Sequestration Potential Of Soils Research Articles

Quantifying the negative effects of dissolved organic carbon of maize straw-derived biochar on its carbon sequestration potential in a paddy soil

Biochar of low-medium temperature may contain abundant dissolved organic carbon (BDOC), affecting its priming effect and carbon sequestration potential in soils. However, the direct and quantitative evidence for such impacts remains lacking. This study conducted incubation experiments on maize straw-derived 300/450 °C biochar, BDOC-extracted biochar residues and BDOC, and applied δ13C analysis to quantify biochar's mineralization and their priming effects on native soil organic carbon in a paddy soil. BDOC contained abundant lipid-, protein-, carbohydrate-like species, serving as nutrients for the metabolism of microorganisms, and thus enhanced native soil organic carbon's mineralization by 15–20%. After BDOC extraction, 300 °C biochar-trigged priming effect shifted from a positive (3.7 mg CO2–C kg−1 soil) to a negative state (−14.4 mg CO2–C kg−1 soil), and 450 °C biochar-induced negative priming effect increased by 31%; biochar's mineralization also decreased by 41–65%. Overall, after BDOC extraction, the net carbon balance in biochar-amended soils reduced by 7–8%. Furthermore, BDOC shifted the dominant priming mechanisms of biochar mainly by enhancing soil macro-aggregates while reducing sorptive protection for native soil organic carbon. Its extraction reduced the amount of soil macro-aggregates by 16–25% but enhanced the sorption affinity of native soil organic carbon by biochar by 68–122%. Additionally, after BDOC extraction, the microbial communities in biochar-amended soils contained more fungi and G+-bacteria. These findings proved that BDOC extraction appears a feasible strategy to enhance the short-period carbon sequestration potential of biochar.

Carbon Farming and the Commission Proposal for a Regulation on a Certification Framework for Carbon Removals: a Legal Perspective

Abstract Carbon farming is a term associated with land-based practices, agricultural practices that aim at reducing emissions and sequestering carbon. These are, for example, agroforestry practices and practices that result in the maintenance and enhancement of soil organic carbon through the exploitation of the carbon cycle and the sequestration potential of soils. Given the evident links with climate change mitigation, the subject matter of carbon and carbon removals has seen important developments in the European Union (EU) in the past few years. This has culminated in the adoption of a Commission Communication on sustainable carbon cycles and a Commission Proposal for a Regulation on a certification framework for carbon removals. This contribution is meant to address the content and the potentially problematic aspects of the Commission Proposal from a legal perspective.

Quantifying the benefits of reducing synthetic nitrogen application policy on ecosystem carbon sequestration and biodiversity

Synthetic Nitrogen (N) usage in agriculture has greatly increased food supply over the past century. However, the intensive use of N fertilizer is nevertheless the source of numerous environmental issues and remains a major challenge for policymakers to understand, measure, and quantify the interactions and trade-offs between ecosystem carbon and terrestrial biodiversity loss. In this study, we investigate the impacts of a public policy scenario that aims to halve N fertilizer application across European Union (EU) agriculture on both carbon (C) sequestration and biodiversity changes. We quantify the impacts by integrating two economic models with an agricultural land surface model and a terrestrial biodiversity model (that uses data from a range of taxonomic groups, including plants, fungi, vertebrates and invertebrates). Here, we show that the two economic scenarios lead to different outcomes in terms of C sequestration potential and biodiversity. Land abandonment associated with increased fertilizer price scenario facilitates higher C sequestration in soils (+ 1014 MtC) and similar species richness levels (+ 1.9%) at the EU scale. On the other hand, the more extensive crop production scenario is associated with lower C sequestration potential in soils (− 97 MtC) and similar species richness levels (− 0.4%) because of a lower area of grazing land. Our results therefore highlight the complexity of the environmental consequences of a nitrogen reduction policy, which will depend fundamentally on how the economic models used to project consequences.

Stability of carbon pools and fluxes of a Technosol along a 7-year reclamation chronosequence at an asbestos mine in Canada

Improved land stewardship is necessary for climate change mitigation. As such, actions are needed to increase carbon (C) sinks and reduce C emissions from land use activities. Residual materials with fertilizing capacity can be used to reconstruct severely degraded soils and recreate a sustainable vegetation cover, leading to reductions in atmospheric CO2 levels. We studied the temporal dynamics of CO2 sequestration potential in soils reconstructed with 1200 Mg ha−1 biosolids along a young chronosequence ranging from 0 to 7 years after initiating reclamation of a decommissioned asbestos mine in southern Québec, Canada. We measured in situ soil CO2 fluxes, soil C pools and soil physicochemical properties. Since bacterial communities are highly responsive to soil physicochemical properties, we also analyzed both their diversity and community structure. The age since soil reclamation did not have a clear effect on soil properties, but it exerted greater control over soil C fluxes and soil bacterial community diversity and structure. Our results suggest large C fluxes to the atmosphere within the first year following soil reconstruction, but soils constitute a stable C pool thereafter.

Influence of Organic Amendments on Soil Carbon Sequestration Potential of Paddy Soils under Two Irrigation Regimes

Soil organic carbon (OC) is one of the most important soil components regulating soil quality, fertility and agronomic productivity as well as the global carbon (C) cycle. Soil acts as a sink for global C, which can be influenced by the water regime and organic matter (OM) management in field. The aim of this study is to evaluate the effect of the application of different organic amendments on C sequestration in paddy soils under contrasting irrigation regimes. A 4-month pot experiment was conducted under net house conditions and the treatments were composed of two organic amendments: rice straw (RS) and poultry manure (PM); four application rates of amendment: 0 g (control), 2.5 g, 5.0 g and 15.0 g kg−1 soil; and two irrigation regimes: (i) continuous waterlogging condition (CWL) and (ii) alternate wetting and drying (AWD). After the incubation period, soil samples were collected from the pot and isolated into labile (>53 µm) and mineral-associated (<53 µm) OM. Bulk (before and after incubation) and fractionated soil samples were analyzed for OC, total nitrogen (N), C:N ratio; and C sequestration percentage was calculated. Relatively higher amounts of soil OC were present in CWL condition (1.23%) than AWD (1.13%). The C sequestration potential also showed the similar trend (CWL: 47% > AWD: 35%). This was explained by the induced aerobic condition in between the anerobic condition in AWD and the continuous anaerobic condition in CWL which resulted in a difference in OM decomposition. The mineral-associated OM fraction (<53 µm) was higher in the CWL condition than AWD condition which also indicated the importance of the chemical stabilization of OC (OC bound to minerals) in the CWL condition. The application of PM led to a significant increase (45%) in C sequestration potential than RS (37%). This could be attributed to C:N ratio and probable biochemical composition of amendments which resulted in lower decomposability of PM than RS, and also in line with the higher distribution of OC in mineral-bound OM than labile fraction. The application of higher organic amendments did not increase OC content, and declined C sequestration potential in soils as the microbial activity presumably did not match with the amendment amount. Overall, C sequestration potential was higher with 5 g PM kg−1 soil application under CWL-irrigated paddy soil. The findings indicated the need to pay more attention to the selection of the proper type and rate of organic amendments for higher C sequestration in soil under a specific irrigation system for sustainable agriculture.

Biochar-Induced Priming Effects in Young and Old Poplar Plantation Soils

The priming effect (PE) induced by biochar provides a basis for evaluating its carbon (C) sequestration potential in soils. A 60 days’ laboratory incubation was conducted, which involved the amendment of biochar (1% of soil mass) produced from rice straw at 300ºC (B300) and 500ºC (B500) to young (Y) and old (O) poplar plantation soils, with the aim of studying the responses of biochar-induced PEs to poplar plantation ages. This incubation included six treatments: Y + CK (control), Y + B300, Y + B500, O + CK, O + B300, and O + B500. Carbon dioxide (CO2) emissions were significantly increased (p < 0.05) in the B300 amended soils, while it was decreased in the B500 amended soils compared to the CK. The primed CO2 emissions were 2.35 times higher in the Y + B300 than the O + B300 treatments, which was measured to be 18.6 and 5.56 mg C·kg-1 with relative PEs of 12.4% and 3.35%, respectively. However, there was little difference between the primed CO2 emissions in Y + B500 and O + B500 treatments, which were measured to be -24.9 and -29.6 mg·C·kg-1 with relative PEs of -16.6% and -17.8%, respectively. Dissolved organic carbon (DOC) was significantly lower in the young poplar plantation soil than that in the old poplar plantation soil regardless of biochar amendment throughout the incubation, indicating greater C-limit of soil microorganisms in the young poplar plantation soil. Using 13C isotope tracing, neither B300 nor B500 decreased native soil-derived DOC, which indicated that the negative B500-induced PEs were not due to a reduction in the availability of native soil-derived C. In conclusion, the response of biochar-induced PEs to poplar plantation age depends on biochar types while soil available C indirectly affects biocharinduced PEs. Further studies should focus on how the interactive effects between soil C availability and microbial community impacts biochar-induced PEs.

Vertical distribution of soil organic and inorganic carbon under different vegetation covers in two toposequences of the Liudaogou watershed on the Loess Plateau, China

Understanding the carbon (C) cycle of the terrestrial ecosystem and estimating the C sequestration potential in soils are critical to evaluate ecosystem function and security. The vertical distribution of soil organic carbon (SOC) and inorganic carbon (SIC) as well as their influencing factors under different types of vegetation in two toposequences of the Liudaogou watershed on the Loess Plateau of China were investigated. Results showed that the measured soil properties were differentiated into two groups: (1) one behaving relatively conservatively (pH, bulk density, silt content, and capillary and total porosity) with coefficient of variations (CVs) &lt; 10% and (2) the other encompassing more labile components (SOC, SIC, noncapillary porosity, clay, and sand and soil water content) with CVs &gt; 10%. Soil organic C under different vegetation covers in the two toposequences (0.62 to 5.12 g kg⁻¹) decreased rapidly with depth in the top 0 to 50 cm soil layer and then remained relatively stable over the 50 to 200 cm depth, which can be described by the exponential model. In contrast, SIC (4.11 to 18.69 g kg⁻¹) was much higher than SOC and showed distinct distribution patterns, which increased initially with depth and then decreased downwards except for the grassland in the west-facing slope (W-grassland) exhibiting an opposite trend. There were no significant differences of SOC either under different vegetation covers or in different slopes over the whole profile (<i>p</i> &gt; 0.05); however, significant differences of SIC were observed for both different vegetation covers in the same slope and for the same vegetation cover in different slopes (e.g., W-grassland versus W-forestland, W-grassland versus NE-grassland) (<i>p</i> &lt; 0.05). This study demonstrated that different soil properties could simultaneously affect SOC and SIC contents; thus attempts to model SOC and SIC based on the independent effects of individual soil property without consideration of their interactions would result in unsatisfactory prediction. We proposed models that quantitatively described SOC and SIC contents as a combined product of different soil properties for each vegetation cover in both northeast-facing and west-facing slopes using multiple regression analysis, which could improve the prediction of SOC and SIC contents for the study area from the simple linear regression models.

Soil carbon stocks along an altitudinal gradient in different land-use categories in Lesser Himalayan foothills of Kashmir

The carbon sequestration potential of soils plays an important role in mitigating the effect of climate change, because soils serve as sinks for atmospheric carbon. The present study was conducted to estimate the carbon stocks and their variation with altitudinal gradient in the Lesser Himalayan foothills of Kashmir. The carbon stocks were estimated in different land use categories, namely: closed canopy forests, open forests, disturbed forests, and agricultural lands within the altitudinal range from 900 to 2500 m. The soil carbon content was determined by the Walkley–Black titration method. The average soil carbon stock was found to be 2.59 kg m–2. The average soil carbon stocks in closed canopy forests, open forests, and disturbed forests were 3.39, 2.06, and 2.86 kg m–2, respectively. The average soil carbon stock in the agricultural soils was 2.03 kg m–2. The carbon stocks showed a significant decreasing trend with the altitudinal gradient with maximum values of 4.13 kg m–2 at 900–1200 m a.s.l. and minimum value of 1.55 kg m–2 at 2100–2400 m a.s.l. The agricultural soil showed the least carbon content values indicating negative impacts of soil plowing, overgrazing, and soil degradation. Lower carbon values at higher altitudes attest to the immature character of forest stands, as well as to degradation due to immense fuel wood extraction, timber extraction, and harsh climatic conditions. The study indicates that immediate attention is required for the conservation of rapidly declining carbon stocks in agricultural soils, as well as in the soils of higher altitudes.

Conservation Effects on Soil Quality and Climate Change Adaptability of Ethiopian Watersheds

AbstractThis study analyzes effects of soil and water conservation (SWC) on soil quality and implications to climate change adaptation and mitigation in the Upper Blue Nile River Basin of Ethiopia by using the Anjeni watershed as a case study site. Disturbed and undisturbed soil samples were collected from two sub‐watersheds of Anjeni: the Minchet sub‐watershed (with SWC measures) and the Zikrie sub‐watershed (without SWC measures). Soil samples were taken from 30‐cm depth from five representative landscape positions and analyzed following the standard soil lab analysis procedures. The results show that soils from the conserved sub‐watershed had improved quality indicators compared with those from the non‐conserved site. Significant improvement due to SWC measures was observed in the soil hydrological [total moisture content (+5·43%), field capacity (+5·35%), and available water capacity (+4·18%)] and chemical [cation exchange capacity (+4·40 cmol(+) kg−1), Mg2+ (+1·90 cmol(+) kg−1), Na+ (+0·10 cmol(+) kg−1)] properties. SWC interventions significantly reduced soil erosion by 57–81% and surface runoff by 19–50% in the conserved sub‐watershed. Reduction in soil erosion can maintain the soil organic carbon stock, reduce the land degradation risks, and enhance the C sequestration potential of soils. Therefore, adoption of SWC measures can increase farmers' ability to offset emissions and adapt to climate change. However, SWC measures that are both protective and sufficiently productive have not yet been implemented in the conserved sub‐watershed. Therefore, it is important that SWC structures be supplemented with other biological and agronomic measures in conjunction with soil fertility amendments appropriate to site‐specific conditions. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Comparison of Three Methods for Measurement of Soil Organic Carbon

Quantification of soil organic carbon (SOC) is an important element in the assessment of the carbon sequestration potential of soils in tree-based intercropping (TBI) systems. The organic carbon (OC) concentrations of soils in TBI systems often differ from those in conventional agricultural systems due to the additional C inputs from litter fall and roots. However, the presence of soil inorganic carbon (SIC) can confound the measurements of SOC. This study compared three methods of measuring SOC: (i) measurement of the total soil C (TC) in one subsample and, after treatment in a muffle furnace (575 °C) for 24 h, measurement of SIC in another subsample; (ii) SOC measured after fumigation with 12 M hydrochloric acid (HCl) to remove SIC; and (iii) SOC measured after digestion with 0.73 M H2SO3 to remove SIC. The TC, SOC, and SIC concentrations were determined by combustion. A correction factor was applied to express SIC and SOC concentrations on an original, untreated soil basis. Measurement of SOC by the muffle furnace method resulted in the greatest SOC concentrations for Populus spp. (hybrid poplar) for samples from two of the three depths (0–10 and 20–40 cm). Measurement of SOC by the HCl fumigation and H2SO3 digestion methods were highly correlated, suggesting complete removal of SIC with minimal oxidation of SOC. These results have implications for the method of measuring SOC in calcareous soils under coniferous and deciduous tree species to a depth of 40 cm.

Tillage impacts on net carbon flux in paddy soil of the Southern China

Scientific regulation of carbon (C) flows under conservation tillage is of great significance for mitigating C emission to the atmosphere and increasing C sequestration potential in soils. The objective of this study was to assess tillage impacts on C cycle from a situ field experiment and identify potential tillage practices for C-smart technology in paddy soils of the Southern China. A field experiment was conducted during 2005–2011, including conventional tillage without residue retention (CT), conventional tillage with residue retention (CTS), rotary tillage with residue retention (RTS), and no-till with residue retention (NTS). We computed SOC concentrations, SOC stocks and C emissions from farm inputs with time, and results in values representing a change in net carbon flux under different tillage systems in a double rice (Oryza sativa L.) cropping system. The annual increase rates of SOC stocks were 452.6, 523.3, 1340.8, and 2385.4 kg ha−1 yr−1 from 2007 to 2011 under CT, CTS, RTS, and NTS, respectively. The annual C emissions under CT, CTS, RTS, and NTS were 1182.5, 1182.5, 1152.5, and 1139.2 kg C-eq ha−1 yr−1, respectively. Among the treatments, NTS treatment had the lowest net C flux with −1246.2 kg C-eq ha−1 yr−1. Taking CT as the baseline, the relative net C flux under RTS and NTS were −918.2 and −1976.1 kg C-eq ha−1 yr−1, respectively. This suggests that adoption of conservation tillage would be beneficial in the reduction of GHG emission and could be a good option for C-smart agriculture in double rice cropping regions.

Effect of integrated nutrient management practice on soil aggregate properties, its stability and aggregate-associated carbon content in an intensive rice–wheat system

We studied the impact of integrated nutrient management practices on the physical properties and structural stability of soil aggregates, and the associated C contents after 18 years of rice–wheat rotation on a sandy loam soil at Project Directorate for Farming Systems Research, Modipuram. Treatments included fertilizer nutrients (NPK), NPK with Zn and/or S; and partial (25%) substitution of N with farmyard manure (FYM), sulphitation press mud (SPM), green gram residue (GR) or rice/wheat residue (CR) in various combinations. Soil aggregate properties and its stability, aggregate associated and particulate fractions of C at 0–7.5, 7.5–15 and 15–30cm depths were studied to document C sequestration potential of different nutrient management options. The aggregate strength and density were lower with organic substitution (p<0.05) while water retention by aggregates at field capacity was 2–4% higher with organic inputs. Macroaggregates (>0.25mm) constituted 58–92% of water stable aggregates and varied significantly among treatments and soil depths. Organic material incorporation improved soil aggregation and structural stability and resulted in higher C content in macroaggregates. The strong linear positive response to C additions indicated C sequestration potential in soils, with preferential location in macroaggregates. However, the kind and source of organic inputs strongly influenced both the soil aggregation and C accumulation in aggregates. A combination of GR in rice and FYM in wheat significantly improved C content in macroaggregates, and residue incorporation was beneficial compared to 100% N application through inorganic fertilizer or GR to rice. Coarse particulate organic matter (cPOM, >0.25mm) accounted most of the increase in C content within macroaggregates and was substantially higher with CR incorporation. A relatively higher C content in microaggregates-within-macroaggregates (isolated following Six et al., 2002a) in organic-amended soil implies potential in bringing higher C stabilization in intensive rice–wheat system through combination of inorganic and organic fertilizers and crop residues.

耕作方式对紫色水稻土有机碳和微生物生物量碳的影响

Changes in soil organic carbon(SOC) storage are closely related to soil quality and the long-term sustainability of agriculture.Accurate assessments of the effects of tillage system on soil organic matter sequestration are needed.A small difference in SOC contents can substantially change soil C storage estimates because the terrestrial carbon pool is so large.Sequestration of C in soils represents a mechanism to reduce atmospheric CO2 levels,but the extent to which soils can sequester C varies with climate,cropping system,and tillage practices.Soil C sequestration represents the accumulation of soil organic matter,and is the difference between C inputs by plants and organic matter decomposition.Hence,microbial activity is an important factor influencing C sequestration potential in soils. The impacts of different tillage systems on SOC and soil microbial biomass carbon(SMBC) were studied in this paper.The tillage experimental site(30°26′N,106°26′E) is located at the farm of Southwest University in Chongqing,China.The experiment was initiated in 1990 and included four tillage treatments: 1) conventional tillage with rotation of rice and winter fallow system(DP),where regular tillage practices were used for rice with three times of plowing and harrowing annually,and after the rice harvest,the field was submerged with water;2) conventional tillage with rotation of rice and rape system(SH),where tillage was the same as in the DP treatment,but the field was alternately submerged and drained for rice and rape cultivation;3) no-till and ridge culture with rotation of rice and rape system(LM),where ridges(five in each plot) with the top of 25 cm width were intervened with the ditches of 30 cm width and 35 cm depth,with no tillage practices performed,rape cultivated on the top of the ridges with the water level being maintained just to the bottom of the ditch,and the field submerged in water to cultivate rice after rape being harvested;4) tillage and ridge culture with rotation of rice and rape system(LF),where ridges were made as in LM treatment,but ridges were made every year for cultivating rice after rape harvest.Soils sampling at the depths of 0-10,10-20,20-30,30-40,40-50 and 50-60 cmwere performed with a soil drill after the rape harvest in the spring of 2009. The results showed that the contents of SOC and SMBC both decreased with the increase of soil depth under four tillage systems;however LM treatment enriched SOC and SMBC contents near the soil surface.The differences of SOC and SMBC contents in the same soil layer among the four tillage systems were the largest in 0-10cm soil layer and the lowest in 50-60cm soil layer.In the whole soil layer(0-60cm),the order of SOC contents was LM(17.57 g/kg) DP(13.91 g/kg) LF(12.50 g/kg) SH(11.29 g/kg),SOC storage was LM(158.52 MgC/hm2) DP(106.74 MgC/hm2) LF(93.11 MgC/hm2) SH(88.59 MgC/hm2),and SMBC contents was LM(258.88 mg/kg) SH(213.23 mg/kg) LF(159.71 mg/kg) DP(144.08 mg/kg).Compared with the other three treatments,LM treatment significantly increased the content and storage of SOC,and SMBC content.Analysis of microbial quotient showed that tillage systems had different impacts on SOC and SMBC.SMBC were significantly correlated with soil organic carbon,total nitrogen,alkali-hydrolyzed nitrogen,total phosphorus,effective phosphorus,total sulfur and effective sulfur which suggested SMBC could be a sensitive indicator for characterizing changes of purple paddy soil fertility in Southwest China.