The potential of green manure to increase soil carbon sequestration and reduce the yield-scaled carbon footprint of rice production in southern China

Green manure(GM)has been used to support rice production in southern China for thousands of years.However,the effects of GM on soil carbon sequestration(CS)and the carbon footprint(CF)at a regional scale remain unclear.Therefore,we combined the datasets from long-term multisite experiments with a meta-analysis approach to quantify the potential of GM to increase the CS and reduce the CF of paddy soils in southern China.Compared with the fallow-rice practice,the GM-rice practice increased the soil C stock at a rate of 1.62 Mg CO_(2)-eq ha^(-1) yr^(-1) and reduced chemical N application by 40%with no loss in the rice yield.The total CF varied from 7.51 to 13.66 Mg CO_(2)-eq ha^(-1) yr^(-1) and was dominated by CH_(4) emissions(60.7-81.3%).GM decreased the indirect CF by 31.4%but increased the direct CH_(4) emissions by 19.6%.In the low and high CH_(4) emission scenarios,the CH_(4) emission factors of GM(EF_(gc))were 5.58 and 21.31%,respectively.The greater soil CS offset the increase in GM-derived CF in the low CH_(4) scenario,but it could not offset the CF increase in the high CH_(4) scenario.A trade-off analysis also showed that GM can simultaneously increase the CS and reduce the total CF of the rice production system when the EF_(gc) was less than 9.20%.The variation in EF_(gc) was mainly regulated by the GM application rates and water management patterns.Determining the appropriate GM application rate and drainage pattern warrant further investigation to optimize the potential of the GM-rice system to increase the CS and reduce the total CF in China.

Proper Particle Size Range for Resistance to Chemical Oxidation: A Perspective on the Recalcitrance of Beanpod Biochar for Soil Carbon Sequestration

The effect of particle size on the recalcitrance of biochar against oxidation has been regarded as one of the most important factors influencing its stability and transportation in soils. Little is known about the peculiar stability of different particle sizes under chemical oxidation conditions. In this study, several sizes of biochar particles derived from beanpod were produced,and their stabilities were tested by using acid dichromate and hydrogen peroxide. We discovered that the 60-100 mesh size of particles produced at 400 and 500 ℃ showed the least carbon loss under the oxidation of both dichromate and hydrogen peroxide. In addition, this particle size also shows great stability at 600 and 700 ℃, but this stability was not observed below 300 °C for all temperature-dependent biochars. Medium-sized particles composed of exclusively heterogeneous components produced a biochar at temperatures over 400 ℃ with comparatively stronger chemical anti-oxidation characteristics. The chemical recalcitrance of biochar should be reevaluated based on particle size before soil application.

Profit Analysis by Soil Carbon Sequestration with Different Composts and Cooperated with Biochar during Corn (Zea mays) Cultivation Periods in Sandy Loam Soil

Despite the ability of biochar to enhance soil fertility and to sequester soil carbon, its potential reduction of green house gas emissions and profit analysis with different organic composts and cooperated with biochar for crop cultivation have been a few evaluated. This study was conducted to estimate their greenhouse gas emission reduction and profit analysis by soil carbon sequestration with different organic composts and cooperated with biochar application during corn cultivation periods. For the experiment, the treatments were consisted of aerobic digestate of swine wastes (AD), pig compost as the control (PC), cow compost (CC) and pig compost cooperated with 1% biochar (PC + 1% biochar). The soil texture used in this study was sandy loam, and application rates of chemical fertilizer were 190-39-221 kg·ha-1 (N-P2O5-K2O) as recommended amount after soil test. The soil samples were periodically taken at every 15 day intervals during the experimental periods. It was observed that soil carbon sequestration by AD, CC and PC + 1% biochar application was estimated to be 429 kg·ha-1, 2366 kg·ha-1, and 3978 kg·ha-1, and their CO2-e emission reductions were estimated to be 0.16 tones for AD, 0.87 tones for CC, and 14.58 tones for PC + 1% biochar per hectar for corn cultivation periods. Their profits were estimated at $14.58 for lowest and $451.90 for highest. In Korea Climate Exchange, it was estimated to be $115.20 per hectar of corn cultivation with PC + 1% biochar. So, the price of CO2 per hectar for corn cultivation with PC + 1% biochar was high at 16.8 times relative to cow compost treatment only. For the plant growth response, it was observed that plant height and fresh ear yield were not significantly different among the treatments. Therefore, these experimental results might be fundamental data for assuming a carbon trading mechanism exists for biochar soil application in agricultural practices.

Grazing effects on the relationship between plant functional diversity and soil carbon sequestration regulated by livestock species

Grazing exerts a profound influence on both the plant diversity and productivity of grasslands,while simultaneously exerting a significant impact on regulating grassland soil carbon sequestration.Moreover,besides altering the taxonomic diversity of plant communities,grazing can also affect their diversity of functional traits.However,we still poorly understand how grazing modifies the relationship between plant functional diversity(FD)and soil carbon sequestration in grassland ecosystems.Here,we conducted a grazing manipulation experiment to investigate the effects of different grazing regimes(no grazing,sheep grazing(SG)and cattle grazing(CG))on the relationships between plant FD and soil carbon sequestration in meadow and desert steppe.Our findings showed that different livestock species changed the relationships between plant FD and soil organic carbon(SOC)in the meadow steppe.SG decoupled the originally positive relationship between FD and SOC,whereas CG changed the relationship from positive to negative.In the desert steppe,both SG and CG strengthened the positive relationship between FD and SOC.Our study illuminates the considerable impact of livestock species on the intricate mechanisms of soil carbon sequestration,primarily mediated through the modulation of various measures of functional trait diversity.In ungrazed meadows and grazed deserts,maintaining high plant FD is conducive to soil carbon sequestration,whereas in grazed meadows and ungrazed deserts,this relationship may disappear or even reverse.By measuring the traits and controlling the grazing activities,we can accurately predict the carbon sequestration potential in grassland ecosystems.

Spatial Analysis of the Soil Carbon Sequestration Potential of Crop-residue Return in China Based on Model Simulation

Crop-residue return is a recommended practice for soil and nutrient management and is important in soil organic carbon(SOC)sequestration and CO2 mitigation.We applied a process-based Environmental Policy Integrated Climate(EPIC)model to simulate the spatial pattern of topsoil organic carbon changes from 2001 to 2010under 4 crop-residue return scenarios in China.The carbon loss(28.89 Tg yr–1)with all crop-residue removal(CR0%)was partly reduced by 22.38 Tg C yr–1 under the status quo CR30%(30% of crop-residue return).The topsoil in cropland of China would become a net carbon sink if the crop-residue return rate was increased from 30%to 50%,or even 75%.The national SOC sequestration potential of cropland was estimated to be 25.53 Tg C yr–1 in CR50%and 52.85 Tg C yr–1 in CR75%,but with high spatial variability across regions.The highest rate of SOC sequestration potential in density occurred in Northwest and North China while the lowest was in East China.Croplands in North China tended to have stronger regional SOC sequestration potential in storage.During the decade,the reduced CO2 emissions from enhanced topsoil carbon in CR50%and CR75% were equivalent to 1.4% and 2.9%of the total CO2 emissions from fossil fuels and cement production in China,respectively.In conclusion,we recommend encouraging farmers to return crop-residue instead of burning in order to improve soil properties and alleviate atmospheric CO2 rises,especially in North China.

Preliminary Estimation of Soil Carbon Sequestration of China’s Forests during 1999–2008

The National Forest Inventory(NFI)is an important resource for estimating the national carbon balance(These data were unpublished data,and we could only obtain the data before 2008 through data search by now).Based on the data from sample plots,the literature,and NFI,as well as the relationships between volume,biomass,annual litterfall and soil respiration of different forest types,the net ecosystem production(NEP),changes in forest biomass carbon storage(△Cbiomass)and non-respiratory losses(NR)of China’s forests during 1999-2008 were estimated,and the forest soil carbon sequestration(△Csoil)was assessed according to the carbon balance principle of the forest ecosystem(△Csoil=NEP-NR-△Cbiomass).The results showed that the total NEP,△Cbiomass,NR and△Csoil values for China’s forests were 157.530,48.704,31.033 and 77.793 Tg C yr^(-1) respectively,and average NEP,△Cbiomass,NR,and△Csoil values were 101.247,31.303,19.945 and 49.999 g C m^(-2) yr^(-1) respectively.There were large spatial differences in forest soil carbon sequestration in different parts of China.The forest soil in Jiangxi,Hunan,Zhejiang,Fujian,Anhui,Shanxi,Shaanxi,Guangxi and Liaoning served as carbon sources and the carbon released was about 25.507 Tg C yr^(-1).The other 22 provinces served as carbon sinks and the average carbon sequestration by forest soil came to 103.300 Tg C yr^(-1).This research established a method for evaluating soil carbon sequestration by China’s forests based on the NFI,which is a useful supplement to current statistical data-based studies on the forest ecosystem carbon cycle,and can promote comparable studies on forest soil carbon sequestration with consistent research methods at the regional scale.

Land Use and Soil Organic Carbon in China’s Village Landscapes

Village landscapes, which integrate small-scMe agriculture with housing, forestry, and a host of other land use practices, cover more than 2 million square kilometers across China. Village lands tend to be managed at very fine spatial scales （≤ 30 m）, with managers both adapting their practices to existing variation in soils and terrain （e.g., fertile plains vs. infertile slopes） and also altering soil fertility and even terrain by terracing, irrigation, fertilizing, and other land use practices. Relationships between fine-scale land management patterns and soil organic carbon （SOC） in the top 30 cm of village soils were studied by sampling soils within fine-scale landscape features using a regionally weighted landscape sampling design across five environmentally distinct sites in China. SOC stocks across China＇s village regions （5 Pg C in the top 30 cm of 2 ×10^6 km^2） represent roughly 4% of the total SOC stocks in global croplands. Although macroclimate varied from temperate to tropical in this study, SOC density did not vary significantly with climate, though it was negatively correlated with regional mean elevation. The highest SOC densities within landscapes were found in agricultural lands, especially paddy, the lowest SOC densities were found in nonproductive lands, and forest lands tended toward moderate SOC densities. Bue to the high SOC densities of agricultural lands and their predominance in village landscapes, most village SOC was found in agricultural land, except in the tropical hilly region, where forestry accounted for about 45% of the SOC stocks. A surprisingly large portion of village SOC was associated with built structures and with the disturbed lands surrounding these structures, ranging from 〉 18% in the North China Plain to about 9% in the tropical hilly region. These results confirmed that local land use practices, combined with local and regional variation in terrain, were associated with most of the SOC variation within and across China＇s village landscapes and may be an important cause of regional variation in SOC.

Effects of afforestation on soil carbon and its fractions:a case study from the Loess Plateau,China

Afforestation has been implemented to reduce soil erosion and improve the environment of the Loess Plateau,China.Although it increased soil organic carbon（SOC）,the stability of the increase is unknown.Additionally,the variations of soil inorganic carbon（SIC） following afforestation needs to be reconfirmed.After planting Robinia pseudoacacia,Pinus tabuliformis,and Hippophae rhamnoides on bare land on the Loess Plateau,total soil carbon（TSC） was measured and its two components,SIC and SOC,as well as the light and heavy fractions within SOC under bare lands and woodlands at the soil surface（0–20 cm）.The results show that TSC on bare land was 24.5 Mg ha^（-1） and significantly increased to 51.6 Mg ha^（-1） for R.pseudoacacia,47.0 Mg ha^（-1） for P.tabuliformis and 39.9 Mg ha^（-1） for H.rhamnoides.The accumulated total soil carbon under R.pseudoacacia,P.tabuliformis,and H.rhamnoides,the heavy fraction（HFSOC） accounted for 65.2,31.7 and 76.2%,respectively; the light fraction（LF-SOC） accounted for 18.0,52.0 and 4.0%,respectively; SIC occupied 15.6,15.3 and 19.7%,respectively.The accumulation rates of TSC under R.pseudoacacia,P.tabuliformis,and H.rhamnoides reached159.5,112.4 and 102.5 g m^（-2） a^（-1）,respectively.The results demonstrate that afforestation on bare land has high potential for soil carbon accumulation on the Loess Plateau.Among the newly sequestrated total soil carbon,the heavy fraction（HF-SOC） with a slow turnover rate accounted for a considerably high percentage,suggesting that significant sequestrated carbon can be stored in soils following afforestation.Furthermore,afforestation induces SIC sequestration.Although its contribution to TSC accumulation was less than SOC,overlooking it may substantially underestimate the capacity of carbon sequestration after afforestation on the Loess Plateau.

The Effect of Soil Enzymes and Polysaccharides Secreted by the Roots of Salvia miltiorrhiza Bunge under Drought,High Temperature,and Nitrogen and Phosphorus Deficits

Root exudates serve as crucial mediators for information exchange between plants and soil,and are an important evolutionary mechanism for plants’adaptation to environmental changes.In this study,15 different abiotic stress models were established using various stress factors,including drought(D),high temperature(T),nitrogen deficiency(N),phosphorus deficiency(P),and their combinations.We investigated their effects on the seedling growth of Salvia miltiorrhiza Bunge and the activities of Solid-Urease(S-UE),Solid-Nitrite Reductase(S-NiR),Solid-Nitrate Reductase(S-NR),Solid-Phosphotransferase(S-PT),and Solid-Catalase(S-CAT),as well as the contents of polysaccharides in the culture medium.The results showed that the growth of S.miltiorrhiza was inhibited under 15 stress conditions.Among them,13 stress conditions increased the root-shoot ratio.These 15 stress conditions significantly reduced the activity of S-NR,two combinations significantly improved the activity of S-NIR,they were synergistic stresses of high temperature and nitrogen deficiency(TN),and synergistic stresses of drought and nitrogen deficiency(DN)(p<0.05).The activity of S-UE was significantly improved under N,D,T,synergistic stresses of drought and high temperature(DT),DN,synergistic stresses of drought and phosphorus deficiency(DP),and synergistic stresses of high temperature,nitrogen,and phosphorus deficiency(TNP)stress conditions(p<0.05).Most stress combinations reduced the activity of S-PT,but D and T significantly improved it.(p<0.05).The N,DN,and TN stress conditions significantly reduced S-CAT activity.The P,DT,and synergistic stresses of drought,high temperature,and phosphorus deficiency(DTP)significantly decreased the total polysaccharide content of the soil(p<0.05).The research suggested that abiotic stress hindered the growth of S.miltiorrhiza and altered the behavior of root secretion.Roots regulated the secretion of several substances in response to various abiotic stresses,including soil nitrogen cycle enzymes,phosphorus transport-related enzymes,and antioxidant enzymes.In conclusion,plants regulate the utilization of rhizosphere substances in response to abiotic stresses by modulating the exudation of soil enzymes and polysaccharides by the root system.At the same time,soil carbon sequestration was affected by the adverse environment,which restricted the input of organic matter into the soil.

Challenges to increasing the soil carbon pool of agro-ecosystems in China

Climate change will place agro-ecological systems and food security at serious risk. At the 21 st Conference of the Parties（COP21） in Paris in December of 2015, parties to the United Nations Framework Convention on Climate Change（UNFCCC） reached a historic agreement（Paris Agreement） to combat climate change and to accelerate and intensify the actions and investments needed for a sustainable low carbon future. An initiative named the "4‰ initiative: Soils for food security and climate" was proposed by the French Minister of Agriculture, and this initiative was launched officially at the COP21 and adopted by many global organizations. The aim of this initiative was to increase carbon sequestration in soil to mitigate fossil fuel combustion emissions of greenhouse gasses. The present study found that China has high CO;emissions but a low soil carbon pool, and indicates that 4‰ increments of the soil carbon pool will not be sufficient to offset national CO;emissions. The current soil carbon sequestration rate would also not reach the mean level requested by the initiative. Therefore, China faces big challenges to achieve this initiative. An integrated use of straw technology may be used more widely to improve carbon sequestration, and other opportunities include improved fertilizer use efficiency and greenhouse gas mitigation through the waste management project under construction in China. This paper suggests that China may put forward the biomass treatment centered high yield and fertilizer-carbon sequestration project to enhance resilience of agro-ecosystems to climate change.

Accumulation of soil organic carbon during natural restoration of desertified grassland in China's Horqin Sandy Land

China＇s Horqin Sandy Land,a formerly lush grassland,has experienced extensive desertification that caused considerable carbon（C） losses from the plant-soil system.Natural restoration through grazing exclusion is a widely suggested option to sequester C and to restore degraded land.In a desertified grassland,we investigated the C accumulation in the total and light fractions of the soil organic matter from 2005 to 2013 during natural restoration.To a depth of 20 cm,the light fraction organic carbon（LFOC） storage increased by 221 g C/m2（84%） and the total soil organic carbon（SOC） storage increased by 435 g C/m2（55%）.The light fraction dry matter content represented a small proportion of the total soil mass（ranging from 0.74% in 2005 to 1.39% in 2013）,but the proportion of total SOC storage accounted for by LFOC was remarkable（ranging from 33% to 40%）.The C sequestration averaged 28 g C/（m2·a） for LFOC and 54 g C/（m2·a） for total SOC.The total SOC was strongly and significantly positively linearly related to the light fraction dry matter content and the proportions of fine sand and silt＋clay.The light fraction organic matter played a major role in total SOC sequestration.Our results suggest that grazing exclusion can restore desertified grassland and has a high potential for sequestering SOC in the semiarid Horqin Sandy Land.

The efficiency of long-term straw return to sequester organic carbon in Northeast China＇s cropland

Black soil is one of the most precious soil resources on earth because it has abundant carbon stocks and a relatively high production capacity. However, decreasing organic matter after land reclamation, and the effects of long-term inputs of organic carbon have made it less fertile black soil in Northeast China. Straw return could be an effective method for improving soil organic carbon（SOC） sequestration in black soils. The objective of this study was to evaluate whether straw return effectively increases SOC sequestration. Long-term field experiments were conducted at three sites in Northeast China with varying latitudes and SOC densities. Study plots were subjected to three treatments： no fertilization（CK）; inorganic fertilization（NPK）; and NPK plus straw return（NPKS）. The results showed that the SOC stocks resulting from NPKS treatment were 4.0 and 5.7% higher than those from NPK treatment at two sites, but straw return did not significantly affect the SOC stocks at the third site. Furthermore, at higher SOC densities, the NPKS treatment resulted in significantly higher soil carbon sequestration rates（CSR） than the NPK treatment. The equilibrium value of the CSR for the NPKS treatment equated to cultivation times of 17, 11, and 8 years at the different sites. Straw return did not significantly increase the SOC stocks in regions with low SOC densities, but did enhance the C pool in regions with high SOC densities. These results show that there is strong regional variation in the effects of straw return on the SOC stocks in black soil in Northeast China. Additional cultivations and fertilization practices should be used when straw return is considered as an approach for the long-term improvement of the soil organic carbon pool.

Effect of potassium on soil conservation and productivity of maize/cowpea based crop rotations in the north-west Indian Himalayas

Plots under conservation tillage may require higher amount of potassium(K) application for augmenting productivity due to its stratification in upper soil layers, thereby reducing K supplying capacity in a medium or long-term period. To test this hypothesis, a field experiment was performed in 2002-2003 and 2006-2007 to study the effect of K and several crop rotations on yield, water productivity, carbon sequestration, grain quality, soil K status and economic benefits derived in maize(Zea mays L)/cowpea(Vigna sinensis L.) based cropping system under minimum tillage(MT). All crops recorded higher grain yield with a higher dose of K(120 kg K2 O ha-1) than recommended K(40 kg K2 O ha-1). The five years' average yield data showed that higher K application(120 kg K2 O ha-1) produced 16.4%(P<0.05)more maize equivalent yield. Cowpea based rotation yielded 14.2%(P<0.05) higher production than maize based rotation. The maximum enhancement was found in cowpea-mustard rotation. Relationship between yield and sustainable indices revealed that only agronomic efficiency of fertilizer input was significantly correlated with yield. Similarly, higherdoses of K application not only increased the water use efficiency(WUE) of all crops, but also reduced runoff and soil loss by 16.5% and 15.8% under maize and 23.3% and 19.7% under cowpea cover, respectively. This study also revealed that on an average 16.5% of left over carbon input contributed to soil organic carbon(SOC). Here, cowpea based rotation with the higher K application increased carbon sequestration in soil. Potassium fertilization also significantly improved the nutritional value of harvested grain by increasing the protein content for maize(by 9.5%) and cowpea(by 10.6%). The oil content in mustard increased by 5.0% and 6.0% after maize and cowpea, respectively. Net return also increased with the application of the higher K than recommended K and the trend was similar to yield. Hence, the present study demonstrated the potential yield and profit gains along with resource conservation in the Indian Himalayas due to annual additions of higher amount of K than the recommended dose. The impact of high K application was maximum in the cowpea-mustard rotation.

Three-dimensional modelling of soil organic carbon density and carbon sequestration potential estimation in a dryland farming region of China

Soil organic carbon density(SOCD)and soil organic carbon sequestration potential(SOCP)play an important role in carbon cycle and mitigation of greenhouse gas emissions.However,the majority of studies focused on a two-dimensional scale,especially lacking of field measured data.We employed the interpolation method with gradient plane nodal function(GPNF)and Shepard(SPD)across a range of parameters to simulate SOCD with a 40 cm soil layer depth in a dryland farming region(DFR)of China.The SOCP was estimated using a carbon saturation model.Results demonstrated the GPNF method was proved to be more effective in simulating the spatial distribution of SOCD at the vertical magnification multiple and search point values of 3.0×106 and 25,respectively.The soil organic carbon storage(SOCS)of 40 cm and 20 cm soil layers were estimated as 22.28×10^(11)kg and 13.12×10^(11)kg simulated by GPNF method in DFR.The SOCP was estimated as 0.95×10^(11)kg considered as a carbon sink at the 20–40 cm soil layer.Furthermore,the SOCP was estimated as–2.49×10^(11)kg considered as a carbon source at the 0–20 cm soil layer.This research has important values for the scientific use of soil resources and the mitigation of greenhouse gas emissions.

Kinetics of native and added carbon mineralization on incubating at different soil and moisture conditions in Typic Ustochrepts and Typic Halustalf

The carbon dynamics in soils is of great importance due to its links to the global carbon cycle.The prediction of the behavior of native soil organic carbon(SOC)and organic amendments via incubation studies and mathematical modeling may bridge the knowledge gap in understanding complex soil ecosystems.Three alkaline Typic Ustochrepts and one Typic Halustalf with sandy,loamy sand,and clay loam texture,varying in percent SOC of 0.2;S_(1),0.42;S_(2),0.67;S_(3) and 0.82;S_(4) soils,were amended with wheat straw(WS),WS+P,sesbania green manure(GM),and poultry manure(PM)on 0.5%C rate at field capacity(FC)and ponding(P)moisture levels and incubated at 35℃for 1,15,30 and 45 d.Carbon mineralization was determined via the alkali titration method after 1,5,714,21,and 28 d.The SOC and inorganic carbon contents were determined from dried up(50℃)soil samples after 1,15,30,and 45 d of incubation.Carbon from residue mineralization was determined by subtracting the amount ofCO_(2)-C evolved from control soils.The kinetic models;monocomponent first order,two-component first or-der,and modified Gompertz equations were fitted to the carbon mineralization data from native and added carbon.The SOC decomposition was dependent upon soil properties,and moisture,however,added C was relatively independent.The carbon from PM was immobilized in S4.All the models fitted to the data predicted carbon mineralization in a similar range with few exceptions.The residues lead to the OC build-up in fine-textured soils having relatively high OC and cation exchange capacities.Whereas,fast degradation of applied OC in coarse-textured soils leads to faster mineralization and lower build-up from residues.The decline in CaCO_(3) after incubation was higher at FC than in the P moisture regime.

SOC storage and potential of grasslands from 2000 to 2012 in central and eastern Inner Mongolia, China

Grassland ecosystem is an important component of the terrestrial carbon cycle system. Clear comprehension of soil organic carbon（SOC） storage and potential of grasslands is very important for the effective management of grassland ecosystems. Grasslands in Inner Mongolia have undergone evident impacts from human activities and natural factors in recent decades. To explore the changes of carbon sequestration capacity of grasslands from 2000 to 2012, we carried out studies on the estimation of SOC storage and potential of grasslands in central and eastern Inner Mongolia, China based on field investigations and MODIS image data. First, we calculated vegetation cover using the dimidiate pixel model based on MODIS-EVI images. Following field investigations of aboveground biomass and plant height, we used a grassland quality evaluation model to get the grassland evaluation index, which is typically used to represent grassland quality. Second, a correlation regression model was established between grassland evaluation index and SOC density. Finally, by this regression model, we calculated the SOC storage and potential of the studied grasslands. Results indicated that SOC storage increased with fluctuations in the study area, and the annual changes varied among different sub-regions. The SOC storage of grasslands in 2012 increased by 0.51×1012 kg C compared to that in 2000. The average carbon sequestration rate was 0.04×1012 kg C/a. The slope of the values of SOC storage showed that SOC storage exhibited an overall increase since 2000, particularly for the grasslands of Hulun Buir city and Xilin Gol League, where the typical grassland type was mainly distributed. Taking the SOC storage under the best grassland quality between 2000 and 2012 as a reference, this study predicted that the SOC potential of grasslands in central and eastern Inner Mongolia in 2012 is 1.38×1012 kg C. This study will contribute to researches on related methods and fundamental database, as well as provide a reference for the protection of grassland ecosystems and the formulation of local policies on sustainable grassland development.

Managing soil quality for humanity and the planet

Rather than a human-centric, the basic strategy of achieving Sustainable Development Goals mustbe focused on restoring and sustaining planetary processes. The urgency of meeting the demands of thehumanity must be reconciled with the necessity of enhancing the environment. Increasing and restoring soilorganic matter content of the degraded and depleted soils is critical to strengthening planetary processes.

Greenhouse gas emissions during the COVID-19 pandemic from agriculture in China

To study the impact of the COVID-19 pandemic on agricultural carbon emissions in China,the greenhouse gas emissions generated by crop and livestock production,and agricultural material and energy inputs in China from 2019 to 2021 were systematically calculated.It was found that from 2019 to 2021,Net greenhouse gas emissions(NGHGE)from agriculture in China had an increasing trend.Methane emissions ranked first in NGHGE,with an annual proportion exceeding 65%and an increasing annual trend.CH_(4)emissions were primarily influenced by enteric fermentation and rice production.Nitrous oxide emissions accounted for around 22%of annual NGHGE and decreased from 2019 to 2021.The main sources of N_(2)O emissions were the use of nitrogen fertilizers and manure management.Carbon dioxide emissions accounted for about 18%annually,with diesel and agricultural electricity use contributing to over 60%of CO_(2)emissions.Soil carbon sequestration represented about a 6.1%lowering of NGHGE.The combined proportion of CH4 emissions from enteric fermentation and rice production accounted for over 50%of total GHG emissions.The changes in NGHGE were mainly caused by disturbance of the livestock industry during the pandemic.

MICROBIAL NECROMASS WITHIN AGGREGATES STABILIZES PHYSICALLY-PROTECTED C RESPONSE TO CROPLAND MANAGEMENT

The interactions of soil microorganisms and structure regulate the degradation and stabilization processes of soil organic carbon(SOC). Microbial necromass is a persistent component of SOC, and its magnitude of accumulation dependent on management and aggregate sizes. A meta-analysis of 121 paired measurements was conducted to evaluate the management effects on contributions of microbial necromass to SOC depending on aggregate fractions. Results showed that the contribution of fungal necromass to SOC increased with aggregate sizes, while bacterial necromass had a higher proportion in silt and clay. Cropland management increased total and fungal necromass in large macroaggregates(47.1% and 45.6%), small macroaggregates(44.0% and 44.2%), and microaggregates(38.9% and 37.6%).Cropland management increased bacterial necromass independent of aggregate fraction sizes. Greater fungal necromass was increased in macroaggregates in response to manure(26.6% to 28.5%) and no or reduced tillage(68.0% to 73.5%). Cover crops increased bacterial necromass by 25.1%in small macroaggregates. Stimulation of microbial necromass was proportional to the increases of SOC within soil aggregates, and the correlation was higher in macroaggregates. Increasing microbial necromass accumulation in macroaggregates can, therefore, be considered as a central component of management strategies that aim to accelerate C sequestration in agricultural soils.