Decomposition Of Maize Straw Research Articles

Soil pore structure shaped compositions and structures of soil microbial community during 13C-labelled maize straw decomposition

Soil pore structure regulates water movement, gas exchange and determines the heterogeneous distribution of nutrients, thereby exerting significant influence on microorganisms. However, the specific contributions and limitations of pores of different sizes on soil microbial communities during straw decomposition, as well as the variations in pore structure throughout this process, remain unknown. To address this, a 57-day soil incubation experiment was conducted, using 13C-labelled maize straw with two soil types: Shajiang black soil (Vertisols) and Fluvo-aquic soil (Cambisols). The experiment was set at two bulk densities: 1.2 g cm−3 and 1.5 g cm−3. The variations in pore structure before and after the incubation experiment were quantified using X-ray micro-computed tomography (μCT). To analyze microbial C content from straw, 13C-Phospholipid fatty acids (13C-PLFAs) were used, and 16S rDNA high-throughput sequencing was employed to determine bacterial community structure after the incubation. The resulted showed that Shajiang black soil exhibited a 50.5 % increase of total PLFA-C content from straw than Fluvo-aquic soil at a bulk density of 1.5 g cm−3 (P < 0.05). Specifically, Gram-positive bacteria (G+), Gram-negative bacteria (G−) and actinobacteria PLFA-C content increased by 105.2 %, 55.0 % and 73.6 % (P < 0.05). Redundancy analysis (RDA) showed that >100 μm pores in diameter (Ø) facilitated the colonization of microorganisms (G+, G− and actinobacteria). Specifically, bacteria (including G+, G−, and common bacteria, accounted for 37.6 %, 15.7 % and 22.1 % of straw-derived PLFA-C in relation to the total amount of straw-enriched PLFA-C) were key contributors to straw decomposition and were associated with the formation of 50–200 μm Ø pores. Meanwhile, fungal activity was primarily responsible for changes in the 20–50 μm Ø pore structure. These findings emphasize that >100 μm Ø pores created a favorable physical environment for microbial communities on straw decomposition, highlighting the pivotal role of microbial activity in shaping soil pore structure.

Effects of size and amount and burial depth on early decomposition of maize straw and the links to microbial and nematode communities in the Mollisol of China

AbstractCrop straw is often incorporated into soil at different depths via agricultural practices like tillage, with regional variation in straw decomposition. However, the relative role of management practices on straw decomposition remains unclear. Here, a 5‐month field experiment using litterbags was conducted in three cold sites within China's Mollisol region, with two burial depths (15 and 30 cm) and four maize straw treatments (big straw and small straw at the amounts of 0.5% and 1.0%, respectively). The objectives were to determine the effects of the size and amount and burial depth of straw on its decomposition, microbial and nematode communities, and to identify the key factors regulating straw decomposition. Straw mass loss was affected by straw treatments rather than burial depths in all sites. Specifically, it was the lowest for 0.5% big straw among four straw treatments. Small straw lost more mass than big straw only at the amount of 0.5%, with the variations declining and even disappearing in the site experiencing relatively high temperatures. Microbial biomss and nematode abundance of specific groups were affected by the size and amount of straw in some cases, where the presence of 0.5% big straw corresponded with the lowest microbial biomass and the highest nematode abundance. All bacterial and fungal biomass and some nematode abundances were higher at 30 cm than at 15 cm in the sites with relatively low temperature. The abundance and Shannon index of nematodes were correlated with Gram‐positive bacterial biomass and microbial diversity and evenness index positively, and with other microbial biomass negatively. The straw decomposition explained 83.60% and 77.25% of variations in microbial and nematode community composition, respectively. These results suggest that the physical traits rather than burial depth dominate straw decomposition via changing microbial growth and their interaction with specific nematodes under similar climatic conditions, and the effects of straw physical traits are changed by climate on a large regional scale. Reducing the size and amount is a potential strategy stimulating straw decomposition, particularly in the cold regions.

Divergent accumulation of microbial necromass and plant lignin phenol induced by adding maize straw to fertilized soils

Plant carbon (C) inputs and their subsequent microbial transformation affect the build-up process of soil organic C (SOC) pool. Nevertheless, there are knowledge gaps on how crop straw addition modifies SOC composition at molecular-level, especially in soils with different fertilization practices. Here, long-term fertilized Mollisols (unfertilized control, NF; inorganic fertilization, IF; inorganic fertilization plus manure, IFM) were incubated with or without maize straw addition in a 900-day field mesocosm experiment. The microbial necromass and plant lignin components contents were synchronously quantified based on amino sugar and lignin phenol biomarkers, respectively. And changes in SOC chemical composition were examined using solid-state 13C nuclear magnetic resonance spectroscopy. Relative to the NF treatment, long-term fertilization increased amino sugar and lignin phenol contents, and manure application enhanced the accumulation of plant lignin components more than that of microbial necromass. Compared with the NF treatment, the IF treatment decreased the relative proportion of alkyl C and SOC content, suggesting that changes in microbial necromass and lignin phenol were not always consistent with changes in SOC. For the NF and IF treatments, maize straw incorporation increased both amino sugar content and its contribution to SOC, indicating that microbial anabolism was important for SOC accumulation after adding maize straw in C-poor soils. For the IFM treatment, maize straw addition decreased lignin phenol content (27 %) and its contribution to SOC but increased the contribution of amino sugar to SOC, reflecting an enlarged contribution of microbial necromass to soil C pool formation under manure application after maize straw addition. The contribution of lignin phenol to SOC was decreased from days 360–900, whereas fungal necromass C content and the contribution of amino sugar to SOC were increased from days 360–900 under the IFM soil with maize straw addition, indicating that plant lignin components might be converted into fungal biomass and its necromass with increasing maize straw decomposition under manure application. Overall, we concluded that maize straw addition favored microbial immobilization in all fertilization treatments.

Persulfate pretreatment facilitates decomposition of maize straw in soils and accumulation of straw residues with high adsorption capacity

Because of the complex and recalcitrant structure of straw, large amounts of straw residues accumulate in soils with straw return practice, and pose various adverse impacts. In this study, both laboratory experiments and field demonstration were conducted to investigate the effects of persulfates (PS) pretreatments on structure and properties of maize straw. PS pretreatment of maize straw was developed to facilitate decomposition of returned straw in soils. Persulfates break the aryl C-O bonds of stable lignin units and destroy dense crystalline structure of cellulose units. The former impact was pronounced at high levels of PS. Both impacts were responsible for the accelerated decomposition of maize straw in field soils. The decomposition of maize straw with 0.1% PS pretreatment was increased by 29% (181 d), often superior to the biological-based methods. Interestingly, all straw residues collected in the soils with PS-treated maize straw return after 43 d displayed higher adsorption capacity of the four commonly used herbicides. The adsorption Kd values of herbicides were about 76%–123% higher than those by straw residues collected in the soils with pristine maize straw return. Additionally, all PS pretreatments posed no adverse impacts to both soil bacterial and fungi community. Some of Top Ten bacteria or fungi were stimulated, highlighted by the increases in relative abundances by 4.02%–963%. These results demonstrate that PS pretreatments can serve as an easy and applicable approach to reducing straw residues in soils. Then PS pretreatment may have environmental significance in alleviating accumulation of straw residue in soils and diffusion of pesticides into aquatic systems.

Conservation tillage and moderate nitrogen application changed the composition, assembly pattern and interaction network of abundant and rare microbial community on straw surface

Microbial-driven straw decomposition is important for soil organic carbon accumulation, nutrient uptake, and crop utilization. However, the mechanism by which tillage and fertilization interactions form the abundant and rare microbial communities that mediate straw degradation in dry farmland remains unclear. Based on an interaction experiment between three tillage practices (zero-till, chisel-till, and conventional plow-till) and three levels of nitrogen fertilizer (180, 240, and 300 kg·N·ha−1), we aimed to understand the community assembly process of abundant and rare microbe in the decomposition of maize straw. We found that the abundant bacterial and fungal communities were governed by stochastic processes, whereas the rare bacterial communities were dominated by deterministic processes. Furthermore, the relative importance of deterministic assembly of all microbial communities was higher in conservation tillage; in addition, the deterministic assembly process of the abundant bacterial and fungal communities was significantly increased by the medium level of nitrogen fertilizer (240 kg·N·ha−1), but the rare microbial community was not significantly affected. Redundancy analysis (RDA) and threshold indicator taxa analysis (TITAN) indicated that soil temperature, pH, and NO3− are the key influencing factors for the abundant and rare microbial communities. Overall, conservation tillage and a medium level of nitrogen fertilizer (240 kg·ha−1) in dry farmland promoted straw decomposition by regulating the development and turnover of straw-decomposing communities, in which they regulated bacterial community succession rather than fungi within a short decomposition time. These findings highlight the distinct responses to conservation tillage and N fertilization in the community assembly of abundant and rare biospheres in maize straw decomposition, and provide additional evidence for the development of conservation tillage applications in drylands.

Combining conservation tillage with nitrogen fertilization promotes maize straw decomposition by regulating soil microbial community and enzyme activities

Straw return can effectively improve farmland soil microenvironment and fertility. However, excessive straw in the topsoil adversely affects seed germination and crop growth. At present, the characteristics and key driving factors of straw decomposition in dry farmlands are unclear. Based on the interactions between tillage practices including zero tillage (ZT), chisel tillage (CT), and plow tillage (PT) and nitrogen (N) fertilization, i.e., low N (N1, 180 kg ha-1), normal N (N2, 240 kg ha-1), and high N (N3, 300 kg ha-1), quantitative polymerase chain reaction technology and an enzymatic detection kit were used to investigate the effects of key straw C-degrading enzyme activities and microbial abundance in soil on maize straw decomposition during the growth period of winter wheat in the winter wheat/summer maize double cropping system in a dry farmland of the Loess Plateau, China. Between 2018 and 2020, ZT and CT significantly increased winter wheat yield (by 10.94% and 12.79%, respectively) and straw decomposition velocity (by 20% and 26.67%, respectively), compared with PT. Compared to N1 and N3, N2 significantly increased wheat yield (by 4.65% and 5.31%, respectively) and straw decomposition velocity (by 26.33% and 13.21%, respectively). The partial least squares pathway modelling showed significant positive direct effects of soil moisture, NO3-, NH4+, total N, bacteria, and cellulase, laccase, and xylanase activities on straw decomposition, while soil pH, fungi, and Actinomycetes had significant negative direct effects. Overall, conservation tillage (ZT and CT) combined with N2 was beneficial for straw decomposition in the drylands of the Loess Plateau and improved straw resource utilization and basic soil fertility. The results of the study clarified the key drivers of straw decomposition in dry farmlands and provided new ideas for developing updated soil management practices and adaptive N application strategies to promote the resource utilization of straw and achieve the goals of carbon peaking and carbon neutrality.

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.

High Level of Iron Inhibited Maize Straw Decomposition by Suppressing Microbial Communities and Enzyme Activities

In order to study the linkages between the crop straw decomposition rate and the change in soil biological properties after the straw returned to the soil with different iron (Fe2+) contents, a 180-day incubation experiment was performed to examine the decomposition of maize straw (MS) under three Fe2+ levels, i.e., 0, 0.3, and 1 mg g−1. Enzyme activities regarding straw decomposition and microbial communities under 0 and 1 mg g−1 Fe addition were also detected. The results showed that Fe2+ addition significantly inhibited MS decomposition. This was evidenced by the higher contents of hemicellulose, cellulose, and lignin in Fe2+ treatments on day 180. High-Fe addition (1 mg g−1) decreased the activity of Laccase (Lac) by 71.82% compared with control on day 30. Furthermore, the principal coordinates analysis (PCoA) indicated that high-Fe mainly affected the bacterial community. In particular, it suppressed the relative abundance of Microbacteriaceae in phylum Actinomycota that, in turn, is a potential decomposer of crop straw by secreting lignocellulolytic enzymes. A high level of Fe2+ inhibited the decomposition of hemicellulose, cellulose, and lignin in MS by reducing the relative abundance of phylum Actinobacteria in bacteria and suppressing Lac activity. Our findings provide guidance for returning crop straws in soils with high-Fe content.

Urea/sodium hydroxide pretreatments enhance decomposition of maize straw in soils and sorption of straw residues toward herbicides

Because of the rigid crystalline structure and recalcitrant components, maize straw returned is slowly decomposed in soils. Straw residues are substantially accumulated in soils and pose detrimental impacts to crop plantation. Here we report the pretreatments of urea and NaOH (USH) to enhance maize straw decomposition in the field. The USH reagents interacted synergistically to destruct straw, mainly through breaking the rigid hydrogen bonding network and chemically hydrolyzing recalcitrant lignin. The synergy was evident for the USH reagents containing 6–8% urea and 0.1–1% NaOH under various temperature conditions (–20 °C to 25 °C). The USH (7%/0.1%) pretreatment resulted in notable enhancement (37%) of straw decomposition in the field within 6 months, superior to current biological-based treatments (6–28%). Moreover, this pretreatment posed no influence on the adsorption of straw residues collected at the early stage of decomposition (27 days) toward five commonly used herbicides. Those straw residues collected on 67 days and later exhibited high adsorption capacity, indicated by 0.5- to 4-folded increases in Kd values. Additionally, the impacts to soil pH and bacterial/fungal community were negligible. The USH pretreatments thus have practical interests in mitigating accumulation of straw residues in straw-returned soils.

Decomposition of Maize Straw between Two Phosphate Solubilizing Fungi: Aspergillus Niger and Penicillium Chrysogenum

Aspergillus niger (A. niger) and Penicillium chrysogenum (P. chrysogenum) can significantly promote the degradation of maize straw and phosphorus release. Compared with P. chrysogenum, A. niger is more efficient in maize straw degradation and phosphorus releasing. After seven days of incubation, the highest degradation ratio and phosphorus content in A. niger+maize straw treatment is 2.58% and 2.3 mg/L, respectively. The mechanisms for maize straw decomposition between these two fungi are different. Oxalic acid is the primary organic acid secreted by A. niger, which is more function in the decomposition of maize straw compared with propionic acid secreted by P. chrysogenum. In addition, A. niger has higher acidic xylanase and lignin peroxidase enzymes activities, which is conducive to the degradation of more stable substances in maize straw, i.e., lignin. This study indicated that A. niger is the primary candidate for the reuse of crop straw in the way of return to the field.

Decomposition Characteristics, Nutrient Release, and Structural Changes of Maize Straw in Dryland Farming under Combined Application of Animal Manure

Straw and animal manure are major organic waste materials from agricultural ecosystems. Different kinds of animal manure combined with straw (AM-S) may have varying effects on the decomposition, nutrient release, and structural changes of maize straw. Using the Humic Cambisols soil as the experimental area, the straw decomposition characteristics under the co-application of animal manure were studied following the nylon net bag landfill method. The experiment involved four treatments: maize straw only (S), maize straw plus ox manure (SO), maize straw plus chicken manure (SC), and maize straw plus pig manure (SP). The treatments with AM-S accelerated the decomposition of straw and increased the release rate of nutrients and organic components (cellulose, hemicellulose, and lignin). During the 240 days of the study, straw decomposition showed a trend of increasing rapidly in the first stages and then increasing slowly in the latter stages in all the treatments. At 240 d, the straw decomposition rates and carbon release rates of the AM-S treatments were 65.25–71.87% and 64.04–69.35%, respectively. At the end of the experiment, the order for the final release rates of nitrogen (N), phosphorus (P), and potassium (K) was K (93.25–96.56%) &gt; P (42.25–55.08%) &gt; N (40.01–52.23%). Moreover, scanning electron microscopy showed that SP treatment had the highest degree of structural changes of the maize straw compared with the other treatments. The purpose of this study was to screen the effective animal manure that can promote straw decomposition and provide a reference for the rational use of straw and animal manure management. In conclusion, the study suggested that the co-application of animal manure and straw should be adopted in agricultural systems, especially SP treatment, as it was more conducive to promoting the decomposition of maize straw and the release of nutrients.

Nutrients addition regulates temperature sensitivity of maize straw mineralization

The study aimed to determine the interactive effect of temperature with nutrients on maize residues decomposition in soil. We conducted an incubation of 87 days by applying maize straw (δ13C value of −11.2‰) to soil (δ13C value of −26.3‰) with low (N0), medium (NM), and high (NH) level of nutrients addition, at two temperature levels of 5 °C (T-L) and 25 °C (T-H). We measured the cumulative CO2-C efflux, residues decomposition, temperature sensitivity (Q10), and extracellular enzyme activities. Increased temperature significantly increased cumulative CO2 efflux and straw decomposition, with an enhanced rate of active (Ka) and slow (Ks) pools of soil and residues C. The mean values of Q10 ranged from 1.4 to 1.6 for the total CO2 efflux and 1.4 to 1.7 for maize straw decomposition. The outcome might be due to temperature-dependent microbial activation at 25 °C. The activities of β-glucosidase, α-glucosidase, cellobiohydrolase, and β-xylosidase enzymes were positively correlated with cumulative CO2 emissions at 25 °C suggesting microbial regulation on SOM decomposition. We found a U-shaped pattern of nutrients regulation on the temperature sensitivity of maize straw decomposition, with the lowest Q10 under NM. Our findings suggest that nutrients regulated the temperature effects on residue C decomposition by adjusting microbial activity (extracellular enzyme activities). Consequently, it may lead to soil C sequestration under the current climate change scenario.

Urea/Sodium Hydroxide Pretreatments Enhance Decomposition of Maize Straw in Soils and Sorption of Straw Residues Toward Herbicides

Urea/Sodium Hydroxide Pretreatments Enhance Decomposition of Maize Straw in Soils and Sorption of Straw Residues Toward Herbicides

Effects of mixing maize straw with soil and placement depths on decomposition rates and products at two cold sites in the mollisol region of China

Crop straw is often retained on the ground as mulch or incorporated into soil through tillage practices. These straw management practices may affect straw decomposition rates and subsequently decomposition products due to mixing straw with soil, straw placement depths and experimental sites. Using litterbags containing maize (Zea mays. L) straw only (STO) or straw-soil mixture (SSM), this study aimed to determine the influence of mixing straw with soil and straw placement depths on decomposition rates and decomposition products, and to understand the relation of chemical composition of straw residues with straw decomposition rates. The litterbags were placed at three soil depths (0, 15 and 30 cm) in the fields at two cold sites (Hailun and Harbin), Northeast China, which had similar precipitations but different temperatures. During the 17-month experiment, the decomposition rate constants were higher by 60 %–160 % at a comparable depth in SSM than in STO. The mixing straw with soil was a more important factor in controlling straw decomposition rates than placement depths and experimental sites at the studied region. The relative abundances of O–alkyl C groups in straw residues decreased during the experimental period, even in the winter, while those of aromatic groups increased profoundly. The relative abundances of O–alkyl C groups in straw residues were lower by 0.4 %–6.9 % and those of aromatic groups were higher by 0 %–4.6 % in SSM than in STO. These findings suggest that the conventional litterbag method underestimated straw decomposition rates. Incorporating straw into soil could enhance maize straw decomposition and the formation of more stable soil organic matter (SOM) in the cold high-latitude studied region.

An Approach to Improve Soil Quality: a Case Study of Straw Incorporation with a Decomposer Under Full Film-Mulched Ridge-Furrow Tillage on the Semiarid Loess Plateau, China

There is limited understanding of the effects of straw incorporation with decomposition agent (refer to decomposer) under full plastic film-mulched ridge-furrow tillage (FM) on straw decomposition rate and soil fertility. A direct field incubation test of straw with and without decomposer (T1 and T2) under FM using the litter bag method and a 3-year field experiment of five treatments including conventional planting (CP, as control), CP with straw incorporation (CPS), CP with straw incorporation plus decomposer (CPSD), FM with straw incorporation (FMS), and FM with straw incorporation plus decomposer (FMSD) were conducted in 2014–2016. The results showed that the initial straw N content, indigenous soil nitrogen content, and soil hydrothermal conditions were all remarkably affected by maize straw decomposition, and C and N release regardless of the decomposer. Applying the decomposer resulted in 80.3% decomposition of maize straw, leading to 81.3% of straw C and 83.3% of straw N release into the soil, which were 1.4, 1.1, and 1.06 times than that of CK, respectively. Meanwhile, the FMSD was significantly better in improving soil nutritional conditions, particularly for the tested parameters of soil organic carbon (SOC), soil total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), and available potassium (AK). Importantly, FMSD drove a strong synergistic effect of decomposer and the modified soil hydrothermal conditions in comparison with CP, which led to the significant increase in SOC, TN, TP, AN, AP, and AK by 4.4–8.7%, 5.2–7.5%, 3.0–6.8%, 11.1–12.6%, 3.6–60.5%, and 6.2–54.6%, respectively. Therefore, FMSD is the best model for more efficient and sustainable soil fertility management in semiarid areas in China.

Enhanced conversion of newly-added maize straw to soil microbial biomass C under plastic film mulching and organic manure management

Management of crop production using plastic film mulching (PFM) has the potential to improve soil health by accelerating nutrient cycling and facilitating stable C pool production; however, a key aspect of this process—microbial immobilization of residue C—is poorly understood, especially under PFM when combined with different fertilization treatments. A 360-day in situ 13C-tracing technique was used to analyze the contribution and dynamics of microbial biomass C (MBC) to soil organic C (SOC). Following 27-year PFM and four fertilization treatments, 13C-labelled maize straw residue was applied to micro-plot topsoil in a cultivated maize (Zea mays L.) field. Over the course of the experiment, MBC content was significantly (P<0.05) higher in treatments of organic manure (M) and manure plus nitrogen (MN) compared to the no-fertilization (CK) and nitrogen (N) treatments, regardless of PFM. Compared to no PFM controls, PFM enhanced the decomposition of maize straw by day 60 in the M and MN treatments, exhibiting increases of 93.0% and 28.6% in straw-derived MBC and 80.4% and 82.9% in the straw-derived MBC/SOC ratio, respectively. Overall, both PFM and organic manure treatments improved soil fertility through microbe-mediated incorporation of C derived from newly-added maize straw. Our results indicate that microbial growth and activity are affected by the utilization of different C sources and most dramatically during early seasonal transition.

Long-term plastic film mulching and fertilization treatments changed the annual distribution of residual maize straw C in soil aggregates under field conditions: characterization by 13C tracing

Plastic film mulching and fertilization strongly affect soil aggregation and dynamics of the total soil organic carbon (C) pool. However, there is limited information on how these agricultural management practices influence the fate and seasonal dynamics of crop residue-derived C in soil aggregates. Therefore, a better understanding of the fate of C derived from crop residues and their location in soil aggregates is crucial to improve our prediction of C sequestration and stabilization in soil. In this study, an in situ 13C-tracing technique was used to identify the dynamic distribution and accumulation patterns of crop residue-derived C in soil aggregates as affected by long-term plastic film mulching and four fertilization treatments (control, CK; nitrogen, N2; organic manure, M2; nitrogen and organic manure, M1N1). The fate of 13C-labeled maize straw in loam soil was studied over 360 days using in situ incubation of 0.2% equivalent dry straw incorporated into the soil and aggregate size fractionation. Soil samples were separated into four particle-size fractions [large (>2 mm) and small (1–2 mm) macroaggregates; large (0.25–1 mm) and small ( M1 N1 > N2 > CK. Both the content of straw-derived 13C in aggregate fractions and the proportion of 13C in total soil samples decreased considerably from the microaggregate fractions and increased moderately in the macroaggregate fractions in a manner enhanced by plastic film mulching and by seasonal transitions, specifically from spring (day 0) to summer (day 60). In addition, the decomposition of maize straw and soil aggregation exhibited a direct correlation in which the content of 13C-SOC and mean weight diameters decreased over the course of the 360-day experiment. Our results suggest that certain amounts of straw-derived 13C could accumulate in microaggregates, which play an important role in long-term C sequestration, while a large part of straw-derived C tends to transfer from microaggregates to macroaggregates over time as affected by long-term plastic film mulching coupled with fertilization. This study improves our understanding of the effect of plastic film mulching and different fertilization regimes on the retention and stabilization processes of straw-derived C in soil.

Coupled incorporation of maize (Zea mays L.) straw with nitrogen fertilizer increased soil organic carbon in Fluvic Cambisol

Soil organic carbon (SOC) level is influenced by incorporation of crop straw and application of nitrogen (N) fertilizer, which are typical farming practices in intensive agricultural regions. However, the interaction between the N fertilization and crop straw incorporation on SOC levels is still not univocally established, especially for calcareous soils. We therefore conducted a 224-day laboratory incubation experiment with four levels of 13C-labeled maize straw amendment (0, 1×, 3× and 5× of maize straw yield) and three N fertilization rates (0, 300, and 600kgNha−1a−1) on a Fluvic Cambisol to investigate the short-term response of SOC content. The 13C-labeled straw allowed partitioning of the CO2 produced from native SOC or crop straw for application to a two-compartment exponential decay model to simulate the addition of new SOC from the straw and the decomposition of the native SOC. The addition of maize straw caused immobilization of inorganic N during the incubation. Increased mineral N fertilization significantly inhibited the decomposition of maize straw, which led to the increased new SOC from maize straw amendment. Priming effect (PE) of native SOC decomposition peaked at 40days after incubation, and then decreased until the end of the incubation. N fertilization significantly enhanced the cumulative PE when maize straw was not added (N2 induced PE at C0 was +19% of C0N0 SOC decomposition), but had no significant effect when the highest rate maize straw was amended (N2 induced PE at C5 was 8% of C0N0 SOC decomposition), indicating that maize straw amendment can moderate the PE promoted by N fertilization. There was a positive linear correlation between the cumulative PE and the input of maize straw C. An increase in maize straw incorporation with N fertilization caused the largest increase in total SOC content at the end of 224-day incubation (the highest 23.7% for C5N2 treatment, i.e., 5× maize straw yield+600kgNha−1a−1). Our findings highlight that in intensively managed agricultural regions, integrating N fertilization with crop residue amendment can promote SOC sequestration and the retention of fertilizer N in the soil. The results are particularly relevant for developing new or improved farming methods in areas with calcareous soils, such as northern China.

Molecular changes of ferric oxide bound soil humus during the decomposition of maize straw

The mechanism of organic carbon sequestration in different genesis of paddy soils has not been well understood. A 6-month incubation experiment, adding maize straw, was performed in three different genesis of paddy soils and an uncultivated marsh soil. Fourier transform infrared (FTIR) spectroscopy was used to investigate the characteristics of Fe/Al bound organic carbon (Fe/Al-OC) extracted with a mixed solution of 0.1 M NaOH and Na4P2O7 from soils. The function groups of Fe/Al-OC such as phenol-C, amide-C, and C–O groups of polysaccharides were demonstrated by FTIR spectroscopy. Compared to control treatment, the proportion of phenol-C of Fe/Al-OC added maize straw increased with time, but the C–O groups of polysaccharides decreased. These results indicate that polysaccharide groups of Fe/Al-OC mainly contribute to the sequestration of Fe/Al-OC during the primary decomposition stage of maize straw, and the phenol group was stable in different genesis of paddy soils. Both of the polysaccharides and phenol groups were important to C sequestration in paddy soils and marsh soil.

Effects of straw returning combined with medium and microelements application on soil organic carbon sequestration in cropland.

A 52-day incubation experiment was conducted to investigate the effects of maize straw decomposition with combined medium element (S) and microelements (Fe and Zn) application on arable soil organic carbon sequestration. During the straw decomposition, the soil microbial biomass carbon (MBC) content and CO2-C mineralization rate increased with the addition of S, Fe and Zn, respectively. Also, the cumulative CO2-C efflux after 52-day laboratory incubation significantly increased in the treatments with S, or Fe, or Zn addition, while there was no significant reduction of soil organic carbon content in the treatments. In addition, Fe or Zn application increased the inert C pools and their proportion, and apparent balance of soil organic carbon, indicating a promoting effect of Fe or Zn addition on soil organic carbon sequestration. In contrast, S addition decreased the proportion of inert C pools and apparent balance of soil organic carbon, indicating an adverse effect of S addition on soil organic carbon sequestration. The results suggested that when nitrogen and phosphorus fertilizers were applied, inclusion of S, or Fe, or Zn in straw incorporation could promote soil organic carbon mineralization process, while organic carbon sequestration was favored by Fe or Zn addition, but not by S addition.