., Thies, J., Masiello, C.A., Hockaday, W. C., and Crowley, D. (2011). “Biochar effects on soil biota – A review,” Soil Biology and Biochemistry 43(9), 1812-1836. DOI: 10.1016/j.soilbio.2011.04.022

Li, C., Ma, S., Shao, Y., Ma, S., and Zhang, L. (2018). “Effects of long-term organic fertilization on soil microbiologic characteristics, yield and sustainable production of winter wheat”, J. Integr. Agric 17, 210–219. DOI:10.1016/s2095- 3119(17)61740-4

Liu, M., Wang, C., Liu, X., Lu, Y., and Wang, Y. (2020). “Saline-alkali soil applied with vermicompost and humic acid fertilizer improved macroaggregate microstructure to enhance salt leaching and inhibit nitrogen losses,” Appl. Soil Ecol 156, 103705. DOI: 10.1016/j.apsoil.2020.103705

Nahm, K. H. (2003). “Evaluation of the nitrogen content in poultry manure and its utilization in agriculture,” Poultry Science 82(4), 523-526. DOI: 10.1093/ps/82.4.523

Naseer, S., Hussain, S., Naeem, N., Pervaiz, M., and Rahman, M. (2018). “The phytochemistry and medicinal value of Psidium guajava (guava),” Clinical Phytoscience 4(1). DOI: 10.1186/s40816-018-0093-8

Parthasarathy, V.A., and Kumar, R. (2008). “Organic horticulture: A sustainable approach,” Indian Horticulture 53(2), 45-48.

Pathak, M. L., and Singh, P. (2009). “Indigenous veterinary practices,” Agricultural Extension in India 5(1), 87-92.

Premuzic, Z., de los Ríos, A., Clozza, M., Vilella, F., Mirabelli, E., and Accorinti, C. (2001). “Influence of fertilisation on the production and vitamin C and sugar content of cherry tomatoes,” Acta Horticulturae 559, 601-606. DOI: 10.17660/ActaHortic.2001.559.88

Premuzic, Z., Gárate, A., and Bonilla, I. (2002). “Production of lettuce under different fertilisation treatments, yield and quality,” Acta Horticulturae 571, 65-72. DOI: 10.17660/ActaHortic.2002.571.6

Rojas-Downing, M.M., Nejadhashemi, A.P., Harrigan, T., and Woznicki, S.A. (2017). “Climate change and livestock: Impacts, adaptation, and mitigation,” Climate Risk Management 16, 145-163. DOI: 10.1016/j.crm.2017.02.001

Scotti, R., Bonanomi, G., Scelza, R., Zoina, A., and Rao, M.A. (2015). “Organic amendments as sustainable tool to recovery fertility in intensive agricultural systems,” Journal of Soil Science and Plant Nutrition 15(2), 333-352.

Shanthirasekaram, K., Vajira, P.B., Manawadu, H., and Gangabadage, C.S. (2021). “Phytochemicals and antioxidant properties of the leaves of wild guava varieties grown in Sri Lanka,” Journal of Science 12(2), 33. DOI: 10.4038/jsc.v12i2.34

Sharifi‐Rad, J., Painuli, S., Sener, B., Kılıç, M., Kumar, N. V. A., Semwal, P., Docea, A. O., Suleria, H. a. R., and Calina, D. (2023). “Revisiting the nutraceutical profile, chemical composition, and health benefits of jaggery: Updates from recent decade,” eFood 4(2). DOI: 10.1002/efd2.75

Sharma, S., and Singh, G. (2008). “Jaggery: A traditional Indian sweetener with health benefits,” Journal of Food Science and Technology 45(6), 515-520. DOI: 10.1007/s11483-008-0147-5

Sohi, S. P., Krull, E., Lopez-Capel, E., and Bol, R. (2010). “A review of biochar and its use and function in soil,” Advances in Agronomy 105(1), 47-82.

Subapriya, R., and Nagini, S. (2005). “Neem: A review of its therapeutic applications and its importance in traditional medicine,” Journal of Biological Sciences 5(3), 297-303. DOI: 10.3923/jbs.2005.297.303

Swain, T., and Hills, W. E. (1959). “The phenolic constituents of Prunus domestica,” Journal of Agricultural and Food Chemistry 10, 63-68.

Trupiano, D., Cocozza, C., Baronti, S., Amendola, C., Vaccari, F. P., Lustrato, G., Di Lonardo, S., Fantasma, F., Tognetti, R. and Scippa, G. S. (2017). “The effects of biochar and its combination with compost on lettuce (Lactuca sativa L.) growth, soil properties, and soil microbial activity and abundance,” International Journal of Agronomy 1–12. DOI: 10.1155/2017/3158207

Vaccari, F. P., Maienza, A., and Miglietta, F. (2015). “Biochar stimulates plant growth but not fruit yield of processing tomato in a fertile soil,” Agriculture, Ecosystems and Environment 207, 163-170.

Wang, Z., Ma, S., Hu, Y., Chen, Y., Jiang, H., and Duan, B. (2022). “Links between chemical composition of soil organic matter and soil enzyme activity in alpine grassland ecosystems of the Tibetan Plateau,” Catena (Amst) 218, 106565. DOI:10. 1016/j.catena.2022.106565

Waqas, M., Nizami, A. S., Aburiazaiza, A. S., Barakat, M. A., Ismail, I. M. I., and Rashid, M. I. (2018). “Optimization of food waste compost with the use of biochar,” Journal of Environmental Management 216, 70-81. DOI: 10.1016/j.jenvman.2017.06.015

Wu, M., Zhao, P., Liu, L., Zhao, Q., Li, Q., Li, L., and Xu, J. (2024). “The organic manure-improved yield and quality in strawberries is attributed to metabolic reprogramming to increase amino acids, sugar/acid ratio, flavonoids and phenolic volatiles,” Plant and Soil. DOI: 10.1007/s11104-024-06651-5

Zhang, Y. J., Yu, S. G., Li, Z. J., Chang, T. T., Xu, Q. C., and Xu, H. L. (2022). “Effects of excessive nitrogen fertilizer and soil moisture deficiency on antioxidant enzyme system and osmotic adjustment in tomato seedlings,” Int. J. Agric. Biol. Eng 15, 127–134. DOI: 10.25165/j.ijabe.20221502.5555

Zhao, H., Li, T., Zhao, Z., Liu, C., Wang, M., and Li, D. (2015). “Cucumber seedling growth as influenced by worm cast medium added with vermiculite and nitrogen-phosphorus-potassium fertilizers,” Acta Agric. Shanghai 9, 13–20. DOI:10. 15955/j.issn1000-3924.2015.05.03

Submitted: August 3, 2024; Peer review completed: August 24, 2024; Revised version received and accepted: August 27, 2024; Published: September 10, 2024.

DOI: 10.15376/biores.19.4.8173-8187