Introduction:Straw returning has the potential to reduce nitrogen (N) input by enhancing soil fertility; however, the optimal N application rate may vary under different crop residue management practices. Methods:Based on a long-term field experiment initiated in 2011, this study investigated the effects of two residue management methods, namely, no tillage with straw mulch (SM, full straw return) and plow tillage incorporating straw mulch to a depth of approximately 15 cm (SP, full straw return), in combination with five nitrogen application rates (0, 90, 150, 210, and 270 kg ha-1) on maize grain yield, nutritional quality, and the partial factor productivity of nitrogen fertilizer (PFPN). Results:The results indicated that the 1000-kernel weight and kernel number under SP were 7.09% and 6.26% higher than those under SM, respectively, resulting in a 9.24% higher yield in SP. Furthermore, PFPN was significantly greater under SP, by 13.88% compared with SM. This difference was more evident when the N application rate was below 150 kg ha-1. Additionally, the comprehensive nutritional quality index (Q value), which integrates crude protein, crude fat, starch, and amino acid contents via the entropy weight method to avoid limitations of single-trait analysis, reached a higher linear plateau under SP than under SM, as SP enhanced the crude fat (by 6.68%) and starch (by 1.90%) contents in the grains. Discussion:In conclusion, SP demonstrated greater potential for N fertilizer savings while achieving high grain yield and superior nutritional quality. The optimal N application rates were 113.82-129.53 kg ha-1 for SP and 129.90-135.81 kg ha-1 for SM, ensuring the coordinated improvement of yield, nutritional quality, and PFPN.

To address the limited accessibility of agricultural expertise, delayed technical support and inaccurate model-generated answers, this study developed PlantExpert, a domain-specific agricultural question answering (QA) system that integrates knowledge graph (KG) and large language model (LLM). Focusing on three major staple crops—wheat, maize, and rice—we first constructed a high-quality agricultural corpus from authoritative sources, including officially recommended technologies and industry standards issued by agricultural authorities, as well as core journal publications and specialized monographs. We then designed an agricultural domain ontology and performed joint entity–relation extraction using a BERT-based model. After manual verification, this process yielded an agricultural KG containing approximately 9,512 entities and 15,047 relations. On this basis, we automatically generated 4289 question–answer pairs (QA pairs) through KG subgraph sampling and used these data to perform domain adaptation on Qwen2.5-7B via low-rank adaptation (LoRA). We further introduced a KG-augmented inference mechanism that transformed relevant subgraphs into structured contextual constraints, thereby mitigating factual hallucinations in the LLM. Experimental results show that, compared with the vanilla Qwen2.5-7B base model, a variant fine-tuned solely via LoRA without KG constraints, and a conventional text retrieval-augmented generation baseline, PlantExpert consistently achieved the best performance across all evaluation metrics. Specifically, it attained 57.8% BLEU-4, 61.6% ROUGE-L, 79.5% Number-Units-Matched, and 82.4% human evaluation. These findings demonstrate that the KG not only supports the construction of high-quality supervised data for agricultural QA, but also provides effective structured factual constraints at inference time, thereby improving the accuracy, consistency, and practical applicability of generated answers. This study offers a practical pathway for deploying LLMs in specialized agricultural domains.

Using wheat bran as substrate, four solid-state fermentation methods were compared for soluble polyphenol release. The effect of Bio-enzymatic synergy (BES) is the most significant, producing 4.85 mg GAE/g of total phenolic substances, which is 45.77% higher than the control group (CK). LC-MS analysis revealed that ferulamide and 2,4,6-trihydroxybenzoic acid predominated in positive ion mode, while salicylic acid dominated in negative mode. Notably, salicylic acid was found almost exclusively in ester-bound and glycoside-bound fractions (>88%), indicating its release requires cleavage of covalent linkages to cell wall components. The release of salicylic acid results from the synergistic action of Bio-enzymatic synergy and alkaline hydrolysis. Both in vitro and in vivo assays confirmed that BES-released polyphenols enhanced antioxidant activity, reducing ROS and MDA levels while increasing GSH-Px activity and extending C. elegans lifespan. These findings provide a mechanistic basis for developing targeted fermentation-enzymatic processes to produce functional wheat bran extracts.

Soil salinization represents a significant environmental challenge that adversely affects the growth and productivity of wheat (Triticum aestivum L.), primarily by impeding root development. Although melatonin (MT) is acknowledged as a crucial phytohormone involved in responses to abiotic stress, the precise mechanisms through which endogenous MT facilitates salt tolerance in wheat roots remain inadequately elucidated. In this study, we observed that salinity stress induces a rapid accumulation of endogenous MT in wheat roots, which is associated with a marked upregulation of the biosynthetic gene TaCOMT. Heterologous overexpression of TaCOMT in Arabidopsis resulted in significantly elevated MT levels and conferred enhanced salt resistance, as evidenced by increased root biomass and length. Mechanistic investigations indicated that MT functions upstream of hydrogen sulfide (H2S) signaling. MT treatment prompted a surge in endogenous H2S production by enhancing the activity of the biosynthetic enzyme L-cysteine desulfhydrase. Pharmacological interventions revealed that the protective effects of MT, particularly in restoring redox homeostasis and maintaining ion balance, were nullified by the removal of H2S. Collectively, these findings suggest a critical role for MT in modulating salt tolerance through H2S signaling pathways.

Incorporating legumes into crop rotation systems is an environmentally sound agricultural practice that improves soil quality and crop productivity. However, the mechanisms underlying these benefits, particularly the relationship between soil properties and microbial communities, remain unclear. This study evaluated the impact of three different rotation patterns, namely wheat-maize (WM), wheat-peanut (WP), and wheat-soybean (WS), on wheat yield, grain quality, soil physicochemical properties, soil enzyme activities, and microbial community. Our results demonstrated that legume-based rotations significantly improved wheat performance. In contrast to WM, WP consistently achieved the highest wheat yield, with a 3 year average increase of 10.7%. Furthermore, significant improvements in key quality parameters were observed in WP. Specifically, crude protein and wet gluten contents increased by 9.2% and 27.4%, respectively. These improvements were attributed to the enhancement of soil health. Legume rotations, particularly WP, led to significant improvements in soil total nitrogen (TN), available phosphorus (AP), and soil water content (SWC). This was accompanied by a strategic shift in soil enzymatic functions, with significantly higher activities of N-cycle (LAP, NAG) and P-cycle (ALP) enzymes. High-throughput sequencing revealed that legume rotations enriched specific bacterial phyla, such as Acidobacteria and Chloroflexi, and fostered a more complex and stable fungal co-occurrence network. Mantel test analysis revealed that wheat yield and quality were significantly correlated with several key soil parameters, including soil pH, TN, and the activities of NAG and ALP. PLS-PM analysis revealed that soil properties enhanced soil enzyme activity by shaping microbial communities, ultimately improving crop performance, demonstrating that microbial communities and soil enzyme activity play crucial roles. Collectively, these findings reveal that introducing legumes, especially peanut, boosts wheat yield and quality by enhancing soil nutrient availability and shaping a beneficial microbial community, serving as a sustainable strategy for wheat production.

This study investigates the effects of varying drying temperatures and humidity levels on the molecular structure and digestive properties of resistant starch (RS). The RS content of 60/95 (temperature/relative humidity) sample was 45.39%, significantly higher than that of all other groups. This sample also exhibited the highest crystallinity at 45.73%. The hydrolysis curves for all RS samples showed a gradual increase from 0 to 180 min, with 60/95 demonstrating the lowest hydrolysis rate. High-temperature and high-humidity drying conditions promoted the development of a more complete B-type crystalline cell structure, forming a denser multi-crystalline phase that enhanced resistance to enzymatic digestion. Conversely, the crystal form of 80/95 transformed from type B to type A, achieving the highest long-range order (IR 1047/1022 = 0.978). However, the A-type crystal structure of 80/95 exhibited defects, with loosely arranged grains. This research provides novel insights and processing strategies for the production of RS with improved functional properties.

IntroductionHigh-temperature stress severely restricts the growth, development and yield formation of summer maize. Foliar application of exogenous melatonin has been widely demonstrated to enhance stress tolerance and alleviate abiotic stress in crops. However, the physiological and molecular mechanisms underlying melatonin-mediated thermotolerance in summer maize under post-flowering high-temperature stress remain unclear.MethodsIn this study, field experiments were conducted using foliar application of melatonin at different concentrations on maize. By integrating agronomic, physiological and transcriptomic approaches, we systematically investigated the mechanisms by which melatonin improves the adaptation of summer maize to post-flowering high-temperature stress.Results and DiscussionThe results showed that exogenous melatonin increased the net photosynthetic rate of ear leaves and maintained high photosynthetic capacity. Melatonin treatment also significantly increased the activities of key antioxidant enzymes and the contents of antioxidant substances in the maize ear leaves, thereby enhancing the antioxidant defense capacity of the plant. Transcriptomic analysis further revealed that melatonin upregulated the expression of key genes involed in the photosynthetic and antioxidant defense systems of maize. In summary, exogenous melatonin application improved the resistance of summer maize to natural post-flowering high-temperature stress by optimizing photosynthetic function and reinforcing the antioxidant defense system, effectively reducing the damage of high-temperature to maize growth, biomass accumulation and grain yield. The 150 µmol L-1 melatonin treatment exerted the optimal mitigating effect under field conditions. These findings help to elucidate the key mechanisms by which exogenous melatonin enhances thermotolerance in maize under post-flowering high-temperature stress, and provide a theoretical basis for research on of maize stress resistance, disaster reduction, yield improvement, and efficient chemical regulation strategies.

Annual wheat-maize rotation is a traditional cultivation pattern in North China, and its fertilization and irrigation often face mismatches between peak demand of the crops for water and nutrients and pronounced seasonal fluctuations in soil water and nutrient availability in some specific stages during growth period of the crops. As such, this could reduce water and fertilizer use efficiency and increase the risk of non-point source pollution, compromising the development of sustainable agriculture. Water and fertilizer integration via coordinated regulation of precise irrigation and demand-driven fertilization offers an effective approach to address these challenges and has been investigated extensively over the past decades. This paper systematically reviews the advances in this technology, from early development and experimental validation to scale-up, optimization and large-scale application. The mechanisms underlying why water-fertilizer integration improves crop performance are analyzed, ranging from optimization of the root-zone water and nutrient environment, regulation of crop physiological and metabolic processes, to improvement in synchronization with nutrient cycling. We also review optimal water-fertilizer integration for wheat-maize rotation systems and its effectiveness in improving water and fertilizer use efficiency. We suggest developing an intelligent decision- support system for water and fertilizer management to evaluate the long-term impact of water-fertilizer integration on soil ecology, and synergistically integrating it with other agronomic practices such as straw return, deep tillage, organic fertilizer application and the use of lodging-resistant and stress-tolerant varieties to make the most of it. These integrated strategies can help improve water and fertilizer use efficiency and promote sustainable agriculture.

Introduction:Optimizing water and nitrogen management is crucial for the sustainable development of wheat-maize rotation system. This study systematically examined the impacts of various water and nitrogen management strategies on the wheat-maize rotation system, with the aim of identifying integrated practices that can simultaneously improve yield, resource use efficiency, economic returns, and environmental outcomes. Methods:A field experiment was conducted from 2022 to 2024 in Tai'an, Shandong Province, China. Strategies involved different nitrogen fertilizers (compound fertilizer, urea, and controlled-release fertilizer) and irrigation methods (flood, drip irrigation DI, and micro-sprinkler irrigation SI). Outcomes were assessed based on yield, water and nitrogen use efficiency, economic benefits, and environmental performance, using entropy-weighted TOPSIS comprehensive evaluation. This research aiming to identify an optimized management practice that can simultaneously. enhance both economic and carbon benefits(carbon sequestration/emission ratio). Results and discussion:Drip irrigation with 60% basal controlled-release fertilizer and 40% top-dressed urea (T4) yielded optimal results. Compared to conventional flood irrigation with 50% basal compound fertilizer and 50% top-dressed urea, T4 synergistically increased annual system yield by 1.08-3.99%, improved water use efficiency to 9.42 kg·m-3 and nitrogen use efficiency to 34.75%, achieved the highest net income (24,347.9 CNY·ha-1), and raised carbon benefits to 21.38. Entropy-weighted TOPSIS comprehensive evaluation further demonstrated that the T4 treatment under drip irrigation obtained the highest closeness coefficient (0.702). These findings show that integrating drip irrigation with the split application of controlled-release fertilizer and urea can facilitate the efficient alignment of water and nitrogen resources. This approach is a viable technical pathway for promoting sustainable and low-carbon production under the wheat-maize rotation system in the Huang-Huai-Hai region of China.

The treatment and recycling of crop straws has become a hot spot in the field of agricultural research, with the need to optimize the management of wheat-maize annual straws, improve the carbon efficiency of cropping systems, and promote the sustainable production of wheat-maize annual straw. Based on an 8-year long-term field trial, two treatments, wheat-maize double cropping （WS-MS） and wheat-maize single cropping （WS-MN）, were set up, and the effects of straw returning on soil organic carbon （TOC） content, oxidizable organic carbon （EOOC） content, soil carbon storage, carbon pool management index （CPMI）, carbon use efficiency, and crop yield were compared between WS-MS and WS-MN treatments. The results showed that the content of TOC in WS-MS and WS-MN increased by 8.1% and 5.5%, respectively, and the content of EOOC in WS-MS and WS-MN increased by 50.4% and 45.5%, respectively. The WS-MS and WS-MN treatments increased organic carbon storage by 20.5% and 18.3%, respectively, but the WS-MS treatment did not significantly increase organic carbon storage compared with that in the WS-MN treatment. The carbon pool index （CPI）, carbon pool activity （CPA）, carbon pool activity index （CPAI）, and CPMI of WS-MS were 3.7%, 20.5%, 2.2%, and 7.9% higher than those of WS-MN, respectively. The annual yield of WS-MN was 0.2% higher than that of WS-MS. The annual production efficiency and ecological efficiency of WS-MN were 136.1% and 64.2% higher than those of WS-MS, respectively. The carbon benefit of the WS-MN treatment was significantly higher than that of the WS-MS treatment. Therefore, considering the straw return method, straw carbon utilization efficiency, and crop yield, the single season return of wheat straw is more suitable for the efficient utilization of annual straw resources in the intensive wheat-maize double cropping system in the Huang-Huai-Hai Region, without significantly affecting the annual grain yield of wheat-miaze and its soil carbon pool.

Controlled-release urea (CRU) can improve nitrogen (N) use efficiency and yield, but comprehensive evaluations of its agronomic, physiological, and environmental impacts remain limited. Through a two-year field experiment comparing three CRU types with conventional urea at five N rates (0-280 kg N ha−1), we demonstrate that CRU at 180 kg N ha−1 maintained high maize yields (13.9 Mg ha−1) while improving N use efficiency, with thermosetting polymer-coated samples (TCU) showing superior performance. There was a significant increase in the net photosynthetic rate by 7.9–32.7% and intercellular CO2 concentration by 20.6–40.0% under CRU treatments during the silking and milking stages. The CRU treatments also sustained optimal levels of hormones, N metabolism enzymes, and sucrase and urease activities. Compared to common urea, life cycle assessment indicates that CRU has achieved a 47.5% reduction in reactive N losses and an 18.7% decrease in greenhouse gas emissions. Economically, CRU outperformed common urea, with TCU providing the highest net benefit through yield stability and labor savings. These findings establish TCU at 180 kg N ha−1 as an optimal strategy of maize production in the North China Plain, balancing productivity, profitability, and environmental protection.

Controlled-release urea (CRU) offers potential for improving nitrogen use efficiency (NUE) in intensive maize systems, but comprehensive evaluations of its agronomic, physiological, and environmental impacts remain limited. Through a two-year field experiment in the North China Plain comparing three CRU types (polymer/sulfur-coated PSCU, thermosetting polymer-coated TCU, and polymer-coated PCU) with conventional urea at five N rates (0-280 kg N ha–1), we demonstrate that CRU at 180 kg N ha–1 maintained high maize yields (13.9 Mg ha–1) while reducing N inputs by 12-19% and improving NUE by 37.6%, with TCU showing superior performance. The significant increase in Pn by 7.9–32.7% and Ci by 20.6–40.0% under CRU during the silking and milking stages. The CRU treatments also sustained optimal levels of hormones, N metabolism enzymes, sucrase and urease activities. Compared to common urea, life cycle assessment indicates that CRU has achieved a 47.5% reduction in reactive nitrogen losses, primarily due to lower ammonia volatilization and nitrate leaching. Additionally, when compared to common urea, CRU has resulted in a 18.7% decrease in greenhouse gas emissions. Economically, CRU outperformed common urea, with TCU providing the highest net benefit through yield stability and labor savings. These findings establish TCU at 180 kg N ha–1 as an optimal strategy for sustainable intensification of maize production in the NCP, balancing productivity, profitability and environmental protection.

Plant growth regulators (PGRs) enhance crop stress resistance but their roles in microbial-mediated phosphorus cycling within intercropping systems are unclear. Thus, We conducted a two-year field study using corn (Zea mays L. cv. Denghai 605) and soybean (Glycine max L. cv. Hedou 22) in fluvisols and luvisols soil according to World Reference Base for Soil Resources (WRB) standard. Under a 4-row corn and 6-row soybean strip intercropping system, three treatments were applied: a water control (CK), and two plant growth regulators—T1 (EC: ethephon [300 mg/L] + cycocel [2 g/L]) and T2 (ED: ethephon [300 mg/L] + 2-Diethyl aminoethyl hexanoate [10 mg/L]). Foliar applications were administered at the V7 stage (seventh leaf) of intercropped corn plants to assess how foliar-applied PGRs (T1/T2) modulated the soil phosphorus availability, microbial communities, and functional genes in maize intercropping systems. PGRs increased the soil organic phosphorus and available phosphorus contents, and alkaline phosphatase activity, but not total phosphorus. PGRs declined the α-diversity in fluvisols soil but increased the α-diversity in luvisols soil. The major taxa changed from Actinobacteria (CK) to Proteobacteria (T1) and Saccharibacteria (T2) in fluvisols soil, and from Actinobacteria/Gemmatimonadetes (CK) to Saccharibacteria (T1) and Acidobacteria (T2) in luvisols soil. Functional gene dynamics indicated soil-specific regulation, where fluvisols soil harbored more phoD (organic phosphorus mineralization) and relA (polyphosphate degradation) genes, whereas phnP gene dominated in luvisols soil. T1 stimulated organic phosphorus mineralization and inorganic phosphorus solubilization in fluvisols soil, upregulating regulation genes, and T2 enhanced polyphosphate synthesis and transport gene expression in luvisols soil. Proteobacteria, Nitrospirae, and Chloroflexi were positively correlated with organic phosphorus mineralization and polyphosphate cycling genes, whereas Bacteroidetes and Verrucomicrobia correlated with available potassium (AP), total phosphorus (TP), and alkaline phosphatase (ALP) activity. Thus, PGRs activated soil phosphorus by restructuring soil type-dependent microbial functional networks, connecting PGRs-induced shifts with microbial phosphorus cycling mechanisms. These findings facilitate the targeted use of PGRs to optimize microbial-driven phosphorus efficiency in strategies for sustainable phosphorus management in diverse agricultural soils.

Plastic film (mulch film) is widely used in saline and alkaline soils because it can effectively reduce salt stress damage. However, it results in the accumulation of microplastics (MPs) in the soil, which pose a threat to crop growth and production. This study investigates the effects of 50 mg l-1 MPs and 100 mM sodium chloride (NaCl), individually or in combination, on the growth and physiological characteristics of maize (Zea mays) seedlings. The results demonstrated that compared to the control, MPs and NaCl single or combined stress reduced seedling biomass and water content, and the combined stress was more serious. Stress significantly reduced N and K contents in leaves, and Na content under combined stress was lower than under single NaCl stress. Compared to single stress, the combined stress further enhanced oxidative damage by increasing H2O2 and MDA content, a disrupted chloroplast structure, and reduced chlorophyll content, ultimately leading to a decline in chlorophyll fluorescence parameters and photosynthetic efficiency. Single MPs or NaCl stress led to the accumulation of proline, soluble proteins, and soluble sugars, while the combined stresses further increased the content of these osmotic substances in plants. Moreover, single or combined stress increased the activity of CAT, POD, SOD and the content of AsA and GsH. Collectively, NaCl and MPs single or combined stress exert notable toxic effects on maize seedling growth. Although the combined stress inhibited seedling growth more than the single stress, the combined stress of MPs and NaCl showed antagonistic effects. These findings underscore the importance of assessing the ecological risks posed by the combined effects of MPs and salt stresses on maize plants.

In saline alkaline soils, microplastics inevitably form a combined stress with NaCl to limit crop growth, but the molecular mechanisms of their toxic effects remain vague and inadequate. We analyzed the molecular mechanisms underlying the response of maize seedlings to single or combined stresses of MPs and NaCl by means of combined metabolomic and transcriptomic analyses. MPs and NaCl single or combined stresses reduced plant fresh weight by 36.78 %, 50.65 % and 73.97 %, respectively. Analyses showed 2476 differentially expressed genes (DEGs) and 809 differential metabolites (DMs) for MPs, 2306 DEGs and 901 DMs for NaCl, and 2706 DEGs and 938 DMs for the combined stresses, compared to CK. Single or combined stresses mainly altered amino acid synthesis and phenylpropane biosynthetic metabolic pathways. Stress up-regulated glutamine synthetase (glnA), alanine transaminase (ALT), aspartate aminotransferase (ASP), ornithine carbamoyl transferase (argF), and glycine hydroxymethyl transferase (SHM) genes expression and promotes glutamine, 2-oxoglutarate, glutamate, fumarate, arginine, aspartate, L-isoleucine, L-valine, and serine synthesis. NaCl stimulated phenylpropanoid biosynthesis (tyrosine, 4-coumarate, and ferulate), whereas MPs decreased it. In addition, both individual or combined NaCl and MPs stress increased the expression of cinnamyl-alcohol dehydrogenase (CAD) and cinnamoyl-CoA reductase (CCR) to promote sinapaldehyde synthesis. Our study provides a molecular perspective on the response of crops, such as maize, to individual or combined NaCl and MPs stress.

Aiming at the problems of excessive soil disturbance caused by deep plowing and stripped straw backfilling in strip tillage machinery, which are induced by the large amount of residual straw before maize sowing in the Huang-Huai-Hai Region, an integrated tillage machine suitable for pre-sowing strip tillage of summer maize—integrating subsoiling, stubble-crushing, and soil-guiding functions—was designed. First, the physical properties of straw were analyzed to determine the tooth profile parameters of the stubble-crushing wheel. The unique convex structure of the tooth disc enables it to simultaneously perform depth-limiting and soil-pressing functions. By calculating the flow characteristics of soil during tillage, the angle and distance between the subsoiling shovel and the stubble-crushing wheel were designed. This not only enhances soil crushing and flow but also reduces the occurrence of blockages. A discrete element simulation test with quadratic orthogonal rotation combination was conducted. The machine’s forward speed, wheel position distance, and wheel deflection angle were selected as test factors to analyze their effects on the soil loss rate of the seedbed strip and straw backflow effect under different combinations. The optimal combination of parameters was determined as follows: forward speed of 7.383 km/h, front–rear position distance parameter of −10.131 cm, and deflection angle of 8.608°, with the soil loss rate of the seedling belt reaching 5.486% under this condition. Field experiments were conducted in combination with the strip tiller to verify the simulation-optimized parameters, and comparative experiments at different speeds were also carried out. The field experimental results showed that the deviation of the actual soil disturbance rate caused by the machine from the simulated value was −1.166%, and the soil disturbance rate within the seedling belt was even lower. The results indicated that after the operation of the improved machine, there were no obvious ruts on the soil surface, and the straw was evenly distributed at the edge of the seedling belt, which meets the agronomic requirements for maize planting.

Straw return into agricultural soil is beneficial to agricultural production and has been widely recommended as a practice to enhance both productivity and soil fertility. However, long-term excessive straw return may be detrimental in intensive and high-yielding cropping systems. Here, we conducted a 3-year field experiment in a wheat-maize (Triticum aestivum and Zea mays) double cropping system to investigate the impacts of various straw return rates on crop productivity and carbon footprint. The soil type of the experimental site is Hapludalf. Our results revealed that during the study period from 2014 to 2017 returning 50 % of the straw from both crops (about 3.8 t C ha-1 input) led to maximum increase in grain yield by 15 % and the maximum efficiency of soil to sequestrate 24 % of carbon contained in returned straw. Returning only 25 % of straw (2.0 t C ha-1 input) maintained the relative balance of soil carbon. 75 % straw return (5.4 t C & sdot;ha-1 straw carbon) resulted in the maximum soil carbon sequestration of 0.8 t C ha-1 yr-1 and minimum carbon footprint of 2.4 t CO2-eq ha-1, but more straw return did not produce significant positive benefits. Straw return promoted farmland CO2 emission, which was equivalent to 43 % of the straw carbon input. Each 25 % increase of straw return amount increased the total direct N2O emissions by 0.5 kg N2O ha-1. Our results clearly indicate that the currently and widely practiced straw management i.e. returning all wheat and maize straw, leads to excessive carbon return, causing imbalance of soil carbon and nutrient and reduced crop yield, is therefore not the best options. Returning 50-75 % of crop straw and using the rest as stock feed, will boost crop productivity while maintaining lower carbon footprint. Our approach provides a practical and reliable method to develop a "win-win" strategy for straw management in the double-cropping systems. The optimal straw management will change with time due to changed climate, soil and management conditions,while the approach can be applied to investigate optimal straw management in all systems across environments. Although our study is constrained to short-term observations, the findings provide valuable guidance for the development of mutually beneficial crop straw management strategies and establish a solid foundation for future long-term research in this area.

IntroductionThe selection and application of nitrogen-efficient maize hybrids have significantly bolstered contemporary food security. Nevertheless, the effects of heightened nitrogen fertilizer demand of these crops on the composition and assembly of soil microbial communities in agricultural production require further elucidation.MethodsIn this study, the effects of four nitrogen fertilizer managements on rhizosphere bacterial and fungal community assembly, co-occurrence network and function of two maize hybrids (LD981 and DH605) were compared.Results and discussionFindings revealed that the bacterial community was primarily shaped by deterministic processes, while stochastic processes played a pivotal role in fungal community assembly. N-efficient hybrid DH605 had a more stable microbial network than N-inefficient hybrid LD981. At N3 (130 g N/m2) rate, the bacterial and fungal community networks were the most complex but unstable, followed by N2 (87 g N/m2), N0 (0 g N/m2), and N1 (43 g N/m2) rates. Excessive nitrogen rate (N3) increased the relative abundance of denitrification genes nirK and norB by enriching nitrogen-related genus such as Nitrolancea and Nitrosospira. It led to an increase in the relative abundance of pathways such as cysteine and methionine metabolism and pyruvate metabolism. The effects of management practices (i.e. maize hybrids and N rates) on microbial communities were ultimately directly or indirectly reflected in microbial functions. Our findings illustrate the relationship between the appropriate selection of crop hybrids and management measures in optimizing rhizosphere microbial community assembly and promoting nitrogen use, which is necessary for sustainable food security.

Microplastics accumulate during saline-alkali land improvement from agricultural inputs such as fertilizers and plastic films, forming a composite stress on crop growth. This study investigated the response mechanisms of maize (Zea mays L.) seedling roots to individual and combined stresses from microplastics and salt. Maize seedlings were exposed to 100 mM NaCl and 50 mg l-1 Polystyrene microplastics. Transcriptomic and metabolomic analyses were conducted to elucidate molecular responses. Salt (NaCl) and microplastics (MPs), both individually and in combination (PNaCl), significantly inhibited root growth and water metabolism. NaCl and PNaCl stresses upregulated phenylalanine ammonia-lyase and 4-coumaroyl-CoA ligase in the phenylpropanoid pathway, promoting the accumulation of phenolic metabolites such as ferulic acid, while MPs stress had the opposite effect. Under NaCl stress, catechol-O-methyltransferase expression increased, enhancing caffeic acid conversion and antioxidant capacity. Additionally, NaCl and PNaCl stresses also promoted the expression of genes involved in the biosynthesis of cutin, suberin, and wax, whereas MPs stress suppressed these genes. Overall, maize roots respond to NaCl and PNaCl stresses by activating phenylpropanoid metabolism, accumulating phenolic compounds, and enhancing the biosynthesis of cutin, suberin, and wax, thereby improving stress resistance and providing insights into plant adaptation to complex environmental conditions.

Topsoil degradation poses a significant threat to agricultural production worldwide. However, whether degraded topsoil is a net nitrogen source or sink depends on crop uptake and nutrient loss, and how it affects the sustainability of agricultural production remains unclear. To fill this gap in understanding, we conducted a three-year experiment with five topsoil depth treatments: 10 cm (D10), 20 cm (D20), 30 cm (D30), 40 cm (D40), and 50 cm (D50). Increasing topsoil depth significantly increased grain yield by a maximum of 49.4% (between D10 and D50). With increasing topsoil depth, the NFUE rises from 14.2% to 64.9% (between D10 and D50 treatments), while the G-NFUE climbs from 9.0% to 36.2% (between D10 and D40 treatments). Increasing topsoil depth reduced topsoil N depletion and the percentage of change in soil N stocks. In addition, N fertilizers applied during the season were generally enriched in soil at a depth of 30–40 cm. Therefore, increasing the depth of topsoil can effectively increase the source of nutrients absorbed by a crop by increasing access to additional resources stored in deeper soils, which ultimately increases maize grain yield and N fertilizer use efficiency. In this study, the threshold for maize to achieve high yields and efficiency was a topsoil depth of 30 cm. This study elucidated the differences in maize grain yield and resource utilization at different topsoil depths and established a link with soil N characteristics, and thus, it will provide a theoretical basis for the sustainable management of topsoil.