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The most of the global organic carbon is stored in the forest soil. The large quantity of CO2 emitted from soil is a consequence of land use change, both through human activities (e.g. agriculture) or natural hazards (e.g. flooding, landslides, erosion). A net carbon loss from soils adds to the increase in the atmospheric CO2 concentration, probabl...
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... this work was used the dominant soil type. Furthermore to re- fine the accuracy of SOC calculation where any HWSD soil unit/topsoil texture doesn't reach 50% of "share" a further soil type has been defined; this new class, defined "Mixed soils" is estimated at around 22% of HWSD cells ( Figure 6). Table 3 shows some sta- tistics (number of soil profiles, mean and standard deviation) of SOC stock for Top and Sub soil for the soil types in HWSD. ...
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Our atmosphere naturally contains CO2, CH4, N2O, water vapor, and other gases creating a natural greenhouse effect. But increased concentrations of these gases in the atmosphere have created an imbalance and have enhanced the greenhouse effect causing warming of the globe. Global warming will adversely affect hundreds of millions of people and will...
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... The initial difference in carbon and nitrogen concentrations in the different types of soil used for the control treatment was caused by the intrinsic soil characteristics at each site; the andosol at the SED and SIC sites being one most carbon-rich soils in the world, which is not the case of the arenosol at the LYC site (Latham et al., 2017). The increase in the concentration of soil carbon observed with all the treatments may have been caused by the increased productivity of the grassland which, in turn, increased carbon inputs through rhizodeposition in the soil (Poeplau et al., 2018). ...
... However, it should be noted that high nitrogen efficiency was maintained with the M2 treatment at the LYC site and, as shown in Fig. 2, the increase in grass yield compared with the control was sustained, which was not the case at the other two sites. This is probably due to the nature of the soils, the arenosol being very poor in carbon and other nutrients (Latham et al., 2017). Thus, the supply of minerals and the improvement in productivity could have increased the organic matter in soil (Poeplau et al., 2018) at the LYC site and hence improved soil quality there. ...
Since the discovery in the early 1950s of fixation of industrial atmospheric nitrogen through physico-chemical processes, mineral fertilisation has become the main means of fertilising cultivated land. However, several studies have shown that continued use of mineral fertilisers can accelerate soil acidification and reduce cation exchange capacity, water-holding capacity, and soil microbial activity, thereby reducing soil fertility. Other studies have underlined the importance of a nutrient balanced fertilisation protocol to sustain high grass yields. On the other hand, by recycling livestock manure, the use of organic fertiliser has been shown to lead to high soil productivity and to provide economic and environmental benefits to farmers. Our study focused on the short-and long-term effects of several types of fertilisers, (mineral, organic, and mixed organic-mineral), and several doses (ranging from 440 to 1,260kgN/ha/year) in a 15-year experiment on highly productive grassland. We showed that, in contrast to organic fertilisation, although the mineral treatments maintained soil nitrogen content, these treatments did not increase phosphorous and potassium concentrations, and in addition, led to soil acidification. Furthermore, although mineral fertilisation led to rapid increases in grass yield, its fertilisation effect weakened over time whereas some of the organic fertilisation treatments resulted in a gradual increase in grass yields. Significant differences in grassland productivity were observed between the effects of liquid manure and compost, liquid manure being more immediately effective while compost had a longer-term positive effect on grass yield. The mixed organic-mineral treatments were shown to be a good compromise, with a significant short-term increase in grass yields plus sustained grass production over time.
... Andosols have sometimes been considered as saturated soils, i.e. very rich in carbon, due to the concentration of Al and Fe in the allophane, as these minerals are effective in binding organic matter (Zieger et al., 2018). On the other hand, sandy soils like arenosols are known to be much less rich in carbon than andosols, their mean carbon content being 26 MgC/ha and 103 MgC/ha, respectively, in the top 30 cm of the soil (according to the Global Soil Organic Carbon Database; (Latham et al., 2017)). ...
... According to the same authors, the quantity of carbon stored in the 30-100 cm horizon is in the same range as that stored in the topsoil, although variation was greater in the deeper horizon (Latham et al., 2017). Previous studies have also shown that the carbon content in the deeper horizon of andosols increased in response to carbon inputs via organic fertilization by migrating from the topsoil to the deep horizons (Zieger et al., 2018). ...
... The naturally low stock of carbon in arenosols is due to their low clay and silt contents compared with those of andosols, as shown by Feller and Beare (1997). However mean carbon content was higher than that recorded in the global soil organic database (Latham et al., 2017). In our study, the total carbon accumulation in the soil after 15 years of fertilization in the first 60 cm of the soil ranged from + 2.8 MgC/ha to + 121.3 MgC/ha, as previous studies showed accumulation varied significantly depending on the intensity and types of fertilization, the type of soil, and the depth (Conant et al., 2001;Fujisaki et al., 2018;Kirkby et al., 2014;Poeplau et al., 2018;Ryals et al., 2014;Wiesmeier et al., 2015;Zieger et al., 2018). ...
Previous long-term experiments conducted more than 10 years ago, showed that long-term application of organic fertilizer increased soil organic carbon (SOC) of grasslands. However, it was usually assumed that, independent of the successive additions of fertilizer, soils have an upper limit to their SOC due to the inability of the soil mineral phase to fix additional carbon. Andosols of the volcanic Reunion Island are typically very rich in carbon and are usually considered as saturated in SOC. To assess the long-term effect of different types of fertilization on SOC in these soils, SOC concentrations were recorded at yearly intervals for 15 years in one arenosol site and in two andosols sites across a topo-sequence. The types of fertilization tested included inorganic, organic, and a mix of inorganic and organic nutrient sources. The addition of organic fertilizers increased soil carbon in the top (0–15 cm) horizon in both the arenosol and the two andosols (up to +250% in the arenosol and up to +41% in the andosol), whereas inorganic fertilizers and the control treatment did not always result in a significant increase in SOC. After 15 years, no plateau was reached in C stocks even with the highest fertilization rates. Our results suggest that the increase in SOC was mainly caused by direct carbon inputs, while the effect of the increase in litter resulting from the increase in yield caused by fertilization, remained uncertain. In the andosol, all the fertilization treatments led to higher concentrations of carbon in the deeper layers. This suggests that SOC inputs lead to downward migration of OC to deep horizons. For C-rich soils like andosols, assessing the variations in carbon in the deep horizon is thus critical in estimating the effects of soil management on carbon sequestration.
... This value is higher than the range of mean SOC densities of 25 FAO's soil grouping orders (5.5-13.7 kg C m À2 ), excluding three orders which have exceptionally high SOC densities (Histosols; 27.8 kg C m À2 , Andosols; 21.4 kg C m À2 , and Chernozems; 16.6 kg C m À2 ), estimated using the Harmonized World Soil Database v.1.21 (Latham et al. 2017). The rough estimate of urban soil SOC density could still have high uncertainty due to the lack of stratified, systematic sampling as well as harmonization. ...
The presence of soil carbon in areas such as urban parks, lawns, and impervious surfaces plays an important role in soil functioning, human well-being, and climate change mitigation. However, because of the heterogeneous definition and the different factors affecting the formation of urban soils, there is limited knowledge on the processes and patterns of urban soil carbon. This study serves to briefly review the process of soil organic carbon (SOC) accumulation as well as the factors affecting it and conduct a meta-analysis of the global patterns of urban SOC. Various factors, including the structure of urban soil cover, urban climate, chemical/physical/biological stresses, and management, directly and indirectly regulate SOC accumulation through complex interactions involving primary production, detritus organic matter input and decomposition, and the mineralization of soil organic matter and humification. In addition, soil inorganic carbon (SIC) and black carbon (BC) could have a meaningful contribution to both soil carbon stock and climate change mitigation. The mean SOC density of urban soils in 63 studies was 8.6 kg C m−2; its estimate up to a depth of 1 m was 14.1 kg C m−2. A higher SOC density in urban soils than rural or native soils was observed in two-thirds of comparative studies (N = 22), suggesting a positive effect of urbanization on SOC accumulation. The median SOC accumulation rate was 0.058 kg C m−2 year−1 when chronosequence or a change-from-baseline design (N = 11) was used. Further research is required on urban soil carbon to effectively extend studies from just focusing on carbon density to including carbon accumulation rate, from SOC to non-SOC fractions (SIC and BC), from temperate to tropical cities, and from surface to deep soils. In conclusion, it is confirmed that urban soils have considerable potential to sequester atmospheric carbon. Managing urban soil carbon is in line with the general practices for enhancing the physicochemical quality and health of urban soils.
Grassland ecosystems occupy more than 40% of the Earth's land area in a variety of edapho-climatic contexts. Their functioning and understanding are essential in the context of climate change and the increasing global demand for animal-based food products. Previous long-term experiments conducted over more than 10 years have shown that the repeated application of organic and mineral fertilisers over several years has an impact on the agronomic and environmental performance of grasslands. These long�term effects are not sufficiently documented for tropical grasslands.
Thus, to assess the long-term agronomic and environmental effects of different types of organic and/or mineral fertilisation on tropical grasslands in Réunion Island, an experimental fertilisation scheme was carried out over a period of 15 years on tropical grasslands composed mainly of tropical grasses on sandy soils and temperate grasslands composed mainly of temperate grasses on volcanic soils. However, field experiments show their limits in their singularity, especially long-term experiments. Thus, the use of mechanistic models and their parameterisation are important to study the functioning of ecosystems in a broader context. We therefore used the data from the in-situ experiment to parameterise the temperate PASIM model to the tropical conditions observed in Réunion. The experimental set-up showed the in-situ effects of these fertilisations on the nutrient status and organic carbon of the soil. Mineral fertilisation shows some of its limitations on forage production and carbon storage, considering its long-term application, with agronomic benefits fading and environmental benefits limited. Whereas organic fertilisation shows strong positive effects in the long term both on agronomic performance by improving soil nutrient status and in terms of carbon storage. The model showed a good level of production both in terms of forage production and soil carbon dynamics, while highlighting certain limitations of the model, in particular with regard to the long-term effects of certain fertilisation and certain specific characteristics of tropical soils. These limitations raise the question of the possible complexification of these models.Thus, this study shows the interest and the need for long-term experiments specific to the tropical context, completed by simulation models integrating the maximum of specificities of the tropical context, in terms of photosynthesis or phenology mechanism representation
