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Soil organic carbon (SOC) accumulation is easily susceptible to tillage managements, which strongly affect soil structure and microbial community structure. Subsoiling is developed for mitigating soil compaction and thus improving soil structure. Coupled with straw residue incorporation, it is expected not only to enhance this improvement but also to promote organic carbon (C) storage in soil. However, how subsoiling tillage managements change soil aggregate microstructure, microbial community structure and SOC fractions, and how soil aggregate microstructure and microbial community structure affect SOC in the topsoil and subsoil layers are equally unknown. An in-situ incubation field experiment was conducted in a Mollisol in northeastern China and included conventional tillage (CT), subsoiling tillage (ST) and subsoiling tillage with straw residue incorporation (ST + S). The methods of synchrotron-based X-ray micro-computed tomography scanning, phospholipid fatty acid and SOC density fractionation were used to analyze aggregate pore characteristics, microbial community structure and SOC fractions, respectively. The results showed that both ST and especially ST + S not only improved soil aggregate microstructure but also enhanced microbial biomass and then favored SOC accrual in the topsoil (0–20 cm). In the subsoil (20–35 cm), ST + S exerted similar positive effects as those in the topsoil. However, ST only improved soil aggregate microstructure but decreased microbial community biomass and SOC in the subsoil. Moreover, soil aggregate structure characteristics explained (solely explained 6 % in the topsoil and 12 % in the subsoil, respectively) a smaller part of the variation in SOC within aggregates than soil microbial characteristics did (solely explained 15 % in the topsoil and 25 % in the subsoil, respectively). Specifically, bacteria explained 26 % and 66 % of the variation in SOC within aggregates in the topsoil and subsoil, respectively. The porosity of macropores (>100 μm) also explained 25 % of the variation in SOC within aggregates in the topsoil, whereas the porosity of micropores (

Medical tools and implants used in clinics can be contaminated with bacteria even with disinfection treatment. To avert this situation, titanium (Ti) plates modified with a MoS2(S)–Ag3PO4 coating were designed to kill Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) effectively under near-infrared (NIR) light irradiation. The introduction of Ag3PO4 nanoparticles (NPs) reduced the bandgap of MoS2 and suppressed the recombination of the photogenerated electron–hole pairs. Therefore, Ti–MoS2(S)–Ag3PO4 exhibited a higher photocatalytic performance, leading to the generation of more radical oxygen species (ROS). Furthermore, cooperating with the good photothermal performance of MoS2, the MoS2(S)–Ag3PO4 coating exhibited a high antibacterial efficacy of 99.76 ± 0.15% and 99.85 ± 0.09% against S. aureus and E. coli, respectively, for 15 min in vitro. Moreover, the MoS2(S)–Ag3PO4 coating had no apparent toxicity to cells. The proposed strategy may provide new insights for rapidly eradicating bacteria on medical tools and superficial implants.

The Mollisol region of Northeast China has a large soil organic carbon (SOC) storage which is important for maintaining soil fertility. SOC is susceptible to various environmental factors; however, the responses of SOC content to environmental factors in different soil layers of cropland remain unclear, particularly in deep soil layers. In this study, we collected 138 soil samples from the surface, subsurface, and subsoil layers among 46 sample sites with monocropping maize and intensive conventional tillage in this region. We assessed the relative importance and effect paths of 12 environmental factors (including geography, climate, and soil properties) on SOC content in different layers using redundancy analysis (RDA), structural equation model (SEM), and variation partitioning analysis (VPA). The VPA results showed that SOC content was mainly affected by climatic factors that explained 68% and 57% for the surface and subsurface layers, respectively. However, SOC content in the subsoil layer was greatly affected by soil properties that explained 27%. Furthermore, the SEMs results suggested that geographical factors indirectly affected SOC content by influencing the climatic factors. Mean annual temperature was the most important factor affecting SOC content directly or indirectly, and its negative effects significantly diminished with soil depth, as it explained 63%, 52%, and 17% of the variation in SOC content for the surface, subsurface and subsoil layers, respectively. In addition, the effects of soil water-holding capacity on SOC content also decreased with soil depth, whereas pH and clay content showed a contrasting pattern. This implies that pH and clay content play important roles in the sequestration of SOC in deep soil layers. Moreover, the organic C content within >53 μm aggregates was more sensitive to environmental factors. This study can be useful for forecasting SOC dynamics and establishing reasonable C management strategies under climate change conditions.

Clay-humic substance complexes play a major role in controlling the mobility of elements and colloids in natural soils. The purpose of the present study is to explore the different reaction mechanisms induced by cations on the humic acid (HA) and montmorillonite (Mt) heteroaggregation and to analyze the binding mechanism of HA-Mt. HA is extracted from soil and colloidal Mt are prepared as K+-saturated. The aggregation kinetics of HA-Mt composite nanoparticles in Ca(NO3)2, Mg(NO3)2, and Cu(NO3)2 solutions were detected by dynamic light scattering. Furthermore, FT-IR spectroscopy was used to characterize the reactive sites involved in interaction with the metal ions. The results revealed that the order of reaction of these three metal cations with the HA-Mt composite was Cu2+ > Ca2+ > Mg2+, as evident from the total average aggregation rate, critical coagulation concentration, and activation energy. The heteroaggregation process was sensitive to the 1% mass percentage of HA; however, more HA (4% mass percentage) did not significantly affect this process compared with 1% HA. Higher cation concentration and higher HA content (10% mass percentage) were two necessary conditions for promoting HA-Mt heteroaggregation. The vibration peak intensities of the carboxyl group C-O bonds and hydroxyl group O-H bonds of HA were affected by the formation of coordinate bonds with different metal ions. Metal cations were preferentially complexed by the carboxyl groups of HA, and due to its polarization-induced and electric field–enhanced oxidizing properties, Cu2+ has the strongest aggregation ability for HA-Mt, followed by Ca2+ and Mg2+. The HA-Mt heteroaggregation is partially reversible by adjusting electrostatic repulsion. The results of this study improve our understanding of the roles of cations and HA in clay-humic substance interactions.

The distribution and dynamic of residue-derived carbon after incorporation into soil at different fertility levels have been well documented. However, the distribution of maize residue–derived C in particulate organic C (POC) from different types of organic residues in soils of different fertility levels is poorly understood. A 540-day in situ field experiment was carried out. In 2016, three types of 13C-labeled maize residues (root, stem, leaf) were added to brown earth of different fertility levels in Northeast China. 13C-POC content in the soil samples was measured on the 60th, 90th, 180th, and 540th days after in situ incubation. The results showed that 13C-POC content was significantly higher in high-fertility soil than in low-fertility soil during the whole incubation time. There were significant differences among different types of maize residues at the beginning of 180 days, with stem (0.13 g kg−1) and root (0.11 g kg−1) residues higher than leaf residue (0.08 g kg−1), and sequestration of residue in POC was similar between the roots, stems, and leaves after the 540-day field incubation. The mean residence time and residue POC in soils at each fertility level increased (P

Subsoil has great potential for increasing soil organic carbon (SOC) stock. Soil compaction decreases the content of SOC in the topsoil layer and leads to the formation of a plow pan in subsoil. However, measures for improving poor soil structure mainly concentrate on topsoil. This study aims to understand the effect of subsoiling management practices on soil aggregation and accumulation of SOC in both topsoil (0–20 cm) and subsoil (20–35 cm). A field experiment was carried out in a Mollisol in northeastern China. The treatments included conventional tillage (CT), subsoiling tillage (ST), and subsoiling with residue incorporation tillage (SST). The results showed that in comparison to CT, ST and SST not only had lower subsoil bulk densities (reduced by 9.42% and 13.61%, respectively) but also promoted the formation of macroaggregates (> 250 μm) in both soil layers; thus, soil structure stability increased. In the topsoil layer, the content of the > 53 μm aggregate-associated carbon (C) under ST and SST was greater than that under CT. In the subsoil layer, compared with CT, SST increased the organic C content (increased by 0.73–12.32%) in all the aggregate classes, but ST decreased the content of the

Mollisols are the most fertile, high-yielding soils in the world. During the past several decades, Mollisols have lost about 50% of their antecedent organic carbon (C) pool due to soil erosion, degradation, and other unsuitable human activities. Therefore, restoring soil organic C (SOC) to Mollisols via reasonable management is crucial to sustainable development and is important for environmental stability. However, the existing literature on SOC and soil quality has focused on one soil type or on a given region where Mollisols occur, and the degree of SOC depletion and stabilization in Mollisols have not been comprehensively evaluated. Overall, we propose to develop an optimum scheme for managing Mollisols, and we outline specific issues concerning SOC restoration and prevention of SOC depletion. In this review, we identify the uncertainties involved in analyses of SOC in Mollisols as related to management practices. According to the existing literature on SOC in Mollisols at the global scale, we analyzed the results of SOC depletion research to assess management practices and to estimate the C amount stabilized in Mollisols. The review shows that the SOC stocks in Mollisols in North America under cropped systems had 51 ± 4 (equiv. mass) Mg ha−1 in the top 30 cm soil layer. The SOC contents in Northeast China decreased from 52 to 24 g kg−1 (46%) after 150 years of cultivation management. All of the Mollisols regions in the world are facing the challenge of SOC loss, and this trend could have a negative influence on global climate change. Hence, it is very important to take proper measures to maintain and enhance organic C contents in Mollisols. We concluded that reasonable management practices, including no-tillage, manure and compost fertilization, crop straw returning, and mulching cultivation, are the recommended technologies. The C restoration in Mollisols is a truly win-win strategy for ensuring the security of food and soil resources while effectively mitigating global climate change. Thus, more attention should be given to protective management and land use for its impacts on SOC dynamics and soil properties in Mollisols regions.

The variable role and fate of soil colloids under different environmental conditions are derived from their dispersion and aggregation properties. In this work, dynamic and static light scattering were used to characterize the original size, aggregation kinetics of natural black soil colloids (BSCs) and structural features of aggregates in electrolytes with different cations (K+, Mg2+, Ca2+), respectively. For these three cations, the aggregation kinetics followed the trend of Ca2+ > Mg2+ > K+ and the critical coagulation concentration (CCC) followed the sequence: K+ (134.30 mmol L−1) > Mg2+ (13.27 mmol L−1) > Ca2+ (4.19 mmol L−1). The results indicated that the aggregation behavior in different valence cation systems followed the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) model qualitatively. However, the quantitative differences of CCC suggest the existence of ion-specific effects. The effective ionic charge coefficient 1.31, 2.20, and 2.78 of K+, Mg2+ and Ca2+ were proposed to consider of all the non-DLVO factors, which were obtained by forming a relationship based on mathematic between the electrostatic repulsion and the van der Waals attractive interaction at the CCC. The non-classical polarization of cations in a strong soil electric field is a primary mechanism of cation effects on soil colloid interactions, causing the difference in colloid interaction energy and further affecting soil colloid aggregation. This result is crucial for enriching the theory of charged colloidal interactions.

Straw incorporation is an effective measure for increasing soil organic carbon (SOC) thereby improving soil quality and crop productivity. However, quantitative assessments of the transformation and distribution of exogenous carbon (C) in soil aggregates under various field fertilization practices have been lacking. In this study, we collected topsoil samples (0–20 cm) from three fertilization treatments (no fertilization control, CK; inorganic fertilizer, IF; inorganic fertilizer plus manure, IFM) at a 29-year long-term Mollisol experiment in Northeast China. We then mixed the soil samples with 13C-labeled maize straw (δ13C = 246.9‰), referred as CKS, IFS, and IFMS, and incubated them in-situ for 360 days. Initial and incubated soil samples were separated into four aggregate fractions (> 2, 1–2, 0.25–1, and −1) prior to incubation, followed by > 2 mm aggregates (2.2–5.8 g kg−1), 1–2 mm aggregates (2.4–4.6 g kg−1), and −1). After 360-day incubation with straw incorporation, organic C content was 2.3–4.5 g kg−1, 2.9–5.0 g kg−1, 7.2–11 g kg−1 and 1.8–3.0 g kg−1 in > 2, 1–2, 0.25–1, and −1, 0.03–0.04 g kg−1, 0.11–0.13 g kg−1, and 0.05–0.10 g kg−1 in > 2, 1–2, 0.25–1, and 2 mm aggregates (9.4–16%). During the incubation, the relative distribution of straw-derived C exhibited a decrease in > 2 mm and 1–2 mm aggregates, but an increase in the

Owing to the existence of the outer membrane barrier, most antibacterial agents cannot penetrate Gram-negative bacteria and are ineffective. Here, we report a general method for narrow-spectrum antibacterial Garcinia nanoparticles that can only be effective to kill Gram-positive bacteria, to effectively eliminate Gram-negative bacteria by creating transient nanopores in bacterial outer membrane to induce drug entry under microwaves assistance. In vitro, under 15 min of microwaves irradiation, the antibacterial efficiency of Garcinia nanoparticles against Escherichia coli can be enhanced from 6.73% to 99.48%. In vivo, MV-assisted GNs can effectively cure mice with bacterial pneumonia. The combination of molecular dynamics simulation and experimental results reveal that the robust anti-E. coli effectiveness of Garcinia nanoparticles is attributed to the synergy of Garcinia nanoparticles and microwaves. This work presents a strategy for effectively treating both Gram-negative and Gram-positive bacteria co-infected pneumonia using herbal medicine nanoparticles with MV assistance as an exogenous antibacterial auxiliary.

The addition of maize residue nitrogen (N) to the soil strongly influences soil N accumulations, but the specific contributions of maize residue N to soil aggregates based on long-term fertilization remain largely unknown. This study involved a 360-day laboratory incubation experiment to determine the dynamics of N derived from maize straw in Mollisol soil aggregates applying different long-term fertilization treatments. In 2015, three soil samples from different fertilizers treatments were collected from the upper layer of soil (0–20 cm) of the field at a long-term Mollisol (Luvic Phaeozem) experimental site established in 1980 in Gongzhuling, Jilin Province, China. The fertilizer treatments included no fertilizer (CK); a combination of nitrogen, phosphorous and potassium fertilizers (NPK); and NPK combined with manure (MNPK). Three treatments of soils were incubated for 360 days at 25 °C, with or without 15N-labeled maize straw and destructively collected on days 45, 90, 135, 180 and 360. Soil samplings were separated into two aggregate fractions (macroaggregates, ≥ 0.25 mm; microaggregates, NPK > CK after 360 days of incubation. The results revealed that the combined application of chemical fertilizer and organic manure had higher capacity to retain maize straw–derived N, and more of it was retained in macroaggregates in the beginning. The addition of straw residue accelerated the formation of macroaggregates in the soils with lower C/N ratios.

Soil aggregates play a crucial role in the sequestration of soil organic carbon (SOC). Returning crop residues to soil is known to strongly influence soil C stocks, but the specific contribution of crop residues to soil aggregates influenced by long-term fertilization remains largely unknown. This study investigated the effects of long-term fertilization on the distribution of 13C-labeled maize straw residue in different aggregate size fractions and their retention in soils over a 1-year incubation. The dynamic variation and the distribution of maize straw-derived 13C in soil aggregates were monitored using a 13C stable isotope mass-balance approach. The following three fertilization treatments were selected: (1) without fertilization (CK), (2) mineral fertilizer (NPK), and (3) cow manure with mineral fertilizer (NPKM). Soil samples were collected from the surface layer (0–20 cm) of a long-term field experiment of Mollisols (Luvic Phaeozem) in 2015 at Gongzhuling, Jilin Province, China, which was established in 1980. Soils were incubated for 360 days at 25 °C, with or without 13C-labeled maize straw and destructively collected on the days of 45, 90, 135, 180, and 360. Soil aggregates were separated into two fractions (macroaggregates, > 250 μm; microaggregate, NPK > CK for all soil aggregates after the 360-day incubation. Our results illustrated that long-term application of manure with mineral fertilizer helps to stabilize or increase the retention of exogenous C in the soil aggregates.

Crop residue return is an effective and low-cost agricultural approach for soil organic carbon (SOC) sequestration. Yet, it is largely unknown to what extent the soil fertility and residue type affect the mineralization of maize (Zea mays L.) residue carbon (C) and the decomposition of native SOC. Therefore, a better understanding of the mineralization of C derived from residues and its priming on native SOC is crucial to accurate assessment of the benefits of crop residue returning in agricultural systems. A 360-day laboratory incubation experiment was carried out with a Cambisol of low and high fertilities amended with three types of 13C-labeled maize residues (root, stem, leaf). The abundance of 13C (δ13C) in the soil samples was measured during different incubation stages. The results showed that the total mineralization of residue C was significantly higher in the low fertility soil than in the high fertility soil, but there were no significant differences among residue types. For the high fertility soil, all the residue types induced a negative priming on native SOC mineralization during the early incubation stage, but a significant total positive priming by the end of incubation, whereas for the low fertility soil, there was no significant effect of residue return on SOC mineralization. The accumulated priming by the end of incubation did not vary across residue types. Moreover, the sum of mineralization of residue C and native SOC in the high fertility soil was 1.4 times as large as that in the low fertility soil. We conclude that mineralization of crop residue C and native SOC is affected by soil fertility rather than residue type.

The labile organic carbon (C) pool plays a vital role in soil biogeochemical transformation and can be used as a sensitive indicator of the response of soil quality to agricultural practice. However, little is known about how residue type and soil fertilization affect the incorporation of residue C into labile organic C pools. A 360-day laboratory incubation was conducted with the addition of 13C-labeled maize residues (root, stem and leaf) to unfertilized and organic-fertilized soils. A greater contribution of residue C to extractable organic C (EOC, 7.2%) was observed in the unfertilized soil than that in the organic-fertilized soil (6.0%). The contribution of residue C to microbial biomass C (MBC) was 20%-50% in the organic-fertilized soil, but only 10%-30% in the unfertilized soil. This suggests that, in organic-fertilized soil, there is accelerated transformation of residue C into microbial biomass and a higher capacity for residue C stabilization through greater, or more efficient anabolism. Moreover, the distribution of leaf C into MBC was higher than that from root and stem in the unfertilized soil, whereas more root C entered to EOC and MBC than from stem and leaf in the organic-fertilized soil. This shows that maize root can also be involved in microbial assimilation, but it depends on the initial soil nutrition. Overall, these findings deepen our understanding of the mechanisms of microbe-mediated C transformation processes, and provide relevant insights into the capture and incorporation of plant residue C into labile organic C pools driven by residue type and soil fertilization.

Objectives: Better dressings are needed for both receiver and donor sites in clinical management of burn wounds. Current study aims to check the efficacy and safety of BloodSTOP iX Wound Heal Nanocellulose Matrix (BSM) in managing burn wound. Materials and methods: Characterization of BloodSTOP iX Nanocellulose Matrix was assayed with scanning electron microscope (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). For the preclinical study, two burn injury animal models were established: a contusion model and partial-thickness burn model. A total of 12 rabbits (male/female; 2.0-2.5 kg) were used in this initial experiment. Assessments were made at two time points: 1 week and 2 weeks post-injury. Six rabbits underwent skin contusion and six partial-thickness skin burn. At 1 week and two weeks post-injury, gross pathologic and histologic observations of changes and scarring were conducted. For clinical trial, during September 2015 to September 2016, a total 46 patients from two medical centers were enrolled in this study, including control group 16 cases and BSM 30 case. Each group has been sub-grouped into skin donor site and transplanted site. At 7, 14 and 20 days post treatment, clinical outcome were assayed. Results: The microstructure of Nanocellulose and nano-structure of BloodSTOP iX Wound Heal Nanocellulose Matrix was confirmed. Preclinical results demonstrated that BSM promoted the burn wound healing in both animal models. In the clinical experiment, BSM decreased recurrence of bleeding post application and burning/pain feeling, while an anti-infection effect was also noted. More strikingly, BSM promoted skin epithelialization and improved scar tissue. Those effects were observed in both donor and receiver sites. Conclusion: BloodSTOP iX Wound Heal Nanocellulose Matrix (BSM) is safe and effective in burn wound care for skin grafting on both donor site and transplanted site.

Soil organic carbon (SOC) has significant implications in regulating soil health. Emerging insights emphasize the important role of microbial anabolism in SOC storage by continuously transforming plant fragments into persistent microbial residues. However, knowledge of the sequestration pathway of root versus shoot carbon (C) is under debate. While recent studies have shown that labile shoot residue is disproportionately important for stable SOC accumulation through microbial assimilation, how plant root vs. shoot residue retention impacts microbial-derived C under different soil fertility conditions remains elusive. Here, we conducted a 500-d in situ experiment using Alfisols with low fertility (LF) and high fertility (HF) amended with maize root or shoot (both stem and leaf) residues. The microbial residues (amino sugar biomarkers) and microbial communities (lipid biomarkers) were analyzed at 60, 90, 150, and 500 d after the amended materials were added. The results showed that shoot residue input facilitated microbial residue accumulation more efficiently than root input before 150 d. However, at the end of the experiment, the treatment containing added root residue accumulated more microbial residues and produced a higher proportion of microbial residue in SOC, compared with shoot treatment. These results provide novel evidence that root residue can also yield SOC efficiently through the organic substrate–microbial anabolism pathway, but it depends on the decomposition period. Moreover, soil fertility plays an important role in regulating the quantity and relative composition of microbial residues. Specifically, crop residue application greatly increased the contribution of microbial residue C to SOC in the LF treatment compared to that in the HF treatment on day 500. Meanwhile, crop residue addition had a more positive effect on fungal residue accumulation in the LF soil, while it facilitated the accumulation of bacterial residue in the HF soil. These findings highlight that crop residue addition (especially root residue) is an effective approach for improving microbial-derived C sequestration in infertile soils.

The subsoiling tillage managements have been recommended to remediate subsoil compaction and maintain crop production. These practices can improve soil properties and fertility due to soil loosening and straw incorporation, and further affect soil microbial community characteristics. However, the response of soil microbial community structure to subsoiling tillage managements is still poorly understood. The objective of this study was to examine the effects of tillage practices (conventional tillage, CT; subsoiling tillage, ST; subsoiling tillage with straw incorporation, STS) on soil microbial community characteristics. Topsoil (0–20 cm) and subsoil (20–35 cm) samples were taken from a 360–day in−situ field experiment in northeast China. Microbial community characteristics were determined by the phospholipid fatty acid (PLFA) method. The contents of subsoil bacterial PLFAs and fungal PLFAs were lower in the ST treatment than those in the other treatments within 60–360 days, and gram−positive (G+) bacteria were more abundant in the subsoil of ST treatment than those in the subsoil of STS treatment. In contrast to the other treatments, the STS treatment had the larger total PLFAs content and the higher ratio of fungal to bacterial PLFAs (F/B) in the subsoil during the whole incubation period, and fungi played a dominant role in straw degradation of subsoil. Compared with the other treatments, the STS treatment had a lower cyclopropyl to precursors (cy/pre) ratio in the subsoil on the 30th day, suggesting that the STS treatment provided more K2SO4−extractable organic carbon (EOC) and some available nutrients (nitrogen, potassium and phosphorous) for soil microbes. The STS treatment relative to the other treatments increased the bacterial PLFAs and fungal PLFAs contents in the topsoil, which were associated with the increase in the EOC/SOC ratio. Accordingly, STS practice had a great potential for improving subsoil and topsoil microbial community characteristics.

Crop residue incorporation is an effective agricultural management to enhance soil organic carbon and nitrogen (N) sequestration, which inevitably affects the crop N uptake, and consequently the allocation of N in the soil-plant system. However, to what extent the crop residue type and soil fertility moderate the contribution and recovery of maize (Zea mays. L) residue-derived N (residue-N) in the soil-plant system is poorly understood. Therefore, a 2-year in situ experiment was conducted on an Alfisol with high fertility (HF) and low fertility (LF), along with the application of 15N-labeled maize root or straw (both stem and leaf) residues. The results showed that the HF treatment had a smaller proportion of residue-N in total N uptake compared with the LF treatment (on average of 2.0% vs. 3.6%), but with a larger recovery rate (on average of 23.5% vs. 12.8%). The application of straw residues increased the proportion of residue-N in plant total N compared with that from the application of root residues in the HF treatment. The percentage of residue-N in total soil N (TSN) and the residue-N recovery in the LF soil were 60.7–108.5% and 9.6–25.8% higher than those in the HF soil, respectively. The proportion of root-derived N (root-N) in TSN was significantly higher than that of straw-derived N (straw-N) in the LF soil. In addition, total residue-N recovery rates were similar among all residue-amended treatments. The results indicated that the soil with high fertility could increase residue-N utilization by plant, especially the straw-N, while the soil with low fertility favored the accumulation of the residue-N in soil, especially the root-N, and its low fertility was more likely to be improved. Overall, soil fertility and residue type could significantly affect the allocation of maize residue-N in the soil-plant system.

Microbial transformation of crop residue is the key process of soil organic matter (SOM) formation and mineralization, which determines soil fertility and affects global climate change. However, utilization dynamics of residue-derived carbon (residue C) by various microbial communities is still not well understood, especially under different residue quality and soil fertility conditions over a long-term scale (i.e., >1 year). In this study, a 500-day in-situ field experiment was conducted using 13C-labeled maize (Zea mays L.) root and shoot (composed of both stem and leaf) to examine the role of microbial community composition on the C processing. Specifically, the mineralization of residue C and incorporation of residue C into microbial biomass in low fertility (LF) and high fertility (HF) soils were investigated. The abundance of 13C in soil samples and microbial phospholipid fatty acids (PLFAs) were measured after 60, 90, 150 and 500 days since the residues added. The results showed that the mineralization rate of residue C was significantly higher in the LF than that in the HF soil for the first 150 days, and the shoot-derived C was more susceptible to degradation than root-derived C, but the final mineralization rates (~78%) were not significantly different among treatments on the day 500. Soil fertility significantly affected the relative composition of different microbial groups and distribution of residue C in microbial communities, but residue type did not do so. Furthermore, residue C contributed more to PLFA-C pool in the LF than HF treatments, and the proportion of root C in PLFA-C pool was higher than that of shoot C, indicating easier immobilization of root C by soil microbial anabolism. Accordingly, soil fertility and residue quality could both regulate the kinetics of the microbial immobilization of crop residue C, but overall the available residual quantity of applied (plant-derived) C to enhance or maintain soil C pool did not depend on them in a long term in the agricultural Alfisols.

Long-term intensive cultivation generally affects even soil fertility by decreasing the soil organic carbon (SOC) content. The returning of maize residues to the soil is documented as an effective measure to increase SOC and improve soil productivity. However, limited information is available on the turnover and storage of organic carbon (C) caused by the addition of different maize residue types to soil with different soil fertility levels. For this purpose, a 540-day in-site field experiment was carried on soils with low and high fertility levels amended with three types of 13C-labeled maize residues (root, stem and leaf) in Northeast China. The abundances of 13C in the soil samples were measured on the 60th, 90th, 180th, and 540th days after incubation. The results showed that the residual rate of the residue-derived C was higher in the high-fertility (HF) soil than that in the low-fertility (LF) soil on the 60th day (an average of 56.6% vs. 52.37%, P