Enhance Soil Organic Carbon Research Articles

Soil Microbial Functions Linked Fragrant Rice 2-Acetyl-1-Pyrroline with Soil Active Carbon Pool: Evidence from Soil Metagenomic Sequencing of Tillage Practices

Improved tillage management in fragrant rice cropping systems can enhance soil organic carbon (SOC) and the content of 2-Acetyl-1-Pyrroline (2-AP), a crucial volatile compound contributing to the aroma of fragrant rice. Despite this, the interplay between 2-AP content in fragrant rice and SOC metabolism, alongside the influences exerted by soil microbial functions, remains poorly understood. This study introduces a comprehensive 6-year field experiment which aims to correlate SOC with rice grain 2-AP content by analyzing soil microbial KEGG functions, such as carbon and amino acid metabolism, using metagenomic sequencing. The experiment assessed three tillage practices, conventional tillage (CT), reduced tillage (RT), and no tillage (NT), with soil samples collected on three dates in 2022. The results indicated that NT significantly (p < 0.05) enhanced SOC content and modified carbon metabolism by upregulating the Calvin cycle (K01601) and reducing hemicellulose degradation (K01710). Additionally, NT notably increased the soil levels of alkaline amino acids, such as histidine and ornithine, which were 165.17% and 1218.42% higher, respectively, than those in CT, possibly linked to an increase in soil pH. Furthermore, the 2-AP content in fragrant rice under NT was significantly higher by 52.02% and 13.90% compared to under RT and CT, respectively. NT also upregulated K00250 (alanine, aspartate, and glutamate metabolism) and K00290 (valine, leucine, and isoleucine biosynthesis), leading to significantly higher levels of 2-AP biosynthesis-related amino acids proline and glutamate in fragrant rice grain. This study links SOC and 2-AP biosynthesis via soil microbial functions, presenting a novel strategy for improving the quality of fragrant rice through soil management practices.

Whether Wheat–Maize Rotation Influenced Soil Organic Carbon Content in Sushui River Basin

Enhancing soil organic carbon (SOC) content in farmland is crucial for soil quality maintenance and food security. However, the relationship between crop rotation and SOC sequestration remains unclear. We used sample data on SOC, collected in September of every year, from cultivated land for quality monitoring from 2017 to 2021, combined with spatially extracted planting system information, and focused on the effects of wheat–maize crop rotation on SOC in the Sushui River Basin. An analysis of variance (ANOVA) indicated that the SOC content was only significantly different between wheat monoculture and maize monoculture. Among the three cropping systems, wheat–maize rotation did not show absolute superiority. The Geodetector analysis showed that the planting system dominated the spatial distribution of soil organic carbon (p = 0.05), but its explanatory factor was only 5%, and the explanatory power was significantly improved after interaction with other factors. Geographically weighted regression showed that wheat–maize rotation had a trade-off effect with elevation and synergistic effects with rainfall and pH. It displayed a synergistic effect with temperature in the southwest and a trade-off effect in the northeast. The degrees of trade-offs and synergy varied spatially among all interacting factors. We focused on the spatial heterogeneity of soil organic carbon in a small watershed, and the results had scientific significance for the layout of planting systems according to local conditions and the improvement in soil organic carbon levels.

Into the unknown: The role of post-fire soil erosion in the carbon cycle.

Wildfires directly emit 2.1 Pg carbon (C) to the atmosphere annually. The net effect of wildfires on the C cycle, however, involves many interacting source and sink processes beyond these emissions from combustion. Among those, the role of post-fire enhanced soil organic carbon (SOC) erosion as a C sink mechanism remains essentially unquantified. Wildfires can greatly enhance soil erosion due to the loss of protective vegetation cover and changes to soil structure and wettability. Post-fire SOC erosion acts as a C sink when off-site burial and stabilization of C eroded after a fire, together with the on-site recovery of SOC content, exceed the C losses during its post-fire transport. Here we synthesize published data on post-fire SOC erosion and evaluate its overall potential to act as longer-term C sink. To explore its quantitative importance, we also model its magnitude at continental scale using the 2017 wildfire season in Europe. Our estimations show that the C sink ability of SOC water erosion during the first post-fire year could account for around 13% of the C emissions produced by wildland fires. This indicates that post-fire SOC erosion is a quantitatively important process in the overall C balance of fires and highlights the need for more field data to further validate this initial assessment.

Maize straw increases while its biochar decreases native organic carbon mineralization in a subtropical forest soil

Organic soil amendments have been widely adopted to enhance soil organic carbon (SOC) stocks in agroforestry ecosystems. However, the contrasting impacts of pyrogenic and fresh organic matter on native SOC mineralization and the underlying mechanisms mediating those processes remain poorly understood. Here, an 80-day experiment was conducted to compare the effects of maize straw and its derived biochar on native SOC mineralization within a Moso bamboo (Phyllostachys edulis) forest soil. The quantity and quality of SOC, the expression of microbial functional genes concerning soil C cycling, and the activity of associated enzymes were determined. Maize straw enhanced while its biochar decreased the emissions of native SOC-derived CO2. The addition of maize straw (cf. control) enhanced the O-alkyl C proportion, activities of β-glucosidase (BG), cellobiohydrolase (CBH) and dehydrogenase (DH), and abundances of GH48 and cbhI genes, while lowered aromatic C proportion, RubisCO enzyme activity, and cbbL abundance; the application of biochar induced the opposite effects. In all treatments, the cumulative native SOC-derived CO2 efflux increased with enhanced O-alkyl C proportion, activities of BG, CBH, and DH, and abundances of GH48 and cbhI genes, and with decreases in aromatic C, RubisCO enzyme activity and cbbL gene abundance. The enhanced emissions of native SOC-derived CO2 by the maize straw were associated with a higher O-alkyl C proportion, activities of BG and CBH, and abundance of GH48 and cbhI genes, as well as a lower aromatic C proportion and cbbL gene abundance, while biochar induced the opposite effects. We concluded that maize straw induced positive priming, while its biochar induced negative priming within a subtropical forest soil, due to the contrasting microbial responses resulted from changes in SOC speciation and compositions. Our findings highlight that biochar application is an effective approach for enhancing soil C stocks in subtropical forests.

The Concurrent Application of Phosphogypsum and Modified Biochar as Soil Amendments Influence Sandy Soil Quality and Wheat Productivity.

Sandy soil covers a significant portion of Egypt's total land area, representing a crucial agricultural resource for future food security and economic growth. This research adopts the hypothesis of maximizing the utilization of secondary products for soil improvement to reduce ecosystem pollution. The study focuses on assessing the impact of combining phosphogypsum and modified biochar as environmentally friendly soil amendments on loamy sand soil quality parameters such as soil organic carbon, cation exchange capacity, nutrient levels, and wheat yield. The treatments were T1: the recommended NPK fertilizer (control); T2: 2.5 kg phosphogypsum m-2 soil; T3: 2.5 kg rice straw biochar m-2 soil; T4: 2.5 kg cotton stalk biochar m-2 soil; T5: 2.5 kg rice-straw-modified biochar m-2 soil; T6: 2.5 kg cotton-stalk-modified biochar m-2 soil; and T7 to T10: mixed phosphogypsum and biochar treatments. The results revealed that the combined use of phosphogypsum and modified cotton stalk biochar (T10) significantly enhanced soil organic carbon (SOC) by 73.66% and 99.46% in both seasons, the soil available N both seasons by 130.12 and 161.45%, the available P by 89.49% and 102.02%, and the available K by 39.84 and 70.45% when compared to the control treatment. Additionally, this treatment led to the highest grain yield of wheat (2.72 and 2.92 Mg ha-1), along with a significant increase in straw yield (52.69% and 59.32%) compared to the control treatment. Overall, the findings suggest that the combined use of phosphogypsum and modified biochar, particularly cotton-stalk biochar, holds promise for improving loamy sand-soil quality and wheat productivity.

Rice straw incorporation and Azolla application improves agronomic nitrogen-use-efficiency and rice grain yields in paddy fields

In paddy soils, excessive application of N fertilizer often results in substantial N losses due to low N utilization efficiency. However, this condition can be mitigated by enhancing soil organic carbon content. Two-year field experiment was carried out at Mkula Irrigation Scheme in Kilombero Valley, Tanzania with the aim of investigating the impact of Azolla, rice straw incorporation and reduced levels of nitrogen input from NPKS-containing fertilizers on N use efficiency, soil chemical properties and rice grain yield. Assuming that this technology will introduce a novel perspective to the research, shedding light on alternative and potentially more sustainable methods for nitrogen management in paddy soils, it will be particularly relevant in sub-Saharan Africa, where the annual cost of chemical fertilizers is expected to continue rising. The treatments involved absolute control, half dose N (50 kg N ha-1), full dose N (100 kg N ha-1), and combination of these N doses with PKS, dry Azolla (3.4 t ha-1) and rice straw (6.9 t ha-1) through omission approach. The soil of the experimental area was sandy clay loam in texture, very strongly acid (pH 4.8), normal electrical conductivity (0.06 dS m-1), low amounts of recorded organic carbon (1.35%), total nitrogen (0.33%), 0.68 mg kg−1 available P, exchangeable potassium (0.15 cmol(+) kg−1), calcium (0.19 mg kg−1) and sodium percentage (3.75%), with very low cation exchange capacity (1.6 cmol(+) kg−1). The results showed that combination of Azolla, rice straw +100 kg N ha-1 + 30 kg P ha-1 + 30 kg K ha-1 + 20 kg S ha-1 resulted in higher rice grain yield, nitrogen uptake and agronomic efficiency of N. Azolla, being an effective biofertilizer, significantly contributes to nitrogen fixation and soil enrichment. Interestingly, this study demonstrates that co-application of Azolla, rice straw, and 50% reduced N is effective for achieving high rice yields, minimizing over-dependence on chemical N fertilizer, sustainable agricultural development, and environmental conservation.

Low Carbon Loss from Long-Term Manure-Applied Soil during Abrupt Warming Is Realized through Soil and Microbiome Interplay.

Manure application is a global approach for enhancing soil organic carbon (SOC) sequestration. However, the response of SOC decomposition in manure-applied soil to abrupt warming, often occurring during diurnal temperature fluctuations, remains poorly understood. We examined the effects of long-term (23 years) continuous application of manure on SOC chemical composition, soil respiration, and microbial communities under temperature shifts (15 vs 25 °C) in the presence of plant residues. Compared to soil without fertilizer, manure application reduced SOC recalcitrance indexes (i.e., aliphaticity and aromaticity) by 17.45 and 21.77%, and also reduced temperature sensitivity (Q10) of native SOC decomposition, plant residue decomposition, and priming effect by 12.98, 15.98, and 52.83%, respectively. The relative abundances of warm-stimulated chemoheterotrophic bacteria and fungi were lower in the manure-applied soil, whereas those of chemoautotrophic Thaumarchaeota were higher. In addition, the microbial network of the manure-applied soil was more interconnected, with more negative connections with the warm-stimulated taxa than soils without fertilizer or with chemical fertilizer applied. In conclusion, our study demonstrated that the reduced loss of SOC to abrupt warming by manure application arises from C chemistry modification, less warm-stimulated microorganisms, a more complex microbial community, and the higher CO2 intercepting capability by Thaumarchaeota.

Enhancing soil organic carbon estimation accuracy: Integrating spatial vegetation dynamics and temporal analysis with Sentinel 2 imagery

This article introduces an improved method for estimating Soil Organic Carbon (SOC) using Sentinel 2 images, with a specific emphasis on the Dakshina Kannada area in India. By examining 364 soil samples, SOC estimation models were constructed using Random forests (RF) and Partial Least Squares Regression (PLSR), focusing on the impact of nearby vegetation pixels. The approach consisted of classifying soil samples by the presence of plant pixels at distances of 0, 10, and 20 m, and evaluating the influence of dry vegetation by the use of the Normalised Burn Ratio 2 (NBR2). The findings demonstrated a significant improvement in the precision of the model (by up to 20 %) when vegetation pixels within a 20-meter radius of the sample locations were omitted. The research also included a temporal analysis utilizing Sentinel-2 images from April 2017 to May 2023. This analysis showed strong relationships between the amount of exposed soil and the accuracy of predicting soil organic carbon (SOC) levels. These results emphasize the need to take into account both the spatial dynamics of vegetation and the temporal variations in bare soil covering to get an accurate estimate of soil organic carbon (SOC). This study improves the accuracy and dependability of SOC evaluations by including geographical and temporal aspects, providing useful insights for agricultural and ecological applications.

Straw management adopted by large farms sustains grain yield but mitigates greenhouse gas emissions

ContextStraw incorporation is a globally recommended strategy for enhancing soil fertility. The methods for straw incorporation adopted by large farms usually differ from those used by small households, primarily because of variations in cost affordability. However, the effects of straw management on rice yields and greenhouse gas (GHG) emissions have not been well explored at different farming scales. ObjectivesThis study aims to compare the grain yield and greenhouse gas emissions under different straw management adopted by large farms than small households. MethodsA three-year field experiment using split-plot design, with straw management as the main plot and preceding tillage as the sub-plot, was conducted in a wheat-rice rotation system. Four treatments were given as rotary tillage with straw removal (RT-S), rotary tillage with straw incorporation (RT+S; small households), ploughing tillage with straw removal (PT-S), and ploughing tillage with straw incorporation (PT+S, large farms) in the preceding wheat season. Soil tillage in the rice season was the same, which was rotary tillage after irrigation. ResultsStraw incorporation significantly increased methane (CH4) and nitrous oxide (N2O) emissions, and 60%-62% of CH4 was emitted during the transplanting to jointing stages while 45–73% of N2O was emitted during the jointing to the booting stage. The stimulation of CH4 and N2O emissions by straw incorporation was closely correlated to enhanced soil organic carbon (SOC) and denitrification enzyme activity, respectively. In the last year, PT+S significantly reduced the global warming potential (GWP) compared to RT+S in the whole rice season, which can be attributed to the dramatically decline of CH4 emission, even though N2O emission was increased. Additionally, the decreased CH4 emission was mainly due to lower methanogenic activity, and the increased N2O emission was mainly resulted from lower nosZ abundance under PT+S compared to RT+S. Straw incorporation increased rice yield by 15.73% on average in the last two years, and rice yield of PT+S in the last year was significantly enhanced by 27.50%, resulting in a lower greenhouse gas intensity (GHGI) by 25.54% compared to RT+S. ConclusionStraw management practices adopted by large farms (PT+S) have the potential to synchronize high rice yields with lower GHG emissions compared to small households (RT+S). ImplicationsOur findings provide some evidence that large-scale agricultural organization may be helpful for sustainable rice production in China.

Enhancing Soil Aggregate Stability and Organic Carbon in Northwestern China through Straw, Biochar, and Nitrogen Supplementation

Enhancing soil stability through the incorporation of straw and biochar is well documented. Nevertheless, the combined impact of straw, biochar, and nitrogen supplementation on soil aggregates and organic carbon still needs to be explored, with limited attention given to various sieving methods in the existing literature. Therefore, the current experiment used four sieving methods—routine wet sieving (RoutW), fast-wetting sieving (FastW), slow-wetting sieving (SlowW), and wetting–stirring sieving (WetS)—to investigate the effects of adding straw (0 or 4.5 t ha−1), biochar (from maize straw, 0 or 15 t ha−1), and N (0 or 100 kg ha−1) on soil aggregate stability and soil organic C in silt–loam soil of rainfed farmland in northwest China. The field experiment was started in 2014; soil samples were collected in 2021. The results revealed that straw returned, biochar, and N addition significantly increased soil mean weight diameter (MWD) and soil organic C (SOC). Compared to CN0 (zero-amendment) plots, straw returned with nitrogen addition (SN100) significantly increased the MWD of aggregates by 130.3% (RoutW), 121.66% (FastW), 73.94% (SlowW), and 91.78% (WetS) in the 0–30 cm soil layer. The addition of biochar and nitrogen (BN100) treatment showed the most significant effects on the relative slaking index (RSI), relative mechanical breakdown index (RMI), and SOC; compared with CN0 treatment, BN100 plots can reduce RSI and RMI by 42.90% and 54.66% and increase SOC by 53.27% for all soil layers. Therefore, adding organic materials with N can enhance the stability of soil aggregates and SOC of silt–loam soils in northwest China. Integrating biochar as an organic soil amendment in the agricultural practices of northwest China presents a multifaceted solution that addresses soil health, crop productivity, and environmental sustainability. The current study provides valuable insights that support adopting this innovative approach, paving the way for future sustainable agricultural practices that can benefit both the region and the global community.

Long-Term Effects of Different Tillage Systems and Their Impact on Soil Properties and Crop Yields

The scientific aim of this article is to elucidate the effects of various tillage practices on soil properties and crop yields; additionally, it seeks to highlight the significant potential of specific farming systems in enhancing soil organic carbon, thereby positively influencing CO2 emissions from soil. In the experimental station of Vytautas Magnus University, Kaunas District, Lithuania (54°52′50″ N and 23°49′41″ E), a long-term field experiment has been established since 1999, and studies have been conducted since 2003. The soil of the experimental site is classified as Epieutric Endocalcaric Planosol (Endoclayic, Episiltic, Aric, Drainic, Endoraptic, Uterquic), according to the World Reference Base (WRB, 2022). Two primary factors were assessed. Factor A incorporated practices of straw removal versus straw chopping and spreading, while Factor B evaluated a spectrum of tillage techniques: conventional deep plowing and two no-tillage practices, one of which involved cover crops. The findings from this long-term study highlight a significant increase in SOC stocks across all treatments over the 20-year period. Notably, the no-tillage practices, coupled with the spreading of chopped straw, demonstrated the most substantial growth in SOC levels, particularly in the top 0–10 cm soil layer. This trend underscores the effectiveness of minimizing soil disturbance and incorporating organic matter in boosting SOC stocks. The different tillage systems influence CO2 emissions from soil. Initially, direct sowing into uncultivated land, both with and without cover crops, led to a notable reduction in CO2 emissions compared to conventional plowing. However, this effect was found to vary over the growth cycle of the plant, highlighting the dynamic interaction between tillage practices, soil properties, and environmental conditions. Collaborative research efforts that involve farmers, scientists, policymakers, and other stakeholders are crucial for the development of holistic, practical, scalable solutions that enhance the sustainability and productivity of agricultural systems. This study contributes to the growing body of knowledge on sustainable agriculture, providing insights for farmers, agronomists, and policymakers in their quest to promote environmentally sound and productive agricultural systems.

Changes in soil aggregate stability and aggregate-associated carbon under different slope positions in a karst region of Southwest China

Soil aggregates are crucial for reducing soil erosion and enhancing soil organic carbon sequestration. However, knowledge regarding influences of different slope positions on compositions and carbon content for different soil aggregates is limited. Soil samples were collected from various slope positions including dip slope, anti-dip slope and valley depression in the Longtan karst valley of Southwest China. Contents of macroaggregate (> 0.25 mm), microaggregate (0.053–0.25 mm) and silt and clay fraction (< 0.053 mm), and aggregate-associated carbon contents under the three slope positions were measured. Compared to the anti-dip slope, the mean weight diameter under the dip slope and valley depression decreased by 28.48 % and 58.79 %, respectively, while the geometric mean diameter decreased by 39.01 % and 62.57 %, respectively. The mean carbon content in silt and clay fraction was 27.59 % and 21.00 % lower than the macroaggregate- and microaggregate-associated carbon content, respectively. Under the valley depression and dip slope, soil organic carbon contents in bulk soil (37.67 % and 10.36 %, respectively), microaggregate (37.56 % and 4.95 %), and silt and clay fraction (39.99 % and 12.84 %, respectively) were significantly lower than those under the anti-dip slope. However, the difference in macroaggregate-associated carbon content among the three slope positions was not significant. The silt and clay fraction was the major contributor to soil carbon pool in bulk soil in the study area because of its high content. Compared to the anti-dip slope, contribution of macroaggregates to soil carbon pool under the dip slope and valley depression decreased by 25.53 % and 47.95 %, respectively, whereas the contribution of silt and clay fraction increased by 22.68 % and 42.66 %, respectively. These results suggested that the anti-dip slope surpassed both the dip slope and valley depression in carbon sequestration and soil and water conservation in karst regions.

Divergent changes of carbon and nitrogen in the density fractions of soil organic matter after revegetation in the Tengger Desert, north China

AbstractRevegetation is an effective measure to enhance soil organic carbon (OC) and nitrogen (N) storage in drylands, but the underlying processes remain poorly understood. Based on density fractionation, the free light fraction (fLF), the occluded light fraction (oLF), and a heavy fraction (HF) were extracted from a chronosequence of revegetated sites aged 10, 22, 34, 48, and 65 years. A mobile sand dune (MSD) was used as the reference site (aged 0 years). The OC and N contents of different fractions and the bulk soils were determined to evaluate the impacts of revegetation and clarify post‐revegetation stabilization mechanisms for the OC and N. The results showed that the dry mass of fLF and oLF in established shrublands were 17.16–31.30 and 17.68–44.87 times greater than those in the MSD, respectively, while the amount of HF decreased by 1.09%–2.51% in 65 years. The contents and stocks of OC and N and C:N ratio in each fraction significantly increased over time but decreased with soil depth, and these three variables decreased sequentially from fLF to oLF to HF. The OC and N contents and their ratios in each fraction were positively and linearly correlated with their corresponding values in the bulk soil. The OC and N percentages contained in the fLF and oLF increased significantly, but those in the HF decreased with increasing site age. Despite this, more than 55.08% of OC and 80.59% of N were remained in the HF across all the sites, indicating that the enhancement of OC and N stocks in SOM following revegetation were mainly derived from an increase in OC and N in protected fractions. Biological and physicochemical factors including microbial biomass C and N, the availability of N, P, and K, bulk density, and clay and silt contents, were the key factors regulating the OC and N dynamics in the density fractions. The initial OC and N accumulation after revegetation occurs mainly in the HF, while vegetation development shifts the OC and N from stable to labile pools. The OC and N accumulation in revegetated soils is attributed to the changes in both the LF and HF whereas OC and N in the light fraction become increasingly important over time. Stabilization by forming aggregates and mineral associations may dominate the long‐term OC and N sequestration in restored ecosystems.

Oilseed rape-rice rotation with recommended fertilization and straw returning enhances soil organic carbon sequestration through influencing macroaggregates and molecular complexity

The sequestration of soil organic carbon (SOC) is influenced by agricultural management practices. However, the mechanisms that underlie the impacts of diverse paddy-upland rotation systems and fertilization strategies on SOC sequestration remain to be elucidated. Within this study, we investigated the variations in SOC sequestration under oilseed rape-rice (OR) and wheat-rice (WR) rotations with various fertilization regimes (CK, without fertilization; EF, excessive fertilization; RF, recommended fertilization; and RF+S, recommended fertilization with straw returning) through a five-year field experiment. Crop C inputs, soil aggregate-associated organic C, SOC functional groups, and their importance in SOC sequestration were examined. The results revealed that both SOC stock and sequestration rate were significantly enhanced by the OR rotation and straw returning. Specifically, SOC stock and sequestration rates were 7.7–14.3% and 28.6–83.7% higher in the OR rotation compared to the WR rotation under the same fertilization treatment. In addition, SOC stocks and sequestration rates were 6.7–13.3% and 24.4–77.6% higher in the RF+S treatment compared to the RF treatment. However, excessive fertilization (EF) did not further promote SOC sequestration. The OR rotation also showed higher values of aggregate mean weight diameter (MWD) and large-macroaggregate C compared to the WR rotation, with increases of 7.7–14.1% and 4.7–33.8%, respectively. The nuclear magnetic resonance studies showed that the OR rotation exhibited an elevated abundance of aromatic C and a more intricate molecular configuration compared to the WR rotation. Furthermore, crop C input increased significantly with fertilization, and crop C input was the highest in the RF+S treatment. The aggregate MWD and large-macroaggregate C also significantly increased after fertilization. Partial least squares path modeling revealed that crop rotation affected SOC sequestration mainly through its effect on large-macroaggregate C and SOC molecular structure complexity, whereas fertilization mainly affected SOC sequestration though its effects on crop C inputs and large-macroaggregate C. We conclude that OR rotation combined with straw returning is an effective measure for enhancing SOC sequestration in paddy-upland rotation systems, contributing to mitigating climate change in agricultural systems.

Deciphering the microbial functional potential of aeration drip irrigation to enhance soil organic carbon content

Aerated drip irrigation (ADI) is an important practice for promoting soil fertility and crop productivity in greenhouse vegetable production, yet little research has comprehensively investigated the effects on functional traits of carbon (C) cycling microorganisms. In this study, we sought to assess the potential efficacy of the ADI in enhancing soil organic carbon (SOC) content mediated via changes in microbial communities and the expression of genes associated with the carbon cycle. To this end, we adopted a metagenomics approach to compare the effects of ADI treatments with three dissolved oxygen concentrations (10, 15, and 20 mg L-1) during a three-season tomato cultivation experiment in northern China. The results revealed that the 10 mg L-1 treatment led to a significant increase in the abundance of KorA/B genes (associated with the rTCA cycle) in the C fixation pathway, whereas the 15 mg L-1 treatment increased the abundances of cbbL/R and coxL/S genes (associated with the Calvin cycle and carbon monoxide oxidation, respectively). In addition, based on a co-occurrence network analysis, we observed a positive correlation between cbbL and coxS. Interestingly, r-selected microorganisms, such as Proteobacteria and Actinomycetes, characterized by rapid cell multiplication and high biomass production, were identified as the primary contributors to C fixation and were the main predictors of SOC pools. In contrast, the 20 mg L-1 treatment was found to adversely influence C fixation, although enhanced C degradation could be attributed to the breakdown of organic matter by extracellular enzymes secreted by K-selected microorganisms. Collectively, our findings indicate that ADI with dissolved oxygen concentrations ≤15 mg L-1 can promote SOC content by altering the life history strategies of r-selected microorganisms and genes associated with C fixation. These findings will provide valuable insights into agroecosystem irrigation management, specifically in improving soil fertility and promoting sustainable production.

The impact of arbuscular mycorrhizal fungi and endophytic bacteria on peanuts under the combined pollution of cadmium and microplastics

It remains unclear how symbiotic microbes impact the growth of peanuts when they are exposed to the pollutants cadmium (Cd) and microplastics (MPs) simultaneously. This study aimed to investigate the effects of endophytic bacteria Bacillus velezens SC60 and arbuscular mycorrhizal fungus Rhizophagus irregularis on peanut growth and rhizosphere microbial communities in the presence of Cd at 40 (Cd40) or 80 (Cd80) mg kg−1 combined without MP or the presence of low-density polyethylene (LDPE) and poly butyleneadipate-co-terephthalate (PBAT). This study assessed soil indicators, plant parameters, and Cd accumulation indicators. Results showed that the application of R. irregularis and B. velezens significantly enhanced soil organic carbon and increased Cd content under the conditions of Cd80 and MPs co-pollution. R. irregularis and B. velezens treatment increased peanut absorption and the enrichment coefficient for Cd, with predominate concentrations localized in the peanut roots, especially under combined pollution by Cd and MPs. Under treatments with Cd40 and Cd80 combined with PBAT pollution, soil microbes Proteobacteria exhibited a higher relative abundance, while Actinobacteria showed a higher relative abundance under treatments with Cd40 and Cd80 combined with LDPE pollution. In conclusion, under the combined pollution conditions of MPs and Cd, the co-treatment of R. irregularis and B. velezens effectively immobilized Cd in peanut roots, impeding its translocation to the shoot.

The Application of Biochar Enhances Soil Organic Carbon and Rice Yields

The freezing winter temperatures in Northeast China hinder the breakdown speed of straw, making it challenging to implement widespread straw return in rice fields, meaning that crop remnants are not efficiently utilised. This study involved a pot experiment conducted on rice plants that were treated with varying quantities of biochar: CK (no biochar); BC1 (5 t ha−1); BC2 (10 t ha−1); and BC3 (20 t ha−1). An investigation was conducted to examine the impact of biochar on the soil organic carbon (SOC), humus (HS) composition, humic acid (HA) structure, and rice yield of paddy fields. The findings demonstrated that the use of biochar led to a substantial rise in SOC and HA-C concentrations in the soil layer between 20 and 40 cm. Additionally, biochar’s application enhanced soil humification. Notably, the treatment with BC3 (20 t ha−1) had the most pronounced impact. The O/C ratio in the HA and the relative strength of the peaks at 1620 cm−1 on the infrared spectra showed a more pronounced response to the BC3 treatment compared to the other biochar treatments. However, the application of the BC1 treatment at a rate of 5 t ha−1 and the BC2 treatment at a rate of 10 t ha−1 had a minimal impact on the fluorescence intensity of humic acid (HA). The application of the BC3 treatment increased the aromatic nature of the humic acid (HA) in paddy soil, leading to the formation of an intricate and enduring HA structure. Furthermore, the use of the BC3 treatment resulted in a notable enhancement in the quantity of spikes, spike weight, and number of grains per spike. Additionally, it positively impacted the accumulation of dry matter in the spike, leading to a substantial 13.7% increase in the rice yield. Applying biochar at a rate of 20 t ha−1 is a sensible and effective approach to enhance the soil organic carbon (SOC) content, enhance the stability of the humic acid (HA)’s structure, and raise the rice yield in the rice-growing area of Northeast China. This study’s findings will establish a theoretical foundation for utilising soil biochar in the rice fields located in Northeast China.

Biocrusts enhance soil organic carbon stability and regulate the fate of new-input carbon in semiarid desert ecosystems

Given their global prevalence, dryland (including hyperarid, arid, semiarid, and dry subhumid regions) ecosystems are critical for supporting soil organic carbon (SOC) stocks, with even small changes in such SOC pools affecting the global carbon (C) cycling. Biocrusts play an essential role in supporting C cycling in semiarid ecosystems. However, the influence of biocrusts and their successional stages on SOC and its fraction contents, as well as their role in regulating new input C into SOC fractions remain largely unknown. In this study, we collected continuous samples of bare soil (BS) and three successional stages of biocrust soils (cyanobacterial (CC), low-cover moss (LM), and high-cover moss (HM)) at 0–5 cm depth every month for one year in a semiarid desert ecosystem. We analyzed SOC changes among the samples and their fraction contents including: labile organic C (LOC) (composed of microbial biomass C (MBC), dissolved organic C (DOC), and easily oxidized organic C (EOC)) and recalcitrant organic C (ROC) fractions, soil nutrient content including: ammonium (NH4+-N), nitrate (NO3−-N), and available phosphorus (AP), and soil temperature and moisture. We also conducted a 13C pulse-labelling experiment in the field to accurately quantify the effects of biocrust successional stage on exogenous C allocation to SOC fractions. Our results showed that the three successional stages of biocrust (CC-LM-HM) increased SOC and ROC contents by an average of 5.3 ± 3.6 g kg−1 and 4.0 ± 3.0 g kg−1, respectively; and the MBC, DOC, and EOC contents increased by an average of 41.7 ± 24.8 mg kg−1, 28.7 ± 12.6 mg kg−1, and 1.2 ± 0.6 g kg−1, respectively, compared to that of BS. These increases were attributed to an increase in photosynthetic pigment content, higher nutrient levels, and more suitable microclimates (e.g., higher moisture and more moderate temperature) during biocrust succession. More importantly, SOC stability was greatly improved with biocrust succession from cyanobacteria to moss, as evidenced by the reduction in soil EOC:SOC and EOC:ROC ratios by an average of 50 ± 34 % and 99 ± 67 %, respectively, while the ROC:SOC ratio increased by 33 ± 16 % with biocrust succession compared to those of BS. The biocrust SOC, DOC, and MBC 13C contents at different stages were on average 0.096 ± 0.034 mg kg−1, 0.010 ± 0.005 mg kg−1, and 0.014 ± 0.005 mg kg−1 higher than those of BS. Similarly, the allocation of new-input C among the DOC and MBC at different biocrust stages (19 ± 10 %) was significantly higher than that of BS (9 ± 6 %). New-input C into the biocrusts was fixed by microbes (43 ± 18 %) within ∼10 days and converted into other forms of C (85 ± 5 %) after 80 days. Our study provides a new perspective on how biocrusts support C cycling in semiarid desert ecosystems by mediating new C inputs into diverse fractional contents, and highlights the significance of biocrust successional stages in maintaining soil C stocks and stability in the dryland soil system.

Enhancing Soil Aggregation and Organic Carbon Retention in Greenhouse Vegetable Production through Reductive Soil Disinfestation with Straw and Fertiliser: A Comprehensive Study

In greenhouse vegetable production, reductive soil disinfestation (RSD) effectively mitigates soil-borne diseases, yet its impact on the dynamics of soil organic carbon (SOC) has not been adequately examined. This study investigated the distribution of soil aggregates and the organic carbon retention mechanism following intensive RSD treatment. Greenhouse experiments, including control (CK), wheat straw (RSD), and wheat straw with chemical fertilizer (RSD + NP) treatments, indicated augmentation in the formation of macro-aggregates (&gt;2 mm and 0.25–2 mm) under RSD, particularly in the RSD + NP treatment. Silty clay particles transform into macro- and micro-aggregates. Fourier infrared spectroscopy highlighted the augmentation of carbon-containing functional groups in SOC, with aliphatic carbon accumulating in macro-aggregates and aromatic carbon in silt clay. Laboratory culture experiments employing different C/N ratios (RSD1 with wheat straw, RSD2 with kiwifruit branches) underscored the beneficial impact of low C/N ratio organic matter on coarse and fine macro-aggregate content, mean weight diameter, geometric mean diameter, and reduced silt clay. Low C/N ratios enhance SOC retention in large aggregates, while high ratios stabilise micro-aggregate carbon. This research underscores the severe degradation in continuous greenhouse cropping systems and emphasises RSD’s dual benefits—disease prevention and improved SOC retention. Implementing RSD requires careful consideration of organic material choices, specifically their C/N ratios, as a pivotal factor influencing SOC dynamics.

Maximizing soil organic carbon stocks through optimal ploughing and renewal strategies in (Ley) grassland

Grassland management effects on soil organic carbon storage under future climate are unknown. Here we examine the impact of ley grassland durations in crop rotations on soil organic carbon in temperate climate from 2005 to 2100, considering two IPCC scenarios, RCP4.5 and RCP8.5, with and without atmospheric CO2 enhancements. We used the DailyDayCent model and a long-term experiment to show that ley grasslands increase soil organic carbon storage by approximately 10 Mg ha−1 over 96 years compared with continuous cropping. Surprisingly, extending ley duration from 3 to 6 years does not enhance soil organic carbon. Furthermore, in comparison with non-renewed grasslands, those renewed every three years demonstrated a notable increase in soil organic carbon storage, by 0.3 Mg ha−1 yr−1. We concluded that management of ploughing and renewal intervals is crucial for maximizing soil organic carbon stocks, through balancing biomass carbon inputs during regrowth and carbon losses through soil respiration.