Straw Decomposition Research Articles

Sugarcane straw management by inoculation of microbial consortia and its impact on short-term N source and amelioration of ratoon sugarcane yield

ABSTRACT The objectives of this study was to assess the effect of the inoculation of sugarcane straw with an artificial microbial consortium (MC) on soil mineral N, soil organic matter (SOM), sugarcane straw decomposition, hydrolytic enzyme activities (β-glucosidase, urease), oxidative enzyme activities (phenoloxidase, peroxidase), nutrient uptake and ratoon cane yield. The experiment consisted of two field experiments, i.e. the experiment I field was sandy soil, and the experiment II field was sandy loam soil in Khon Kaen Province. After planted cane harvest, there were three treatments, namely, burn (B), incorporation (I) and I+ MC treatments. Experiment II consisted of three treatments, namely, B, mulch (M) and M+ MC treatments. Sugarcane straw was applied at a rate of 6.25 tons ha−1. The results revealed that sugarcane straw management by inoculation of microbial consortia had a higher soil mineral N content than that of other treatments, improved the straw decomposition, hydrolytic and oxidative enzyme activities, SOM accumulation (7.60, 20.58 g kg−1 respectively), yield (49.47, 131.51 ton ha−1 respectively), nutrient uptake and nutrient use efficiency of ratoon cane. Thus, sugarcane straw management by inoculation of microbial consortia becomes a short-term N source and a potential application to enhance decomposition leading to increased ratoon cane yield.

Response of seasonal variation in soil detachment capacity to straw incorporation in sloping farmland on the Loess Plateau

AbstractSoil detachment capacity by rill flow (Dc) is sensitive to changes in topsoil properties generated by crop straw incorporation. In the present study, we investigated the effect of crop straw incorporation on the seasonal variation in Dc, the knowledge regarding which is limited currently, and identified the key influencing factors. Three typical crop straw types (wheat, soybean, and maize) were selected for this study. Soil samples incorporated with crop straw and without crop straw were collected over 375 days (from October 1, 2020 to October 10, 2021) and were subjected to a hydraulic flume (length, 4.0 m; width, 0.2 m) to determine Dc. The topsoil properties soil bulk density (BD), soil cohesion (Coh), soil penetration resistance (PR), soil organic matter content (SOM), mean weight diameter (MWD), and straw decomposition rate (SDR) were measured to explain the seasonal variation in Dc. The results showed that crop straw incorporation effectively reduced Dc, and the Dc for the soil incorporated with straw decreased by 25.92%–38.76% compared with that without straw incorporation. Dc exhibited a significant decreasing trend over time, and the Dc at the end stage decreased by 83.00%–88.31%, compared with the initial stage. Seasonal variation in Dc was significantly correlated with BD, Coh, PR, SOM, MWD, and SDR. The measured Dc decreased with BD and Coh as a power function and with SOM and MWD as an exponential function. The influence of straw incorporation on Dc is time‐dependent and can be divided into short‐term and long‐term effects. Natural soil consolidation gradually masked the effect of straw residue with the decomposition of the incorporated straw. The comprehensive response of seasonal variation in Dc to straw incorporation was described by a power combination equation (Dc = 1.23 τ1.65 BD−2.63 Coh−1.33 SOM−0.70; R2 = 0.96). Thus, the seasonal variations in Dc with straw incorporation were mainly controlled by the changes in soil properties triggered by the decomposition of incorporated straw and natural soil consolidation. The results of this study provided a scientific reference for soil erosion prediction and control in sloping farmlands.

Fall Straw Incorporation with Plastic Film Cover Increases Corn Yield and Water Use Efficiency under a Semi-Arid Climate

Corn straw incorporation in soil has been regarded as an environment-friendly approach for straw utilization. However, straw incorporation has been a challenge under a cold and dry climate due to slow decomposition. This field study was to use a novel approach to incorporate corn straw into the soil during the fall season with a plastic film cover in an effort to enhance the straw degradation, soil water use efficiency, and corn growth and yield. Two-year field experiments were conducted in northeast China to investigate the effects of four treatments on soil properties and corn growth: (1) straw incorporation with film cover, (2) straw incorporation only, (3) film cover only, and (4) control. Soils and corn plants were collected during the growing season and analyzed for soil temperature and moisture, straw degradation, corn biomass, grain yield, and water use efficiency. Results indicated that straw incorporation with film cover increased grain yield by 53% as compared to straw incorporation only and by 102% to control. The straw decomposition under film cover was 20% faster, significantly higher than that of the straw incorporation treatment. In all cases, soil water content before planting, corn water uptake, and corn water use efficiency under straw incorporation with film cover were significantly higher than straw incorporation and control. Surface film cover resulted in 10-day earlier corn tasseling in compared to treatments without film cover. This field study demonstrated that straw incorporation with film cover would enhance straw degradation in soil, improve soil properties, and increase corn yield and water use efficiency, which could be potentially used as a sustainable soil management practice in northeast China.

Assessing the influence of contaminated rice straw decomposition on the speciation of cadmium and arsenic in a naturally contaminated soil

Assessing the influence of contaminated rice straw decomposition on the speciation of cadmium and arsenic in a naturally contaminated soil

Characteristics of rice straw decomposition and bacterial community succession for 2 consecutive years in a paddy field in southeastern China

The characteristics of long-term rice straw decomposition and succession in the bacterial community in the double-rice system are still unclear. Here a 2-year continuous straw bag decomposition experiment was conducted to explore changes in nutrient release, enzyme activity, and bacterial community composition during rice straw decomposition in the double-rice system in Southeast China. After burial in soil, the cumulative dry matter loss rates of rice straw were 38.9%, 72.6%, and 82.7% after 2, 12, and 24 months, respectively. The change in the release rate of straw nitrogen and phosphorus was similar to the dry matter loss, but 93.5% of straw potassium was released after 1st month. Bacterial abundance and community diversity in straw increased rapidly, reaching peaks after 7 and 12 months, respectively. Straw extracellular enzyme activities were the highest in the first 2 months and then gradually decreased over time, and they significantly and positively correlated with straw decomposition rate. Straw decomposition was dominated by copiotrophic Bacilli and Flavobacteriia in the early stages and evolved to be dominated by oligotrophic Acidobacteria, Anaerolineae, Deltaproteobacteria, Saccharibacteria, and Sphingobacteriia in the later stages. Changes in the C/N and K content of straw are the main reasons for bacterial community succession during rice straw decomposition. This study can provide a scientific basis for developing efficient decomposing bacteria agents for rice straw.

Effects of rumen microorganisms on straw returning to soil at different depths

Slow decomposition of straw returning will lead to the aggravation of diseases and insect pests, affecting the growth of the next crop and causing the reduction of grain crops. This research was designed to investigate the effects of rumen microorganisms at different depths on straw returning to soil. By pot experiments finding, rumen microorganisms can accelerate straw decomposition. When straw returning to soil at 20 cm showed the best decomposition performance, which the straw degradation rate compared with the returning depth of 5, 10 and 30 cm, it has increased by 19.2%, 8.7% and 10.7%. At the optimal burial depth of 20 cm, the degradation rate of straw reached 46.4% on day 30, which 44.5% faster than that of the control. Moreover, the straw structure analysis proved that microorganisms derived from rumen fluids addition were conducive to destruction of functional groups and degradation of cellulose on straw surface. Additionally, it was demonstrated that rumen fluids could promote the rot of straw so that soil nutrients and enzyme activities were increased. According to high-throughput sequencing technology, the addition of rumen fluids significantly increased the abundance and diversity of soil microorganisms with strong straw decomposition ability, including bacteria and funguses. Experimental results provided an innovative approach for further development and utilization of rumen microorganisms. Most importantly, it provides new ideas for speeding up the straw returning.

Microbial gut diversity in four grasshopper species and its correlation with cellulose digestibility.

Grasshoppers are common pests, and their intestinal microbes have coevolved with them. These microorganisms have varied community structures, and they participate in the nutritional absorption and metabolism of grasshoppers. Here, we describe the gut microbiota diversity of four species of grasshoppers, Oxya chinensis, Pararcyptera microptera meridionalis, Gastrimargus marmoratus, and Calliptamus abbreviatus. We constructed a 16S rDNA gene library and analyzed the digestibility of cellulose and hemicellulose in grasshoppers using moss black phenol and anthrone colorimetry. The grasshopper with the highest microbial diversity in the gut among the four species was Oxya chinensis, and there were no significant differences in gut microbial diversity between the two geographic collections of Oxya chinensis. The most dominant phyla of the four grasshopper gut microorganisms were Proteobacteria, Bacteroidetes, and Firmicutes, and the most dominant genus was Enterobacter. The gut microbiota features of the four grasshoppers were correlated with their cellulose and hemicellulose digestibility. There was a significant positive correlation with cellulose digestibility for Pantoea. A significant negative correlation was found with cellulose digestibility for Acinetobacter, Enterococcus, Citrobacter, Serratia. A significant negative correlation was found with hemicellulose digestibility for Pantoea. This study contributes to the understanding of the structural composition of different species of grasshoppers gut microbiota, which may be useful for developing grasshopper digestive tracts as bioreactors for cellulose decomposition, improving the decomposition and utilization of agricultural straw, producing clean biomass energy, and processing biologically derived products.

Future climate conditions accelerate wheat straw decomposition alongside altered microbial community composition, assembly patterns, and interaction networks

Although microbial decomposition of plant litter plays a crucial role in nutrient cycling and soil fertility, we know less about likely links of specific microbial traits and decomposition, especially in relation to climate change. We study here wheat straw decomposition under ambient and manipulated conditions simulating a future climate scenario (next 80 years) in agroecosystems, including decay rates, macronutrient dynamics, enzyme activity, and microbial communities. We show that future climate will accelerate straw decay rates only during the early phase of the decomposition process. Additionally, the projected climate change will increase the relative abundance of saprotrophic fungi in decomposing wheat straw. Moreover, the impact of future climate on microbial community assembly and molecular ecological networks of both bacteria and fungi will strongly depend on the decomposition phase. During the early phase of straw decomposition, stochastic processes dominated microbial assembly under ambient climate conditions, whereas deterministic processes highly dominated bacterial and fungal communities under simulated future climate conditions. In the later decomposition phase, similar assembly processes shaped the microbial communities under both climate scenarios. Furthermore, over the early phases of decomposition, simulated future climate enhanced the complexity of microbial interaction networks. We concluded that the impact of future climate on straw decay rate and associated microbial traits like assembly processes and inter-community interactions is restricted to the early phase of decomposition.

Linking nitrogen- and straw-sensitive indicator species and their co-occurrences to priming effect in agricultural soil exposed to long-term nitrogen fertilization

The increasing input of nitrogen (N) fertilizers has a considerable impact on agricultural soil carbon (C) cycling due to its influence on soil microbial abundance and assemblages. However, the microbial mechanism underlying the response of straw-induced priming effect to long-term N application remains an open question. Here, using soils with three N fertilization levels (0, 300, and 570 kg N ha−1 y−1) from a long-term experimental site, we established a 40-day microcosm experiment to investigate the priming effect of straw addition on SOM mineralization and the associated microbial activity and community composition. We found that long-term N application significantly inhibited soil respiration while increasing straw-induced priming effect. The soil microbial biomass (including bacterial and fungal abundance) decreased with increasing N levels, accompanied by decreased bacterial α-diversity and altered β-diversity. In addition, the N fertilization level significantly influenced bacterial and fungal indicator species that were sensitive to straw addition (siOTUs) and long-term N fertilization (niOTUs), as well as their co-occurrence patterns. In the first three days of straw decomposition, long-term N fertilization decreased the oligotroph-to-copiotroph ratio of bacterial siOTUs. In contrast, long-term N fertilization increased this ratio on days 20 and 40, along with facilitated microbial investment in extracellular enzymes and microbial N demand. This caused a stronger “N mining” process and consequently enhanced the priming effect in soil exposed to long-term N fertilization at the later stage of incubation. Linking indicator species analysis with priming effect, these results advance our understanding of the complex C cycling in agricultural soils undergoing long-term nitrogen management.

Continuous straw return for 8 years mitigates the negative effects of inorganic fertilisers on C‐cycling soil bacteria

AbstractTo elucidate the identity and mechanisms by which specific bacterial members drive efficient decomposition and utilisation of straw, the succession and co‐occurrence patterns of 13C‐labelled bacteria were analysed using DNA‐stable isotope probing (SIP) techniques. Microcosms with 13C‐labelled maize straw incorporated into soils subjected to no nitrogen (N) fertiliser (CK), chemical fertiliser (NPK) and chemical fertiliser with straw return (NPKS) treatments for 8 years were incubated for 360 days. The results showed that fertilisation regimes changed the 13C‐labelled bacterial groups by abundance but not taxonomic composition, where N fertiliser application (NPK and NPKS treatments) reduced the relative abundance of maize straw carbon assimilators affiliated with Arthrobacter, Sphingomonas, Streptomyces, Burkholderia‐Caballeronia‐Paraburkholderia and Kribbella, but increased the relative abundance of Nocardioides, Rhodanobacter, Granulicella and Chujaibacter. Compared with CK and NPKS‐treated soils, continuous inorganic fertilisation reduced the α‐diversity of the 13C‐labelled bacterial community and resulted in a loose and less competitive co‐occurrence network of straw C‐assimilators with more hubs needed to sustain its structural stability. Interestingly, straw return mitigated the negative effects of inorganic fertilisation by forming a tight and complex co‐occurrence network of maize straw utilizers associated with NPKS‐treated soils. Taken together, we emphasise the vital function of long‐term straw return for sustaining soil biodiversity under intensive fertilised agricultural conditions and provide reference bacterial members for efficient straw utilisation.Highlights DNA‐SIP enabled the concise identification of straw C assimilating bacterial members. Inorganic fertilisation reduced straw C‐utilizer community diversity and their interactions. Straw return mitigates the negative effects of inorganic fertilisers on straw C‐cycling bacteria. Varying taxa sustained the interaction network of straw C‐utilizers in different fertilised soils.

Nitrogen input level modulates straw-derived organic carbon physical fractions accumulation by stimulating specific fungal groups during decomposition

Microbial-driven straw-derived soil organic carbon (SOC) sequestration plays pivotal role in promoting soil productivity and achieving C neutrality, while nitrogen (N) and phosphorus (P) input levels are the impetus of this process. However, our understanding of the microbial mechanism underpinning the straw-derived SOC fractions accumulation within aggregates under contrasting N and P application rates is rudimentary. Here, a 90-day incubation experiment was conducted to observe the dynamics of straw-derived SOC fractions accumulation within aggregates by adding C3 straw (natural 13C-labeled substrate) to a Mollisol (in which C3 plants had never been grown). Treatments included straw combinations of half N and regular P (N1/2 +P + SR), regular N and half P (N + P1/2 +SR) and regular N and P (N + P + SR). Regular N input accelerated the succession of the microbial community from bacteria-dominated to fungi-dominated and increased the contents of straw-derived particulate OC (POC) at 10 days and mineral-associated OC (MOC) at 30 days within aggregates. Differential abundance analysis and slopes of linear regression models showed that the fungal community, especially the core enriched taxon of Chaetomiaceae, was strongly positively correlated with straw-derived MOC after N input. Random forest models strengthened the view that N input rate and Chaetomiaceae richness may directly mediate straw-derived POC and MOC accumulation process, respectively, during incubation. To verify our conjecture, another 60-day incubation experiment was carried out to elucidate the effects of Chaetomium globosum inoculation and N application on SOC turnover after straw addition. Chaetomium globosum inoculation with regular N input promoted straw decomposition and SOC sequestration than other treatments, but no difference was observed in soil respiratory quotient compared with control. The slopes of linear regression model show the more significant and positive correlations between SOC content and Chaetomiaceae richness in the present study than data from previous references, impling the important role of Chaetomiaceae in SOC sequestration in Mollisols. Our work provides new ecophysiological angles for understanding the effect of Chaetomiaceae richness on the accrual of SOC in response to varying N levels in agroecosystems on the Northeast China Plain.

Seasonal Temporal Characteristics of In Situ Straw Decomposition in Different Types and Returning Methods

Seasonal Temporal Characteristics of In Situ Straw Decomposition in Different Types and Returning Methods

Deep-injected straw incorporation improves subsoil fertility and crop productivity in a wheat-maize rotation system in the North China Plain

Deep-injected straw incorporation (DI-SI) is a novel soil tillage and straw management, which allowed for the formation of maize straw layer structure in the subsoil (20–38 cm) in wheat-maize rotation systems. However, little is known about how DI-SI affects soil physicochemical and enzymatic processes, as well as crop productivity. Therefore, we conducted a field experiment during 2018–2020 in the North China Plain to determine whether DI-SI would improve soil structure, nutrients, enzyme activities, and crop yield. Three treatments were included: straw removal (SR), conventional straw incorporation (SI), and DI-SI. The results showed that DI-SI improved soil structure and water retention through decreasing the bulk density and penetration resistance in 20–40 cm soil layer. DI-SI significantly increased soil organic C (67.5%), total N (61.3%), and available nutrients (i.e. NO 3 - , NH 4 + , dissolved organic C) compared with SI in the subsoil (20–40 cm), while no differences were detected among straw managements in the topsoil (0–20 cm). This was mainly attributed to the accumulation of microbial biomass C and C-, N-acquisition enzymes in the straw layers, which promoted the straw decomposition and nutrient release. Finally, with the combined effects of soil ecological processes, DI-SI significantly increased the grain yields of wheat and maize by 12.0% and 11.8% compared with SI in the second year, respectively. Our study suggested that deep placement of straw would better promote the utilization of crop residue for farming, and deep-injected straw incorporation represents a viable strategy to improve subsoil physical, chemical, and biological processes, and subsequently crop productivity in wheat-maize rotation systems. • DI-SI improves soil structure and water retention through decreasing the bulk density. • DI-SI considerably increases the SOC, TN, and available nutrients in the subsoil. • DI-SI stimulates microbial and C-, N-acquisition enzymes activities in the straw layers. • Wheat and maize yields were increased under DI-SI, especially in the second year.

Effects of Agronomic Measures on Decomposition Characteristics of Wheat and Maize Straw in China

The utilization of crop straw resources has been highly emphasized by governments and academia in recent decades. The growing importance of straw decomposition in the wheat-maize rotation system and the remarkable diversity of accumulated information on this topic inspired us to quantitatively explore variations in the outcomes of individual studies. We conducted a data analysis of 46 experimental studies reporting the effects of agronomic measures on the straw decomposition rates of wheat (14 studies) and maize (38 studies). Statistical results showed that maize straw crushed and buried in soil with turn-over or rotary tillage can significantly increase straw decomposition rates. Further, with the increase in nitrogen input and straw burial depth in the soil, the maize straw decomposition rate increased significantly, while the amount of straw return showed the opposite trend. Among all agronomic measures in this research, burial depth has demonstrated a significant positive effect on the wheat straw decomposition rate. The random forest analysis identified decomposition time as the most important predictor of straw decomposition rates for wheat and maize. In addition, some agronomic measures and straw decomposition time jointly affect the decomposition rate of straw. In general, agronomic measures are effective factors in controlling straw decomposition in a wheat-maize rotation system.

Incorporation of calcium cyanamide and straw reduces phosphorus leaching in a flooded agricultural soil

Calcium cyanamide and straw additions coupled with one-month of flooding conditions can effectively inhibit soil diseases by generating anaerobic conditions and hydrolysing cyanamide during the summer fallow period in agricultural settings. However, the response of soil phosphorus (P) forms and mobility to the calcium cyanamide and straw additions under flooding conditions remain unknown. This study employed column leaching devices to monitor the P fractions and related movement in a flooded soil with six treatments: control, 0.5 g kg−1 calcium cyanamide (CC), 2 g kg−1 straw (S2), 0.5 g kg−1 calcium cyanamide coupled with 2 g kg−1 straw (CS2), 10 g kg−1 straw (S10) and 0.5 g kg−1 calcium cyanamide coupled with 10 g kg−1 straw (CS10). The results showed that the CC significantly reduced the cumulative P leaching by 26.3%, compared with the control, attributed to the fixation of dissolved P by calcium hydroxide hydrolyzed from calcium cyanamide. The S2, CS2, S10 and CS10 reduced the cumulative P leaching by 10.4%, 41.0%, 70.0% and 80.5%, and enhanced soil P adsorption maximum and the proportions of NaOH-P fraction, compared with the control, respectively. The reason for low P mobility in treatments with straw addition could be attributed to the strengthened association between dissolved P and poorly crystalline Al/Fe/Mn oxides in soils due to an acidification effect induced by decomposition of straw under flooded conditions. Such acidification further coupled with calcium hydroxide was responsible for the lowering of P mobility in CS2 and CS10 treatments. Redundancy analysis indicated that topsoil organic carbon is the most important factor explaining 32.9% of the variations in soil P fractions and cumulative leached P across the treatments. This study highlights that calcium cyanamide in combination with straw additions suppressed soil P leaching under flooded conditions during the summer fallow period, which provided a net water quality benefit slowing release of P to the environment. Future studies should be carried out in agricultural regions with various soil mineral matrices.

Where the straw-derived nitrogen gone in paddy field subjected to different irrigation regimes and straw placement depths? Evidence from 15N labeling

Straw-derived N is an organic N source, that plays an important role in agroecosystems. However, quantitatively tracing the release and fate of exogenous straw-derived N in a rice-soil system amended by irrigation regime and straw placement depth is poorly understood. The objectives of this study were to determine the release and fate of straw-derived N in the rice-soil system under different irrigation regimes and straw placement depths. 15N-labeled rice straw was used for two consecutive years in a field experiment in Northeast China, and four treatments were established: (i) controlled irrigation + shallow straw return (5 cm depth, CSD1); (ii) controlled irrigation + deep straw return (15 cm depth, CSD2); (iii) flooded irrigation + shallow straw return (5 cm depth, FSD1); and (iv) flooded irrigation + deep straw return (15 cm depth, FSD2). We found that the temporal patterns of straw N release were best described by the one-pool model, which was helpful to predict the straw-derived N fluxes during straw decomposition under different irrigation regimes and straw placement depths. Controlled irrigation and shallow straw placement depth increased the straw N release rate, which was consistent with their effects on straw mass loss, especially in the first rice season, showing a decreasing order of CSD1 > CSD2 > FSD1 > FSD2. Irrigation regime and straw placement depth significantly affected the fate of straw-derived N in the rice-soil system. Controlled irrigation will not only increase plant utilization rates of straw-derived N at different straw placement depths but also promote soil sequestration of straw-derived N and reduce the loss of straw-derived N. Additionally, we also found that placing straw at a shallower depth can also increase straw-derived N utilization by plants. Coupling controlled irrigation and placing straw at a shallower depth (CSD1) resulted in the highest utilization of straw-derived N by plants. However, it is worth noting that placing straw at a shallower depth also increases the loss of straw-derived N, which may increase the risk of environmental pollution in a soil-rice system. This study expanded the theory of straw N release and effective utilization in agroecosystems, which is helpful to better predict gross N fluxes and fates of straw-derived N in the agroecosystem to formulate a scientific and reasonable mode of field management with straw return.

Rapid decomposition of rice straw by application of a novel microbial consortium and study its microbial community dynamics.

Rice straw decomposition is an attractive solution to open-field burning but the traditional method has slow kinetics and takes 60-90days to obtain mature compost. In this study, we propose to boost up the decomposition process by addition of a novel microbial consortium rich in lignocellulolytic microbes. C: N ratio of the compost reached 11.69% and degradation efficiency of cellulose and hemicellulose was found to be 64 and 87% respectively within 25days. Lignocellulolytic activity of the microbial consortium was confirmed by plate and activity assay. These parameters clearly indicated that a mature compost was obtained in 25days. The 16S rRNA gene amplicon sequencing and functional analysis of predicted genes indicated amino acid and carbohydrate metabolism as the major metabolic pathway during composting. The tertiary level of functional analysis revealed the major metabolic pathways in the bacterial communities as pentose phosphate pathway, glycolysis and tricarboxylic acid cycle.

Improving soil aggregates stability and soil organic carbon sequestration by no-till and legume-based crop rotations in the North China Plain

Conservation agriculture (CA) has been adopted worldwide on about 200 Mha to enhance soil organic carbon (SOC) for mitigating climate change. However, as a crucial mechanism to sequester SOC, how the protection of aggregates responds to the interaction between no-till and crop rotations (two principles of CA) remains unknown. Thus, a field experiment with six treatments [e.g., no-till or rotary tillage under the maize-wheat-soybean-wheat system (NT-MWSW, RT-MWSW), no-till or rotary tillage under the maize-wheat system (NT-MW, RT-MW), and no-till or rotary tillage under the soybean-wheat system (NT-SW, RT-SW)] was conducted from June 2018 to June 2021 in the North China Plain (NCP) to assess their effects on aggregation and SOC. Results indicated that macroaggregates (> 0.25 mm) were the main contributors to the soil carbon (C) pool, comprised 64.7–87.3 % of aggregates, and encompassed 64.9–73.1 % of the SOC stock. NT increased not only the proportion of macroaggregates but also aggregate stability (i.e., mean weight diameter and geometric mean diameter). Significant positive effects from legumes were observed under NT. SW increased by 13.6 % macroaggregate-associated SOC under NT in 0–20 cm compared to that under MW. Additionally, the conversion rate of straw C input under NT-SW was higher than that in other treatments, augmenting it by 9.4–21.9 %. This may be attributed to the higher macroaggregate total nitrogen (increased by 1.7–15.9 %) in 0–10 cm under legume-based crop rotations compared to that under MW, resulting in lower C: N ratios, which promoted the decomposition of straw. Furthermore, the total potential mineralization of macroaggregates under NT legume-based crop rotations was 3.0–16.0 % higher than that of MW. Thus, a legume-based NT system can significantly improve soil macro-aggregation, increase the conversion rate of straw C input, and reduce C loss, which can be a viable practice to enhance SOC sequestration capacity under CA in the NCP.

Faster carbon turnover in topsoil with straw addition is less beneficial to carbon sequestration than subsoil and mixed soil

AbstractIn arable soils, the topsoil and subsoil are commonly mixed in the operation of deep tillage. It is not yet clear whether the influence of crop straw on soil organic matter (SOM) mineralization of the mixed soil (from the topsoil and subsoil) is different from that of solely the topsoil or subsoil. We conducted a 120‐d incubation experiment with the addition of 13C‐labeled maize (Zea mays L.) straw to study SOM mineralization and straw decomposition in the topsoil (0–15 cm), subsoil (15–30 cm), and their mixture (0–30 cm). Straw addition promoted SOM mineralization and thus induced a positive priming effect. The mineralization of SOM in topsoil with straw addition was 122% higher than in subsoil, and 45% higher than in mixed soil. After the 120‐d incubation, 12–16% of straw C was mineralized as CO2, contributing approximately 50–70% to the total CO2 production. Furthermore, straw C was also incorporated into SOM fractions, with 34, 7, and 59% in the light fraction, particulate organic C (coarse and fine), and mineral‐associated organic C (MAOC) in topsoil, respectively. The SOM mineralization and priming were greater in the topsoil with higher dissolved organic C and NO3–N throughout the incubation. Despite more straw C retained in MAOC in topsoil, the significant decrease in total MAOC with straw addition indicated that SOM turnover induced by fresh C application was probably faster in topsoil than the subsoil and mixed soil. Our findings indicated that both subsoil and mixed soil tended to sequester C with straw addition, whereas topsoil C turnover was faster than subsoil in the presence of straw addition.

Studying the Effect of Straw Returning on the Interspecific Symbiosis of Soil Microbes Based on Carbon Source Utilization

Heilongjiang province has made great contributions to ensuring the food security of China. Grain production has increased year by year, followed by a large amount of straw—especially the production of corn straw. Straw returning is the best treatment method from the perspective of ecology. This study simulated modern mechanized operation conditions from the field of soil biological characteristics to explore the impact of straw decomposition on the changes in the soil microbial community. In this study, in the black soil region of Northeast China (45°45′27″~45°46′33″ N, 126°35′44″~126°55′54″ E), the orthogonal experimental design was used to experiment for two years (2019–2020), using straw length, amount, and buried depth as returning factors. The carbon source utilization intensity algorithm that was developed by our team was used to extract a single carbon source. A compound mathematical model was constructed based on path analysis and grey relation analysis. This study analyzed the interspecific symbiotic relationship of soil microbes in the process of straw returning and explored the regulatory methods and schemes with which to promote straw decomposition. The results showed that in the first year after straw returning, the cumulative decomposition rate of straw could reach 55.000%; the supplement of the carbon source was glycyl-l-glutamic acid, which was helpful for the decomposition of straw. It was found that cyclodextrin should be added within 90–120 days after straw returning to promote decomposition. In the second year of straw returning, the cumulative decomposition rate of straw can reach 73.523% and the carbon sources α-d-lactose and d-galactonic acid γ-lactone should be supplemented appropriately to promote straw decomposition. This study provides an experimental basis for corn straw returning to the black soil of the cold regions, along with the scientific and technological support for the sustainable development of agriculture and a guarantee of national food security.