Total Organic Carbon Stocks Research Articles

Multifaceted effects of microplastics on soil-plant systems: Exploring the role of particle type and plant species

Microplastics have emerged as a global environmental concern, yet their impact on terrestrial environments, particularly agricultural soils, remains underexplored. Agricultural soils, due to intensive farming, may serve as significant sinks for microplastics. This study investigated the effects of different types of microplastics—polyester microfibers, polyethylene terephthalate microfragments, and polystyrene microspheres—on soil properties and radish growth, while a complementary experiment examined the impact of polyester microfibers on the growth of lettuce and Chinese cabbage. Through both horizontal and vertical comparisons, this research comprehensively evaluated the interactions between microplastic particles and plant species in soil-plant systems. The results showed that polyester microfibers significantly affected soil bulk density, with effects varying based on planting conditions (p < 0.01). Polyethylene terephthalate microfragments and polystyrene microspheres reduced the proportion of small soil macroaggregates under radish cultivation (p < 0.01). Additionally, polystyrene microspheres significantly altered the total organic carbon stock in radish-growing soil, potentially affecting the microclimate (p < 0.01). Interestingly, polyester microfibers promoted lettuce seed germination and significantly enhanced the root biomass of Chinese cabbage (p < 0.05). Overall, the environmental effects of microplastic exposure varied depending on the type of particle and plant species, suggesting that microplastics are not always harmful to soil-plant systems and may even offer benefits in certain scenarios. Given the crucial role of soil-plant systems in terrestrial ecosystems, and their direct connection to food safety, human health, and global change, further research should explore both the positive and negative impacts of microplastics on agricultural practices.

Early-stage soil organic carbon stabilization in conservation agriculture-based cereal systems

In South Asia, the sustainability of conventional tillage and input-intensive cereal-based cropping systems (such as rice-rice and rice-wheat) is under scrutiny due to soil organic carbon depletion, stagnant productivity, and adverse environmental impacts stemming from greenhouse gas emissions (N2O, CH4, and CO2). Against this backdrop, a long-term field experiment was initiated in 2009 at three sites in India (Karnal, Patna, and Aduthurai) and one site in Bangladesh (Gazipur) to assess four scenarios (S) reflecting current and future diversified crop rotations and conservation agriculture (CA) practices: S1 - double cereal rotation with conventional practices; S2 - double cereal plus legume rotation with partial CA; S3 - double cereal plus legume rotation with full CA; and S4 - futuristic diversified cereal-legume rotations with full CA. This study delved into the dynamics and stabilization of soil organic carbon across all scenarios and sites. Replicated soil samples were collected from depths of 0–15 cm and 15–30 cm after two crop cycles. We analyzed Walkley-Black carbon (WBC), total organic carbon (TOC), and various carbon pools with different oxidizability, determining the amount of carbon stabilized under CA-based scenarios and identifying optimal systems for carbon economy in South Asia. On average, active and passive carbon pools, TOC, and WBC stocks followed the order: S4 > S3 > S2 > S1 at all sites, except Gazipur, where the order was S3 > S4 > S2 > S1. CA practices stabilized applied carbon inputs to soil organic carbon at an annual rate of 1.7 %, with greater stabilization observed under S4 (11.7 %) > S3 (10.6 %) > S2 (7.8 %), regardless of location. Rice-rice sites exhibited a higher carbon stabilization rate (13.4 %) compared to rice-wheat sites (6.7 %). A significant proportion of stabilized carbon (63 %) was allocated to passive pools in soils under S2, S3, and S4, highlighting CA's potential to enhance carbon stability. Using a linear indexing technique, we identified that both S3 and S4 are conducive to better carbon stabilization, yield sustainability, and environmental co-benefits. Consequently, full CA systems with best management practices (S3) and best management practices with crop diversification (S4) are recommended for sustainable crop production in the major double cereal growing regions of South Asia, including India and Bangladesh.

Carbon accumulation in the soil and biomass of macauba palm commercial plantations

Commercial cultivation of the Macauba palm is growing due to its agro-energy potential. This study quantified carbon stock in two macauba plantations (4.8 and 9.0 years old), considering carbon stored in soil and biomass. We assessed total organic carbon (TOC) stocks in labile (EOC and LF-C) and non-labile (NL-C) soil fractions, comparing these with a forest regenerating for over 30 years. Soil samples were collected within the palm plantation (rows and inter-rows) and the forest area at five depths (0–10, 10–20, 20–40, 40–60, and 60–100 cm). The impact of plantation age and sampling position on TOC stocks and organic matter fractions across different soil layers (0–100 cm) was assessed. The Carbon Management Index (CMI) was calculated to evaluate carbon recovery. Plantation age and sampling position influenced soil TOC stocks across all depths up to 1 m. Higher TOC and NL-C soil stocks were observed in the older plantation (9.0 years) and inter-row. EOC and LF-C fractions varied by soil layer. The inter-row region of the 9.0-year-old plantation exhibited higher carbon recovery based on the CMI. Over 4.2 years of palm cultivation (between 4.8 and 9.0 years), carbon accumulation in biomass and soil reached 75.36 Mg C ha−1. These findings underscore the potential of commercial macauba plantations to enhance soil carbon stocks rapidly, particularly in inter-row areas. Plantations younger than a decade surpassed the soil carbon stock of a forest regenerating for over 30 years, highlighting significant environmental benefits of macauba cultivation, including soil and biomass carbon sequestration.

Soil organic carbon stocks and fractions under integrated systems and pasture in the Cerrado of Northeast Brazil

The adoption of integrated systems can reduce the pressure for the conversion of areas under native Cerrado to agricultural lands. However, little is known about how these systems affect total organic carbon pools and stocks in the Cerrado of Northeast Brazil. We aimed to evaluate the dynamics of soil organic carbon (SOC) and C and N stocks in a Cerrado under different cropping systems, in the agricultural frontier of Matopiba, Brazil. The systems were (i) Native Cerrado vegetation (NCF), (ii) integrated crop-livestock-forest system (ICLF), (iii) integrated crop-livestock system under no-tillage (ICL1), (iv) integrated crop-livestock with recent soil tillage (ICL2), and (v) pasture (PA). Soil samples were collected at 0.0–0.10, 0.10–0.20, 0.20–0.30, and 0.30–0.50 m depths to determine the soil C and N stocks, SOC fractions, and the carbon management index (CMI). Total C stocks in the 0.0–0.50 m soil profile were highest in ICL2 (127 Mg ha−1), ICL1 (112 Mg ha−1), and PA (101 Mg ha−1) and lowest in NCF (61 Mg ha−1) and ICLF (67 Mg ha−1). Similarly, total N stocks were highest in ICL1 (6.7 Mg ha−1), PA (6.7 Mg ha−1) and ICL2 (6.5 Mg ha−1), and lowest in NCF (4.7 Mg ha−1) and ICLF (4.8 Mg ha−1). ICL2 and ICL1 presented the greatest amount of humic fractions among the systems. The adoption of conservationist management systems that provide a permanent input of organic residues in the long-term is crucial for SOC stabilization and increases in soil C and N stocks. Integrated crop-livestock systems are the most suitable alternative for sequestering C and N in grain production systems in the Cerrado of Matopiba region.

Nitrogen and carbon stocks in sandy soil cultivated with corn subjected to 17 years of animal manure and mineral fertilizer application

Animal manure can be used as a source of nutrients in cropping systems throughout the world. However, in subtropical climates, the impacts of animal manure application over multiple years on crop productivity and on the total organic carbon (TOC) and total nitrogen (TN) stocks in the soil profile are not well understood. In this study, we aimed to evaluate how animal manure application carried out over more than 17 years can impact corn productivity and TOC and TN stocks in different soil layers. This long-term study was conducted from 2004 to 2021 under no-till conditions in southern Brazil. The treatments included pig slurry (PS), cattle slurry (CS), pig deep litter (PDL), mineral fertilizer (NPK) and a control (no fertilizer application). To determine soil TOC and TN stocks, soil samples were collected from the 0.00–0.10, 0.10–0.20, 0.20–0.30, 0.30–0.40 and 0.40–0.50 m layers in December 2008, 2012, 2016 and 2020. Corn productivity was evaluated for the 2008/09, 2012/13, 2016/17, and 2020/21 crops. The highest yields and TOC and TN stocks were observed in soils with pig deep litter and cattle slurry application. In the sandy soil under a no-till system after 26 animal manure applications over 17 years, the highest TOC and TN stocks were observed in the 0.00–0.10 m layer. On average, the TOC stocks obtained for the 0.00–0.10 m layer were 11.21, 14.88, 15.82, 22.59 and 15.16 Mg ha−1 for the control, PS, CS, PDL and NPK treatments, respectively. The soil TN stocks in the 0.00–0.10 m layer were 1.06, 1.40, 1.65, 2.03 and 1.43 Mg ha−1 for the control, PS, CS, PDL and NPK treatments, respectively. The application of pig deep litter to the soil over 17 years resulted in a notable increase in TOC and TN levels, playing a crucial role in increasing the productivity of maize crops.

Chemical characterization of soil organic matter in differents management practices in the Cerrado-Pantanal ecotone

Different land uses and occupations have a direct impact on edaphic attributes, which can be identified by soil quality indicators, with organic matter being an excellent edaphic quality indicator. The objective of the work was to chemically characterize soil organic matter (SOM) in different management systems in the municipality of Aquidauana, Mato Grosso do Sul, Brazil. Soil samples were collected in five areas with different management practices, in addition to an area of native Cerrado forest (NF), and the managed areas were: exposed soil (ES), conventional tillage system (CTS), no-tillage (NTS), permanent pasture (PP) and sugarcane (SC). In addition to the determination of bulk density (Bd), total organic carbon (TOC) contents and stocks were quantified, as well as carbon (C) contents and stocks of the humified fractions: humic acid (AH), fulvic acid (AF) and humin (HUM), with subsequent calculation of HA/FA and alkaline extract/humin (AE/HUM) and TOC stratification index (SI). There were no significant changes for Ds after six years of implementation of management systems. TOC levels and stocks were higher in PP and NTS areas. The HUM fraction was predominant, with higher contents and stocks of all fractions for the PP and NTS areas, demonstrating the greater intensity of the humification process in these management systems, with greater stability of C in the soil after six years of experiment. The PCA indicated a difference between the areas that present conservation practices in the ES and CTS areas. The NF, NTS, PP and SC areas contribute to SOM stabilization.

Soil quality and vegetation cover characteristics as influenced by diverse grazing regimes and soil disturbance histories in a semi-arid rangeland (Iran)

This study investigates the soil functioning and regeneration processes in a semi-arid rangeland subject to an eleven-year conservation grazing (CG) program within the Gonbad paired watershed in Hamadan, Iran. Five distinct sites with varying rangeland vegetation cover were selected based on differences in grazing regimes and soil disturbance histories. These sites include: CG site with Astragalus-Artemisia vegetation (CG(A-A)); CG site with Astragalus-Bromus vegetation (CG(A-B)); CG site, easily accessible to grazing livestock, with Astragalus-Lactuca vegetation (CG(EA)); CG site with a history of past rainfed farming and Centaurea-Grasses vegetation (CG(PRF)); and free grazing (FG) site with Astragalus-Euphorbia vegetation. In addition, a long-term rainfed farming site (RF) was studied as the dominant land use. Rangeland management practices had a discernible impact on nearly all soil quality (SQ) indicators. However, due to their strong interdependence, only soil aggregate stability, carbohydrates, and phosphatase activity proved to be critical indicators representing soil functioning in the area. The general SQ index illustrated a decline in soil functioning at RF (58%), CG(PRF) (55%), FG (42%), and CG(EA) (22%) sites compared to sites classified as "good" (CG(A-A) and CG(A-B)). Total organic carbon and carbon stock were only recovered in well-restored sites, characterized by a predominance of shrubs and perennial grasses. Meanwhile, active carbon and carbohydrates revealed the positive effects of conservation grazing in moderately and poorly restored sites, characterized by a predominance of forbs and annual grasses. Our findings suggest that soil disturbance history and grazing accessibility are critical factors for successfully implementing conservation grazing management in the area.

Nutrient cycling and soil quality in threatened veredas in two Protected Areas of the Brazilian cerrado

Veredas are humid environments of significant importance for the Brazilian Cerrado. Understanding soil quality and ecological processes between the soil and vegetation in veredas can provide insights into ecosystem dynamics. This study was aimed to assess litter deposition and decomposition, as well as soil quality, including chemical, physical, and microbiological attributes, in two threatened veredas at various stages of conservation in Brazil. The research was conducted in Almescla (a preserved vereda) within the Environmental Protection Area of the River Pandeiros, and Peruaçu (a degraded vereda) located at the Veredas do Peruaçu State Park. Litter deposition was measured using collectors, and decomposition was assessed with litter bags. Soil granulometry, carbon and nutrient contents, and soil microbial biomass were also evaluated to a depth of 20 cm. The litter production was higher in Peruaçu, with the leaf fraction accounting for more than 70% of the total in both studied areas. The decomposition constant (kc) was higher in Almescla vereda. Nutrient concentrations followed a decreasing order of Ca &gt; N &gt; K &gt; Mg &gt; S &gt; P in both areas. Peruaçu vereda exhibited higher levels of clay, available P, and Ca. Microbial carbon, total organic carbon, microbial quotient, and carbon stock were higher in Almescla, whereas the metabolic quotient was higher in Peruaçu. Our results suggest that the degradation of vereda ecosystems may lead to changes in nutrient cycling, with reduced litter deposition and decreased carbon storage.

Estimation of organic carbon stocks in bottom sediments of Middle Kaban lake (Kazan, Republic of Tatarstan)

The lakes has an enormous sediment carbon storage potential. This study aims to estimate sediment organic carbon stock in the of Middle Kaban lake, Republic of Tatarstan. The study revealed that the in the surface layer of lake sediments carbon stocks amount to 1134 tons. Total organic carbon stocks in the bottom sediments of Middle Kaban lake amount to 5986 tons. In CO2 equivalent, 21949 tons of greenhouse gases are accumulated in the lake bottom sediments.

Exploration of microbial signature and carbon footprints of the Nilgiri Hill Region in the Western Ghats global biodiversity hotspot of India

Land use change (LUC), alters the multifarious biodiversity hotspots directly and indirectly through the loss of soil quality. A comparative study on soil carbon status and soil microbiome in undisturbed natural forest ecosystems with that of other land uses which gradually altered over time can serve as a suitable indicator for understanding LUC impact on carbon cycles. With this aim, the current investigation was initiated to infer the cyclic effects of LUC on the soil carbon status under six major ecosystems viz., cropland (CL), deciduous forest (DF), evergreen forest (EF), forest plantation (FP), scrubland (SL) and tea plantation (TP) of the Nilgiri Hill Region (NHR) (India's first biosphere reserve). The total organic carbon (TOC) and carbon stocks were highest in evergreen forest (10.25 %, 322.06 t ha−1) and they decreased with increasing depth of the soil profile across the pools of varying carbon lability. The proportion of active carbon pools (AP) in total carbon was higher in crop land and tea plantation (57.47 %, 58.38 %), however, in the case of evergreen forest, deciduous forest, forest plantation and scrub land the passive carbon pools (PP) (54.99 %, 61.28 %, 59.43 % and 60.70 %) was higher. We discovered LUC has altered the proportion of soil carbon pools, and the efficiency of soil microbiome and has resulted in higher carbon dioxide (CO2) emissions in tea plantation (71.87 t ha−1) and crop land (82.39 t ha−1). However, the native ecosystems (evergreen forest and deciduous forest) with higher recalcitrant carbon pools (46.96 g kg−1 and 34.89 g kg−1) prevent such carbon degradation and thereby hinder the soil carbon emissions as recorded in evergreen forest (48.43 t ha−1) and deciduous forest (56.47 t ha−1). Conclusively, our study demonstrates that LUC has substantially influenced the carbon cycle by altering the carbon stocks and CO2 emissions in relation to soil microbes. Henceforth, in order to maintain carbon footprints and attain carbon net neutrality under the current climate change scenario, suitable carbon management measures must be implemented in carbon-degraded ecosystems (crop land and tea plantation) of NHR.

Effect of Different Rice Establishment Methods on Soil Nutrient Status and Carbon Stock in Paddy Growing Soils of Jagtial, Telangana, India

The study was conducted to know the nutrient status, yield, straw and harvest index in 4 different cropping systems viz., (i) manual transplanting; (ii) dry direct seeding; (iii) drum seeding and (iv) machine transplanting 120 soil samples were analysed, 30 from each establishment method. The soil fertility status from different establishment methods was studied by analysing the samples for pH, EC, bulk density, organic carbon, available nitrogen, phosphorous, potassium, iron, zinc, total organic carbon and carbon stock. The study revealed that there is a significant difference in bulk density ranged high in machine transplanting (1.48 Mg m-3) and low in dry direct seeding (1.45Mg m-3). pH of soils was neutral to slightly alkaline in nature and iron content of soils ranged from 5.75 to 8.97 mg kg-1.

Assessment of Carbon Stock and CO2 Production Potential for Soils of Coniferous-Broadleaved Forests

—The assessment of carbon stocks in soils of coniferous and broadleaved forests, agrocenoses, fallow lands, and floodplains has been performed for the territory of the Chashnikovo Agrobiological Station of Moscow State University. The typology of litter horizons, the contents of plant detritus in the them, and the ratio of the thicknesses of litter subhorizons have been determined as indicators of the organic matter decomposition intensity. For mineral soil profile, total organic carbon stocks in the layers of 0–30 and 0–100 cm layers and the stock of biologically active carbon in the layer of 0–20 cm layer have been determined. Maximum organic matter accumulation in litters and moderate accumulation in mineral profile is typical of soddy-podzolic soils (Retisols) under coniferous forests. The litter carbon stocks in spruce forests differ by almost an order of magnitude depending on the position in the tessera. Minimum carbon accumulation in litters is characteristic of the soils of upland and floodplain meadows. Alluvial soils of floodplain meadows are characterized by the highest stock of total carbon, as well as carbon of biologically active soil organic matter. The potential of CO2 production by soil determined the structural and functional litter characteristics and the stock of biologically active organic matter in the upper (0–20 cm) soil layer depend on several factors: vegetation type, hydromorphism degree, and agricultural use at present and in the past. Soils of coniferous forests in comparison with soils of broadleaved forests are characterized by lower rates of litter decomposition due to the biochemical features of plant remains and are assumed to have a lower potential for CO2 production. Soils of natural herbaceous ecosystems, especially floodplain meadows, are characterized by the maximum potential production of carbon dioxide due to intense decomposition of plant residues and high stock of biologically active organic matter carbon.

Carbon, nitrogen, and physical fractions of organic matter in recovered pastures of the Maranhense Amazon

In Maranhão State, Brazil, soils are naturally acidic, nutrient-deficient, and prone to cohesion and erosion. Removing the natural cover to establish pastures causes physical, chemical, and biological changes in the soil. Therefore, this study aimed to evaluate the contents and stocks of carbon (C), nitrogen (N), and particle-size fractions of soil organic matter (SOM) in pastures with different years of recovery, and compare them with a secondary forest in the Legal Amazon. Four treatments were evaluated: secondary forest, perennial pasture, and perennial pastures recovered for five years and eight years, both of the latter through corn + brachiaria intercropping. The contents and stocks of total organic carbon, total nitrogen, C, and N from the soil organic matter particle-size fractions, as well as the carbon management indexes (CMI) of the 0.00–0.10, 0.10–0.20, 0.20–0.30, and 0.30–0.40 m layers were evaluated. The perennial pasture environment presented the highest total soil C and N contents; however, when observing the granulometric fractions and CMI, these increases were qualitative in relation to the secondary forest. Pasture recovery over eight years contributed to an improvement of soil quality similar to secondary forest, indicating that an increase in SOM quality, quantity, and recovery time related to increased pasture capacity to accumulate C and N in the soil.

The Variability of Sedimentary Carbon Stock in Seagrass Ecosystem in Central Tapanuli, Indonesia

Blue carbon is a term to underline coastal ecosystem such as mangrove, seagrass, and tidal marshes capability as carbon sequestration where the organic carbon that stored in coastal sediment is greater than the organic carbon in living biomass. This study analysed the variability of sediment carbon stock in seagrass ecosystem in Central Tapanuli, Indonesia. LOI method was used to determine the carbon stock. Regression analysis showed that depth, and dry bulk density strongly influence the sedimen carbon stock in seagrass ecosystem (R2 = 0.77 in Hajoran and R2 = 0.79 in Jago-jago) where the total organic carbon stock in upper layer and denser sediment was higher than the organic carbon stock in middle/bottom layer sediment. Moreover, sediment type also influenced the carbon stock where sediment with finer grain size (11.80 – 13.46 Mg C/ha) captured more organic carbon than sand (6.54 – 10.34 Mg C/ha). By knowing this capacity, monitoring and maintaining coastal sediment and vegetation should become priority to mitigate the climate change.

A comprehensive analysis of soil health indicators in a long‐term conservation tillage experiment

AbstractConservation tillage (CT) is a ploughless tillage with a reduced number of operations, and its positive effect on soil functions and health is widely known. Multivariate analyses are required to choose indicators that adequately characterize the changes in soil health. However, there is little research on the comprehensive analysis of the full spectrum of soil physical, chemical and biological properties. Therefore, we examined 21 soil parameters in a long‐term CT experiment conducted in Hungary. Four pairs of similarly sized CT and conventional ploughing tillage (PT) plots were set up in 2003 on Luvisols. The soil samples were collected after 17 years. The total organic carbon (TOC) increased significantly in the 0–15 cm layer at CT sites compared to those in PT, indicating a total increase of 5.22 t ha−1 TOC stock. In addition, the increasing biological activity and improved soil structure were the most important processes at the CT sites. Furthermore, more complex humic substances with higher molecular weights are characteristic of water‐extractable organic matter (WEOM) as a result of CT. The potentially available nitrogen, phosphorus and potassium were also measured with a relatively high response ratio. Slowly changing parameters, such as cation exchange capacity and base saturation, are important soil physical and chemical parameters, but are not good indicators of the impact of tillage practices. Based on principal component analysis, we suggest the use of water‐extractable organic C, amino‐nitrogen, water‐stable aggregates, available P and K and photometric analysis of WEOM to identify the soil improving processes.

Continuous decrease in soil organic matter despite increased plant productivity in an 80-years-old phosphorus-addition experiment

The objective of this study was to understand how eight decades of tillage affected soil element dynamics. We measured soil chemical properties and the 14C:12C ratio (Δ14C) of organic carbon in one of the oldest cropland experiments in Europe with different levels of phosphorus addition. Soil total and organic phosphorus stocks in the uppermost 20 cm did not differ significantly between the control and the phosphorus addition treatments after 80 years, indicating plant phosphorus uptake from the subsoil. Crop yields increased from 220 g dry weight m−2 in 1936 to more than 500 g dry weight m−2 in the 2010s. The soil total organic carbon and total organic phosphorus stocks decreased by 13.7% and 11.6%, respectively, in the uppermost 20 cm of the soils during the experiment, irrespective of phosphorus addition. Based on modeling of Δ14C, we show that the mean transit time of carbon in the soil was below 10 years, indicating that a large share of the carbon inputs to soil is quickly respired. Our results suggest that the current agricultural practice at this long-term experiment is not sustainable because it led to a continuous decrease in soil organic matter over the last decades, despite increases in plant productivity.

Assessing the effect of arable management practices on carbon storage and fractions after 24 years in boreal conditions of Finland

Soil organic matter (SOM) plays an important role in soil functions that are crucial for sustainable agriculture. Understanding how agricultural management and soil properties affect SOM in different soil depths would aid in maintaining and increasing SOM throughout the soil profile. We sampled a 24 year-old cultivation field experiment with organic and conventional cropping systems, and an adjacent unmanaged meadow to 70 cm soil depth to assess the total organic carbon (OC) stocks and the distribution of OC into mineral-associated (MAOM), particulate (POM) and dissolved (DOM) organic matter. We found that >83% of the soil OC was in the MAOM fraction, and that the distribution of OC across the MAOM, POM and DOM within a soil depth was not strongly affected by soil management. Largest OC stocks (169 t ha−1) together with the largest plant root biomass was found in the unmanaged meadow, which highlights the potential of deep-rooting plants in sequestering OC into the soil. The OC saturation state of the soil was assessed based on the clay to OC ratio and Hassink's Equation (Hassink 1997). Hassink's Equation seemed to underestimate the MAOM accrual capacity of these soils and thus overestimated soil OC saturation state, whereas the clay to OC ratio indicated potential for OC accrual in all soil depths except for the meadow topsoil. These varying results suggest that the applied metric should be soil type and -depth specific. We also determined the contribution of clay content and aluminum and iron oxides in explaining the amount of total OC, MAOM-C and POM-C. In contrast to the aluminum and iron oxides, clay was not well correlated to any of the OC fractions below the 20 cm depth, suggesting that estimating the OC accrual potential of the deeper soil should not be based on the soil texture alone. Our results indicate that aluminum and iron oxides can play an important role in transporting and stabilizing of OC in the soil profile.

Soil chemical attributes under west indian cherry fertigated with nitrogen and humic substances

The use of humic substances (HS) in the soil can increase the efficiency of nitrogen fertilizers and contribute to the increment in soil organic matter and plant nutrient availability. Hence, this study aimed to evaluate, in two production cycles, the effect of applying HS and different nitrogen (N) doses on the chemical attributes and organic matter fractions of a soil cultivated with West Indian cherry in the Brazilian semiarid region. The experiment was set up in split plots, arranged in strips with four replicates. The absence or presence of HS using KS100 as the source was tested in the plots, and N fertilization (50; 75; 100; 125 and 150% of the recommended dose), using urea, was tested in the subplots. Soil pH, H+Al, Al3+, and Na+, K+, P, Ca2+, Mg2+, Fe2+, Mn2+ and Zn2+ contents were determined, and cation exchange capacity and bases saturation (V %) in the 0-0.2 and 0.2-0.4 m layers were calculated. Analyses of stocks of total organic carbon and carbon (C) of the humic acid, fulvic acid and humin fractions, and humic substances were performed. It was possible to observe that, in the second production cycle of West Indian cherry, the soils showed higher contents of nutrients available to plants. Increase in N availability did not enable a clear trend in the behavior of chemical attributes and organic C stocks in the soil. Under the studied conditions, KS100 application allowed a reduction in the C stocks of the HS of the soil.

Soil carbon stocks after eucalyptus planting to replace sugarcane cultivation

The conversion of areas of agricultural crops to eucalyptus plantations is considered effective for the global supply of wood, protecting natural forests and for increasing the fixation and global storage of carbon (C) in the soil, contributing to the mitigation of climate change. In this sense, the impact of the conversion of sugarcane to eucalyptus in the carbon stock in an argisol (acrisols) and a oxisol (ferralsols) from the Zona da Mata of Pernambuco, Brazil, was evaluated. One area of forest, two areas of eucalyptus, with seven years of planting and two areas of sugarcane, with 15 and 17 years of planting, were selected. The granulometric analysis of the soil was performed and determination of the carbon stock was performed through the values of density (Ds) and soil total organic carbon (TOC). The sand content was higher than clay, in the three uses and in the two soil classes. Lower Ds was observed in eucalyptus soil in both soil classes. In the acrisols, the highest concentrations of TOC and carbon stocks were in the eucalyptus soil when compared to sugarcane. However, in the ferralsols, the concentrations of TOC and carbon stock were higher in sugarcane. It is concluded that the planting of eucalyptus has the potential to store carbon, but this will depend on the soil conditions of the area in which the eucalyptus is inserted.

Mountain wetland soil carbon stocks of Huascarán National Park, Peru.

Although wetlands contain a disproportionately high amount of earth's total soil carbon, many regions are still poorly mapped and with unquantified carbon stocks. The tropical Andes contain a high concentration of wetlands consisting mostly of wet meadows and peatlands, yet their total organic carbon stocks are poorly quantified, as well as the carbon fraction that wet meadows store compared to peatlands. Therefore, our goal was to quantify how soil carbon stocks vary between wet meadows and peatlands for a previously mapped Andean region, Huascarán National Park, Peru. Our secondary goal was to test a rapid peat sampling protocol to facilitate field sampling in remote areas. We sampled soil to calculate carbon stocks of four wetland types: cushion peat, graminoid peat, cushion wet meadow, and graminoid wet meadow. Soil sampling was conducted by using a stratified randomized sampling scheme. Wet meadows were sampled to the mineral boundary using a gouge auger, and we used a combination of full peat cores and a rapid peat sampling procedure to estimate peat carbon stocks. In the lab, soils were processed for bulk density and carbon content, and total carbon stock of each core was calculated. We sampled 63 wet meadows and 42 peatlands. On a per hectare basis, carbon stocks varied strongly between peatlands (avg. 1092 MgC ha-1) and wet meadows (avg. 30 MgC ha-1). Overall, wetlands in Huascarán National Park contain 24.4 Tg of carbon with peatlands storing 97% of the total wetland carbon and wet meadows accounting for 3% of the wetland carbon in the park. In addition, our results show that rapid peat sampling can be an effective method for sampling carbon stocks in peatlands. These data are important for countries developing land use and climate change policies as well as providing a rapid assessment method for wetland carbon stock monitoring programs.