Search Results (381)

Organic amendments, such as straw, biochar, and animal manure, have been demonstrated to enhance soil phosphorus (P) availability effectively; however, the long-term impacts and underlying mechanisms require further study. Based on a long-term field experiment, this research systematically analyzed the effects of biochar (BIO), biochar-based fertilizer (BF), straw-returning (CS), and pig manure compost (PMC) on soil phosphorus transformation and crop phosphorus uptake. Results showed that biochar significantly boosted soil available phosphorus (AP) by releasing soluble phosphorus, raising soil pH, reducing phosphorus fixation by iron and aluminum oxides, and enhancing soil cation exchange capacity (CEC) to promote phosphorus dissolution and transformation. Notably, biochar increased the proportion of NaOH-P, facilitating phosphorus accumulation in peanut grains and improving the phosphorus harvest index and utilization efficiency. Straw-returning primarily elevated soil AP by promoting organic phosphorus mineralization and inorganic phosphorus release; however, its acidification of the soil impaired phosphorus translocation to grains, resulting in lower phosphorus-use efficiency compared to biochar. Pig manure compost reduced soil phosphorus fixation and increased soil total organic carbon (TOC), thereby boosting phosphorus transformation. Despite enhancing phosphorus dry-matter production in plants, most phosphorus remained in stems and leaves, with limited translocation to grains, leading to lower phosphorus-use efficiency than biochar. In conclusion, biochar was most effective in enhancing soil phosphorus availability and crop phosphorus-use efficiency, highlighting its potential in sustainable soil fertility management and optimized crop production. Full article

Straw return is widely adopted to promote agricultural sustainability, but it can also increase cadmium (Cd) bioavailability in contaminated paddy soils, potentially leading to higher Cd accumulation in rice grains. Although numerous studies have investigated straw incorporation, the specific differences between early- and late-season straw return regarding Cd dynamics within double-cropping rice systems remain inadequately characterized. To address this knowledge gap, we conducted a two-year field experiment comparing early-rice (ER) and late-rice (LR) straw return, complemented by controlled pot experiments simulating ER (ER-S, ER-CK; July–September 2023) and LR (LR-S, LR-CK; December 2022–March 2023) straw incorporation. The results revealed that the Total-Cd exhibited an upward trend following both ER and LR straw incorporation. The ER treatment caused a rapid yet short-lived increase in CaCl₂-extractable Cd (CaCl₂-Cd) concentration, peaking around 60 days following straw return and exhibiting a 28.83% increase compared to the LR treatment. In contrast, the LR treatment induced a slower but more prolonged Cd release, with CaCl₂-Cd concentration peaking around 210 days and exhibiting a 34.89% increase relative to the ER treatment. Additionally, at the late-rice stage, grain Cd concentration in the ER treatment increased by 23.64% relative to the LR treatment. In the subsequent year, grain Cd concentrations in the LR treatment increased significantly by 32.12% to 45.08% compared to the ER treatment for both early- and late-rice crops. These differences were attributed to variations in straw decomposition rates, soil pH, and redox potential between warm, aerobic summer–autumn conditions and cooler, anaerobic winter–spring conditions. This suggests that returning late-rice straw constitutes an elevated hazard to soil health and rice safety compared to early-rice straw return. Full article

An appropriate drip irrigation amount and the straw return method are important ways to save water and achieve efficient maize production in semi-arid areas. A 2-year controlled field plot experiment was performed with two factors: straw return (straw removal, straw mulching) and differing drip irrigation amounts (200, 350, and 500 mm). Changes in growth, development, photosynthesis, yield, the components, and the water-use characteristics of maize under the intercropping conditions of drip irrigation amount and straw return were studied. The results showed that an increase in drip irrigation favored an increase in the net photosynthetic rate (P_n), stomatal conductance (G_s), and intercellular carbon dioxide concentration (C_i) of maize, and promoted an increase in maize plant height and leaf area index, which resulted in the accumulation of more dry matter and increased the maize yield. Compared with straw removal, straw mulching maintained a higher photosynthetic capacity at the later stages of maize growth and development under irrigations of 200 and 350 mm; the average increase in P_n over two years ranged from 4.06 to 19.19%; and good plant growth was maintained, thereby leading to the accumulation of more dry matter, with the average increase over two years ranging from 0.51 to 27.22%. Straw mulching also significantly improved water-use efficiency (WUE) at 350 mm of irrigation, with the average increase in yield over two years ranging from 4.58 to 4.83%. Overall, straw mulching had a positive impact on maize when irrigation was low, and when it was high, straw mulching did not adversely affect maize. Therefore, irrigation combined with straw mulching technology may be used to improve maize yield and WUE in semi-arid areas of Jilin Province. Full article

Soil organic carbon (SOC) represents a crucial factor in agricultural production, and its accumulation is influenced by soil microbial community and microbial metabolism. Straw returning combined with decomposing agents is recognized practice to enhance SOC. On the other hand, the impacts of controlled-release nitrogen fertilizer (CR) on the function of the decomposing agent in degrading straw are underexplored. In this study, an incubation experiment with ¹³C labeled straw in three nitrogen fertilizer treatments (CK, no nitrogen applied; UR, urea applied; CR, controlled-release fertilizer applied) was carried out to elucidate how CR regulates the straw decomposition agent and bacterial community to influence the SOC sequestration, based on field experiments. And we examined the changes in soil organic carbon and the stability of the bacterial networks by combining co-occurrence networks and a structural equation model. In the incubation experiment, the results demonstrated that CR increased the relative abundance of straw decomposition agent and straw-derived SOC (SO¹³C). Additionally, CR enhanced the stability of soil bacterial networks, compared with UR, by strengthening the interactions within the soil bacterial community. Pearson correlations confirmed that straw decomposition agent was positively associated with SO¹³C. Moreover, the straw decomposition agent was positively correlated with the activities of the nitrogen-cycling enzyme (urease, N-acetyl-β-glucosaminidase) and carbon-degrading enzyme (β-1,4-glucosidase, cellulase). Furthermore, structural equation modeling indicated that soil inorganic nitrogen played the most direct role in changes in the straw decomposition agent and then indirectly stimulated the activity of cellulase, ultimately increasing straw-derived carbon in the soil. This study elaborates the mechanism of straw returning combined with straw decomposition agent and controlled-release fertilizers to enhance the SOC of coastal saline–alkali soil from the perspective of underground biology. Collectively, the results of this research might improve the management of straw returning and sustainable utilization of fertility in saline–alkali soil. It provides a new perspective on fertilization for increasing soil carbon sequestration in future farmland ecosystems. Full article

Combining straw return with nitrogen fertilizer application is an effective strategy to enhance farmland productivity, improve soil structure, and mitigate climate change. Although straw return practices are widely recommended in agricultural ecosystems targeting sustainable agriculture, few studies have investigated the combined effects of consecutive years of straw return and nitrogen-fertilizer interactions on rice yield, nitrogen use, and lodging resistance, as well as the potential interactions among these variables. To investigate the effects of consecutive years of rice straw return and nitrogen fertilizer inputs on rice growth, a straw return experiment was conducted in 2021–2022 in Northeast China. The test crop was rice (cv. Jinongda No. 667), with four nitrogen fertilizer levels: 0 kg/ha (N0), 125 kg/ha (N1), 150 kg/ha (N2), and 175 kg/ha (N3). Five straw-return treatments were applied: no straw (S0), straw return to the field for one year (S1), continuous straw return to the field for two years (S2), continuous straw return to the field for three years (S3), and continuous straw return to the field for four years (S4). Results indicated that under the same straw return year, the N3 yield, nitrogen accumulation, nitrogen use efficiency, and apparent utilization were the highest. Under the same nitrogen treatment condition, S1 significantly reduced yield, nitrogen accumulation, nitrogen use efficiency, apparent nitrogen utilization, and lodging index compared to S0. However, under N3 conditions, S3 did not significantly differ from S0. Both S3 and N3 enhanced nitrogen uptake, translocation, and accumulation in rice. Their significant interactive effect increased yield while simultaneously enhancing the lodging resistance and stem strength. The study findings highlighted the effects of years of straw return and nitrogen fertilizer application on crop yield and resistance traits. They further demonstrated that the combination of straw return and optimized nitrogen fertilizer inputs could improve resource utilization and result in a high-yielding and efficient crop population. Full article

Aiming at the problems of intensified soil compaction under the conditions of no-tillage operations and machine blockage caused by large-scale straw returning to the field, an operation mode of “straw strip collecting-strip subsoiling” was proposed, and a Monomer Profiling Strip Tillage Machine (MPSTM) with Straw-Strip-Collecting and Subsoiling Functions was designed to achieve anti-blocking operation and three-dimensional soil compaction reduction. The principle and mechanism parameters of monomer profiling in strip tillage are analyzed, and the effective profiling conditions are clarified. It is determined that the deflection angle, inclination angle, and installation spacing have a key influence on the straw clearance effect. The theory of soil failure and soil compaction reduction under the operation of the subsoiling and strip tillage mechanism is studied, and a combination of a medium-sized Subsoiler shovel handle and a 150 mm double-wing shovel is adopted. Using the EDEM discrete element method, taking the spatial parameters of the stubble clean disc (SCD) as the test factors and the straw removal rate (SRR) as the test indicator, a quadratic orthogonal rotation test is conducted to clarify the influence of each parameter on the straw clearance. The optimal SCD spatial parameters were determined as a deflection angle of 16.5°, an inclination angle of 25°, and an installation spacing of 100 mm, achieving a maximum SRR of 95.34%. Field test results demonstrated stable machine operation. Post-operation measurements yielded the following results: the width of the straw-cleaning band (WSCB) in the sowing strip is 193.7 mm; the overall straw removal rate (OSRR) is 84.82%, which is basically consistent with the simulation results; the subsoiling depth (SD) is 271.7 mm; the subsoiling depth stability (SDS) is 91.85%; the soil fragmentation rate (SFR) is 81.19%; and the reduction of soil compaction in the 0–10, 10–20, and 20–30 cm soil layer is 50.08%, 21.78%, and 40.83%, respectively. These results confirm that the machine effectively cleaned straw within the seeding band and reduced soil compaction, meeting the agronomic and technical requirements for strip tillage. Full article

This study aimed to develop an effective method to overcome the challenge of straw return in cold-region soil. We systematically investigated the synergistic mechanism of montmorillonite (MMT) and composite amino acid (CAA) on straw humification and carbon sequestration through a low-temperature litterbag field experiment. The results indicate that the combined treatment (MMT-CAA) significantly increased the decomposition rate of straw by 42.1% compared to the control (CK), with MMT showing particular efficacy in lignin degradation (28.3% reduction), while the CAA preferentially decomposed cellulose (19.7% reduction). An FTIR analysis of the decomposition products confirmed these findings. Water-soluble organic carbon (WEOC) and its three-dimensional fluorescence spectra exhibited a 25.0% increase in MMT-CAA and enhanced aromaticity of humic acid-like substances. Humic substances and their ¹³C-NMR revealed that MMT-CAA enhanced humic acid formation and molecular stability by 31.4% (with a 47.8% increase in aromaticity). A further redundancy analysis and symbiotic network of microorganisms demonstrated that MMT-CAA increased the abundance of lignocellulose-degrading phyla (Actinomycetes and Stramenomycetes) and the formation of a complex co-degradation network. Field corn planting trials indicated that MMT-CAA increased plant height by 55.1%, stem thickness by 58.7%, leaf area by 70.2%, and the SPAD value by 41.1%. Additionally, MMT significantly reduced CO₂ and N₂O emission fluxes by 35.6% and 15.8%, respectively, while MMT-CAA increased CH₄ uptake fluxes by 13.4%. This study presents an innovative strategy, providing mechanistic insights and practical solutions to synergistically address the challenges of slow straw decomposition and carbon loss in cold regions. Full article

The yield of corn straw is huge, and returning straw to the field is an efficient utilization measure. The challenge in this approach is how to efficiently degrade the straw returned to the field. The study of efficient straw-degrading bacteria and their application conditions is an important approach. Therefore, after enrichment, separation, screening, and strain identification, three strains (X−2, X−4, and X−6) of highly efficient cellulose-degrading bacteria were obtained, namely Pseudomonas aeruginosa PA14, Brevibacillus parabrevis M3, and Bacillus cereus PgBE247. Based on antagonistic experiment results in which the strains were observed to not be antagonistic to each other, they were combined to prepare a bacterial consortium (M−1) for straw degradation. The CMCase, FPA, and β-Gase of the M−1 consortium were 28.46 U/mL, 30.93 U/mL, and 27.94 U/mL, respectively, higher than the values for single bacteria. On the 35th day, the degradation rate of corn straw by M−1 reached 79.81% in liquid medium, significantly increased by 72.06% (p < 0.01) compared to the sterile control (CK), and was significantly higher than single bacteria (p < 0.05). The straw degradation rate of M−1 was the highest at 69.69% in the simulated straw return, significantly increased by 59.84% compared to CK (p < 0.05), and increased by 18.32%, 11.59%, and 14.92% compared to the straw degradation rates of X−2, X−4, and X−6, respectively. The response surface condition optimization verification results showed that the straw degradation rate was 72.15 ± 1.21% when the amount of bacterial suspension was 25%, corn straw dosage was 9 g, initial pH was 7, and reaction temperature was 30 °C. Overall, this study revealed a new bacterial consortium for corn straw decomposition and optimized the conditions for its return to the field, providing a theoretical basis for subsequent studies. Full article

Straw return directly increases carbon inputs, enhancing soil organic carbon (SOC) stocks. However, long-term straw return leads to carbon saturation in the topsoil (0–20 cm). While most studies focus on the topsoil, the effects of long-term straw return on deep soil (100–200 cm) carbon sequestration remain poorly understood. This study investigated carbon dynamics in an arid region by analyzing 0–200 cm soil profiles under different straw return treatments: control (uncultivated) and cotton straw return for 5 (SR5), 10 (SR10), and 20 years (SR20). Straw return significantly improved soil properties by reducing electrical conductivity (EC), increasing nutrient availability, and enhancing bacterial activity. SR20 resulted in the most pronounced SOC increase (18.6–252.7%) across the entire profile and significantly enhanced soil inorganic carbon (SIC) (27.7–52.7%) in deep layers. In contrast, SOC in the topsoil (0–20 cm) increased initially but plateaued after 5–10 years. Principal component and random forest analyses showed that SOC sequestration was primarily driven by sucrase, urease, available phosphorus, dissolved organic carbon (DOC), microbial diversity indices, and available calcium (p < 0.05), while SIC dynamics were significantly influenced by sucrase, urease, DOC, CO₂ emissions, available calcium, and EC (p < 0.05). These findings underscore the importance of exploring subsoil carbon sequestration mechanisms in arid ecosystems. Full article

Context: To revive the practice of planting legume green manure (GM) in the fallow period in rainfed agricultural areas, it is essential to demonstrate the benefits of this practice on the yields and water use efficiency (WUE) of subsequent crops, especially when integrating with optimized water and fertilizer management. Objectives: We conducted a field experiment to determine the positive effects of planting legume GM in the summer fallow on the yield, WUE, and nitrogen uptake efficiency (NupE) of subsequent winter wheat, which was grown with plastic film mulching and integrated fertilization in the Loess Plateau of China. Methods: A split-plot-designed experiment was arranged with two main treatments, namely (1) wheat planting followed by GM planting in the summer fallow (GM) and (2) conventional wheat monoculture followed by bare land summer fallow (BL), and three sub-treatments: (1) control treatment without any chemical fertilizer (Ct), (2) application of chemical N, P, and K as basal fertilizer (B), and (3) application of basal fertilizer plus wheat straw return (BS). Results: In the initial two years, even in a dry year, GM did not decrease the soil water content and storage (0–200 cm layer) during the subsequent winter wheat season, relative to BL. But in the third and fourth years, GM increased the grain yield of winter wheat by 3.2% and 3.8%, respectively. B and BS increased the grain yield of winter wheat by 14.4% and 22.2%, respectively, during the third experimental year, and by 12.7% and 19.4% during the fourth experimental year, primarily through increasing the population density of winter wheat. The increase in the grain yield contributed to a higher WUE of winter wheat. In the third year, GM increased the water consumption (WC) and WUE of wheat by 2.4% and 1.7%, respectively, though they were far lower than B (8.3% and 5.6%) and BS (10.4% and 10.7%). B and BS resulted in a higher yield and N nutrition than GM alone, but GM combined with B and BS resulted in the highest yield and N nutrition, thus greatly decreasing the NupE and increasing N productivity. Conclusions: Planting legume GM in the fallow can further increase the long-term yield, WUE, and N utilization of winter wheat when integrated with chemical fertilization and wheat straw return in rainfed agriculture. Implications: Our study yields new insights into the agronomic benefits of legume GM application in semi-arid or analogous rainfed agroecosystems and underscores the critical role of water conservation in ensuring dryland agricultural production, particularly in regions undergoing optimization of fertilization. Full article

Straw removal is a method used to reduce cadmium (Cd) concentration in contaminated farmland. Experiments in Hunan Province tested different stubble heights (0, 15, 30, 45 cm) in three Cd-polluted paddy fields with different contamination levels. The results showed that lower stubble heights resulted in larger straw biomass and more Cd removed from the field, while the residual biomass and Cd returned to the field decreased accordingly. At stubble heights of 0, 15, 30, and 45 cm, the removed straw biomass accounted for 100%, 69.19%, 48.84%, and 28.17% of the total straw biomass, respectively. The corresponding Cd removal amounts were 12.89, 7.18, 4.18, and 1.83 g ha⁻¹, which constituted 100%, 54.06%, 29.85%, and 12.54% of the total Cd accumulation in straw for the season, respectively. According to the fitted curve, the biomass of returned and removed straw was equal at a stubble height of 31 cm, while at 23 cm, the Cd return and removal amounts were balanced. Rice varieties Huanghuazhan and Nongxiang 42 had better Cd removal but risked grain Cd exceeding limits. Since Cd concentration in straw determines removal efficiency, varieties with high straw Cd accumulation and low grain Cd are more suitable for remediation, rather than high-Cd-accumulating types. Full article

Straw returning (ST) significantly improves soil quality and profoundly impacts soil microorganisms. However, the effects of different ST application amounts on the soil bacterial community remain unclear, and more studies on optimal ST application amounts are warranted. This study aimed to investigate the bacterial diversity and composition, as well as physicochemical properties, of soil in a corn field with 5-year ST amounts of 0, 3, 4.5, 5, and 6 t/hm², respectively. The results indicated that ST significantly reduced soil bulk density and increased soil pH and nutrients. Meanwhile, ST had a significant effect on the bacterial composition, and the bacterial diversity increased significantly after ST. The relative abundance of Proteobacteria and Acidobacteria increased dramatically, whereas that of Actinobacteria significantly decreased after ST. The amount of ST had threshold effects on soil physicochemical properties and the dominant bacterial phyla. Moreover, the co-occurrence networks indicated that bacterial stability first increased and then decreased with the increase in ST amounts. Soil organic carbon and total nitrogen concentrations were the main drivers of bacterial diversity, whereas soil pH and total nitrogen concentrations were the main drivers of bacterial composition. This study strengthens the fact that ST amounts have threshold effects on the soil physicochemical properties and soil microorganisms, and ST amounts of 3–5 t/hm² were appropriate. Full article

Straw-returning is an effective way to improve straw utilization efficiency and reduce environmental pollution. Various straw-returning methods exist; however, their effects on soil microbial diversity and community composition in cool regions have been little studied. This study investigated the changes of soil microbial diversity and community composition under three straw-returning methods, i.e., straw mulching, straw mulching and overturning, straw crushed and mixed, as compared to straw removal as control. The results showed that straw-returning could alter the soil microbial community composition and abundance compared with straw removal. Alpha diversity analysis showed that straw mulching treatment, and straw crushed and mixed treatment significantly increased the diversity of both soil bacteria and fungi compared with straw mulching and overturning treatment. Moreover, this study preliminarily screened Trichoderma, Chaetomium and Streptomyces as potential straw-degrading microorganisms. This study provides basis for further enhancement of straw degradation by using soil microorganisms and sheds light on future work for improving straw degradation efficiency. Full article

To address the problems of low crushing efficiency and uneven distribution in traditional straw crushing and returning machines for cotton stalk return operations in Xinjiang, a vertical straw crushing and returning machine with large and small dual-blade discs was designed, adapted to Xinjiang’s cotton planting model. The machine employs a differentiated configuration of large and small blade discs corresponding to four and two rows of cotton stalks, respectively, effectively reducing tool workload while significantly improving operational efficiency. A simulation model of the crushing and returning machine was developed using the discrete element method (DEM), and a flexible cotton stalk model was established to systematically investigate the effects of machine forward speed, crushing blade rotational speed, and knife tip-to-ground clearance on operational performance. Single-factor simulation experiments were conducted using crushing qualification rate and broken stalk drop rate as evaluation indicators. Subsequently, a multi-factor orthogonal field experiment was designed with Design-Expert software (13.0.1.0, Stat-Ease Inc, Minneapolis, MN, USA). The optimal working parameters were determined to be machine forward speed of 3.5 m/s, crushing blade shaft speed of 1500 r/min, and blade tip ground clearance of 60 mm. Verification tests demonstrated that under these optimal parameters, the straw crushing qualification rate reached 95.9% with a broken stalk drop rate of 15.5%. The relative errors were less than 5% compared to theoretical optimization values, confirming the reliability of parameter optimization. This study provides valuable references for the design optimization and engineering application of straw return machinery. Full article

A multi-parameter optimization-based design method for soil-mixing blades was proposed to address the issue of excessive straw residue in the seeding layer after maize straw incorporation. A discrete element model simulating the interaction between the soil-mixing blades, soil, and corn straw was established. The key structural parameters included the bending line angle (α), bending angle (β), side angle (δ), tangential edge height (h), and bending radius (r); the straw burial rate (Y₁) and straw percentage in the seeding layer (Y₂) were selected as evaluation indicators. Single-factor experiments determined the significance level (p < 0.05) and the parameter range. A Box–Behnken response surface design, combined with analysis of variance (ANOVA), was employed to elucidate the influence patterns of the structural parameters and their interactions regarding straw burial performance. Multi-objective optimization yielded an optimal parameter combination: α = 55°, β = 100.01°, δ = 130°, h = 40.05 mm, and r = 28.67 mm. The simulation results demonstrated that this configuration achieved a Y₁ of 96.04% and reduced Y₂ to 35.25%. Field validation tests recorded Y₁ and Y₂ values of 96.54% and 34.13%, respectively. This study quantitatively elucidated the relationship between soil-mixing blade parameters and straw spatial distribution, providing a theoretical foundation for optimizing straw incorporation equipment. Full article