# Soil and plant carbon sequestration under sugarcane based cropping system.

Ajeet Kumar, Sunita Kumari Meena, Anil Kumar Singh

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Ajeet Kumar, Sunita Kumari Meena, Anil Kumar Singh. Soil and plant carbon sequestration under sugarcane based cropping system. Agrobios Research, 1 (1), pp.47-60, 2022, 978-93-94380-08-0. hal-04881434

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## 5. Soil and Plant Carbon Sequestration under Sugarcane-Based Cropping System

AJEET KUMAR, SUNITA KUMARI MEENA AND A. K. SINGH

Carbon management may be serious concern confronting the world nowadays. Several summits have been organized on this subject ranging from the Stockholm to Kyoto protocol. The current level of carbon within the atmosphere is 375 ppm. It is calculable that if the carbon increases in the atmosphere at the present rate and no positive efforts are pursued, the level of carbon in the atmosphere would go up to 800-1000 ppm by the end of century, which can create havoc for all living creatures on earth. Soil is an important sink for the carbon storage in the form of soil organic carbon. This form of carbon is also a matter of serious concern for sugarcane scientists because various researches reveal that the soil underneath intensive cultivation results in declining potential productivity due to deterioration in soil organic carbon, thereby proving a hurdle for sustainable agriculture. Sugarcane plants are the main source of the soil organic carbon, either from the decomposition of aerial plant parts or underground plant parts, e.g., root in the form of root death, root exudates and root respiration. About 40% of the photosynthates synthesized within the plant parts are lost through the root system into the rhizosphere within an hour and the rate of loss is influenced by many factors, e.g., plant age, several biotic and abiotic stresses etc. The rhizospheric surrounding of the plant is totally different compared to bulk soil with respect to physical, chemical and biological properties. Thus, the aim of this chapter is to provide an insight on the contribution of sugarcane plant roots for transfer of carbon from atmosphere to rhizosphere and further their significance in sustainable agriculture.

Since the starting of the industrial revolution, carbon dioxide concentration in the atmosphere has been rising alarmingly. Before the industrial revolution carbon concentration was around 270 ppm, however
these days it's around 372 ppm (Sage, 1995). If the pace of increase in carbon concentration remains constant and efforts are not made to reduce it, carbon concentration within the atmosphere would go up to 800-1000 ppm by the turn of the current century (Whipps, 1996). Carbon sequestration is a process of taking carbon dioxide from the atmosphere through crops and storing the carbon in soil in the form of soil organic matter. An endeavor has been made to understand how roots play a significant role in carbon transfer from the atmosphere into the soil.

World population is growing exponentially and there's a requirement to fulfil its' food requirements. A crucial strategy for increasing labour utilization per unit area of available land and productivity is to accentuate land use. The agricultural practice of cultivating two or more crops in the same space at the identical time is an old and commonly used cropping practice which aims to match efficiently crop demands to the available growth resources and labour is called intercropping. The advantage of intercropping is the production of greater yield on a given piece of land by making more efficient use of the available growth resources. Sugarcane is a long duration crop and takes 90-120 days for canopy development, which allows for growing intercrops during the early stage. Taking benefits of this, sugarcane cultivators grow many short duration crops like pulses and vegetables as intercrops to get interim return since small sugarcane growers cannot wait for a longer duration of time to get financial return from sole sugarcane crop. Since sugarcane is a commercial crop and most suitable for intercropping, this chapter focuses on sugarcane based intercropping system and carbon capturing by soil and sugarcane plant.

India is the second largest producer of sugar after Brazil with a global share of 17 percent. Over 5 million farmers are involved in cultivation of sugarcane; there are 2 distinct agroclimatic regions of the sugarcane crop within the country. Presently the area under sugarcane is 5.03 million hectares with production and productivity of 356.56 Mt and 70.8 t/ha, respectively. Tropical region shares about 45 percent and 55 percent of the total sugarcane area and production in the country, respectively along with the average productivity of 70 t/ha. Tamil Nadu stand first in average cane productivity, viz. 105 t/ha during 2014-15. Uttar Pradesh, Maharashtra, Karnataka and Tamil Nadu account for nearly 85 percent of total sugar production. Tropical India has even sunshine throughout the year, well distributed rainfall and ideal conditions for good growth of the crop leading to high productivity. Presently the productivity levels have more or less stagnated over the last two decades. Intercropping is a method of growing two or more crops simultaneously on the same piece of land with a definite row-planting pattern to obtain higher productivity per unit area. Fast increasing population, increased demand
for food, limited scope for extension of cultivation to new areas, diversified needs of farmers for food and cash etc. has necessitated the adoption of intercropping systems. In case of sugarcane, much of the space between rows of sugarcane remains unutilized for an initial period of 90-120 days, due to slow crop growth. Under sugarcane cultivation companion cropping offers an opportunity for profitable utilization of available space. The growers of sugarcane can take advantage of this space and grow several short duration crops like cereals, pulses, vegetables and spices as intercrops to obtain interim return. Sugarcane growers need not wait until the harvest of sole sugarcane crop to obtain financial returns. Intercropping of short duration crops with sugarcane through utilization of the land resources would help to sustain sugarcane cultivation and provide additional return to farmers, besides meeting the increasing demand for vegetables and pulses. The potassium, like nitrogen, also boosts strong cane development, long internode, wide cane girths and yield. Nutrient supplies need to be balanced alongside those of nitrogen. Magnesium, sulfur and iron increase photosynthetic activity maintaining good growth and high yields. Sugarcane is cultivated for its juice from which sugar is processed. The sugarcane is mostly grown in subtropical and tropical areas.

# 1. SUGARCANE BASED INTERCROPPING SYSTEM

Sugarcane is a multi-purpose crop. It is the most important commercial crop after cotton is the efficient converters of solar energy into sugars and other renewable forms of energy. The main planting season in the tropical region is from December to March. The crop completes its germination in five weeks from planting and attains the stage of canopy closure by the 15th week after planting. Since the underutilized growth resource prevails only for a short time, the intercrops and cultivar selected should be of dwarf type with compact canopy and short duration. Short duration legumes, oilseeds and vegetables are the most suitable intercrops in main season planted sugarcane. In tropical India, maize can also be taken as an intercrop especially for fodder purpose. Attempts should be taken to diversify agriculture production through exploitation of inter row spacing by raising maize and potato also. Finger millet is also taken as an intercrop. Intercropping of soybean positively influences the cane yield. Intercrop density and planting geometry has also positive impact on yield and quality of Juice in sugarcane. There is less scope of increasing area under sugarcane due to heavy competition for food, fiber, oilseed, pulses etc. the only alternative is to increase the vertical production of sugarcane and sugar by finding out the efficient agronomic management practices. In current years, several changes in cropping system
been observed. The sole cropping has been shifted to intercropping which has proved to be productive, economically feasible and sustainable. Growing pulses with sugarcane increase the area under pulse and also reduces the weed intensity and provides mid-season income along with additional employment opportunities.

Soil carbon sequestration refers to a process in which CO₂ is removed from the atmosphere and stored in the soil carbon pool. This process is mediated by plants through photosynthesis, with carbon stored in the form of soil organic carbon.

<figure><img src="image_3.png" /><figcaption>FIGURE 5.1: Soil carbon storage</figcaption></figure>

## 2. CARBON SEQUESTRATION IN SUGARCANE PLANT AND SOIL

Sugarcane farms have the capability to sequestrate carbon into soil and plant but it is less documented in literatures. The carbon sequestration in
sugarcane plant and soil in traditional cultivation system of sugarcane is studied. The soil samples randomly collected at 0-30 cm top layer and soil organic carbon analysed in laboratory. Simultaneously, both aboveground and underground parts of sugarcane plants sampled and the carbon content of each part measured separately. The carbon stored in the aboveground parts like leaves and shoots contains approximately higher (1292 kg/ha) than that (655 kg/ha) of underground roots. The total soil organic carbon (1987.3 kg/ha) is not considerably higher than the sequestrated carbon (1947 kg/ha) in plant parts. Furthermore, a positive and significant correlation observed between SOC and soil clay content. Overall, 3934.5 kg/ha sequestrated carbon equal to 14439.6 kg/ha atmospheric CO₂ was estimated in sugarcane farms.

The leading cause of climate change is the growing concentration of greenhouse gases, including carbon dioxide mainly emitted from human activities. As Intergovernmental Panel on Climate Change (IPCC, 2015) reported, the earth surface temperature is expected to rise by 1.4°C to 5.8°C at the end of the century as a result of GHGs emission. In order to stabilize the global temperature, the anthropogenic CO₂ has to be mitigated to a significant level (Davis *et al.*, 2010) and the surplus atmospheric CO₂ in plants, soil and the oceans has to be sunk. One of the sustainable approaches might be enhancing the CO₂ capture by extending natural vegetation and sustainable farming practices. Crop and soils as important carbon sinks (Nadeu *et al.*, 2015) that play a significant role in reduction of atmospheric carbon. Sugarcane is a perennial grass cultivated economically and commercially. It is mainly used for sugar production and also used for livestock feeding and producing ethanol as a biofuel. However, in many parts of country in an unsustainable management, the leaves and trashes of this crop are burned to facilitate harvesting. This leads the emission of GHGs, particularly CO₂. Burning leaves and litters also releases soot and charcoal to the atmosphere causing health problems. Studies indicated that leaving sugarcane leaves and trashes on soil instead of burning, improves physical, chemical and biological characteristics of soil (Meier *et al.*, 2006).

Leaving the sugarcane residues on the soil improves soil biological activity, decreases soil bulk density, enhances soil aggregation stability and infiltration rate and reduces gas emissions compared to the traditional burning system. For example, a farm with burned residues had 30% lower carbon content particulate organic matter and microbial biomass carbon than those of a farm where the trashes and residues were left on the soil. Leaving the sugarcane residue biomasses in soil returned a remarkable organic matter compared to the soils where the sugarcane residues were burned. On the other hand, huge sugarcane biomasses in above and underground parts of the
soils could act as important pools for carbon sequestration and consequently enhancing the mitigation of climate change impacts.

## A. Soil Carbon Sequestration

Soil is the largest carbon reservoirs of the terrestrial carbon cycle. Soil contains about three times more C than vegetation and twice as much as that present in the atmosphere (Batjes, 1996). Soil contains much more C (1500 Pg of C to 1 m depth and 2500 Pg of C to 2 m; 1 Pg = 11015 g) than is contained in vegetation (650 Pg of C) and twice as much C as the atmosphere (750 Pg of C) (USEPA, 1995). Carbon in the form of organic matter (OM) is a key element to healthful soil. It is calculated that each tone of soil organic matter releases 3.667 tonnes of CO₂ which is lost into the atmosphere. Similarly, the build-up of each tone of soil organic matter removes 3.667 tonnes of CO₂ from the atmosphere (Bowen, 1999). The conversion of natural habitats to cropland & pasture, and unsustainable practices such as excessive tillage frees carbon from organic matter, releasing it to the atmosphere as CO₂. On depletion of organic carbon, soils develop a carbon deficit. Soil may regain lost carbon by reabsorbing from the atmosphere. This process is called carbon sequestration. In photosynthesis, plants convert CO₂ into organic forms of carbon like, sugars, starch and cellulose, also known as carbohydrates. In natural habitats, carbon from plants is deposited in the soil through roots and plant residues, such as fallen leaves.

## B. Plant Roots and Soil Carbon

The roots of plant have ability to synthesize, accumulate and secrete a diverse array of compounds. More than 200 carbon compounds released from plant roots in the form of exudates, which is termed as rhizodeposition. The root exudates contain simple water-soluble compounds such as amino acids, organic acids, sugar and various plant secondary metabolites to complex polymeric compounds like polysaccharides, polypeptides and enzymes. On the basis of molecular weight, it may be grouped into high molecular weight compounds such as gelatinous material, mucilage, covering root surfaces, ectoenzymes and low molecular weight compounds like organic acids, sugars, amino acids, phenolics, phyto-siderophores, flavonoids and vitamins. Secretion of compounds into the rhizosphere is most remarkable metabolic features of plant roots. Cereals transfer 20-30% of total assimilated carbon into the soil and half of this amount is subsequently found in the roots and about 1/3 is lost in the form of CO₂ by root respiration and microbial utilization of root-borne organic substances. The rest part of underground translocated carbon is incorporated into the soil microorganisms and soil organic matter.
Pasture plants transfer about 30-50% of assimilate below the ground and their translocation patterns are similar to cereals. The photo-synthetically fixed carbon in cereals and grasses is transported rapidly towards the root and reaches the external environment of the root within an hour. The total amount of carbon translocated into the soil by cereal and pasture plants is approximately the same (1500 kg C/ha), if we consider the same growth period. However, during one vegetative period, cereal and grass allocated below the ground are about 1500 and 2200 kg C/ha respectively. This accounted for nearly 5 to 21% of all photo-synthetically fixed carbon transferred to the rhizosphere through root exudates and ranged from 20 to 50% of plant biomass. The Possible root exudate components in the rhizosphere are Phenolics, Organic acids, Amino acids and phyto-siderophores, Vitamins, Purines, Enzymes, Inorganic ions/gaseous molecules, Root border cells and Sugars.

Every kind of the organic carbon found in the soil is primarily plant derived. The two main sources of carbon in the soil are: (1) accumulation of soil organic matter due to the humification after plant death and (2) root exudates and root-borne organic substances released in the rhizosphere during plant growth as well as sloughing of root hairs and fine roots. The first mode of carbon sequestration is well documented, but carbon sequestration by plant roots is still under investigation. CO₂ fixed by plants and its translocation into the roots is a simultaneous process. Figure 2 reveals the pathway of carbon transfer from biosphere towards the rhizosphere. Carbon is added in the soil system by roots through root death, root exudates and root respiration. It is very difficult to quantify the contribution of all the three separately. Metabolically active respiring roots are responsible for exudation and respired CO₂. However, non-metabolically active roots release carbon in its soluble form, which is termed as lysis. The mechanism of root death provides a greater insight in the understanding of carbon sequestration in the soil. There are three states of root death: (1) non-apoptotic death, where metabolic activity immediately ceases and all the carbon and nutrients from the roots enter into the soil (e.g., mechanically damaged roots). (2) Non-apoptotic death, where the root becomes excised, remains metabolically active and slowly depletes and exhausts internal soluble C reserves (e.g., sewerage of the main roots). (3) Apoptotic death, where re-translocation of both carbon and nutrients occurs to the other growing areas of the plants.

The almost all soluble components present inside the root can be lost into the rhizosphere, but exudation is dominated by low molecular-weight solutes present in the cytoplasm in high concentration (Kuzyakov et. al., 2001). The continuous release of carbon compounds from the root into the soil falls into
two categories: exudates that are lost as a result of passive diffusion and over which the plant exerts little control (basal exudation), and exudates which are released for a specific purpose and over which the plant exerts a close degree of control. Photosynthesates transfer towards root vicinity via root is in the form of organic molecules by the process of root lysis, root exudation and root death.

### C. Plant Roots and Rhizospheric Carbon

The compounds released by plant roots which deposit in the rhizosphere are many and complex (Table 5.1), often ranging from mucilage, root border cells, extracellular enzymes, simple and complex sugars, phenolics, amino acids, vitamins, organic acids, nitrogenous macromolecules as purine and nucleosides to inorganic or gaseous molecules such as HCO₃⁻, OH⁻. Transfer of carbon from the atmosphere to the soil through the plant system is dependent on a gradient which is maintained continuously as a result of constant removal of exudates carbon from the soil solutions either by biotic (soil microbial uptake) or abiotic process, like sorption. Soil provides technical barriers in measuring the flux of individual carbon compounds, but in a study on maize it was found that 0.5-10% of fixed carbon is transferred into the soil.

<figure><img src="image_4.png" /><figcaption>FIGURE 5.2: Soil carbon sequestration through plant roots.</figcaption></figure>
<table><caption>TABLE 5.1: Carbon compounds released by roots into rhizosphere.</caption><thead><tr><th>Amino acids</th><th>Organic acids</th><th>Sugars</th><th>Vitamins</th><th>Purines /Nucleosides</th><th>Enzymes</th><th>Inorganic ions/ gaseous molecules</th></tr></thead><tbody><tr><td>a-Alanine</td><td>Citric</td><td>Glucose</td><td>Biotin</td><td>Adenine</td><td>Acid/alkaline phosphatase</td><td>HCO<sub>3</sub><sup>-</sup></td></tr><tr><td>a-Alanine</td><td>Oxalic</td><td>Fructose</td><td>Thiamin</td><td>Guanine</td><td>Invertase</td><td>OH<sup>-</sup></td></tr><tr><td>Asparagine</td><td>Malic</td><td>Galactose</td><td>Niacin</td><td>Cytidine</td><td>Amylase</td><td>H</td></tr><tr><td>Aspartate</td><td>Fumaric</td><td>Maltose</td><td>Pantothenate</td><td>Uridine</td><td></td><td>CO<sub>2</sub></td></tr><tr><td>Cystine</td><td>Acetic</td><td>Xylose</td><td></td><td></td><td></td><td></td></tr><tr><td>Glutamate</td><td>Butyric</td><td>Rhamnose</td><td></td><td></td><td></td><td></td></tr><tr><td>Glycine</td><td>Valeric</td><td>Arabinose</td><td></td><td></td><td></td><td></td></tr><tr><td>Leucine</td><td>Piscidic</td><td>Deoxyribose</td><td></td><td></td><td></td><td></td></tr><tr><td>Lysine</td><td>Formic</td><td>Oligosaccharides</td><td></td><td></td><td></td><td></td></tr><tr><td>Methionine</td><td>Aconitic</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Serine</td><td>Lactic</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Threonine</td><td>Pyruvic</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Proline</td><td>Glutaric</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Valine</td><td>Malonic</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Tryptophan</td><td>Aldonic</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ornithine</td><td>Erythronic</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Histidine</td><td>Tetronic</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Arginine</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Homoserine</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Phenylalanine</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Aminobutyric</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Aminoadipic acid</td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>
## D. Sugarcane Roots and Carbon Sequestration

The carbon sequestration in soils has been recognized as a potential option to mitigate climate change. Organic matter constitutes 1 to 8% of the weight of most soils. Because of the weight of soils to the plant rooting depth at which carbon accumulates. This represents a carbon storage capacity of the soil that is twice compared to the atmospheric carbon. The annual global rate of photosynthesis is generally balanced by decomposition and represents of the carbon in the atmosphere or one-twentieth of the carbon in soils. Carbon, nitrogen, oxygen and hydrogen are the building blocks of life on earth. They also are the most important constituents of soil organic matter. The earth's carbon cycles have the ability to restore and even increase the soil organic matter content, improve fertility, increase the water-holding capacity. Soil organic carbon is decomposed at different rates depending on their chemistry, soil temperature and moisture, organisms present, association with soil minerals and the extent of aggregation. Heavy exploitation results in loss of soil fertility and can be attributed to the misuse of soil and its organic matter. A proportion of the soil organic carbon present in undisturbed soils has been burned or lost through agriculture practices. This contributed to the rise of CO2 in the atmosphere. The soil organic carbon is a renewable resource. Plant roots increase soil organic matter, which store atmospheric carbon and result in greater soil fertility, better soil tilth & water-holding capacity and reduced erosion. It also makes plants more stress-resistant and thus be able to better withstand the predicted climatic fluctuations. Control of water levels during periods of non-plant growth result in carbon sequestration, improved water quality and flood control. Deposit of carbon in soil result in the building of soil organic matter, which reduces soil erosion, nutrient loss, environmental pollution and improve nutrient mobilization, water retention capacity and microflora. Thus, this could play an important role in sustainable agriculture.

## E. Sugarcane is Champion Crop for Carbon Sequestration

Scientist has recently discovered that a process that occurs naturally in plants especially sugarcane, plays an important role in countering CO2 emissions and global warming. This is termed as plantstone carbon and is also referred to as phytolith occluded carbon. The plantstone carbon has been extracting 300 million tonnes of CO2 per year from the atmosphere and storing it securely in soil for thousands of years.

### i. Plantstones Carbon

Plantstones form as microscopic grains of silica in plant leaves, particularly grass crops such as sugarcane and wheat. During the plant growth period
a small proportion of organic carbon becomes encapsulated within the microscopic silica grains. Regardless of whether the plants die, burns or harvested, the carbon entrapped in the plantstone is highly resistant to decomposition. Therefore, unlike most plant matter, which readily decomposes and returns CO₂ to the atmosphere, the carbon in plantstone effectively removes CO₂ from the atmosphere. This process suggests that crop choice decisions by farmers could be a major contributing factor in the reduction of CO₂ from the atmosphere. The research of Parr and Sullivan's in crop plantstone yields has shown that different plant types produce varying amounts of plantstone carbon. Few crops have identified as producing 1,000 times more plantstone carbon than other crop types. Moreover, varieties within a single crop type, such as sugarcane, have found to produce widely differing quantities of plantstone carbon. Thus, the farmer's decision of choice of crop type and/or cultivar has a considerable impact on the amount of CO₂ extracted from the atmosphere and securely stored in the soil of their farms. Some of the plantstone research shows that sugarcane is champion crop for carbon sequestration. It sequestrates up to 0.66 tonnes of CO₂ per ha per year in plantstones while many other crops (especially legumes) sequestrate comparatively little or no CO₂ by this process. Thus, the benefit that farmers growing sugarcane is not just limited benefits such as the sugar they produce, but also to the environmental services they provide by locking up increased amounts of carbon in the plantstones that are produced abundantly by the crop. Increasing carbon sequestration by plantstones is by no means limited by a need to change the types of crops that farmer grows. For a sugarcane farmer, the decision to choose to grow one sugarcane variety instead of another can result in an extra 0.25 tonnes of CO₂ per ha per year being sequestered in the soil inside plantstones. The research shows that there are no crop yield penalties involved in choosing to grow high plantstone carbon yielding cultivars over low plantstone carbon yielding cultivars.

There should be provision by the governments, for an incentive to farmers to grow high plantstone yielding crops and crop varieties. Carbon trading systems result in farmers having the potential to earn additional income without detracting from existing income. Plantstone carbon is powerful tools to counter CO₂ emissions providing land managers the opportunity to play an even greater role in the fight against global warming. The discovery of phytolith is interesting and timely. Farmers should participate in emerging carbon markets; it is necessary to demonstrate that carbon can be sequestered in the soil in a way that is permanent and measurable. The plantstone turned into an income source. It can be recognised in future carbon trading scheme.
## ii. Sugarcane Plant Carbon Storage

The carbon stock in different plant parts of sugarcane, including roots, shoots and leaves differ significantly. The highest amount of carbon stock observed in leaves followed by roots while the carbon stock in shoots demonstrates the lowest value. Leaves showed around 11-24% more carbons stored in the leaves compared to the roots and shoots. The total carbon storage in sugarcane biomass including aboveground parts (shoots and leaves) and belowground part (roots) in different cultivation systems like planted cane and ratoon of different years vary significantly. The highest root carbon stock observed in planted cane and ratoon of first year and further the root carbon contents in next coming year ratoon gradually diminishes. The stored carbon in shoots of ratoon first (R-I) occurs highest compared to that of shoots of ratoon second (R-II) and ratoon third (R-III) and in other cultivation systems. The carbon stored in leaves of R-I cultivation system and in planted cane cultivation system indicate the highest and the lowest values observed in other ratoon cultivation systems.

## 3. SUGARCANE CULTIVATION PRACTICES FOR CARBON SEQUESTRATION

The carbon content of most soils is now about one-third less than that in its native condition. Fortunately, the sugarcane cultivation has stopped this net loss to the atmosphere. This has come through higher levels of biomass production by sugarcane crop, the return of greater proportions of crop residue, use of by-product of these crops and less tillage of succeeding ratoon and no till. Simultaneously, better fertility management through soil testing and proper nutrient application also lead to lowering of greenhouse gas emissions. Irrigation water traps some CO₂ because irrigated soil produces high crop residues which sequester carbon at a rate of 0.16 to 0.27 Pg per year. The enhanced soil organic matter levels sequester CO₂, that enhances sustainability and reduce soil erosion.

## 4. CONCLUSION

The review showed that the sugarcane ratoon has the highest potential to sequester carbon than other. The sugarcane farming practices act as an important pool for carbon sequestration and consequently enhancing the mitigation of climate change impacts. It seems that changing the sugarcane traditional harvesting system which was predominantly based on burning the residues can enhance the capability of carbon sequestration even more. Sugarcane root acts as a medium for transfer of atmospheric carbon into soil
in the form of root exudate components in the rhizosphere like phenolics, organic acids, amino acids and phyto-siderophores, vitamins, purines, enzymes, inorganic ions/gaseous molecules, root border cells and Sugars etc. Root lysis and root exudates contribute significant quantity of carbon deposited in sub-surface. These deposits have the potential for contribution to long-term soil carbon sequestration due to slow oxidation in sub-surface soil. Carbon components affect production by reducing pH, nutrient mobilization and microbial growth. The exact amount of sequestration depends on soil-management practices, edaphic factors, climate and the amount and quality of plant and microbial inputs. The carbon transfer via roots generates a new idea that allow better decisions on the specific use of crop rotation, fertilization and soil amelioration. These approaches provide tools for addressing problems in both natural and agricultural soils. Carbon sequestration certainly contributed in reducing atmospheric CO₂ concentration and mitigate drought, salinity stress and desertification. It is most viable approach towards sustainable agriculture. Thus, sequestered soil carbon used for agriculture, forestry and potential option to mitigate global climate change.

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