Increased Soil Organic Carbon Content Research Articles

Paddy straw biochar amended sediment enhances pond productivity, growth and physiological profile of Penaeus vannamei cultured in inland saline nursery ponds.

The growing interest in commercial Inland saline aquaculture has taken momentum across the globe due to the available technologies for aquaculture and the abundant resources of saline groundwater. However, the critical problems in inland saline ponds are degraded soil and imbalanced or deficient nutrients. To address these issues, a 75-day experiment was conducted to explore the effects of Paddy Straw Biochar (PSB) as a sediment amendment on sediment quality, water characteristics, growth parameters, and the well-being of Penaeus vannamei reared in inland saline environments. PSB was applied to the nursery ponds at 1 ton/hectare (Treatment, T1) and 2 ton/hectare (Treatment, T2). The findings of water quality parameters showed a significant increase in K+ and Mg++ with a decrease in ammonia-N levels in biochar-applied ponds. Similarly, the addition of biochar to ponds (T2) resulted in improved sediment characteristics with enhanced water holding capacity (24.75%), increased soil organic carbon content (77.94%), pH levels (0.37 units), cation exchange capacity (43.15%), available potassium (16.3%), and lower bulk density (12.61%) compared to ponds subjected to control conditions at the end of the experiment. Over the experiment, improvements in sediment and water quality parameters followed the T2 > T1 > control trend. Growth characteristics showed a significant rise in the percentage of weight gain (12.398 ± 0.12), SGR (11.80 ± 0.01% day-1) and PER (2.39 ± 0.01) with reduced FCR (1.19 ± 0.00) in biochar-treated ponds (T2), followed by T1 and control. The digestive enzyme activity (amylase) and metabolic enzymes like hepatopancreatic alanine aminotransferase (ALT) and muscle ALT activities were significantly higher in shrimps raised in the biochar-applied ponds. On the other hand, the oxidative stress enzyme superoxide dismutase (SOD) in gills, muscles, and hepatopancreas (HP) exhibited lower values, suggesting reduced oxidative stress due to the biochar amendment of the pond sediment. Overall, the study recommends incorporating PSB at a rate of 2 t/ha into nursery pond sediment to enhance water quality, physiological status, and the growth of P. vannamei juveniles. Moreover, this approach improves soil and water characteristics in saline soils, making it an effective culture practice in degraded environments.

Co-culture of rice and aquatic animals enhances soil organic carbon: A meta-analysis

Co-culture of rice (Oryza sativa) and aquatic animals (CRAAs) is an efficient eco-agricultural model and has been widely implemented in many Asia countries. However, its impact on soil organic carbon (SOC) content has not been synthesized and the relative effects of different CRAAs practices on SOC have not been assessed. Our meta-analysis aims to synthesize the effect of diverse CRAAs regimes on SOC content based on results from 200 field experiments. Our results showed that overall, CRAAs significantly increased SOC content by 11.6 % (P < 0.05). The highest relative effect on SOC content was found under the rice and amphibian coculture (P < 0.05). Also, CRAAs increased SOC content more significantly in temperate regions (19.1 %) than in subtropical (9.7 %) and tropical (12.1 %) regions (P < 0.05). In addition, CRAAs were more effective in enhancing SOC content in paddy soils with high nitrogen content (total nitrogen [TN] >1.2 g·N kg−1 soil) or alkaline soils. Further, SOC increased more in the CRAAs with japonica than indica rice, increasing 17.8 % and 6.1 % as compared to their respective rice-monoculture controls. Random forest analysis revealed that animal type was the most important factor influencing SOC under CRAAs. Together, these results indicate that CRAAs can significantly enhance SOC, particularly in low-N, alkaline paddy soils. Our findings suggest that CRAAs with appropriate rice and animal varieties can provide unique opportunities for soil C sequestration, while enhancing farmers' profitability.

Temporal and Spatial Variations of Soil Organic Carbon and the Influencing Factors in Shaanxi Province in Recent 30 Years

Soil organic carbon （SOC） variation is a significant indicator for the soil quality dynamic and global carbon cycle. Therefore, it is necessary to study the regional temporal and spatial distribution of SOC pool and the influencing factors. In this study, a total of 540 soil data and environmental variables were collected from Shaanxi Province during a 30-year period from 1985 to 2015, and univariate analysis of variance and path analysis were used to explore the temporal and spatial distribution characteristics of SOC content and the influencing factors of SOC change. The results showed that the SOC contents of Shaanxi Province in both 1985 and 2015 were the highest in central Shaanxi, followed by those in southern Shaanxi, and they were significantly higher than those in northern Shaanxi. From 1985 to 2015, the increase in SOC in southern Shaanxi was the highest （21.28%）, and that in central Shaanxi was 15.33%. The content of SOC in northern Shaanxi was decreased by 10.23%, caused by significant decrements in the bottom horizons of 60-80 cm and 80-100 cm. Compared with that in 1985, the increases in SOC content in the 0-100 cm soil profile （with every 20 cm as a horizon） ranged from 3.21% to 29.39% in 2015. The increase in SOC content of skeletal soils was largest, followed by that of alluvial soils. Correlation analysis and path analysis showed that SOC content was positively correlated with altitude, average annual precipitation, normalized vegetation index, and total nitrogen content and was in significant negative correlation with curvature, bulk density, and pH. Total nitrogen content was the main controlling factor affecting SOC content. The results of the study can provide reference for future carbon management measures in the region.

Soil health impact of long‐term sugarcane vinasse recycling

AbstractThe efficient use of vinasse, the primary byproduct of sugarcane ethanol production, is important for the economic and environmental sustainability of the industry. Few studies have quantified the soil health response to long‐term vinasse application, even though this byproduct is generally applied as a potassium (K) source in sugarcane fields. The Soil Management Assessment Framework (SMAF) was used to assess the integrated soil health response in soils with contrasting textures. Chemical, physical, and biological indicators were selected, measured, and integrated into a soil health index for clay‐ and sandy‐textured soils in Brazil. Overall, the application of vinasse improved soil health components in both soils. The results showed that the benefits of vinasse go beyond increasing the K content. Vinasse application showed increased soil organic carbon content, nutrient recycling, and soil physical quality. The long‐term application of vinasse increased the soil health from 49% to 62% in the clayey soil and from 43% to 61% in the sandy clay soil. The findings therefore revealed the potential of vinasse application to reduce the need for synthetic fertilizer and promote the circular economy and soil health regardless of soil type. This study verifies that the long‐term application of vinasse to sandy‐ and clay‐texture soils in Brazil has both economic and environmental benefits because it recycles an important ethanol byproduct and enhances soil health.

Accumulation of soil microbial necromass carbon and its contribution to soil organic carbon after vegetation restoration in the Tibetan Plateau

Vegetation restoration has been proved as an effective strategy to increase soil organic carbon (SOC) sequestration in degraded ecosystems. However, due to different vegetation restoration practices and climate zones, changes of SOC content, dynamics, sources and their controlling mechanisms after vegetation restoration remain inadequately addressed. Taking the advantage of four-year vegetation restoration, we explored the effects of vegetation restoration on SOC through its fractions, soil aggregates, soil enzymes and microbial necromass contribution to SOC in a desertification region in the Tibetan Plateau (TP). Results showed that vegetation restoration increased SOC contents by 68% for 0 – 10cm, 29% for 10 – 30cm and 11% for 30 – 50cm compared to site without vegetation restoration. Vegetation restoration increased soil macroaggregates (> 0.25mm) and decreased soil microaggregates (0.53 – 0.25mm), but increased their associated SOC contents. Meanwhile, vegetation restoration enhanced microbial necromass and its contribution to SOC. Structural equation model revealed that increasing microbial necromass carbon, changing soil aggregates and their associated SOC were the main mechanisms of increasing SOC content after vegetation restoration. Our result further indicated a large potential of SOC sequestration through vegetation restoration in the TP. These findings have important implications for natural based solution for carbon neutrality for China.

Enhancing Agroecology in Pepper (Piper nigrum L.) Cultivation with Centrosema pubescens Ground Cover: A Study from Central Bangka, Indonesia

&lt;p&gt;Pepper cultivation in Bangka Island primarily takes place on sandy land. Legume cover crops, such as &lt;em&gt;Centrosema pubescens&lt;/em&gt;, which has been widely used as a ground cover, are anticipated to improve land quality by maintaining soil temperature and humidity, increasing soil organic carbon content, increasing soil porosity, and improving soil fertility. This research aims to analyze the agroecosystem of pepper plants, by comparing the use of the cover plant &lt;em&gt;C. pubescens&lt;/em&gt; as a soil treatment and the absence of using these cover plants as a control. The research was conducted in farmers’ pepper gardens in Perlang Village, Central Bangka Regency, Bangka Belitung Province. The research employed a randomized block design, with &lt;em&gt;C. pubescens&lt;/em&gt; and natural vegetation as treatments, each replicated 3 times. The variables measured were soil temperature and humidity; abundance of microorganisms; weed density, frequency, and dominance; chlorophyll a, chlorophyll b, and anthocyanin content of pepper leaves; photosynthesis rate; transpiration rate; stomatal conductance; soil chemical and physical properties. The results showed that &lt;em&gt;C. pubescens&lt;/em&gt; as ground cover could reduce the dominance of the &lt;em&gt;Bidens pilosa&lt;/em&gt; weed (relative dominance of 36.16%) but led to an increase in the dominance of &lt;em&gt;Chromolaena odorata&lt;/em&gt; (relative dominance of 38.7%). &lt;em&gt;C&lt;/em&gt;.&lt;em&gt; pubescens&lt;/em&gt; ground cover could also maintain stable soil temperature and moisture, and increase P, K, Ca, and Mg soil content by 100%, 100%, 43.6%, and 48.3%, respectively. Furthermore, pepper plants grown with &lt;em&gt;C. pubescens&lt;/em&gt; exhibited 25%, 23.7%, and 16% higher chlorophyll a, total chlorophyll, and carotenoid content, respectively, compared to those grown without the cover crop.&lt;/p&gt;

Analyzing the Trade-Offs between Soil Health Enhancement, Carbon Sequestration, and Productivity in Central India’s Black Soil through Conservation Agriculture

The impact of conservation tillage (CST) practices on soil properties, carbon sequestration and yield sustainability over short, medium, and long durations remain insufficiently understood, especially in semiarid Central India. Therefore, our objective was to investigate the effects and optimal duration of CST adoption for enhancing soil properties, carbon sequestration, and sustainable yields. We conducted a study in farmers’ fields in the Akola district of Central India, where CST had been practised for 4 to 15 years, within a soybean + pigeon pea–chickpea cropping sequence. Our findings revealed significant (p &lt; 0.05) improvements in soil physical properties with short-term CST practices (4 to 6 years), alongside increasing availability of nitrogen and phosphorus, with longer durations of CST implementation (10 to 15 years). The lowest soil organic carbon (SOC) was observed in conventional tillage (CT_y), while all CST practices increased SOC content over CT_y, ranging from 22.2 to 38.4%. Further, experimental soil dominated passive C pools (Cfrac3 + Cfrac4). Consequently, long-term CST practices facilitated positive C sequestration rates, contrasting with negative or minimal sequestration observed in CT_y and short-term CST treatments. However, compared to CST, CT_y demonstrated higher soybean equivalent yields and comparable chickpea equivalent yields mainly due to delayed germinations induced by lower soil temperatures in CST plots. We conclude that integrating site-specific characteristics, management practices, and regional climate conditions into conservation agriculture frameworks maximizes efficacy and ensures sustainable productivity. These findings help optimize agricultural practices considering potential yield losses or minimal changes despite implementing CST.

Effects of Fertilization and Planting Modes on Soil Organic Carbon and Microbial Community Formation of Tree Seedlings.

Biochar and organic fertilizer can significantly increase soil organic carbon (SOC) and promote agricultural production, but it is still unclear how they affect forest SOC after. Here, low-quality plantation soil was subjected to four distinct fertilization treatments: (CK, without fertilization; BC, tea seed shell biochar alone; OF, tea meal organic fertilizer alone; BCF, tea seed shell biochar plus tea meal organic fertilizer). Cunninghamia lanceolata (Lamb.) Hook and Cyclobalanopsis glauca (Thunb.) Oersted seedlings were then planted in pots at the ratios of 2:0, 1:1, and 0:2 (SS, SQ, QQ) and grown for one year. The results showed that the BCF treatment had the best effect on promoting seedling growth and increasing SOC content. BCF changed soil pH and available nutrient content, resulting in the downregulation of certain oligotrophic groups (Acidobacteria and Basidiomycetes) and the upregulation of eutrophic groups (Ascomycota and Proteobacteria). Key bacterial groups, which were identified by Line Discriminant Analysis Effect Size analysis, were closely associated with microbial biomass carbon (MBC) and SOC. Pearson correlation analysis showed that bacterial community composition exhibited a positive correlation with SOC, MBC, available phosphorus, seedling biomass, and plant height, whereas fungal community composition was predominantly positively correlated with seedling underground biomass. It suggested that environmental differences arising from fertilization and planting patterns selectively promote microbial communities that contribute to organic carbon formation. In summary, the combination of biochar and organic fertilizers would enhance the improvement and adaptation of soil microbial communities, playing a crucial role in increasing forest soil organic carbon and promoting tree growth.

Carbon sequestration through conservation tillage in sandy soils of arid and semi-arid climates: A meta-analysis

This meta-analysis assessed soil organic carbon (SOC) percent changes in sandy soils, transitioning from conventional tillage (CT) to conservational tillage (CST) in arid and semi-arid climates. High levels of SOC in sandy soils are difficult to attain especially when precipitation levels are very low, contributing to low biomass production, and increased decomposition of organic matter. While CT practices are known to reduce SOC through the breakdown of soil aggregates, accelerated decomposition of soil organic matter, and promote erosion, CST methods (i.e., mulch tillage, no tillage, reduced tillage, ridge tillage, etc.) offer the potential to preserve soil aggregates and increase SOC concentration. Analyzing 55 peer-reviewed publications in arid and semi-arid climates with ≥ 45 % sand content, this study compared SOC content between CST and CT over short- and long-term periods (349 paired observations). Results showed that CST increased SOC in sandy soils, with an estimated 12.74 ± 1.46 % increase. Specifically, reduced tillage (RdT), mulch tillage (MchT), and no tillage (NT) exhibited the highest increases of SOC by 18.94 ± 2.48 %, 11.45 ± 2.46 %, and 10.06 ± 2.46 %, respectively, compared to CT. Studies with durations of up to 15 years (n = 297) showed a progressive increase in SOC concentrations under CST; however, the long-term stability of the accrued carbon content in sandy soils of arid and semi-arid climates is still uncertain, as studies extending beyond 15 years (n = 52) did not demonstrate significant changes in SOC levels. CST significantly raised SOC concentrations in precipitation up to 600 mm, though no significant changes were observed for precipitation over 600 mm. In soils with over 56 % sand content, CST increased SOC by approximately 13 %. This study highlights both positive and limited impacts of CST practices for soil conservation and climate change mitigation, emphasizing their significance for both existing agricultural areas in arid regions and those in parts of the world where aridity is on the rise.

Chestnut soil organic carbon is regulated through pore morphology and micropores during the seasonal freeze–thaw process

Soil aggregates are basic structural units in soil organic carbon (SOC) protection. In alpine ecosystems, the seasonal freeze–thaw (FT) process characterizes soil formation and nutrient cycling. However, previous studies were mostly based on simulated FT experiments, which amplified the effects of natural FT processes. And, the regulations of pore structure on SOC protection/loss of aggregates during the FT processes were still not well understood. To investigate the effect of the seasonal FT process on SOC and pore structure of aggregates, as well as the interactions among them, soil samples were selected during a whole seasonal FT cycle, which can be divided into four periods: unstable freezing (UFP), stable frozen (SFP), unstable thawing (UTP), and stable thawed periods (STP). The results demonstrated that freezing increased SOC concentration as the total organic carbon (TOC) content of all aggregate fractions peaked in the SFP (17.46 g/kg on average). The TOC content of aggregates in the UFP dropped to 7.91 g/kg on average, which revealed a dramatic SOC loss after thawing began. Thawing also decreased the proportions of particulate organic carbon (POC) compared with mineral-associated organic carbon (MAOC). The highest microbial abundance was also found in the SFP. Freezing promoted the formation of pores > 80 μm while thawing increased the regularity of pore morphology. Pore structure explained 48.77 % of the SOC variance in the thawing period, but only 19.29 % of that in the freezing period. Overall, in the freezing process, soil pore structure impacted the SOC input by mediating pore morphology. In the thawing process, soil pore structure inhibited SOC loss by enhancing the formation of pores < 15 μm. These results demonstrate new perspectives on the soil aggregate microstructure–microbe–SOC interactions.

Molecular-level insight into the effect of fertilization regimes on the chemodiversity of dissolved organic matter in tropical cropland

Fertilization is a critical agronomic measure for croplands in tropical regions, owing to their low fertility. However, the effects of fertilization on the quantity and chemodiversity of latosolic dissolved organic matter (DOM) in tropical regions remain largely unknown. Therefore, in this study, the variations in latosol DOM concentrations and chemodiversity induced by inorganic fertilization and the co-application of inorganic fertilization with straw return, sheep manure, biochar, and vermicompost fertilizers at a molecular level were systematically investigated using multispectral techniques and ultrahigh-resolution mass spectrometry. In line with our expectations, the results showed that combined inorganic-organic fertilization improved soil quality by increasing soil organic carbon content compared to that under inorganic fertilization. However, as the most active and bioavailable organic carbon pool, dissolved organic carbonconcentrations between the fertilization treatments were not significantly different (p = 0.07). However, the dissolved organic carbon concentrations under combined inorganic-organic fertilization treatment (NPK plus straw return, 263.45 ± 37.51 mg/kg) were lower than those under inorganic fertilization treatment (282.10 ± 18.57 mg/kg). Spectral analysis showed that the DOM in the combined inorganic-organic fertilization treatments had a higher degree of humification and lower autogenetic contributions. Furthermore, Fourier transform ion cyclotron resonance mass spectrometry analysis indicated that the combined inorganic-organic fertilization increased the chemodiversity of latosolic DOM and promoted the production of large, oxidized, and stable molecules, including lignin, aromatic, and tannin compounds, which potentially benefits soil carbon sequestration in tropical regions. This study could provide a theoretical basis for elucidating on the potentially relevant ecological functions and environmental effects of DOM under fertilization regimes.

Effects of Different Straw Return Methods on the Soil Structure, Organic Carbon Content and Maize Yield of Black Soil Farmland

Straw return is an effective measure to increase soil sustainability. However, few studies have examined the effects of different straw return methods on soil structure, soil organic carbon content and maize yield or the potential relationships between those variables. Therefore, we developed a field orientation experiment to study the effects of different straw return methods on soil porosity, soil aggregate stability, the soil organic carbon content and maize yield. Four treatments were established: flat no-tillage with full straw mulching (FM), ridge no-tillage with full straw mulching (LM), rotary tillage with full straw incorporation (LX), and conventional tillage without straw (CK) as the control treatment. Compared with those of the CK treatment, the soil porosities (f) in the FM, LM and LX treatments significantly increased by 6.7%, 8.8% and 7.9%, respectively; the soil aggregate destruction rates (PAD) decreased by 17.3%, 34.3% and 16.9%, respectively. In addition, the FM, LM and LX treatments effectively increased the mean mass diameters (MWDs) of the soil aggregates and the soil organic carbon content. Compared with those in the CK treatment, the three-year average yields in the FM, LM and LX treatments significantly increased by 5.2%, 7.2% and 4.1%, respectively. Moreover, the f, MWD, soil organic carbon content and corn yield were positively correlated. Our study indicates that the LM treatment was most effective in improving soil structure and increasing soil organic carbon content with corn yield.

The long-term nitrogen fertilizer management strategy based on straw return can improve the productivity of wheat-maize rotation system and reduce carbon emissions by increasing soil carbon and nitrogen sequestration

ProblemFacing the multiple objectives of increasing production, carbon sequestration, and nitrogen reduction in farmland, optimizing straw and nitrogen fertilizer management to achieve a balance between grain production and ecological safety in the wheat-maize rotation system has become increasingly critical and urgent. MethodsThis study conducted a five-year field experiment in the Guanzhong Plain of China from 2017 to 2021 to investigate the effects and synergistic regulatory mechanisms of straw disposal methods (straw return, no-straw return) and nitrogen application rates (0, 150, 225, 300 kg ha−1) during the maize season on soil greenhouse gas (GHG) emissions, crop yield, and soil organic carbon (SOC) and soil toatl nitrogen (STN) content. ResultsThe results showed that under the scenario of no-straw return, fertilization increased soil nitrous oxide (N2O) emissions by 35.9–64.0 %, and annual total crop yield by 16.4–22.8 %; however, under the straw return scenario, the increase in soil N2O emissions due to fertilization decreased to 26.7–62.0 %, while the yield increase rose to 19.5–25.9 %. The interaction effect between straw return and nitrogen application was significant, with straw return boosting the contribution rate of nitrogen application to yield (2.2–4.4 %) and simultaneously reducing the contribution rate of nitrogen application to N2O emissions (3.0–27.5 %). The study also indicated that the yield-increasing effect of straw return continued to increase with the duration of straw return, with the contribution rate to yield reaching 9.9 % after three years of continuous straw return, while the contribution rate of nitrogen application to yield increased by an average of 3.0 % per year. This suggests that there is significant potential for coupling straw return with reduced nitrogen application. Straw return combined with nitrogen fertilizer increased SOC content by 7.9–40.1 % and 3.7–12.5 %, STN content by 1.0–22.8 % and 6.1–13.9 %, respectively, compared to sole nitrogen application and sole straw return. Pathway analysis indicated that straw return combined with nitrogen fertilizer mainly enhanced soil carbon-nitrogen sequestration, improved fertilizer utilization efficiency and crop nutrition levels, reduced net global warming potential (GWP) and greenhouse gas intensity (GHGI), and synergistically regulated to increase yield while reducing GHG emissions. ConclusionThe study highlights that straw return lowers the threshold for nitrogen application levels, suggesting that regulating nitrogen application levels between 224 and 256 kg ha−1 during the maize season, and maintaining a nitrogen application level of 195 kg ha−1 during the wheat season, is beneficial for long-term stable production and emission reduction in the wheat-maize rotation system farmland.

Cover crops and deep‐soil C accumulation: What does research show after 10 years?

AbstractThe extent to which cover crops (CCs) accumulate soil organic carbon (SOC) in the entire soil profile is still unclear. We measured SOC, permanganate oxidizable C (POX‐C), and particulate organic matter (POM) concentrations down to 60‐cm soil depth in early [2–3 week before corn (Zea mays L.) planting]‐ and late‐terminated (at corn planting) winter rye (Secale cereale L.) CCs in rainfed and irrigated no‐till continuous corn systems in the U.S. Corn Belt after 10 years. CCs increased SOC stock and SOC, POX‐C, and POM concentrations but only in the irrigated system in the upper 5‐cm depth. Late‐terminated CC increased SOC concentration by 4.710 ± 3.501 g kg−1 and accumulated SOC at 0.207 ± 0.145 Mg C ha−1 year−1. It increased POX‐C and POM concentrations, on average, by 1.194 times. CCs likely increased SOC in the irrigated system by producing more biomass (2.247 ± 0.370 Mg ha−1) than in the rainfed system (0.949 ± 0.338 Mg ha−1). At least 2 Mg ha−1 of CC biomass may be needed to increase SOC. Because winter CCs often produce &lt;1 Mg ha−1 of biomass when typically planted late and terminated early, extending the CC growing window by terminating CCs at or after crop planting (planting green) may boost CC biomass and SOC accumulation, although high‐C soils or Mollisols, such as our study soils (&gt;22 g C kg−1), may limit SOC gains. We submit CCs would sequester more SOC in low‐C, eroded, and low‐fertility soils. Overall, winter rye CCs minimally alter soil C in the soil profile in no‐till continuous corn systems after 10 years.

Mixed Eucalyptus plantations enhance soil organic carbon accumulation and chemical stability through soil microbial community and multifunctionality

Forest conversion can impact soil organic carbon (SOC) fixation and ecosystem functions. The newly proposed “evenness of SOC chemical components” index can indicate the permanence of stored SOC during environmental disturbances. However, how the mixing of tree species impacts SOC accumulation and persistence and changes in soil microbial communities and multifunctionality remain unknown. Thus, we conducted a field experiment (11 years) of monospecific Eucalyptus urophylla × E. grandis plantation for evaluating the influences of the mixed planting of a non-nitrogen (N)-fixing tree, Castanopsis hystrix, and an N-fixing tree, Dalbergia odorifera, on SOC accumulation and chemical stability. Compared with pure plantations, mixed Eucalyptus plantations (particularly those mixed with D. odorifera) exhibited significantly increased SOC concentrations by 28.60–33.71 % and increased SOC chemical component evenness by 3.96–4.67 % (P < 0.05). We also found that the concentrations and chemical component evenness of SOC were strongly linked with litter quality, soil N, phosphorus and their availability, multifunctionality, microbial activity, carbon use efficiency (CUE), biomass, diversity, and network complexity. Furthermore, tree species mixing increased litter quality, soil nutrient availability, microbial biomass, activity, diversity, CUE, and network complexity. Soil microbial anabolism, community characteristics and multifunctionality influenced the SOC concentrations and SOC chemical components evenness. Specifically, microbial diversity enhanced the concentrations and chemical component evenness of SOC by increasing network complexity and soil multifunctionality. These findings revealed differential responses and mechanistic controls of SOC accumulation and chemical stability in different Eucalyptus planting patterns. Overall, mixed plantations, particularly those in which N-fixing species were introduced, effectively improved SOC accumulation and stabilization by positively altering soil quality and microbial properties, potentially representing a sustainable forestry management strategy to improve soil C benefits and multifunctionality in forest ecosystems.

How nitrate and ammonium impact soil organic carbon transformation with reference to aggregate size

While nitrogen (N) deposition and over-fertilization enrich N in soil, it is unclear how it impacts soil organic carbon (SOC) transformation at the aggregate scale. Herein, a 90-day study reveals the transformation mechanisms of SOC in soil aggregates under nitrate and ammonium enrichment conditions. Results showed that nitrate treatment (NT) and ammonium treatment (AT) significantly increased SOC content by 15.6 % and 18.9 %, respectively. In addition, NT increased SOC accrual in large macro-aggregates (LMA), while AT increased SOC accrual in small macro-aggregates (SMA) and micro-aggregates (MA). Further analysis of pyrolysis products showed that N enrichment drove the transformation of labile soil organic matter (SOM) composition into recalcitrant SOM, with polysaccharides declining from 19–30 % to 2–13 %, while lipids rose from 18–27 % to 33–45 %. LMA and SMA contained more aromatic compounds than MA. This is linked to the inhibition of the expression of C degradation function genes, while almost all genes encoding SOC degradation are down-regulated under N enrichment. In the meantime, NT increased the abundance of genes encoding the degradation of N-containing compounds in LMA. Moreover, NO3− enrichment exerted a higher inhibitory effect on labile SOC degradation while NH4+ enrichment substantially inhibited recalcitrant SOC. Finally, Random Forest analysis confirmed that N enrichment elevated the importance of N-containing compounds' metabolism, which diminished when the size of soil aggregates decreased. In contrast, the importance of genes encoding saccharides and cellulose metabolism increased in smaller aggregates. This study highlights that both N type and aggregate size were determining factors in shaping SOC transformation in the N enrichment process.

Alfalfa-livestock system promotes the accumulation of soil organic carbon in a semi-arid marginal land

Developing cropland in marginal lands presents a potential solution to address food security challenges. However, the low organic carbon (C) content in these soils severely constrains crop productivity, and developing cropland aggravates the loss of soil organic carbon (SOC). Therefore, it is essential to elevate the SOC content via a profitable solution for food production. In this study, we examine the impacts of land use changes (fallow, cropland, and Alfalfa-livestock system [AL]) over 12 years on SOC content, composition, and mineralization rate in a semiarid marginal land. SOC was categorized into three components: plant necromass C, microbial necromass C, and "other C." We utilized lignin and amino sugars as biomarkers to assess plant and microbial necromass C content, respectively, and the remaining component was other C. We found that AL increased SOC contents in 0–15 cm by 142 % and 123 % compared to fallow and cropland. Other C was the main factor driving SOC accumulation in AL compared to fallow and cropland, which contributed 2 times more than microbial necromass C (63 % VS 31 %), while plant necromass contributed less than 7 %. Furthermore, AL decreased C mineralization per unit of SOC than fallow and cropland due to increased soil available N contents. In conclusion, AL facilitated a rapid increase in SOC contents on marginal lands by fostering the accumulation of microbial necromass C and other C while inhibiting SOC mineralization. This finding helps improve the productivity and sustainability of marginal croplands.

A comparative analysis of soil organic carbon stock and soil aggregation in two crop sequences in the Rolling Pampa (Argentina)

Understanding how farming practices affect soil organic carbon (SOC) accumulation is essential for sustainable agriculture. Agronomic decisions, such as crop sequence, significantly influence various soil properties. However, the overall benefits of crop rotation on soil structure and SOC storage remain uncertain. We compared the effects of soybean (Glycine max L.) monocropping with a three-year crop rotation comprising wheat (Triticum aestivum L.)/soybean double crop, maize (Zea mays L.), and soybean on the vertical distribution of SOC up to one metre depth. Additionally, we examined carbon accumulation as particulate organic matter-carbon (POM-C), soil aggregation, and structural stability in the topsoil. Compared to monocropping, crop rotation increased SOC concentrations (19 vs. 16 gC kg soil⁻¹), stock (12 vs. 10.7 MgC ha⁻¹), and POM-C content (6 vs. 3.2 gC kg soil⁻¹) in the first 5 cm of soil. At 20–65 cm depth, rotation showed a marginal increment of SOC stock with respect to soybean monocropping. The increased surface SOC content in the rotation positively affected the POM-C content and macro-aggregation. However, soil structural stability showed a tendency to be higher in the monocropping, especially at a depth of 5–20 cm. Overall, crop rotation demonstrated potential for enhanced carbon sequestration in temperate agroecosystems within three years, despite not significantly improving soil structural stability.

The regulation pathways of biochar and microorganism in soil-plant system by multiple statistical methods: The forms of carbon participation in coastal wetlands

Coastal wetlands possess significant carbon storage capabilities. However, in coastal soil-plant systems augmented with biochar and microorganisms, the mechanisms of these amendments and carbon participation remain unclear. This study utilized pot experiments to explore how Enteromorpha prolifera biochar and Arbuscular mycorrhizal fungi (AMF) affect soil organic carbon (SOC), carbon-related microbes, photosynthetic and osmotic system of Suaeda salsa. The results showed biochar reduced exchangeable sodium percentage by 6.9% through adsorption and ion exchange, and increased SOC content by 34.4%. The abundance of carbon-related microorganisms (Bacteroidota and Chloroflexi) was increased and carbon metabolizing enzyme (cellulase and sucrase) activity in the soil was enhanced. AMF significantly improved plant growth compared with CK, as evidenced by the enhanced dry weight by 2.34 times. A partial least squares pathway model (PLS-PM) and correlation analysis suggested that the combined effect of biochar and AMF could be outlined as two pathways: soil and plant. Biochar increased SOC, improved the growth of soil carbon metabolizing microorganisms, and further promoted the activity of carbon-related enzymes. Additionally, AMF facilitated nutrient absorption by plants through root symbiosis, with biochar further enhancing this process by acting as a nutrient adsorber. These combined effects of biochar and AMF at soil and plant level enhanced the photosynthetic process of Suaeda salsa. The transport of photosynthetic products to the roots can increase the carbon storage in the soil. This study provides quantitative evidence supporting the increase of carbon storage in coastal wetland soil-plant systems through a combined application of biochar and AMF.

Root Influences Rhizosphere Hydraulic Properties through Soil Organic Carbon and Microbial Activity.

Processes of water retention and movement and the hydraulic conductivity are altered in the rhizosphere. The aim of this study was to investigate the physical-hydric properties of soil aggregates in the rhizosphere of annual ryegrass (Lolium multiflorum) cropped in a Kandiudalfic Eutrudox, taking into account aspects related to soil aggregate stability. Soil aggregates from rhizosphere soil (RZS) and soil between plant rows (SBP) were used to determine soil water retention curves (SWRCs) and saturated hydraulic conductivity (Ksat). In addition, properties related to soil aggregate stability, such as water-dispersible clay, soil organic carbon (SOC), and microbial activity, were also assessed. The higher microbial activity observed in the RZS was facilitated by increased SOC and microbial activity, resulting in improved soil aggregation (less water-dispersible clay). For nearly all measured matric potentials, RZS had a higher water content than SBP. This was attributed to the stability of aggregates, increase in SOC content, and the root exudates, which improved soil water retention. The increase in total porosity in RZS was associated with improved soil aggregation, which prevents deterioration of the soil pore space and results in higher Ksat and hydraulic conductivity as a function of the effective relative saturation in RZS compared to SBP.