Loss Of Organic Carbon Research Articles

Assessing the source and delivery processes of organic carbon within a mixed land use catchment using a combined n-alkane and carbon loss modelling approach

PurposeUnderstanding fluxes of soil organic carbon (OC) from the terrestrial to aquatic environments is crucial to evaluate their importance within the global carbon cycle. Sediment fingerprinting (SF) is increasingly used to identify land use-specific sources of OC, and, while this approach estimates the relative contribution of different sources to OC load in waterways, the high degree of spatial heterogeneity in many river catchments makes it challenging to precisely align the source apportionment results to the landscape. In this study, we integrate OC SF source apportionment with a carbon loss model (CLM) with the aim of: (i) reducing ambiguity in apportioning OC fluxes when the same land use exists in multiple locations within a catchment; and (ii) identifying factors affecting OC delivery to streams, e.g., buffer zones.MethodsTwo main approaches were used in this study: (i) identification of the sources of freshwater bed sediment OC using n-alkane biomarkers and a Bayesian-based unmixing model; and (ii) modelling and analysis of spatial data to construct a CLM using a combination of soil OC content modelling, RUSLE soil erosion modelling and a connectivity index. The study was carried out using existing OC and n-alkane biomarker data from a mixed land use UK catchment.ResultsSediment fingerprinting revealed that woodland was the dominant source of the OC found in the streambed fine sediment, contributing between 81 and 85% at each streambed site. In contrast, CLM predicted that arable land was likely the dominant source of OC, with negligible inputs from woodland. The areas of the greatest OC loss in the CLM were predicted to be from arable land on steeper slopes surrounding the stream channels. Results suggest extensive riparian woodland disconnected upslope eroded soil OC and, concomitantly, provided an input of woodland-derived OC to the streams. It is likely the woodland contribution to streambed OC is derived from litter and leaves rather than soil erosion.ConclusionThis study demonstrates how location-specific OC sources and delivery processes can be better determined using sediment fingerprinting in combination with CLM, rather than using sediment fingerprinting alone. It highlights that, although wooded riparian buffer strips may reduce the impact of upslope, eroded soil OC on waterways, they could themselves be a source of OC to stream sediments through more direct input (e.g., organic litter or leaf debris). Characterising this direct woodland OC as a separate source within future fingerprinting studies would allow the contributions from any eroded woodland soil OC to be better estimated.

Mineral-enhanced biological pump—A strategy based on mineral-microbe interactions for increasing carbon sink in water

<p indent=0mm>Addressing the threats posed by global climate change by reducing the number of greenhouse gases is currently one of the most important research goals of the scientific community. Ocean iron fertilization (OIF) is a geoengineering strategy aimed at mitigating global warming through human intervention. The OIF concept is based on the idea that artificial adding of iron nutrients into iron-depleted regions of the ocean will lead to a rapid boost of phytoplankton populations and the mass sinking of organic matter that ultimately leads to the sequestration of significant amounts of atmospheric CO₂ in the deep sea and sediments. The OIF experiments have been conducted in past over the time and the space scales of weeks and kilometres in polar, subpolar and tropical areas of the oceans. The results have generated new knowledge and a better understanding of the role of iron in regulating marine ecosystems and have confirmed that the iron supply is one of the key controls on the dynamics of phytoplankton blooms, such as diatom as the base of the marine food chain, which in turn affect the whole biogeochemical cycling of carbon. However, the OIF as an effective carbon control strategy is not adequately supported with concerns about potential significant impacts on marine ecosystems. The iron fertilization also did not significantly strengthen the vertical carbon export to the deep sea and thereby the sequestration of CO₂. The efficacy by which the OIF vertically exports organic carbon associated with diatom blooms to the deep sea remains constrained due to the remineralization and the loss of organic carbon during the sinking process of diatomaceous biogenic silica (BSi). Therefore, to address these limitations, the next generation of the IOF geoengineering experiments should be designed to improve the low efficiency of the vertical export of bloomed phytoplankton, which will reduce the loss of organic carbon during the sinking of biomass. In our recent studies, we observed a noticeable dissolution-inhibition effect of Al-bearing lake diatomaceous BSi, which is caused by the high content of Al incorporation in the structure of the BSi. This finding inspired a new idea about the possibility of incorporating naturally occurring, environmentally safe and Al-rich minerals as an Al source for the geoengineering experiments. We hypothesize that clay minerals, with characteristically high contents of Al and Si, might be good ingredients for mineral fertilization in geoengineering experiments to enhance the efficiency of the vertical carbon export of the biological pump. This new proposed mineral-aided process is termed mineral-enhanced biological pump (MeBP). In this paper, the concept, background and theoretical basis of MeBP for CO₂ sequestration in water bodies as a new and inexpensive geoengineering strategy are explained. The basic idea of the MeBP concept is to use finely grained powders of minerals, such as clay minerals as nutrients for geoengineering or ecological engineering experiment to enhance the efficiency of the complexes of microbial organic matter and minerals and to hinder the loss of particulate organic carbon by adjusting the mineral ratios and regulating the particle properties. If so, the improved carbon sequestration efficiency of the biological pump and the CO₂ sink enhancement in water bodies could be achieved. The MeBP offers several potential advantages such as application simplicity, low-cost, scalability, environmental friendliness, and flexibility, and it could be applied alone or in combination with other carbon sequestration strategies. Also, the approaches for the research and application of MeBP, the environmental and ecological risks of applying MeBP and the possible ways of avoiding these risks are discussed. These discussions aim to stimulate new thinking toward the development of new technologies of increasing carbon sink in water bodies that are sustainable, ecologically acceptable and scalable, and can be translated into real applications and engineering practices.

Nutrient and organic carbon losses by erosion, and their economic and environmental implications in the drylands of Kenya

Erosion causes soil nutrients and financial losses, and negatively impacts the environment. We sought to assess the effects of integrated soil fertility and soil & water management practices on nutrient losses, their equivalent economic losses, and environmental disturbance in the drylands of Tharaka-Nithi County. An experiment was set in a randomized complete block design with four replications. Six treatments implemented included manure + fertilizer + tied ridging under 120 kg ha−1 and 30 kg ha−1 nitrogen (N) application rate, manure + fertilizer + minimum tillage with crop residue mulch under 120 N kg ha−1 and 30 N kg ha−1, Managing Beneficial Interactions in Legume Intercrops with 60 N kg ha−1, and conventional control. A two (120 N kg ha−1 and 30 N kg ha−1) by two (Minimum tillage with mulch and tied ridges) split-plot arrangement was used to evaluate the interaction effect of soil fertility, and soil & water conservation practices. Soil & water conservation and soil fertility management practices reduced soil nutrients and organic carbon losses, ecosystem disturbance, and monetary nutrient losses when isolated or integrated. Minimum tillage with mulch had a higher reduction in the nutrient loss by 20–165% compared to tied ridges. The 120 N kg ha−1 reduced nutrient loss by 16–19% more than 30 N kg ha−1. The enrichment ratio (ER) under all the treatments was above unity, which indicated ecosystem disturbance. Minimum tillage with mulch reduced ER more than the tied ridges, whereas 30 N kg ha−1 had lower ER than 120 N kg ha−1. The equivalent monetary losses of nutrients were as high as 30 US$ ha−1for soil organic carbon, 28 US$ ha−1 for nitrogen, 73 US$ ha−1 for phosphorus, and 140 US$ ha−1 for potassium per season. The combined treatment with the least economic losses was manure + fertilizer (120 N kg ha−1) + minimum tillage with mulch. Hence, the technology should be promoted for sustainable agricultural productivity.

Liming tropical high upland acid soils improves soil fertility and cardamom productivity

Increasing the productivity of Indian cardamom is revolving around both soil and forest canopy management. Maintaining tropical acid soil fertility and its productivity is the prime concern for successful cardamom cultivation under ongoing deforestation of fragmented rainforest. A field experiment with two doses each (1 and 2 kg plant-1) of burnt lime, dolomite and ground lime stone was carried out in an acidic soil. Results showed that all of the liming materials have had significant effect on correcting the soil acidity. Liming with dolomite at 2 kg plant-1 considerably improved soil chemical properties and increased the soil pH from very acidic to near neutral. Correction and improvement in the soil pH led to significantly enhance the growth and yield of cardamom. However, utmost care must be taken on the environmental implications of liming; particularly the ratio of soil Calcium and Magnesium as well as organic carbon loss and evolution of CO2.

Predicting Soil Organic Carbon Dynamics of Integrated Crop-Livestock System in Brazil Using the CQESTR Model

Land degradation and reduction in productivity have resulted in losses of soil organic carbon (SOC) in agricultural areas in Brazil. Our objectives were to 1) evaluate the predictive performance of CQESTR model for a tropical savannah; and 2) examine the effect of integrated management systems, including Integrated Crop-Livestock System (ICLS) scenarios on SOC stocks. Two long-term paddocks, under similar edaphic and climate conditions were used in this study. In Paddock 4 (P4) the rotation was corn (Zea mays L.) and 3.5/4.5 years pasture (Urochloa ruziziensis), while rotations in Paddock 5 (P5) included 2.5 years of soybean (Glycine max L.), dryland rice (Oryza sativa L.), and corn followed by 2.5/3.5 years pasture (U. brizantha). Measured and CQESTR simulated values were significantly (0.0001) correlated (r = 0.94) with a mean square deviation (MSD) of 7.55, indicating that the model captured spatial-temporal dynamics of SOC. Predicted SOC increased by 18.0 and 12.04 Mg ha−1 at the rate of 0.90 and 0.60 Mg ha−1 year−1 under current ICLS management for P4 and P5, respectively, by 2039. ICLS increased soil C sequestration compared to simple grain cropping systems under both NT and CT due to high biomass input into the production system.

Urban development enhances soil organic carbon storage through increasing urban vegetation

Anthropogenic activities can lead to the loss of soil organic carbon (SOC) or improve its storage, hence they have the potential to exacerbate or help mitigate climate change. Urban expansion results in an initial loss of soil carbon, but long-term SOC changes during urban development are poorly understood. Herein, we studied SOC changes in the suburban and urban areas of cities with high levels of urbanization based on a long-term resampling campaign in Beijing, and a compilation of SOC content data from 21 other cities with high levels of urbanization across China over the past three decades. Our results revealed that the SOC of topsoils decreased by 17.2% in the suburban areas and increased by 104.4% in the urban areas of cities with high levels of urbanization. The changes in SOC were positively correlated with the changes in vegetation coverage and productivity. Partial least square method structural equation model analyses showed that changes in vegetation could directly affect SOC changes, and the changes in vegetation coverage and productivity were induced by human activities and climate changes in Beijing. The topsoils in the urban areas of cities with high levels of urbanization can act as carbon sinks due to the increase in vegetation. This study can help improve our understanding of the role of the SOC content of cities within the global C cycle and provide suggestions for achieving the goal of carbon neutrality in China.

Continental United States may lose 1.8 petagrams of soil organic carbon under climate change by 2100

AbstractAimsHigh‐resolution information on soils’ vulnerability to climate‐induced soil organic carbon (SOC) loss can enable environmental scientists, land managers, and policy makers to develop targeted mitigation strategies. This study aims to estimate baseline and decadal changes in continental US surface SOC stocks under future emission scenarios.LocationContinental United States.Time period2014–2100.MethodsWe used recent SOC field observations (n = 6,213 sites), environmental factors (n = 32), and an ensemble machine learning (ML) approach to estimate baseline SOC stocks in surface soils across the continental United States at 100‐m spatial resolution, and decadal changes under the projected climate scenarios of Coupled Model Intercomparison Project Phase Six (CMIP6) earth system models (ESMs).ResultsBaseline SOC projections from ML approaches captured more than 50% of variability in SOC observations, whereas ESMs represented only 6–16% of observed SOC variability. ML estimates showed a mean total loss of 1.8 Pg C from US surface soils under the high‐emission scenario by 2100, whereas ESMs showed no significant change in SOC stocks with wide variation among ESMs. Both ML and ESM predictions agree on the direction of SOC change (net emissions or sequestration) across 46–51% of continental US land area. These differences are attributable to the high‐resolution site‐specific data used in the ML models compared to the relatively coarse grid represented in CMIP6 ESMs.Main conclusionsOur high‐resolution estimates of baseline SOC stocks, identification of key environmental controllers, and projection of SOC changes from US land cover types under future climate scenarios suggest the need for high‐resolution simulations of SOC in ESMs to represent the heterogeneity of SOC. We found that the SOC change is sensitive to key soil related factors (e.g. soil drainage and soil order) that have not been historically considered as input parameters in ESMs, because currently more than 95% variability in the SOC of CMIP6 ESMs is controlled by net primary productivity, temperature, and precipitation. Using additional environmental factors to estimate the baseline SOC stocks and predict the future trajectory of SOC change can provide more accurate results.

Using the Taguchi experimental design for assessing within-field variability of surface run-off and soil erosion risk

Water erosion is one of the soil degradation processes driven by environmental and field factors such as rainfall intensity, slope gradient, dynamics of vegetation cover, soil characteristics, and management practices. Most of the studies assess the separate contribution of these factors under controlled conditions. However, there is a lack of adequate knowledge regarding the complex interactions between prevailing factors and soil erosion processes under heterogeneous field conditions. This study investigated 16 combinations of 5 factors at 4 levels of each factor on the soil erosion process using Taguchi's fractional factorial experiment design, identifying the factor combinations resulting in maximum sediment yield, runoff, organic carbon, and nitrogen losses. We considered the factors: Soil organic matter and silt content (SiltOM), vegetation cover (VC), slope steepness (SS), rainfall intensity (RI), and depth to a loamy layer (DLL). The interactive effects of these factors and their combinations were visualized from the analysis of signal-to-noise (S/N) responses. Results indicated that interactions between the selected factors and soil erosion processes exist and multiple linear regression models were developed to predict sediment yields, runoff, carbon, and nitrogen losses at the sub-field scale. Results revealed that 1) RI with 40.6% showed the highest contribution to sediment yield followed by SS (23.8%), VC (17.74%), SiltOM (14.77%), and DLL (3.17%), indicating a strong rainfall-erosion relationship; 2) the combination of levels of factors generating highest sediment yield was determined; 3) A simple multiple linear regression model developed for predicting local sediment yield showed the highest agreement with field observations (R2 = 82.5%). The findings suggest that Taguchi design could be used reliably for modeling soil erosion at field and sub-field scales. Using local calibration data such models have great potential for soil erosion risk assessments at the field scale, especially in areas where contributing factors and factor levels change at small spatial scales.

Additive effects of warming and grazing on fine-root decomposition and loss of nutrients in an alpine meadow

AbstractFine-root decomposition is a critical process regulating ecosystem carbon cycles and affecting nutrient cycling and soil fertility. However, whether interaction between warming and grazing affects fine-root decomposition is still under-researched in natural grasslands. A two-factorial experiment with asymmetric warming (i.e. daytime vs. nighttime and growing season vs. nongrowing season) and moderate grazing (i.e. about average 50% forage utilization rate) was conducted to explore whether warming and grazing affect fine-root decomposition and loss of nutrients during a 2-year decomposition period in an alpine meadow on the Tibetan Plateau. Both warming and grazing facilitated carbon cycling through increase in fine-root decomposition, and influenced element cycling which varies among elements. The effects of warming and grazing on fine-root decomposition and loss of nutrients were additive. Both warming and grazing significantly increased cumulative percentage mass loss and total organic carbon loss of fine roots during the 2-year experiment. Only warming with grazing treatment reduced percentage nitrogen loss, whereas warming, regardless of grazing, decreased percentage phosphorus loss. Warming and grazing alone increased percentage loss of potassium, sodium, calcium and magnesium compared with control. There were no interactions between warming and grazing on fine-root decomposition and loss of nutrients. There was greater temperature sensitivity of decreased phosphorus loss than that of decreased nitrogen loss. Different temperature sensitivities of percentage loss of nutrients from fine-root decomposition would alter ratios of the available nutrients in soils, and may further affect ecosystem structure and functions in future warming.

Physiological acclimatization in Hawaiian corals following a 22-month shift in baseline seawater temperature and pH

Climate change poses a major threat to coral reefs. We conducted an outdoor 22-month experiment to investigate if coral could not just survive, but also physiologically cope, with chronic ocean warming and acidification conditions expected later this century under the Paris Climate Agreement. We recorded survivorship and measured eleven phenotypic traits to evaluate the holobiont responses of Hawaiian coral: color, Symbiodiniaceae density, calcification, photosynthesis, respiration, total organic carbon flux, carbon budget, biomass, lipids, protein, and maximum Artemia capture rate. Survivorship was lowest in Montipora capitata and only some survivors were able to meet metabolic demand and physiologically cope with future ocean conditions. Most M. capitata survivors bleached through loss of chlorophyll pigments and simultaneously experienced increased respiration rates and negative carbon budgets due to a 236% increase in total organic carbon losses under combined future ocean conditions. Porites compressa and Porites lobata had the highest survivorship and coped well under future ocean conditions with positive calcification and increased biomass, maintenance of lipids, and the capacity to exceed their metabolic demand through photosynthesis and heterotrophy. Thus, our findings show that significant biological diversity within resilient corals like Porites, and some genotypes of sensitive species, will persist this century provided atmospheric carbon dioxide levels are controlled. Since Porites corals are ubiquitous throughout the world’s oceans and often major reef builders, the persistence of this resilient genus provides hope for future reef ecosystem function globally.

Changes in carbon and phosphorus storages and humic substances in a Ferralsol, after tillage and animal manures applications

The evaluation of the dynamics of storage and loss of soil organic carbon (OC) and available phosphorus, associated with humic substances, in areas under no-tillage (NT) that receive solid or liquid animal manure, has been little reported in the literature. This study aimed to evaluate the effect of different doses of liquid (liquid swine slurry) and solid (poultry manure) animal manures on OC and available phosphorus (PAV.) storages and humic substances (fulvic and humic acids, and humin) of a Ferralsol recently managed under a no-tillage system (four years). The experiment was carried out in a very clay Ferralsol. Two periods were sampled: in 2011, before tillage for incorporation of chemical fertilizer (CF) and start of the NT system, and in 2015, after four years of NT management and animal manure applications. Poultry manure (PM) and liquid swine slurry (LSS) were applied in three rates as follows: 2.00, 5.00, and 8.00 t ha−1 of PM and 45.00, 90.00, and 135.00 m3 ha−1 of LSS semi-annually applied without CF complementation. The CF was used as a reference. The use of LSS recovered the OC content of the 0.00–0.10 m depth at levels similar to those observed in 2011, indicating the interaction of the liquid form with the soil. The similarity of humic substance between CF and animal manures of the 0.00–0.10 and 0.10–0.20 m depths was mainly due to LSS use, which contents of fulvic and humic acids were significantly higher than those observed in the soil that received PM. Although the use of the LSS increased the SOC content, no difference in storage was observed among the treatments. Soil tillage for NT system start and CF use resulted in a PAV storage loss of − 2 kg ha−1 yr−1 in 0.10–0.20 m depth from 2011 to 2015. The LSS promoted PAV. sequestration of up to 33.50 Kg ha−1 yr−1 at 0.00–0.10 m depth and 19.93 Kg ha−1 yr−1 at 0.10–0.20 m depth. The LSS was more effective in increasing PAV. storage at the two soil depths compared to CF and PM. The fulvic and humic acids were more than two times higher in LSS than in the PM applications at 00.00–0.10 and 0.10–0.20 m depths. Thus, the liquid form has a greater potential to recover OC content and PAV storage after short-term of NT start (four years), indicating that it is more suitable for the recovery of Ferralsols recently tillage or degraded.

Potential effects of sea level rise on decomposition and nutrient release of dead fine roots in a Kandelia obovata forest

Fine roots play an important role in the carbon dynamics and nutrient cycles of mangroves. Mangrove forests are threatened by sea level rise (SLR). Therefore, it is critical to understand how SLR affects dynamics of decomposition and nutrient release of dead fine roots to evaluate carbon dynamics and nutrient cycles of mangroves. Dynamics of decomposition and nutrient release of dead fine roots were compared among three sites under different intertidal elevations in a 11-year-old Kandelia obovata mangrove forest, representing tidal flooding situation of SLR values of 0, 40 and 80 cm, respectively. Mangroves at site SLR 80 cm had the highest dry weight loss of dead fine roots in the 10 and 30 cm soil layers. Mean rate of decomposition (MRD) at site SLR 80 cm was significantly higher than those at other sites, increasing by approximately 0.48 and 0.27 mg gDW−1 d−1 in the 10 cm and 30 cm soil layers due to SLR 80 cm, respectively. Site SLR 80 cm had significantly higher organic carbon (OC) losses of dead fine roots and OC loss percentages in the 10 cm soil layer than the other sites, while higher values were found at site SLR 40 cm in the 30 cm soil layer. Moreover, significantly higher nitrogen (N) losses of dead fine roots and N loss percentages were also found at site SLR 40 cm. These indicate that SLR will increase the rates of decomposition and release of nutrients of dead fine roots, which will accelerate carbon dynamics and nitrogen cycles of mangroves.

Is it possible to attain the same soil organic matter content in arable agricultural soils as under natural vegetation?

Clearing natural vegetation to establish arable agriculture (cropland) almost invariably causes a loss of soil organic carbon (SOC). Is it possible to restore soil that continues in arable agriculture to the pre-clearance SOC level through modified management practices? To address this question we reviewed evidence from long-term experiments at Rothamsted Research, UK, Bad Lauchstädt, Germany, Sanborn Field, USA and Brazil and both experiments and surveys of farmers’ fields in Ethiopia, Australia, Zimbabwe, UK and Chile. In most cases SOC content in soil under arable cropping was in the range 38–67% of pre-clearance values. Returning crop residues, adding manures or including periods of pasture within arable rotations increased this, often to 60–70% of initial values. Under tropical climatic conditions SOC loss after clearance was particularly rapid, e.g. a loss of &gt;50% in less than 10 years in smallholder farmers’ fields in Zimbabwe. If larger yielding crops were grown, using fertilizers, and maize stover returned instead of being grazed by cattle, the loss was reduced. An important exception to the general trend of SOC loss after clearance was clearing Cerrado vegetation on highly weathered acidic soils in Brazil and conversion to cropping with maize and soybean. Other exceptions were unrealistically large annual applications of manure and including long periods of pasture in a highly SOC-retentive volcanic soil. Also, introducing irrigated agriculture in a low rainfall region can increase SOC beyond the natural value due to increased plant biomass production. For reasons of sustainability and soil health it is important to maintain SOC as high as practically possible in arable soils, but we conclude that in the vast majority of situations it is unrealistic to expect to maintain pre-clearance values. To maintain global SOC stocks at we consider it is more important to reduce current rates of land clearance and sustainably produce necessary food on existing agricultural land.

Continuous maize cropping accelerates loss of soil organic matter in northern Thailand as revealed by natural 13C abundance

AimsThe loss of soil organic matter (SOM) has widely been reported in the tropics after changing land use from shifting cultivation to continuous cropping. We tested whether continuous maize cultivation accelerates SOM loss compared to upland rice and forest fallow.MethodsBecause litter sources include C4 plants (maize in maize fields and Imperata grass in upland rice fields) in Thailand, C3-derived and C4-derived SOM can be traced using the differences in natural 13C abundance (δ13C) between C3 and C4 plants. We analyzed the effects of land use history (cultivation or forest fallow period) on C stocks in the surface soil. Soil C stocks decreased with the cultivation period in both upland rice and maize fields.ResultsThe rate of soil organic carbon loss was higher in maize fields than in upland rice fields. The decomposition rate constant (first order kinetics) of C3-plant-derived SOM was higher in the maize fields than in the upland rice fields and the C4-plant-derived SOM in the forest fallow. Soil surface exposure and low input of root-derived C in the maize fields are considered to accelerate SOM loss. Soil C stocks increased with the forest fallow period, consistent with the slow decomposition of C4-plant-derived SOM in the forest fallows.ConclusionsContinuous maize cultivation accelerates SOM loss, while forest fallow and upland rice cultivation could mitigate the SOM loss caused by continuous maize cultivation.

Evaluating the oxidation inhibition of sulfide in urban sewers using a novel quantitative method

Sulfide inhibition is a critical task for the secure operation of sewer systems, and oxidation is usually utilised to achieve this purpose. However, the effects and mechanism of oxidation during the transformation of sulfur-associated pollutants in gas-liquid-solid phases of sewers have not been extensively evaluated. In this study, a method for quantifying sulfur-associated pollutant exchange pathways in gas-liquid-solid phases of sewers was established. The results showed that although the concentration of sulfide decreased under different oxidation conditions, the consumption of sulfate in sewers clearly increased. The transformation strength of elemental sulfur was high (18.65 mg/L, 35.52% of sulfate from the influent) and the accumulation of sulfate in sediment was obvious (3.49 mg/L, 6.65% of sulfate from the influent). Higher concentrations of sulfate in the influent promoted the generation of sulfide in sediment (8.98 mg/L, 17.10%). Thus, the oxidation process led to the generation of more absolute sulfide. In addition, promoting the metabolism of sulfate-reducing bacteria enhanced the loss of organic carbon in sewers, which might weaken the efficacy of nitrogen and phosphorus removal in wastewater treatment plants. Based on the evaluation of the exchange pathways of sulfur-associated pollutants in sewers, further studies into sulfide inhibition in sewers should consider the above issues to enhance the safe management of urban sewers.

A Landscape Evolution Modeling Approach for Predicting Three‐Dimensional Soil Organic Carbon Redistribution in Agricultural Landscapes

AbstractSoil erosion diminishes agricultural productivity by driving the loss of soil organic carbon (SOC). The ability to predict SOC redistribution is important for guiding sustainable agricultural practices and determining the influence of soil erosion on the carbon cycle. Here, we develop a landscape evolution model that couples soil mixing and transport to predict soil loss and SOC patterns within agricultural fields. Our reduced complexity numerical model requires the specification of only two physical parameters: a plow mixing depth, Lp, and a hillslope diffusion coefficient, D. Using topography as an input, the model predicts spatial patterns of surficial SOC concentrations and complex 3D SOC pedostratigraphy. We use soil cores from native prairies to determine initial SOC‐depth relations and the spatial pattern of remote sensing‐derived SOC in adjacent agricultural fields to evaluate the model predictions. The model reproduces spatial patterns of soil loss comparable to those observed in satellite images. Our results indicate that the distribution of soil erosion and SOC in agricultural fields can be predicted using a simple geomorphic model where hillslope diffusion plays a dominant role. Such predictions can aid estimates of carbon burial and evaluate the potential for future soil loss in agricultural landscapes.

Erosion and covered zones altered by surface coverage effects on soil nitrogen and carbon loss from an agricultural slope under laboratory-simulated rainfall events

Soil erosion, one of the most serious environmental concerns, might remove topsoil and essential element from terrestrial land. However, few attentions have been given to investigating how soil erosion regimes affect soil carbon and nitrogen loss. Therefore, this study investigated the effects of surface coverage rates (83%, 67%, 50%, 33%, 17% and 0%) and two positions (up- and downslope) on erosion regimes and its associated soil nitrogen and carbon loss under a sequence of six rainfalls (R1-R6). These results showed that the sediment concentrations with 33% (R4) and 17% (R5) coverage downslope were significantly lower than those with coverage upslope, whereas there was no significant difference between the runoff rates of the two slopes. Thus, surface coverage at different positions induced two soil erosion regimes (deposition- and transport-dominated processes). Dynamics of the DON and DIN concentrations indicated different release processes of soil nitrogen into runoff. The DON contributed to a substantial amount of soil nitrogen loss, which accounted approximately 81% of the organic form. The SBOC is significantly correlated with sediment-enriched clay particles from the deposition-dominated processes and is higher than that from the transport-dominated processes. The DOC is significantly correlated with Rr for transport-dominated processes. These results illustrated the critical role of erosion regimes in soil organic carbon loss in dissolved or sediment-bound form. It is concluded that erosion/covered zones altered by surface coverage could produce transport- and deposition-dominated erosion regimes and consequently affect soil carbon and nitrogen loss. In addition, these results demonstrated that surface coverage pattern may efficiently control soil erosion and soil carbon and nitrogen loss.

Diversification of rice growing areas in Eastern India with integrated soil–crop system management for GHGs mitigation and higher productivity

Mono-cropping, burning of crop residues, imbalanced fertilization and limited use of farm manure are resulting in loss of soil organic carbon (SOC). In this study, integrated soil-crop management (ILMsoil), improved management (IMsoil) and conventional management (CMsoil) was studied to enhance the soil carbon sequestration for mitigation of greenhouse gas (GHG) emissions. The life cycle assessment (LCA) approach was used to estimate carbon footprint from successive crops of rice, mustard and jute with or without intercrops or mixed crops. The adoption of ILMsoil helped in reducing the carbon footprint by 78%. The overall economic yield increased by 25% over IMsoil as well. Net CO2-eq emission was 68% less under ILMsoil as compared to other systems. The reduction in net LCA-GHG emission was mainly due to high SOC sequestration by jute crop and leguminous intercrops and mixed crops. Improved crop diversification and agronomic productivity as used in ILMsoil system may decrease the inputs of non-renewable energy and consequently reduce the emission of GHGs from agroecosystems. Improvement of soil health, minimization in nutrient and water losses, and application of the increased amount of organic fertilizers were found helpful in reducing the carbon footprint. ILMsoil method of cultivation in 0.70 million hectare of jute growing area may reduce about 0.40 million tonnes of CO2-eq from atmosphere every year and provide carbon credit of 1.22 million US$to the farmers of eastern India.

Indicators of sustainable development of safety land use and assessment of degradation processes development of soil cover using gis models

The article describes some of the UN-adopted indicators of sustainable development of land use safety associated with the development of soil degradation processes, approaches to assessing the development of soil degradation using mathematical modeling tools, namely geoinformation models. Indicator 15.3.1 of sustainable development goals reflects the ratio of the area of degraded land to the total land area of the assessed area, and degradation is considered as an integral indicator of such parameters as land productivity, soil organic matter content and type of land use. It is established that when using remote sensing data obtained from open sources, which serve as a basis for calculating land degradation indices by the Trends.Earth tool via QGIS software, it is possible to establish such changes at the administrative level (map scale 1: 100000) and spatio-temporal analysis of such changes. At the same time, it is difficult to ensure higher spatial resolution, which would allow the analysis at the level of an individual farm or an enterprise. This is due to the spatial resolution of the data that form the basis for such a calculation. In the Forest-Steppe zone of Ukraine, the predominant type of land use is agricultural activity with land plowing. Some farms practice minimizing tillage, which, in particular, should affect the value of the indicator of land degradation. With some convention of such an approach, the indicator allows to display in the map space the data of changes in the condition of the land, the loss of soil organic carbon according to remote sensing data and the nature of soil degradation for the selected time interval. Due to difficult economic conditions, part of the lands for the period 2001-2019. was not used in agricultural production, some fields were overgrown with woody vegetation and were not actively cultivated, which was reflected in the indicators of indicator 15.3.1. At the same time, most of the lands (over 66%) did not undergo positive or negative changes during the studied period. The use of indicators of soil condition, monitoring of the development of degradation processes based on operational data and the possibility of their comparison for different time intervals plays a particularly important role in the context of the impact of global climate changes on the soil cover, prospects for agricultural production and, in general, on the quality of life of people.

EFFECTS OF DIFFERENT TILLAGE PRACTICES ON SOIL FERTILITY PROPERTIES: A REVIEW

Soil tillage is an important factor affecting soil fertility properties and crop yield. Tillage impact certain soil physical and chemical properties such as bulk density, soil porosity and water-holding capacity, infiltration rates, hydraulic conductivity, soil temperature, soil organic carbon, pH, CEC, available nitrogen, phosphorus and exchangeable potassium amongst others. The main objective of the present work was to compare the effect of no-tillage systems and the conventional tillage systems. Tillage systems can be generally categorized into plow tillage (conventional tillage), reduced tillage using chisel plow, disc plow, harrow disc or cultivators and no-till systems. Conservation tillage and its various types generally improve the soil quality indicators including soil organic carbon (SOC) storage. Whereas, conventional tillage practices give birth to a finer and loose-setting soil structure with a modified soil bulk density and soil moisture content, hence, causing loss of soil organic carbon and deterioration in other soil properties. Generally, soil fertility properties are more favourable with no-till than tillage-based systems. However, some researchers observed no significant effect of tillage methods (no-tillage and plow till) on bulk density (BD), pH and total porosity, while others found otherwise. The magnitude of these discrepancies could be due to the differences in crop species, soil properties, climatic characteristics and their complex interactions as well as tillage system adopted.