Effect OF carbon stock on growth, yield and quality of Mango, Aonla and Custard Apple fruit crops

Introduction

Soil carbon stock refers to the total amount of carbon stored in various pools, including above-ground biomass, below-ground biomass, plant litter, deadwood and soil organic carbon (SOC). The key factors controlling SOC levels are climate, hydrology, parent material, soil fertility, biological activity, vegetation patterns and land use (Jenny and Raychaudhuri, 1967) [8] . In tropical and subtropical Indian soils, high temperatures and low rainfall often lead to rapid SOC decomposition, resulting in low SOC concentrations. In contrast, humid climates with high rainfall and lush vegetation tend to maintain higher SOC levels. Notably, soil is the largest carbon pool, holding approximately 1500 Pg C, which is roughly twice the amount in the atmosphere and three times the amount in terrestrial vegetation. Land use changes can lead to significant carbon transfers from terrestrial ecosystems to the atmosphere, with 1-2 Pg C yr -1 attributed to SOC decomposition. The Food and Agriculture Organization (FAO) recommends "perennialization" of agricultural lands as a strategy to mitigate climate change, enhance food security and promote ecosystem services. However, degradation of soil physical quality is a common issue in agro-systems, particularly in open field cropping systems. Notably, India is the second-largest fruit producer globally, accounting for 13% of the world's total fruit production. Despite this, perennial fruit crops occupy only about 1% of the global agricultural land area. In India, the fruit industry spans 6.82 million hectares, producing 80.96 million tons of fruit. Fruit tree ecosystems have significant potential for carbon sequestration, with the ability to remove 240-1250 g C m -2 year -1 , according to Montanaro et al. (2010) [10] . A well-maintained fruit orchard can sequester 20-25 Mg C ha -1 in above and belowground biomass over 15-20 years. Horticulture plays a vital role in ensuring global food security, improving farmer livelihoods and mitigating climate change, making it a crucial sector for sustainable development. However, the impact of different fruit orchards on soil aggregation, aggregate-associated carbon and soil carbon stock is often overlooked, particularly in the context of soil organic carbon (SOC) dynamics. This knowledge gap is especially pronounced in fruit-based land use systems in India, where the effects of various fruit orchards on soil carbon sequestration and dynamics remain poorly understood.

Materials and Methods

The experiment carried out at Horticulture farm, College of Agriculture, Dhule on Effect of Carbon stock on Growth yield and quality of mango, Aonla and Custard Apple during the year of 2024 -2025. Healthy trees of uniform growth and vigour was selected for the experiment. The present research programme was laid out in Randomized Block Design (RBD) consisting ten treatments replicated four times two plants were selected under each treatment. The treatment consists of (T1) mango plant 1, (T2) mango plant 2, (T3) mango plant 3, (T4) aonla plant 1, (T5) aonla plant 2, (T6) aonla plant 3, (T7) custard apple plant 1, (T8) custard apple plant 2, (T9) custard apple plant 3 and (T10) Control (land with no vegetation). Total 75 soil samples were collected from all the various location throughout the experimental area with depth i.e. 0-30 cm, 30-60 cm and 60-90 cm. Then the samples were dried under shade to remove the moisture content and crushed with the help of wooden mortar and pestle. After that the soil was sieved through 2 mm sieve to obtain a uniform sample. Total carbon content of soils is determined by Nelson and Somner method (1982) [3] . The height and diameter at breast height (DBH) are two main biophysical measurements which measured for each tree sample. The mango, aonla and custard apple tree heights were measured by using measuring tape and bamboo stick. The tree diameter was measured at breast height (DBH) by using measuring tape (at 1.3 meters height from ground).

Growth parameters Estimation of above and below ground biomass

The above ground biomass (ABG) has been calculated by multiplying volume of tree and wood density (Ravindranath and Ostwald, 2008). The volume was calculated based on diameter and height. AGB (kg) = Volume of tree (m 3 ) x wood density (kg m -3 )

The below ground biomass (BGB) has been calculated by multiplying above ground biomass taking 0.26 as the root to shoot ratio (Ravindranath and Ostwald, 1997) [2] . BGB (kg) = AGB (kg) x 0.26 Volume of tree was estimated by using diameter at breast height (DBH) of tree and computed as per the standard formula (Ravindranath and Ostwald, 1997) [2] .

Volume of tree (V) (m 3 ) = π x r 2 x H Where, V = volume of tree in cubic centimetres or cubic metre r = radius of the tree 1.3 m above ground = DBH / 2 H = height of the tree in centimetres or metres.

Total plant biomass is the sum of the above and below ground biomass (Chavan and Rasal 2011) [4] .

TPB = AGB+BGB (All values are in kilogram)

Generally, for any plant species 50% of its biomass is considered as carbon (Chavan and Rasal 2011) [4] .

Plant Carbon = total plant biomass x 50% or Biomass / 2 Soil organic carbon stock Soil organic carbon stock at two depths i.e. 0-30, 30-60 and 60-90 cm were estimated by using following standard formula (Jasmine, Wagner and Abbott 2021).

SOC Stock= TOC x BD x D

Where, TOC = Total organic carbon BD = Bulk density of soil D = Depth of soil layer Total Organic Carbon (TOC) Total carbon content of soils is determined by dry combustion at high temperatures in a furnace with the collection and detection of evolved CO2 (Nelson and Sommer, 1982) [3] .

Yield was recorded after weighing fully mature fruits at each harvest, it was totalled and expressed in kilograms per plant.

The total weight of fruits was taken at each harvesting for each observational plant. The total harvesting from each plant was done to get total weight of fruit harvested during the season in kilogram per tree and it was converted to tones

The titratable acidity was estimated by the method suggested by Ranganna (1986) [1] . The acidity was expressed in terms of percentage.

Burette reading × Normality of NaOH × Volume made × Eq.wt of acid Weight of sample × aliquot of sample × 1000 × 100

Total soluble solids ( 0 BSSrix)

The Total Soluble Solids content of the pulp was measured by using Erma Hand Refractometer (0-32 0 Brix) and expressed in 0 Brix (Ranganna, 1986) [1] .

The total sugars were estimated by Fehling's reagent as per the method of suggested by Ranganna (1986) [1] . The total sugar content was expressed as percentage in terms of inverts sugars according to the formula.

The reducing sugars were determined by using Fehling's reagent as per the method of suggested by Ranganna (1986) [1] . Reducing sugars were worked out as per the formula given below.

The non-reducing sugars were estimated by using following formula.

Non-Reducing Sugar = (Total sugar -Reducing sugar) x 0.95

Results and Discussion

Growth parameters Table 1. Shows the impact of mango, aonla and custard apple trees on total plant biomass and plant carbon.

Growth Parameters

Tree height, diameter at breast height (DBH), and volume of the tree showed significant differences among the treatments. Mango trees (T1-T3) exhibited higher tree heights (515-585 cm) and DBH (82.91-88.15 cm) compared to Aonla (T4-T6) and Custard Apple (T7-T9) trees. Aonla trees (T4-T6) had higher tree volumes (18411905-2430764 cm³) compared to Mango and Custard Apple trees.

Biomass Production

Above-ground biomass, below-ground biomass, and total plant biomass showed significant differences among the treatments. Mango trees (T1-T3) had higher above-ground biomass (1890-2426 kg tree⁻¹) and total plant biomass (2381.1-3057.4 kg tree⁻¹) compared to Aonla and Custard Apple trees. Aonla trees (T4-T6) had higher below-ground biomass (383.1-505.6 kg tree⁻¹) compared to Custard Apple trees.

Carbon Sequestration

Plant carbon content showed significant differences among the treatments. Mango trees (T1-T3) had higher plant carbon content (1190.5-1528.7 kg tree⁻¹) compared to Aonla and Custard Apple trees. These findings have implications for optimizing horticultural practices, such as pruning, irrigation, and fertilization, to enhance the productivity and sustainability of these fruit tree species (Nath et al., 2008) [6] .

Yield contributing characters

The study evaluated the impact of different treatments on yield and fruit characteristics of Mango, Aonla, and Custard Apple trees. The results showed significant variations among the treatments, with Aonla trees (T4-T6) exhibiting exceptionally high yields, ranging from 9.4 to 14.0 t/ha. Treatment T6 (Aonla) showed the highest yield (14.0 t/ha), attributed to the high number of fruits per plant (2236) and average fruit weight (35 g). Mango trees (T1-T3) and Custard Apple trees (T7-T9) also showed promising yields, ranging from 3.8 to 4.6 t/ha and 4.3 to 6.5 t/ha, respectively. Treatment T2 (Mango) and Treatment T9 (Custard Apple) exhibited superior performance in terms of yield and fruit characteristics. These findings highlight the potential of horticultural practices to enhance fruit production and contribute to carbon sequestration. Fruit tree-based systems can play a significant role in mitigating climate change by sequestering carbon in trees, soils, and other biomass (Lal, 2004; Kumar et al., 2018) [7] . The carbon sequestration potential of these fruit tree species can be substantial, considering their biomass production and yield. As reported by Smith et al. (2020) [12] , sustainable horticultural practices can help reduce greenhouse gas emissions and promote ecosystem services.

Quality contributing characters

The study evaluated the impact of different treatments on the physio-chemical characteristics of Mango, Aonla, and Custard Apple fruits. The results showed significant variations among the treatments for Total Soluble Solids (TSS), Titratable Acidity, Reducing Sugar, Non-Reducing Sugar, and Total Reducing Sugar.

Total Soluble Solids (TSS)

The Total Soluble Solids (TSS) content varied significantly among the treatments, with Custard Apple fruits exhibiting the highest TSS values (21.87-23.48°Brix), followed by Mango (15.14-16.42°Brix) and Aonla (9.85-10.91°Brix). Treatment T9 in Custard Apple showed the highest TSS value (23.48°Brix), indicating optimal sugar development. These results suggest that the treatments had a significant impact on the sugar content of the fruits, with implications for fruit quality and consumer preference.

Titratable Acidity

The titratable acidity content showed significant variations among the treatments, with Mango fruits exhibiting the highest acidity values (1.84-2.09%), followed by Aonla (1.14-1.33%) and Custard Apple (0.22-0.34%). Treatment T3 in Mango showed the highest titratable acidity value (2.09%), indicating a potential impact on fruit flavour and shelf life. These results highlight the importance of considering acidity levels in fruit production and processing.

Reducing Sugar

The reducing sugar content varied significantly among the treatments, with Custard Apple fruits exhibiting the highest reducing sugar values (16.94-18.80%), followed by Mango (4.69-5.04%) and Aonla (1.98-2.36%). Treatment T9 in Custard Apple showed the highest reducing sugar value (18.80%), indicating optimal sugar development. These results suggest that the treatments had a significant impact on the sugar profile of the fruits, with implications for fruit sweetness and flavor.

Non-Reducing Sugar

The non-reducing sugar content showed significant variations among the treatments, with Mango fruits exhibiting the highest non-reducing sugar values (8.80-9.42%), followed by Custard Apple (1.49-2.76%) and Aonla (1.19-1.97%). Treatment T2 in Mango showed the highest non-reducing sugar value (9.42%), indicating optimal sugar development. These results highlight the importance of considering the sugar profile of fruits in production and processing.

Total Reducing Sugar

The total reducing sugar content varied significantly among the treatments, with Custard Apple fruits exhibiting the highest total reducing sugar values (18.45-21.60%), followed by Mango (13.55-14.50%) and Aonla (3.17-4.33%). Treatment T9 in Custard Apple showed the highest total reducing sugar value (21.60%), indicating optimal sugar development. These results suggest that the treatments had a significant impact on the overall sugar content of the fruits, with implications for fruit quality and consumer preference. In custard apple orchard treatment T9 was observed significantly higher for SOC Stock content i.e. 25.81 Mg ha - 1 at depth 0-30 cm and goes on decreasing as the depth increases as 23.76 Mg ha -1 (30-60 cm) and 21.94 Mg ha -1 (60-90 cm) respectively as compared to treatment T10 i.e. control was observed 19.46 Mg ha -1 at 0-30 cm depth and 19.34 Mg ha -1 and 16.25 Mg ha -1 at depth 30-60 cm and 60-90 cm respectively. The SOC Stock content in treatment T8 (25.13 Mg ha -1 ) and T7 (24.46 Mg ha -1 ) was observed. Surface layer soils (0-30 cm) had greater soil organic carbon (SOC) content than subsurface soil (30-60 cm)and (60-90 cm) in mango orchard soil which indicated a declining trend as depth increased due to low nutrients and biological activity in lower layer, as compared to greater organic matter at surface layer soils (Bhat et al. 2017) [13] .

The data pertaining on soil total organic carbon (TOC) in mango, aonla and custard apple orchards soil which are presented in Table 4.

In mango orchard treatment T2 was observed higher TOC content i.e. 1.82% at depth 0-30 cm and goes on decreasing as the depth increases as 1.07% (30-60 cm) and 0.76% (60-90 cm) respectively as compared to treatment T10 i.e. control was observed 0.60% at 0-30 cm depth and 0.35% and 0.43% at depth 30-60 cm and 60-90 cm respectively. The TOC content in treatment T1 (1.36%) and T3 (0.87%) was observed.

In aonla orchard treatment T6 was observed significantly superior for TOC content i.e. 1.42% at depth 0-30 cm and goes on decreasing as the depth increases as 1.16% (30-60 cm) and 0.76% (60-90 cm) respectively as compared to treatment T10 i.e. control was observed 0.60% at 0-30 cm depth and 0.35% and 0.43% at depth 30-60 cm and 60-90 cm respectively. The TOC content in treatment T5 (1.31%) and T4 (1.06%) was observed.

In custard apple orchard treatment T9 was observed significantly higher for TOC content i.e. 1.39% at depth 0-30 cm and goes on decreasing as the depth increases as 1.15% (30-60 cm) and 0.68% (60-90 cm) respectively as compared to treatment T10 i.e. control was observed 0.60% at 0-30 cm depth and 0.35% and 0.43% at depth 30-60 cm and 60-90 cm respectively. The TOC content in treatment T8 (1.33%) and T7 (1.25%) was observed. The total organic carbon content exhibited a declining trend with soil depth, with higher concentrations in the surface soil layer attributed to the substantial addition of organic matter from tree root and leaf litter, which gradually decreased with increasing depth was observed by Ingram and Fernandes (2001) [14] .

Conclusion

On the basis of finding of present investigation, on above basis it could be concluded that, the effect of carbon stock on growth, yield and quality of mango, aonla and custard apple fruit crops were found to be promising. The carbon stock observed in this study was found to be significantly higher in mango orchard soil because of the annual litter fall which helped in balancing the pH of soil enhancing the microbial activity and thus leading to increased nutrient content of soil. Among all the treatments taken treatment T2 (Mango), T6 (Aonla) and T9 (Custard apple) has shown highest performance in terms of growth, yield and quality parameters. Thus the results of this study concludes that the carbon sequesterd from the perennial fruit crops such as Mango, Aonla and Custard apple orchard is significantly higher than the control part i.e. soil without vegetation adjacent to fruit orchard in the order Mango> Aonla> Custard apple. This indicates the potential of horticultural crops both in securing rural livelihood as well as mitigating climate change.

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