Estimation of terrestrial carbon stock as influenced by mango orchard at Dhule region

Introduction

Information on the dynamics of soil organic carbon in agricultural soils is becoming more essential due to the consequences for climate change and crop yield. Expanding forests, forest understory plants, litter, and forest soils retrieve almost two-thirds of terrestrial carbon. The global production of greenhouse gases (GHGs; CO2, CH4, N2O) is increasing by the day, but there are several methods for reducing these emissions, the most common of which is the cultivation and protection of trees such as fruit orchards or agroforestry. This strategy, often known as "climate-smart farming," might significantly decrease harmful gasoline emissions and has various beneficial environmental consequences. The cultivation of fruits is viewed as a potential tool for improving agricultural practices that may be harmed by climate change. The combination of trees, frequently in different systems, promotes productivity, improves the nutrient cycle, and assists in ecological balance due to the "biological carbon sequestration potential". Carbon sequestration in terrestrial ecosystems refers to the process of removing carbon sources from the environment, such as CO2, or reducing CO2 emissions from terrestrial ecosystems and storing them productively. Natural vegetation has a significant influence on soil organic carbon concentration, showing a sink capacity for tree cultivation. Increased carbon emissions are a major cause of anxious across the world, and the Kyoto Protocol does an excellent job of tackling them. Carbon sequestration is the long-term storage of carbon in the oceans, soils, plants (especially forests), and geological formations. India serves as a wide variety of soil types and climates that are perfect for growing horticulture and agricultural items. As a result, these fields may be planted with permanent horticultural crops to ensure lucrative and effective commercial horticulture. Mango (Mangifera indica) is regarded as "king of fruits" and is the leading fruit crop of India. Mango accounts for approximately 36% of total fruit area (2019-20), covering 2.3 million hectares and producing 20.44 million tonnes, accounting for 40.50% of total global mango output (National Horticultural Board, 2022). Major mango producing states area wise are Andhra Pradesh (16.5%), Uttar Pradesh (12.1%), Odisha (8.3%), Karnataka (7.7%) and production wise Uttar Pradesh (23.4%) ranks first closely followed by Andhra Pradesh (23.1%). In Telangana mango is cultivated in 1, 28, 000 ha with productivity of 992 kg ha -1 (Horticulture Statistics Division, DAC&FW, 2021). It is estimated that, total C sequestered per mango tree across the country varied from 446.2 to 934.7 kg tree-1 and, grafted mangoes sequestered 733.03 kg C tree-1, thus Indian mango orchards had carbon sequestration potential of 285.005 m t of carbon (Ganeshamurthy et al., 2019) [16] . In terms of nutrient supply, dissolved organic N (DON), labile organic nitrogen (LON) and light fraction organic matter (LFOM) respond more quickly to management than SOM content (Biederbeck et al. 1994) [4] and they are believed to play a role in regulating N mineralization patterns in various soils (Bonde and Rosswall, 1988) [7] . Soil organic carbon sequestration is influenced by several factors, including climatic and soil conditions (Chabbi et al. 2009) [10] soil erosion, vegetation types, cropping systems (Jagadamma et al. 2010) [21] and managements including tillage (Ogle et al. 2005) [33] and fertilization (Bhattacharyya et al. 2008) [5] . Keeping the factors mentioned above in mind, study was conducted at the College of Agriculture, Dhule to better understand soil organic carbon sequestration after mango planting, with the following objectives. To estimate the soil carbon storage in a mango orchard.

Materials and Methods

At a height of 250 meter above mean sea level. Field is located at 20 0 53'59" N latitude and 74 0 46'11" E longitude. Field experiment was undertaken at the Horticulture Farm, College of Agriculture, Dhule, in Agro climatic Zone-6, i.e. the scarcity zone condition of Northern Maharashtra. 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). The height and diameter at breast height (DBH) are two main biophysical measurements which measured for each tree sample. The mango tree height measured by 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).

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) [43] . 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, 2008) [43] . 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, 2008) [43] .

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) [11] .

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) [11] . Plant Carbon = total plant biomass x 50% or Biomass / 2

Estimation of 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) [22] .

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) [32] .

Water Soluble Carbon (WSC)

Water soluble carbon at three depths were analysed by following Water extraction method given by Mc Gill et al. (1986) [28] .

Soil Microbial Biomass Carbon (SMBC)

The soil microbial biomass carbon from soil was determined by the fumigation-extraction technique in fresher incubated soil samples at 27 °C described by Vance et al. (1987) [44] .

POSC

Permanganate oxidizable soil carbon at three depths was analysed by following Permanganate oxidation method given by Blair et al. (1995) [6] .

Humic Acid and Fulvic Acid Carbon

The principal extraction procedure (Stevenson, 1994) was followed by separation after extracting with freshly prepared sodium hydroxide (0.5 M NaOH) at pH 13.0 with acid wash (0.1 M HCl, pH 2.0). The results of the experiment were statistically examined using RBD, according to Panse and Sukhatme (1967) [34] .

Results and Discussion

Table 1. Shows the impact of the various mango trees on total plant biomass and plant carbon. In comparison to the treatment in the mango orchard treatment T 8 was found higher volume of tree (3206.37 m 2 ) above ground biomass (AGB) i.e. (2180.33 kg tree -1 ), below ground biomass (BGB) i.e. (566.89 kg tree -1 ), total plant biomass (TB) i.e. (2757.80kg tree -1 ), and plant carbon (PC) i.e. (1373.61 kg tree -1 ). Maximum tree height and maximum diameter recorded in T 5 (527 cm) (88.39) respectively. Furthermore, on the other side lower data on plant biomass was found in treatment T 1 e.g. volume of tree (1969.02 m 2 ), above ground biomass (ABG) (1338.94 kg tree -1 ), below ground biomass (BGB) (348.12 kg tree -1 ), total plant biomass (TB) (1687.06 kg tree -1 ) and plant carbon (PC) (843.53 kg tree -1 ) and their height and diameter at breast height was (470 cm) and (72.13 cm) respectively Among the different treatments, above ground biomass, below ground biomass, and total plant biomass were greater than the rest of the treatments, and on the basis of these biometric observations, higher plant carbon were reported after calculation than the rest of the treatments. It might be owing to increased leaf fall or litter fall over a nineteen-year period, its genetic makeup, and successful adaptation to climate circumstances. Similar observations were also be recorded by Kaur et al. (2002) [24] and Chavan and Rasal (2012) [12] .

Total Organic Carbon

According to the findings in Table 2, the total organic carbon content of orchard soil was measured at depths of 0 to 30 cm, 30 to 60 cm, and 60 to 90 cm. Carbon accounts for a sizable component of soil organic matter, which also contains nutrients, cations, and trace elements essential to the growth of plants.

At a depth of 0 to 30 cm, where treatment T8 (0.94%) was significantly superior however, it was at par with treatments T4 (0.91%), T 5 (0.90%), T 7 (0.89%), T 1 (0.88%), T 3 (0.88) and T 2 (0.87%). At depth 30-60 cm, treatment T 8 (0.83%) was superior to other treatments while it was at par with treatments T 2 (0.79%), T 3 (0.79%), T 7 (0.78%), and T 5 (0.77%). Significant observations were recorded at a depth of 60 to 90 cm, where treatment T 8 (0.58%) was significantly superior to other treatments, however, it was at par with treatments T 1 (0.57%), T 2 (0.56%), T 6 (0.56%), T 3 (0.55%), T 5 (0.55%) and T 7 (0.55%).

On the other side in all treatment T 9 i.e. control shows minimum organic carbon. Due to organic matter addition from natural vegetation, top soil has the highest total organic carbon concentration when compared to subsurface soils (Ingram and Fernandes 2001). As the depth of the soil increases, it decreases (Dar et al. 2017) [20,13] .

Water Soluble Carbon

According to the data represented in Table 2 water-soluble carbon content of orchard soil recorded from a depth of 0 to 30 cm, 30 to 60 cm and 60 to 90 cm. It regulates the turnover of nutrients and the expansion of microbe and it provides energy for soil organisms. Significant observations were found at a depth of 0 to 30 cm, where treatment T8 (173.15 mg kg -1 ) was showed numerically higher and it was at par with treatments T 7 (171.45 mg kg -1 ), T 3 (170.42 mg kg -1 ), T 2 (147.33 mg kg -1 ), T 6 (147.33 mg kg -1 ) and T 4 (146.75 mg kg -1 ). . At a depth of 30 to 60 cm, significant observations were recorded, showing that treatment T 8 (150.00 mg kg -1 ) was found numerically higher over all other treatments and it was at par with treatments T 4 (124.67 mg kg -1 ), T 6 (118.12 mg kg -1 ), T 2 (118.08 mg kg -1 ) and T 7 (117.33 mg kg -1 ). Significant observations were found at a depth of 60 to 90 cm, where treatment T 8 (90.67 mg kg -1 ) was significantly superior.

Whereas however, it was at par with treatments T 3 (87.33 mg kg - 1 ), T 6 (71.00 mg kg -1 ), T 2 (70.41 mg kg -1 ), T 1 (70.08 mg kg -1 ).

The decrease in water soluble carbon concentration in deep soil strata may be due to the water soluble carbon's adsorptive interaction with the mineral matrix's reactive surface (Kalbitz et al. 2000 and Brar et al. 2013) [23,2] . Similar results depth wise distribution of water soluble carbon content was observed by Thangavel et al. (2015) [42] .

Soil Microbial Biomass Carbon

Table 2 shows the soil microbial biomass carbon content of orchard soil at depths of 0-30 cm, 30-60 cm, and 60-90 cm. It is the living portion of soil organic material and is necessary for nutrient cycling, soil organic matter decomposition, and soil organic matter transformation (Liang et al. 2012) [26] .

Significant observations were recorded at a depth of 0 to 30 cm, where the treatment T 8 (480.61 mg kg -1 ) was recorded numerically higher over all the treatments however, it was at par with treatments T 3 (476.78 mg kg -1 ), T 2 (472.71 mg kg -1 ), T 4 (466.23 mg kg -1 ), T 1 (450.59 mg kg -1 ), T 6 (430.34 mg kg -1 ) and T 7 (423.35 mg kg -1 ). At a depth of 30 to 60 cm treatment T 8 (402.27 mg kg -1 ), was markedly higher than other treatments however, it was at par with treatments T 3 (379.74 mg kg -1 ), T 2 (373.13 mg kg -1 ) and T 1 (362.19 mg kg -1 ). At a depth of 30 to 60 cm, treatment T 8 (318.31 mg kg -1 ) showed numerically higher and it was at par with treatments T 3 (308.19 mg kg -1 ), T 2 (307.76 mg kg -1 ), T 1 (290.96 mg kg -1 ), T 4 (286.96 mg kg -1 ), T 6 (274.06 mg kg -1 ) and T 7 (273.26 mg kg -1 ). Similar result on Soil microbial biomass carbon content depth also decrease was reported by Purakayastha et al. (2007) [35] . Result is close confined with (Ramesh et al. 2013) [36] .

Permanganate Oxidizable Soil Carbon

According to the findings in Table 3. the permanganate oxidizable soil carbon content of orchard soil from a depth of 0 to 30 cm, 30 to 60 cm and 60 to 90 cm. different amounts of soil organic carbon, this fraction is thought to be a useful method for characterizing that carbon (Liang et al. 2012) [26] .

Significant observations were recorded at a depth of 0 to 30 cm, where treatment T 3 (1350.67 mg kg -1 ) was significantly superior and treatments T 8 (1213.50 mg kg -1 ) was found numerically higher over all the treatments however, it was at par with treatments T 5 (1203.00 mg kg -1 ), T 7 (1175.55 mg kg -1 ), T 2 (1148.25 mg kg -1 ), T 3 (1146.75 mg kg -1 ), T 1 (1103.25 mg kg -1 ) and T 6 (1085.25 mg kg -1 ) . At a depth of 30 to 60 cm, significant observations were recorded, showing that treatment T 8 (965.24 mg kg -1 ) was recorded numerically higher over all the treatments however, it was at par with T 7 (962.25 mg kg -1 ), T 5 (958.50 mg kg -1 ), T 2 (929.25 mg kg -1 ), T 1 (909.08 mg kg -1 ), T 4 (908.08 mg kg -1 ) and T 6 (900.00 mg kg -1 ). At a depth of 60 to 90 cm, where treatment T 8 (798.40 mg kg -1 ) was found numerically higher over all the treatments however, it was at par with treatments T 3 (769.07 mg kg -1 ) and T 1 (728.29 mg kg -1 ). Similar results on mango orchard's POSC was substantially higher compared to conventionally cultivated soil (Naik et al. 2016) [29] . Sofi et al.

(2012) [39] , who found that cover plant root exudates and decaying residues improved carbon content, which stimulated microbial population responsible for improved nutrient retention and cycling.

Fulvic Acid Carbon

According to the results in Table 3, the fulvic acid carbon content of orchard soil at depths of 0 to 30 cm, 30 to 60 cm, and 60 to 90 cm. Although fulvic acids are commonly regarded as humic acid precursors, they may also be humic acid breakdown products.

Significant observations were recorded at a depth of 0 to 30 cm, where treatment T 8 (21.63 mg kg -1 ) was significantly superior to all treatments however treatment T 5 (21.28 mg kg -1 ) and T 3 (21.26 mg kg -1 ) were observed at par with T 8 . At a depth of 30 to 60 cm, treatment T 8 (19.48 mg kg-1) was markedly higher than all treatment. Whereas treatment T 3 (18.85 mg kg -1 ) and T 5 (18.59 mg kg -1 ) were at par with treatment T 8,. At a depth of 60 to 90 cm, where treatment T 8 (12.28 mg kg -1 ) was significantly superior to all treatment however, it was at par with T 3 (11.25 mg kg -1 ), T 6 (10.94 mg kg -1 ), T 7 (10.44 mg kg -1 ), T 5 (10.22 mg kg -1 ) and T 4 (9.85 mg kg -1 ). Due to continuous supply of fresh organic matter and litter fall in forest soil in surface layer as compare to subsurface layer caused high proportion of fulvic acid carbon at surface layer than lower layer (Aswathy et al. 2018) [1] .

Humic Acid Carbon

According to the findings in Table 3. the humic acid carbon content of orchard soil from a depth of 0 to 30 cm, 30 to 60 cm and 60 to 90 cm. Significant observations were recorded at a depth of 0 to 30 cm, where treatment T 8 (13.70 mg kg -1 ) was found numerically higher over all the treatments however, it was at par with T 1 (13.28 mg kg -1 ), T 5 (13.20 mg kg -1 ), T 6 (13.01 mg kg -1 ), T 4 (12.69 mg kg -1 ) and T 2 (12.55 mg kg -1 ). At a depth of 30 to 60 cm, treatment T 8 (11.22 mg kg -1 ) was showed numerically higher over all the treatments and it was at par with treatments T 2 (10.27 mg kg -1 ), T 1 (10.24 mg kg -1 ), T 3 (10.20 mg kg -1 ), T 5 (10.16 mg kg -1 ) and T 4 (10.04 mg kg -1 ). At a depth of 60 to 90 cm, where treatment T 8 (7.75 mg kg -1 ) was markedly higher whereas treatments T 1 (5.72 mg kg -1 ), T 4 (6.09 mg kg -1 ) and T 9 (3.62 mg kg -1 ) i.e. control. Other all rest treatments T 2 (7.60 mg kg -1 ), T 7 (7.41 mg kg -1 ) T 3 (6.91 mg kg -1 ), T 5 (6.65 mg kg -1 ) and T 6 (6.42 mg kg -1 ) were found at par with the treatment T 8 (7.75 mg kg -1 ). Humic acid carbon levels may have decreased with depth due to a slower rate of humification or decomposition. Similar results were noticed by Aswathy et al.

Soil Organic Carbon stock (SOC) in Orchard

According to the findings in Table 4. The Soil Organic Carbon stock sample from orchard varied from a depth of 0 to 30 cm, 30 to 60 cm and 60 to 90 cm. Significant observations were recorded at a depth of 0 to 30 cm, where treatment T8 (36.42 Mg ha -1 ) was found numerically higher over all the treatments however, it was at par with T 4 (34.50 Mg ha -1 ), T 3 (33.29 Mg ha -1 ) and T 5 (33.07 Mg ha -1 ). at a depth of 60 to 90 cm, where treatment T 8 (23.44 Mg ha -1 ) was found numerically higher over all the treatments and it was at par with treatments T 1 (22.31 Mg ha -1 ), T 6 (22.11 Mg ha -1 ), T 3 (21.58 Mg ha -1 ), T 4 (21.11 Mg ha -1 ), T 5 (21.10 Mg ha -1 ) and T 7 (21.01 Mg ha -1 ). In comparison to subsurface soil (30-60 cm), the surface soils (0-30 cm) displayed larger content SOC stock, which may be explained by the higher organic matter at the surface soil (Bhat et al. 2017) [3] . Similar results have been reported by Gupta and Sharma (2011) [17] and Gupta and Negi (2012) [18] .

Conclusion

Among the treatments used in the orchard, T8 was found to be the most effective for improving carbon fractions, carbon stock, and carbon sequestration at depths of 0-30, 30-60, and 60-90 cm, with the exception of T5, which is suitable for tree height. On an average, 1116.31 kg tree -1 i.e. 111.63 t ha -1 plant carbon has been sequestered in 19 years old mango orchard.

Acknowledgement

AcknowledgementAuthor wish to thank Dr. V. Bhalerao Associate Professor and Rushikesh Bhusari (Ph.D. Scholar) for their untiring guidance, constant support and much needed suggestions to improve the quality of this manuscript.

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