Managing soil organic matter is the key to healthy soil and air and water quality. In eastern Oregon, application of cattle manure at 11.2 MT ha−1 yr−1 over a 56-year period resulted in an increase in SOC of 0.02 Mg C ha−1 yr−1 (Liebig et al., 2005). ‘Soil organic carbon’ (SOC) – the amount of carbon stored in the soil is a component of soil organic matter – plant and animal materials in the soil that are in various stages of decay. The SOC changes were dependent on the aboveground and root biomass response to N fertilization (Huggins and Fuchs, 1997). Nopt decreased with increase in SOC. In a study covering six northeastern states of India (excluding Arunachal Pradesh and Mizoram), Choudhury et al. Soil aggregates improve the structure of the soil and consequently its water retention; Prevention of soil erosion: It was found that an increase in soil organic matter from 1 to 3 % would result in lessening erosion up to 20-33%. Our results indicate a positive effect of SOC in terms of a reduction of mineral N needed to obtain the potential crop yield, and a negative effect on Ypot. (2015) conducted a study on the impact of the topographic setting on soil carbon stock under different crop management regimes at altitudinal gradient ranges from 880 to 1880 m msl at different locations of Ri-Bhoi and the East Khasi Hills district of Meghalaya in northeastern India. On the one hand, soil biodiversity contributes greatly to the formation of SOM from organic litter, thereby contributing to the enhancement of SOC content. The magnitude of increase in yield (Mg ha− 1) in respect to control is from: (1)0.78 to 1.03 in groundnut with 50% RDF + FYM 4 Mg ha− 1, (2) 0.40 to 1.34 and 0.82 to 3.96 in groundnut and finger millet, respectively, through FYM 10 Mg ha− 1 + 100% NPK in groundnut–finger millet rotation, (3) 0.84 to 3.28 in finger millet through FYM 10 Mg ha− 1 + 100% NPK, (4) 0.61 to 1.19 in winter sorghum through 25 kg N ha− 1 (Leucaena clippings) + 25 kg N ha− 1 (urea), (5) 0.43 to 0.81, 0.32 to 0.58 and 0.44 to 0.83 in pear millet, cluster bean, and castor, respectively, through 50% RDN (fertilizer) + 50% RDN (FYM), (6) 1.04 to 2.10 and 0.63 to 1.49 in soybean and safflower, respectively, through FYM 6 Mg ha− 1 + 20 kg N + 13 kg P ha− 1, and (7) 1.08 to 1.95 and 0.48 to 1.04 in rice and lentil, respectively, through 50% N (FYM) + 50% RDF treatment. The term SOM is used to describe the organic constituents in soil in various stages of decomposition such as tissues from dead plants and animals, materials less than 2mm in size, and soil organisms. Altitudinal variation has a strong influence on SOC content irrespective of the land uses. Several As carbon stores in the soil increase, carbon is “sequestered”, and the risk of loss of other nutrients through erosion and leaching is reduced. Erosion Control is Not Enough. Changes in agricultural practices often influence both the quantity and quality of SOC and its turnover rates. Yields of important rainfed production systems in long-term manurial experiments under different climate and soil types show declining trends even with adoption of some recommended management practices (RMPs). The simulated SOC loss in the manure plot, with 90% straw removal until 1950, was 3.5 Mg C ha−1 under MP. Soil organic carbon (SOC) is one of the most important characteristics of soils that result from the interplay of net primary producers, decomposers, and mineralogy. Dissolved organic matter (DOM) is a small and reactive fraction of total organic matter in soil and is important in various biogeochemical processes (Battin et al., 2009; Kindler et al., 2011).Its movement through soil pores and interaction with solid organic matter make it a highly dynamic carbon pool subject to physical, chemical, and biological alteration. Declines in SOC at rates of 0.18 Mg C ha−1 yr−1 in the fertilized plots and of 0.15 Mg C ha−1 yr−1 with manure application for the 30–60 cm soil depth were predicted by CQESTR. Soil Organic Carbon Stabilization in the Three Subtropical Forests: Importance of Clay and Metal Oxides Mengxiao Yu Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China We build on soil as well as with it and in it. Agriculture SOC sequestration alone would only result in about only half expected outcome promoted in the 4PT initiative, and that may be optimistic. During humification (a process where soil organisms form complex and stable organic matter) some organic matter breakdown does not occur completely, especially in soils like peat, owing to its high acid and water content. Yet, the data from long-term experiments show that increasing SOC concentration by C sequestration and stabilization positively affects yields of several crops. Productivity levels of rainfed dryland crops are far below those of global average. A first step would be to combine liming treatments with either organic and/or inorganic nutrient fertilisation (N, P, K, Mg, etc.). Manure application for 73 years in a wheat–fallow cropping system slightly increased SOC in the top 30 cm depth. Figure 3.6. Soil structure aggregation: Organic matter results in clumping of the soil to form aggregates. A combination of agricultural practices that promote the formation of stable soil aggregates will improve soil quality and sustainability. At lower altitudes (< 500 m msl), SOC concentration was 1.65–1.84% and it increased with the increase in elevation and attained the peak value of 3.53% (± 0.22%) at higher altitudes (2500–3500 m msl). Soil organic carbon (SOC) is a strong determinant of soil fertility through its positive effects on soil structure and soil chemical and biological properties which in turn stimulate primary production. Drought stress, high temperatures reaching up to 45 °C for 8–10 weeks in a year, coupled with low biomass productivity are common features of dry agroecosystems. Hero T. Gollany, ... Y. Liang, in Managing Agricultural Greenhouse Gases, 2012. Adopted from Choudhury, B.U., Fiyaz, A.R., Mohapatra, K.P., Ngachan, S., 2016. Chemical, physical, and biological. For example, the plow depth with moldboard plow is about 20 cm compared with hardly 10 cm in RoT system. Higher soil organic carbon promotes soil structure or tilth meaning there is greater physical stability. 6). Maintaining or improving SOC concentration in rainfed dryland agroecosystems is a major agronomic challenge. The carbon, aggregation, and structure turnover (CAST) model was used to simulate SOC sequestration, aggregate formation, and structure dynamics in three field sites including nontilled soils of natural ecosystems and tilled soils of agricultural fields in Europe (Critical Zone Observatories (CZO) of the SoilTrEC network) and one site in North America. MBC, microbial biomass carbon; LF, light fraction of soil carbon; HF, heavy fraction of soil carbon. Improved structure aids aeration, water holding capacity, etc. The model reliably simulated C and soil structure dynamics in various land uses, climatic conditions, and soil properties providing support for the underlying conceptual and mathematical modeling and evidence that the CAST model is a reliable tool to interpret soil structure formation processes and to aid the design of sustainable soil management practices. Increasing SOC as mentioned earlier has positive effects on crop yield potential and is a key in promoting main ecosystem services associated with water and air quality. Figure 4.9. pH(H2O) (left) and pH(KCl) (right) as a function of time for the eight different fertilization scenarios (n = 4); p-values and small letters refer to statistical analysis using one-way ANOVA and post hoc pairwise comparisons; ∗significant difference at the 5% level. Despite much research, a lower threshold of SOC for sustainable crop production has not been identified across soil types. Generally, throughout the world, SOC content increases with elevation (Choudhury et al., 2016; Sinoga et al., 2012), because climatic variables change with altitude. Climate change may alter temperature and moisture regimes that could influence decomposition rates and stability of SOC. In another study, analysis of soil samples for SOC concentration along an altitudinal gradient of 700–1800 m msl from different land uses [agriculture, horticulture (fruits and vegetables), jhum land, and natural vegetation] in Mizoram, another northeastern state of India, it was observed that SOC concentration increased in an inconsistent manner along the altitudinal gradient. Soil organic carbon dynamics: Impact of land use changes and management practices: A review, Thangavel Ramesh, ... Oliver W. Freeman II, in. The decomposition of SOM further releases mineral nutrients, thereby making them available for plant growth, while better plant growth and higher productivity contribute to ensuring food security. Manure addition can improve soil physical properties such as available water holding capacity (Estevez et al., 1996; Hudson, 1994; Rawls et al., 2003; Olness and Archer, 2005). In terms of temporary sown grasslands and renovation via ploughing, a key step is to increase the time between re-seeding to at least five years, as this will contribute to an organic matter build-up though reduced tillage events. Soil inorganic carbon consists of mineral forms of carbon, either from weathering of parent material, or from reaction of soil minerals with atmospheric CO 2. Soil organic carbon, SOC, is derived from living tissue: plant leaves and roots, sap and exudates, microbes, fungi, and animals. Impact of land uses, agrophysical variables and altitudinal gradient on soil organic carbon concentration of North-Eastern Himalayan Region of India. Soil organic carbon is also important to chemical composition and biological productivity, including fertility and nutrient holding capacity of a field. Soil organic carbon is also important to chemical compositionand biological productivity, including fertility and nutrient holding capacity of a field. 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