Different Strategies For Maintaining Carbon

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Different Strategies For Maintaining Carbon Sequestration In Crop Lands Article · January 2014 DOI: 10.15192/PSCP.SA.2014.3.1.2539

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4 authors: Fahad Khan

Saddam Hussain

Huazhong Agricultural University

Christ University, Bangalore

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Shah Fahad

Shah Faisal

Huazhong Agricultural University

Northwest A & F University



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Scientia Agriculturae www.pscipub.com/SA E-ISSN: 2310-953X / P-ISSN: 2311-0228 DOI: 10.15192/PSCP.SA.2014.3.1.2539

Sci. Agri. 3 (1), 2014: 25-39 © PSCI Publications

Different Strategies For Maintaining Carbon Sequestration In Crop Lands Fahad khan1, Sehrish khan2, Saddam Hussain1, Shah Fahad1, Shah Faisal3 1. National Key Laboratory of Crop Genetic Improvement, MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, No.1, Shizishan Street Hongshan district, Wuhan, Hubei 430070, China 2. Department of Environmental Science, University of Peshawar, KPK, Pakistan. 3. Northwest Agricultural University, xian, China. Corresponding Author email: [email protected] Paper Information

ABSTRACT Carbon sequestration in the agricultural system is related to the Received: 14 May, 2014 productivity of crop plants and it is considered one of the best ways to store carbon in the biological system. It is the storage of carbon in a stable solid Accepted: 2 July, 2014 form through direct or indirect fixation of atmospheric carbon dioxide. It is also a prominent approach to mitigate CO2 into the atmosphere. In the Published: 20 July, 2014 global carbon cycle, carbon continuously moves between the soil and the atmosphere. It moves into the soil via photosynthesis in plant leaves and plant derived organic matter (CO2 influx), and it moves out via respiration of plant roots and soil microorganisms during the decomposition of the organic matter. Croplands are estimated to be the largest biospheric source of carbon lost to the atmosphere. CO2 fluxes from agricultural soils are as the result of complex interactions between climate and soil biological, chemical and physical properties. Therefore, crop management practices have been given importance in the storage and release of C with in the terrestrial C cycle. Present manuscript reviews the suitable options to increase the carbon sequestration in crop lands including management of tillage, organic additives, crop residues, irrigation, fertilizer inputs, crop rotation and cropping frequency. © 2014 PSCI Publisher All rights reserved. Key words: Carbon sequestration, crop management practices, fertilizer, green-house gas, irrigation, tillage.

Introduction About 35 percent of the total land area worldwide is occupied by agriculture (Betts and Falloon, 2007). Because of its size and strength, agriculture releases a large amount of green-house gases into the atmosphere (Salinger, 2007). Global climatic warming and rapidly increasing CO2 concentrations, primarily resulting from anthropogenic activities and land use changes, have led to growing concerns about measures for energy saving, emission mitigation, and carbon sink enhancement. Worldwide, nearly 25% of CO2, 50% methane and 70% of nitrous oxide are emitted by various human activities. Soil is an important component of the global carbon (C) cycle. There is consequently a growing demand to reduce atmospheric CO 2 levels by (i) reducing anthropogenic emissions to the atmosphere, and (ii) removing carbon from the atmosphere by sequestration in the biosphere. Restoring and enhancing soil quality can increase soil organic carbon (SOC) content and soil productivity, and may partially mitigate the greenhouse effect (Upadhyay et al., 2005; Bayer et al., 2006; Yang et al., 2008; Zhang et al., 2 008). Paustian et al. (2000) estimated that crop-based agriculture occupies 1.7 billion hectares, globally, with a soil C stock of approximately 170 Pg. The oxidation of soil organic matter in cultivated soils is estimated to have contributed approximately 50 Pg C to the atmosphere. Returning the lost soil carbon via increasing C storage in soils is a clear sequestration possibility (Lal et al., 1998), and the potential increases in soil carbon associated with land-use changes and managed agro-ecosystems should logically be included. Agronomists have long recognized the importance of maintaining and improving soil organic matter, increasing soil fertility, water retention, and crop production benefits. Moreover many soil scientists now believe that atmospheric carbon dioxide derived from fossil fuel combustion, the benefits should be added to this list, contributing to the Kyoto Protocol (Bruce et al., 1999). Currently, IPCC panel on land use, land cover and forestry is to develop guidelines to

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alter soil carbon may be included in the national carbon accounts. In the United States, lands having small sink of atmospheric CO2 are set to aside by the conservation reserve program (CRP) accumulated a rate of up to 110 g/m2 /yr, or 17 × 12

10 g C/yr, over the past decade (Gebhart et al., 1994). Conservation tillage, including tillage, is also an effective process, archive under some agricultural soils (Rasmussen and Collins, 1991; Reeves, 1997; Lal, 1997; Paustian et al., 1998), although with soil texture its success varies (Needelman et al., 1999), and soil organic matter increase in the surface layer are sometimes matched by losses at depth (Angers et al., 1997; McCarty et al., 1998; Campbell et al., 1999; six et al., 1999). The emission of CO2 from fossil fuel use in the agricultural sector is also reduced by reducing the frequency of cultivation and conservation tillage (Fry, 1984). Kern and Johnson (1993) found conservation tillage of a large area of cropland in the next 30 years from the agricultural activities to impound all of the CO 2 emitted the total annual emissions of fossil fuels up to 1% (in today's level) in the United States. Agricultural soil with improved management and alternative land use could potentially provide a net sink for about 0.8% from the fossil fuel combustion of the world’s current annual CO2 release (Smith et al., 1997). In addition to conservation tillage and many other technical recommendations to increase carbon sequestration in soils contains hidden carbon costs in terms of green-house gases and greater emissions of CO 2 to the atmosphere. Besides tillage, several other crop management options have been known to influence the storage and release of C in soil. In present manuscript, we reviews the suitable crop management options to increase the carbon sequestration in crop lands including management of tillage, organic additives, crop residues, irrigation, fertilizer inputs, crop rotation and cropping frequency. Characterization Of Carbon Sequestration In the agro-ecological systems research, it is possible to distinguish three levels of crop production potential, achievable and actual (Rabbinge and van Ittersum 1994; van Ittersum and Rabbinge, 1997). A given crop potential gain is theoretically possible, when there is an increase in soil or climate constraint is generalized the optical synthesis of physiological processes. However, this theoretical maximum target cannot be achieved, in addition to climate constraints; environmental factors (e.g. sub-optimal supply of nutrients and water) limit the productivity and agricultural utility only to a certain extent. Management settings to achieve production levels (can be very close to potential, input high, climate favorable). However, in this field also exposes all crop " yield reduction " and other factors weeds , pests, disease and pollution sometimes , which further reduces the actual level of production may have reached . Yield reducing factor is uncontrolled, so a serious, practical production rate may be a small part of the potential yield. Between potential and actual yield differences are known as the "output gap." The use of "potential" concept, "reach" and "actual" soil carbon sequestration management will help to provide a conceptual framework for argument of managing consideration, it will also assist by providing extensively applicable terminology. Figure.1 (adapted from van Ittersum and Rabbinge's (1994) the diagram shows three carbon sequestration projects "situation" plot SOC level. SOC of any given half-life of the x-axis is indicated about 10 years, the input of fresh organic material is not to be considered, although this may be followed by a large, for example, harvesting, but because of the relatively rapid decomposition of the limited storage value . This 10-year period, but also reflects a number of management plans in line with the time scale. (Range of time of important considerations to be discussed below). The y-axis as shown in the case of the three equivalent sequestration type of carbon sequestration. "Potential" is defined by setting the maximum storage limit of physical and chemical factors. "To achieve" set limits carbon soil system input factors. "Actual" is a factor, which reduce carbon-storage. Five major management related factors of the actual level (that is, reducing the level attained). First, the loss of soil material by erosion results in reduction in soil volume, clay content and soil carbon. Second, the increase in oxidation due to vegetation cover, in order to eliminate such as tillage or increase soil temperature can quickly lower SOC levels. Third, carbon inputs are reduced by removal of the organic residues. Fourth, the disrupt input is responsible for the breakdown of organic soils will reduce the biological processes suitable for forming a stable organic, inorganic composite SOC fraction availability. Fifth, soil carbon oxidation which is promoted by the drainage aeration of the soil. Global potential for Carbon sequestration About 20 % of the anthropogenic carbon dioxide emission is contributed by land use changes and agriculture (Dumanski and Lal, 2004). The world average soil organic carbon (SOC) in the top 30 cm of native soil is about 15 Mg ha -1. However, when the cultivation, approximately 20-30% of the Carbon is released into the atmosphere in the first 20 years in temperate regions, and in the tropics 50-75% (Dumanski and Lal, 2004). However, there is significant potential to regain some of this lost Carbon by taking soil and water conservation measures on farmland. For example, Dumanski and Lal, (2004) -1

proposed the following scenario: Carbon sequestration potential of farmland in the United States is 75-208 Tg C year . Under 26

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the Kyoto protocol the United States reduction commitments is about 24 %. In Canada the potential for carbon sequestration in -1

crop land is approximately 24Tg C year , under the Kyoto protocol reduction commitment of Canada is about 10%. In -1

European Union the potential carbon sequestration in cropland is about 90–120Tg C year , they implemented the best land management practices. In china and India the potential carbon sequestration in cropland is about 105– 198 Tg C year-1 and 39– 49 Tg C year-1, approximately 47% of the current annual emissions from fossil fuels. From the humid tropics recent evidence suggests that these regions have substantial potential for carbon sequestration. For example, tropical agro forestry system, -1

carbon accumulation rate ranges from 4 to 9 mg carbon ha-1 year , more on the ground than in the soil. Normal rotation in 2025 years, above ground plant biomass Carbon accumulation is high as 50 mg ha1 and Carbon accumulation in the soil up to 50 mg carbon ha-1. Strategies and practices to improve Soil Carbon Sequestration A number of management practices have been shown to increase soil carbon stock like tillage, organic additives, crop residues, irrigation, fertilizer inputs, crop rotation and cropping frequency. The detail of each section is discussed as under; Conservation tillage Carbon sequestration using enduring novel soil and crop management practices is required to increase soil carbon storage for carbon trading, mitigate green house gas emission and improvement of soil quality. Soil organic matter as indicated by soil carbon, can directly impact crop production. Bauer and Black, (1994) reported that an increase in soil organic carbon of 1 Mg ha-1 in the surface 3 cm of soil increase wheat grain yield by 15.6 kg ha-1. Conservation tillage with cover cropping can increase carbon storage in the soil (Jastrow, 1996; Allmaras et al., 2000; Sainju et al., 2002a, 2006). Studies suggest that conversion of conventional till (CT) to no-till (NT) can sequester atmospheric CO2 by 0.1 % ha-1 at the 0-5 cm soil depth every year, a total of 10 tons in 25-30 years (Lal and Kimble, 1997; Paustian et al., 1997). Sequestration of carbon in the soil by converting CT into NT can conserve nitrogen, because soil organic carbon and total N levels are highly related (Franzluebbers et al., 1995, 1999; Kuo et al., 1997; Sainju et al., 2002b). However, soil organic carbon and soil total nitrogen levels belo w the 7.5 cm depth can be higher in tilled areas, depending on the soil texture, due to residues incorporation at greater depths (Jastrow, 1996; Clapp et al., 2000). Similarly, cover cropping can increase soil organic carbon in tilled and non-tilled soil by increasing the amount of crop residues returned to soil (Kuo et al., 1997a.b; Omay et al., 1997; Sainju et al., 2002a. 2006). In croplands, reduced tillage intensity is one of the most effective practices for C sequestration. It depends on the soil texture, which is proportional to the clay content and the crop frequency with soil region (Campbell et al., 2005). For example, SOC gains under reduced tillage in the semi-arid conditions, regardless of cropping frequency was about 0.25 Mg C ha-1 year-1 which was greater than for tilled systems. Humid prairie environment, rotation with fallow the advantage was about 0.05 mg C ha-1 year-1 but with continuous cropping it was about 0.25 mg C ha-1 year-1. This increases associated with the use of reduced tillage soil moisture usually results in higher crop yields; reduced tillage is often combined with snow management especially in the arid and semi-arid environments. However, rapid soil carbon decomposition can be cause by higher moisture. In contrast, the soil Carbon decomposition is reduced by the low temperatures and more partial soil aeration at higher soil moisture. So it is no surprise that there are conflicting views on reducing the impact of tillage on soil carbon, depending on the measurements (Campbell et al., 2005). In addition, due to reduced tillage is accompanied by the use of the machinery and tractors (Dyer and Desjardins, 2003) to reduce fossil fuel emissions. Under conservation tillage the surface residue layer significantly conserve soil moisture (Campbell et al., 1986), but also conducive to continuous cropping in semi-arid environments, resulting in high crop yield and soil Carbon input with shorter damp soil, which assist decomposition of carbon. In arid or semi-arid conditions, with reduced tillage yield is greater conserving water, while the latter benefit may not be significant in more humid areas or may even be damaging in heavy soils. Reduced tillage can increase soil organic carbon at a given site, prevent erosion, although this does not mean that the Carbon is removed from the atmosphere. Campbell et al., (2001b) results show that if there is no enough fertilization with reduced tillage, soil Carbon will not increase. Sainju et al., (2008) in long-term experiment (10 years) found that mulch tillage showed higher soil organic carbon (42.4 g C kg-1) at 0-20 cm , as compared to conventional tillage (40.55 g C kg-1) (Table 1). The tillage effect on soil organic Carbon varies with depth. The chisel plough treatment increased soil organic Carbon concentration 6.4 % in top 10 cm of soil but reduced soil organic Carbon content by 7.8 % at a depth of 10-20 cm compared to the mould board plough treatment (Yang et al., 2001). In the study of McConkey et al., (2003) soil organic Carbon 63.13 (Mg C ha -1) with No-tillage at 7.5-15 cm depth was recorded, which was higher than cultivar (full) tillage (Table 1). Deen et al., (2003) conducted an experiment which indicates that soil organic Carbon for the entire 0–60 cm soil depth was highest for Spring MB + 2 (mould board plough + secondary tillage consisting of cultivation or discing followed by packing) followed by the Zero tillage treatment. The chisel plough + 2 treatments had the lowest soil organic Carbon. Soil organic Carbon storage from 0 to 5 cm depth was highest for the Zero tillage treatment, which was 11–16% higher than other tillage treatments. Differences between Zero tillage and Spring 27

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MB + 2 were significant at this soil depth. The trend in soil organic Carbon for the 0–10 cm soil depth was similar to that of the 0–5 cm depth, while differences between tillage treatments for the 0–20 cm depth were non-significant. The Spring MB + 2 had the highest soil organic Carbon storage for the 0–40 and 0–60 cm soil depth, this value being 6–24% higher than the soil organic Carbon concentration of other tillage treatments. Dolan et al., (2005) found that at 45 cm depth with both chisel plough and mould board plough had a significant influence on soil organic Carbon which was 117 (Mg C ha -1) while no tillage treatment, the value was lower 106 (Mg C ha-1). Crop residues management Plants contains organic compounds like as cellulose, hemi cellulose, starches, proteins, lipids and poly phenols, but the proportions of each, which depend on the species and maturity, may manipulate the degree and rate of decomposition (Kononova, 1966). The decomposition of more recalcitrant organic residues is considered to be controlled by the lignin content (Fogel and Cromack, 1977) or lignin-to-N ratios (Melillo et al., 1982; Tian et al., 1992). Soil aggregates are the basic units of soil structure (Lynch and Bragg, 1985) and organic residues applied to soil has been shown to improve structure by increasing soil aggregate stability (Waksman, 1936; Kononova, 1961). Research has shown that the longevity of the changes in soil properties considered with organic residue addition is related to the rate of residue decomposition. One of theories implies that soil polysaccharides from plant and microbial sources play a vital role in the stabilization of soil micro aggregates (Martin, 1971; Cheshire, 1979). In the decomposition stages, biotic and abiotic reactions lead from the decomposition of plant residues to a complex mixture of aromatic compounds of plant and microbial origin that compose the bulk of stable organic matter (Haider et al., 1975). Humus formation has been reported to promote long-term soil aggregation (Fortun et al., 1989a, 1989b; Piccolo and Mbagwu, 1989). In many proposed theories for soil aggregation involve the sequestration of carbon by macro and micro aggregates. If the stabilization of soil micro aggregates by organic residue is regulated by the rate of residue decomposition and the rate of decomposition is determined by the residue's chemical composition, then improvement in aggregate stability and carbon sequestration should be directly related to the chemical composition of the plant residue. D.A. Martens, (2000) studied Plant residue biochemistry regulates soil carbon cycling and carbon sequestration and found that the soil organic carbon content was 39.50 ± 21.84 (g C kg-1 soil) high in soil with corn residues treatment followed by prairie residue treatment 36.87 ± 22.02 (g C kg-1 soil), while in case of canola it was less 33.25 ± 0.94 (g C kg-1 soil) (Table 2). Duiker and Lal, (1999) studied Crop residue and tillage effects on carbon sequestration in a Luvisol in central Ohio for eight years and observed a linear relationship between the residue application rate and volumetric soil organic carbon content for plow till and no-till, but not for ridge till. The conversion efficiency of residue carbon into soil organic carbon was lower for plow till (8%) than for no-till (10%), confirming that carbon sequestration rates under no-till are higher than under plow till. The soil organic carbon levels increased with residue level in both, no-till and plow till. R. Lemke et al., (2010) studied Crop residue removal and fertilizer N: effect on soil organic carbon in a long-term crop rotation experiment on a Udic Boroll. In 2007 fertilizer had increased soil organic carbon in the F-W-W (N+P) (fallow–wheat–wheat rotation fertilizer applied and straw retained) 34.0 Mg ha-1 compared to soil organic carbon in F-W-W treatment at 30.8 Mg ha-1, for a difference of 3.2 Mg ha-1(Table 2). The study of R. Lemke et al., (2010) shows that proper fertilization is required to gain soil organic carbon. It was observed that reserved amounts of straw residues could be removed from the soils under wheat-fallow cropping systems without a measureable effect on soil organic carbon content, but sufficient nitrogen fertilizer is required to maintain the carbon inputs necessary to preserve the soil organic content. Modifying irrigation patterns In field practices, irrigation has shown to increase both C and N retention in the soil–crop system particularly in arid and semi-arid areas (Follett, 2001; Gillabel et al., 2007; Lal, 2008). Though, in these areas the crops are often irrigated with a volume less than the maximal plant evapotranspiration due to limited freshwater resource. Therefore, deficit irrigation that partially compensates the evapotranspiration demand of the crops has become a common practice in drought prone areas. Though deficit irrigation practices are able to enhance crop water productivity, a reduced irrigation water volume will irreversibly decrease crop productivity hence decreasing carbon and nitrogen retention in the plant biomass. Therefore, in order to sustain crop yield under reduced irrigation amount, water use efficiency (WUE) has to be further enhanced. Deficit irrigation technique named alternate partial root-zone drying irrigation (PRD) that exploits the role of the ABA-based root-toshoot signaling in regulating plant physiology during soil drying has been developed (Liu et al., 2006). Besides saving irrigation water and improving WUE, the PRD induced drying and wetting cycles of the soils have shown to stimulate mineralization of soil organic matter and improve crop N nutrition (Miller et al., 2005; Saetre and Stark, 2005; Shahnazari et al., 2008; Wang et al., 2009, 2010a, b, 2012). This may, however, potentially lead to great carbon and nitrogen losses from the soil due to increases in soil respiration (Wang et al., 2010b) and denitrification (Vale et al., 2007). However, the improved crop nitrogen status and WUE under PRD treatment may increase plant biomass resulting in greater carbon retention in the plant and compensating the carbon losses from the soil (Wang et al., 2010c). Yanqi Sun et al., (2013) studied Drying/rewetting cycles of the soil under alternate partial root-zone drying irrigation reduce carbon and nitrogen retention in the soil–plant 28

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systems of potato. It was found that in potato the amount of C retained in the soil-plant systems was lower in PRD than in DI (Fig. 2). Its been reported that drying and wetting cycles of the soils can cause increase of microbial activities and respiration rate, and hence may lead to an elevated C loss from the soil. (Van Gestel et al., 1993; Xiang et al., 2008; Wang et al., 2010). PRD significantly decreased soil carbon as compared with the DI treatment and which was mostly attributed to an enhanced soil organic carbon. Based on notion that soil microbes discriminate carbon during decomposition of soil organic carbon and leave the soil enriched with carbon (Balesdent and Mariotti, 1996), a greater carbon in the PRD soil may indicate a higher degree of soil organic carbon decomposition as compared with the DI soil. Soil additives and mineral fertilizers Fertilizer addition on a regular basis leads to an increase in soil organic carbon, soil microbial biomass and also changes soil carbon and nitrogen dynamics (Smith et al., 1994). Soil organic carbon is reported to increase by the continuous application of different combinations of N, P and K, whereas it decreased in unfertilized soils (Yadav et al., 1998). The use of FYM/GM along with incorporation with crop residues has been found to be beneficial (Singh et al., 2007). The incorporation of organic manures and crop residues to soil on long-term basis helps in carbon sequestration, but the rate of carbon sequestration can vary with the type and nature of organic manure. The change in soil organic carbon fractions like labile carbon, water soluble carbon, and microbial biomass carbon can be promptly influenced by changes in carbon inputs (Bolinder et al., 1999). Labile C is the fraction of total C that declines faster and is restored faster and is sensitive to best management practices (Tirol-Padre and Ladha, 2004). Kundu et al., (2006) studied the Carbon sequestration and its relationship between carbon addition and storage under rain fed soybean–wheat rotation in a sandy loam soil of the Indian Himalayas for 30 years and found that the use of nitrogen with farm yard manure significantly increased the soil organic carbon 60.3 (Mg C ha -1) at 0-45 cm depth of soil, while low soil organic carbon was found in initial soil and in control fertilization. Also low soil organic carbon was found at 20N + 33K (NK) which was 37.6 (Mg C ha-1) (Table 3). After 13 years of experiment, tillage and nitrogen fertilization affected soil organic carbon stock in 0-30 cm soil layer. Average over the three N fertilization rates, the mean soil organic carbon stock were 29.1 and 31.9 Mg C ha-1 respectively. The higher soil organic carbon 31.9 Mg C ha-1 was found at 120 Kg N ha-1 followed by 29.4 Mg C ha-1 at 60 Kg N ha-1. D. Mahanta et al., (2013) studied the influence of farm yard manure application and mineral fertilization on yield sustainability, carbon sequestration potential and soil property of garden pea-french bean cropping system in the Indian Himalayas for six years and found that farm yard manure at the rate of 20 t ha -1 increased the soil organic carbon 26.6 Mg C ha-1 at 0-15 cm soil layer, while low soil organic carbon 20.2 Mg C ha-1 in control (Table 3). In the study of Z. Zhengchao et al., (2013) the accumulation rate of soil organic carbon was more at N+P+M. These results showed that fertilizer application could accelerate the accumulation of soil organic carbon. These findings were consistent with a large body of data indicating that fertilizer treatment generally increased soil organic carbon and nitrogen contents of arable soil (Glendenning & Powlson, 1995; Brye et al., 2002). However accumulation rate of soil organic carbon content, even in N+P+M are lower than reported previously. In the study of B.S. Brar et al., (2013) Soil organic carbon content was lowest in the control and maximum in treatment of 100% NPK + FYM. At a soil depth of 0–5 cm, an application of 100% N, 100% NP and 100% NPK significantly increased the soil organic carbon content by 3.77 g kg-1, 3.90 g kg-1 and 4.33 g kg-1 over the control, respectively (Table 3). Such a beneficial effect of long-term use of chemical fertilizers has also been reported by (Campbell and Zentner , 1993). However, the soil organic carbon content in 0–5 cm layer 100% NPK + FYM treatment 5.07 g kg-1 was significantly higher over the 100% NPK dose alone. Similar was the trend in 5–10 cm layer. The effect of balanced nutrient application (100%NPK) with and without organic manure (FYM) on soil organic carbon content was significant over all other treatments in surface soil layer (up to 0–15 cm layer). Similar results have also been reported in literature (Clark et al., 1998; Padre et al., 2007; Kaur et al., 2008). The buildup of soil organic carbon content was more in surface layer due to more addition of root biomass, root exudates and plant biomass and it decreased with increase in depth irrespective of fertilizer treatments. Similar results were also reported by Sharma et al., (1992) and Kaur et al., (2008). The variation in soil organic carbon content at different soil depths due to farmyard manure and fertilizer’s application may be attributed to the accumulation of varying amounts of root biomass, root exudates and plant residues left in respective soil layers (Sharma et al., 1992; Brar and Pasricha, 1998; Padre et al., 2007). Manure applications are typically assumed to increase carbon sequestration in soils (Smith et al., 1997), but the manure is impossible to produce a soil net sink of C, as required by the Kyoto Protocol. (Buyanovsky and Wagner, 1998) showed that increasing soil organic matter as a utility of escalating C inputs from the residue in the Sanborn plots in Missouri. 2

Manure in corn and wheat fields was applied at the rate of 1340 g/m / year. Highest levels of plant production were found in 2

corn in those same fields, ranging up to 1100 g/m /yr. If this is used as silage and livestock digestive efficiency of 60% 2

(National Research Council, 1996), and the production of organic fertilizer will be of 440 g/m . The entire aboveground plant production 3.0 hectares of land will be required to supply manure to each hectare of manured land. (Liang and McKenzie, 1992) reported on carbon increase in 6 years experiment in eastern Canada with corn growing 29

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2

with the addition of crop residues (355g C/m /yr) and manure (160g C/m /yr). Again, 60 % digestion efficiency assumed, 160g 2

C/m /yr was produced by the required 400 g C in plant materials which were added as manure. Theoretical annual plant 2

production of 755g C/m was equivalent to the total organic residues input in these fields. Organic inputs of around 23.4% 2

2

2

(120g C/m /yr) were maintained in the soil, or 37g C/m /yr resulting from manure and from crop residues 83g C/m /yr. On the other hand, 177 g C would accumulate in soil organic matter if 755g C were allowable to decompose in situ. In agronomy manuring has many practical applications but the net carbon sequestration does not seem to be one of them. Biochar and compost Biochar is a byproduct of biomass pyrolysis, one of the technologies used to produce bio energy (Bridg water AV, 2003). It has been recommended that the application of Biochar could be a potential approach to increase soil carbon sequestration and reduce greenhouse gas emissions from soils (Lehmann J and Joseph S, 2009). The organic wastes which are used as soil changes have been shown to have more benefits to improve vegetation establishment, reduce compaction, (Bernal et al., 2006), to provide strength against erosion (Craul, 1999; Whalen et al., 2003), strap heavy metals (Song and (Greenway, 2004), the adsorption of organic carbon dissolved (Pietikainen et al., 2000), rapid mobilization and vertical movement of trace metals, high increase pH of soil and major soil macro-elements, and decrease in trace metals in leachates (Novak et al., 2009). Latest studies investigating Biochar have focused on its mitigating effects on climate change. Certainly, the production of Biochar from biomass represents a net withdrawal of CO2 from the atmosphere (Lehmann J, 2007). Contribution of composting can play a vital part in a positive manner for the two main objectives of restoring soil quality and sequestering carbon in soils. When the organic residues are applied, can lead either to a build-up of soil carbon with time or it can cause a reduction in the rate at which the organic matter is depleted from soils. Therefore, the application of organic residues is likely to reverse the decline in soil carbon storage that has occurred in past, thus, it can contribute in the build-up of the stable carbon fraction in soils (De Neve et al., 2003). W. -Y. Lai et al., (2013) studied the effects of woodchip Biochar application on crop yield, carbon sequestration and greenhouse gas emissions from soils planted with rice or leaf beet and found that relative to the BK2 control, treatments 5% BC700 and 2% BC700 significantly reduced CO2 emissions from the Pc soil planted with rice (Table 4). However, a similar reduction was not found when these soils were planted with leaf beet. It could not conclude the cause for the reduction based on that study. It has previously been suggested Clough TJ et al., (2010) that the application of woodchip Biochar might result in reduced CO2 emission as a consequence of a reduced utilization of water soluble carbon. However, recent studies have indicated that Biochar application could actually increase CO2 emissions as a consequence of enhanced soil respiration Zimmerman et al., (2011), Bell et al., (2011). In the latter case, the emissions could be derived from labile carbon from Biochar decomposition during the short-term incubation Novak et al. (2010), Zavalloni et al. (2011). The 5% BC700 treatment resulted in the highest soil carbon sequestration of all of the treatments, in the rice experiments. It has been observed previously that a higher temperature of pyrolysis produces more stable Biochar Chen B and Chen Z, (2009). P–Thi Ngo et al., (2013) after the 3 years of experiment showed that the utilization of organic amendments increased the amount of soil organic carbon compared with the control soil. This is in agreement with the studies of Gabrielle et al., (2005) and Lashermes et al., (2009). There were no significant differences between compost and Vermicompost treatments. However Biochar showed significant effect on soil organic carbon. The highest soil organic carbon content was (52 Mg g-1) for the treatment of Vermicompost with Biochar L Beesley et al., (2010) studied the effects of Biochar and green waste compost changes on mobility, bio-availability and toxicity of inorganic and organic chemicals in the soil polluted with multi-elements and observed that the percentage of soil organic carbon was high in (S+C+B) treatment, while it was low in (S) treatment. G.P.S. Sodhi et al., (2009) studied the soil aggregation and distribution of carbon and nitrogen in different fractions under long-term application of compost in rice-wheat system and found that long-term application of rice straw compost and inorganic fertilizer significantly increased soil organic carbon. From the mean values, highest increase in soil organic carbon was observed in plots with Rice straw compost without rock phosphate at 8 tones ha-1 15.40(g C Kg-1) followed by RSC 120 kg N ha-1 + 2 tones ha rice straw compost with rock phosphate 12.77(g C Kg-1) (Table 4). Crop frequency and crop rotation Agricultural land is an important carbon pool of the biosphere (Buyanovsky and Wagner, 1998) and a potential sink of atmospheric carbon (Lal, 2004; UNFCCC, 2009). Previous studies have showed that there were both negative and positive effects of cropping practices on carbon storage and stability of soil in agricultural lands (Paustian et al., 1997; Bruce et al., 1999; Six et al., 2002). Generally, inappropriate cropping practices i-e excessive cultivation can induce dramatic soil organic carbon losses and soil quality degradation (Elliott, 1986; Six et al., 2002; Yu et al., 2006. Soil organic carbon protected by the macro-aggregates shows a short-term storage, and the most stable carbon is stored in the smallest silt + clay size fraction (