Biodegradable microplastics such as polylactic acid (PLA) are emerging contaminants that can exacerbate crop stress, particularly when combined with heavy metals like lead (Pb) in agricultural soils. While intercropping is known to enhance crop resilience, the specific mechanisms for mitigating combined PLA-Pb stress remain poorly understood. This study investigated the potential and underlying mechanisms of faba bean-wheat intercropping to mitigate combined PLA-Pb stress by assessing faba bean disease incidence, growth performance, Pb(II) accumulation, and rhizosphere microenvironment. Results demonstrated that faba bean-wheat intercropping effectively alleviated combined PLA-Pb stress. Compared to monoculture, intercropping significantly increased shoot and root biomass (by 29.16% and 27.67%), reduced Fusarium wilt incidence and disease index (by 19.00% and 18.57%), and decreased Pb(II) accumulation in leaves and roots (by 21.14% and 17.30%). Additionally, intercropping enhanced the plant antioxidant system (by increasing SOD, CAT, and APX activities), alleviated oxidative stress, and improved rhizosphere properties by reducing available Pb(II) content (by 23.87%) and increasing nutrient availability and enzyme activities. Furthermore, intercropping enriched beneficial rhizosphere bacteria (e.g., Sphingomonas), upregulated defense-related metabolites (including phenylpropanoids, alkaloids, flavonoids), and activated key resistance-related pathways such as α-linolenic acid metabolism. The partial least squares path model confirmed that intercropping promotes plant growth and disease control primarily through rhizospheric microbial and biochemical reprogramming. This research illustrates how intercropping systemically alleviates PLA-Pb co-toxicity, highlights the practical value of intercropping in managing combined pollution stress, and provides a mechanistic basis for its application in sustainable legume production.

BACKGROUND:Continuous cropping of faba bean severely degrades the soil ecosystem, leading to the accumulation of autotoxic compounds and pathogenic fungi, which further aggravates soilborne diseases. Among available strategies, the rational application of biochar has the potential to reshape soil microbial communities. This study aimed to elucidate the rhizosphere microbial mechanisms by which biochar (BC) mitigates Fusarium wilt. Wheat straw BC was applied at 0%, 0.5%, 1%, 1.5%, 2% and 3% to evaluate its effects on soil microbial community. Based on this, a pot experiment was conducted to systematically assess the effects of BC on Fusarium wilt incidence, autotoxic compound accumulation, soil microbial diversity and root pathogenesis-related protein (PR) expression following inoculation with BC-conditioned soils. RESULTS:Compared with the control, BC application mitigated Fusarium wilt, reducing the disease index by 16.66%-52.11%, with the greatest effect observed at 1%. At this level, BC decreased soil phenolic acid accumulation, increased the relative abundance of Proteobacteria, and reduced that of Ascomycota. BC-induced shifts enhanced the diversity, structure, and composition of rhizosphere microbial communities. Specifically, 1% BC increased the absolute abundance of Bacillus sp. by 119.01% and Sphingomonas sp. by 98.93%, decreased the absolute abundance of Fusarium commune sp. by 77.41%, and upregulated root PR protein gene expression, thereby alleviating Fusarium wilt. CONCLUSION:The application of 1% wheat straw BC effectively reshaped the soil microbial community, reduced autotoxic compound accumulation, improved soil health and suppressed Fusarium wilt. © 2026 Society of Chemical Industry.

Context Continuous monocropping can impair soil functioning and reduce crop performance, but its consequences for seed quality and the potential of intercropping to mitigate quality decline remain insufficiently understood. Objective This study aimed to determine whether long-term faba bean–wheat intercropping can alleviate continuous monocropping-induced declines in faba bean seed quality and to clarify the underlying rhizosphere nutrient, microbial, and metabolomic mechanisms. Methods A field experiment was conducted to compare two planting systems, namely faba bean monocropping and faba bean–wheat intercropping, under two continuous cultivation durations, 2 and 10 years. Faba bean seed nutritional quality, antinutritional factors, and metabolomic profiles were analyzed together with rhizosphere soil nutrient availability, nutrient-cycling enzyme activities, microbial community composition, and predicted microbial functional potential. Results Long-term monocropping reduced seed nutritional quality, as indicated by lower soluble sugar, starch, and crude protein contents, while increasing antinutritional compounds including tannins, proanthocyanidins, and lectins. In contrast, long-term intercropping alleviated these negative changes and maintained a more favorable seed quality profile, characterized by higher accumulation of primary nutrients and quality-related secondary metabolites and lower levels of antinutritional compounds. Intercropping increased rhizosphere nutrient availability and nutrient-cycling enzyme activities, enriched plant-associated and nutrient-cycling microbial taxa such as Rhizobium, Rhizophagus, and Penicillium, reduced the relative abundance of Fusarium, and enhanced the predicted functional potential associated with carbon, nitrogen, and phosphorus cycling. Seed metabolomic analysis further showed that flavonoids, lipids, and fatty acid derivatives were enriched under long-term intercropping and were positively associated with seed sugar, starch, and protein contents. Partial least squares structural equation modelling identified rhizosphere nutrient availability as the main direct factor associated with seed nutritional quality, whereas seed metabolite changes appeared mainly as downstream responses linked to improved nutrient supply. Conclusion Long-term faba bean–wheat intercropping substantially improves faba bean seed nutritional quality by modulating rhizosphere microbial nutrient-cycling functions, thereby sustaining an enhanced supply of available nutrients for seed nutrient synthesis. Implications These findings highlight long-term legume–cereal intercropping as a viable strategy for quality-oriented legume production, in which rhizosphere microbial nutrient cycling contributes to seed quality improvement. Prioritizing sustained operation, complementary species pairing, and timely nutrient replenishment can help translate this ecological intensification into consistent improvements in crop quality with reduced reliance on chemical inputs.

Phosphorus(P)in soils predominantly occurs in insoluble forms,resulting in its low bioavailability.The bioavailability of soil P is influenced by multiple factors,including soil properties,P fractions,microbial communities,and crop types.Analyzing changes in soil physicochemical properties,P fractions,and P-solubilizing microbial communities under different fertilization practices in crop rotation systems can reveal the mechanisms of P activation,fixation,and transformation,thereby contributing to improving P use efficiency.The Luhe Monitoring Site in Nanjing is a nationally designated key monitoring point for non-point source pollution and represents a typical long-term positioning monitoring site for a sweet potato-wheat rotation system.This dataset is derived from this site,and includes soil P data collected after the harvest of wheat and sweet potato in 2020,as part of a long-term positioning experiment(involving 4 fertilization treatments)at the Jiangsu Cultivated Land Conservation Scientific Observation and Experiment Station,Ministry of Agriculture and Rural Affairs/National Agricultural Environment Liuhe Observation and Experiment Station.The dataset comprises 10 components:experimental design of the long-term positioning trial;fertilization details for different treatments in the long-term trial;soil physicochemical properties after the harvest of wheat and sweet potato under different fertilization practices in 2020;status of soil organic P fractions;status of soil inorganic P fractions;diversity of microbial communities involved in soil organic P mineralization;diversity of microbial communities involved in soil inorganic P solubilization;taxonomic composition of microbial communities involved in soil organic P mineralization;taxonomic composition of microbial communities involved in soil inorganic P solubilization;and the records of methods used to measure all indicators.Data collection and processing strictly followed the monitoring specifications for observation and experiment stations issued by the Ministry of Agriculture and Rural Affairs.Data quality was ensured through review and verification by laboratory quality control personnel and the project team leader.This dataset provides a reliable foundational for investigating the effects of different fertilization practices on soil P forms in soil,P bioavailability,and the mechanisms governing P dynamics.

Trace element contamination, like cadmium (Cd), threatens agriculture and health. This study assessed Cd stress effects on photosynthesis in faba bean and evaluated mitigation using intercropping with wheat and calcium oxide nanoparticles (CaO NPs). Five treatment groups were established: faba bean monoculture without Cd addition (M), monoculture with Cd addition (M + Cd), monoculture with both Cd and CaO NPs (M + Cd + CaO NPs), wheat-faba bean intercropping with Cd addition (I + Cd), and intercropping with both Cd and CaO NPs (I + Cd + CaO NPs). Compared with M, the M + Cd treatment significantly suppressed faba bean growth by 34.1–102.9

ABSTRACTLong‐term positioning experiments have demonstrated significant benefits in agricultural production and environmental protection. Faba bean‐wheat intercropping with nitrogen fertiliser can effectively mitigate the occurrence of faba bean wilt disease. Identifying the optimal nitrogen application rate is essential for enhancing the disease control efficacy of intercropping. This study aimed to investigate the long‐term effects of varying nitrogen application levels on the physical, chemical, and biological changes in the rhizosphere soil of faba bean under intercropping conditions and to examine their relationship with the incidence of faba bean wilt disease. In a 9‐year field experiment, two treatments of faba bean‐wheat intercropping for 1 year (IF‐1) and 9 years (IF‐9) were established to investigate the incidence of faba bean wilt under four nitrogen levels (N0: 0 kg ha−1; N1: 45 kg ha−1; N2: 90 kg ha−1; N3: 135 kg ha−1). Rhizosphere soil from faba bean plants was collected to assess the corresponding physical, chemical, and biological indicators. Long‐term intercropping promoted the growth of faba bean plants and effectively controlled faba bean wilt disease by improving soil structure and fertility and soil quality (SQI). Under different nitrogen application levels, certain soil physical properties (moisture content, macroaggregate proportion, MWD, and GMD) and chemical properties (SOM, total carbon, SOC, total nutrients, and available nutrients) peaked under N2 (90 kg ha−1), with SQI showing a similar trend. Additionally, long‐term intercropping enhanced enzyme activity in the faba bean rhizosphere, reshaped microbial community composition, maximised the benefits of beneficial microbes, reduced the abundance of the pathogenic fungus Fusarium, and achieved optimal disease control under N2. Under long‐term intercropping with nitrogen fertiliser application at N2 (90 kg ha−1), the physical structure of the faba bean rhizosphere soil was significantly improved, soil quality and fertility were enhanced, and the abundance of plant pathogens was reduced by modifying the microbial community composition. This effectively alleviated faba bean disease, promoted healthy plant growth, and maintained soil function.

Interspecific root interactions are common in intercropping systems. However, limited information exists on whether specialized metabolites, such as benzoxazinoids (BXs) secreted by cereals in intercropping, mediate rhizosphere metabolite interactions between crops to enhance nitrogen (N) and iron (Fe) uptake. Compared with monoculture wheat (MW), intercropping wheat (IW) significantly increased the total BXs concentrations in the roots and rhizosphere. Additionally, BXs secreted by IW were detected in the rhizosphere of intercropped fava bean (IF), indicating their absorption by its roots. To analyze these interactions, three sets of rhizosphere differential metabolite profiles (IW_vs_MW, IF_vs_MF, and IF_vs_IW) were established, identfitying 251, 257, and 643 significant differential metabolites, respectively. These metabolites were primarily amino acids, phospholipids, monoterpenoids, and flavonoids. KEGG enrichment analysis revealed that the differential metabolites were significantly enriched in pathways such as BX biosynthesis and isoflavonoid biosynthesis, both of which belong to the biosynthesis of other secondary metabolites. Notably, BX biosynthesis was a shared pathway between IW_vs_MW and IF_vs_MF. Intergroup differences and correlation analyses of all compounds in the three differential metabolite sets highlighted that pyroglutamic acid, formononetin, and other flavonoids, along with perillic acid and other monoterpenes, were significantly affected by interspecific root interactions and positively correlated with 6-methoxy-2-benzoxazolinone (MBOA). These differential metabolites enhanced the activation and preference of intercropped plants for available N and Fe, thereby improving their uptake. In summary, our findings offer new insights into boosting N and Fe absorption through interspecific root DMs mediated by specialized metabolites (such as BX) in cereal-legume intercropping systems.

Unique rhizosphere metabolites, such as benzoxazinoids (BXs), are secreted by cereal crops, such as wheat, which influence the rhizosphere microbiota and affect the growth of offspring crops. However, the feedback effect of this microbiota interaction on the rhizosphere environment of neighboring intercropped plants and their growth performance remains unclear. This study combined pot and field experiments to explore the intercropping system between wheat (IW) and fava bean (IF). Compared with monoculture wheat (MW), IF significantly increased BXs release from wheat roots and enhanced BXs synthesis in both wheat leaves and roots. BXs not only drove changes in the diversity and richness of the rhizosphere microbiota in wheat but also altered the microbiota composition in the IF rhizosphere through horizontal transfer. Actinomycota, the dominant bacterial phylum, was strongly influenced by BXs in the rhizosphere of IF, showing a positive correlation with Pseudomonadota. In terms of fungi, BXs promoted the enrichment of Penicillium in IW and IF while inhibiting the growth of Fusarium and Gibberella. The BXs-driven rhizosphere effect enhanced enzyme activities, including CAT, urease, sucrase, and neutral phosphatase, in IW and IF rhizosphere soil. These changes improved both aboveground (plant height, leaf length, and fresh weight) and belowground (root length and root weight) growth as well as crop grain yield. In conclusion, this study demonstrates for the first time that BXs secreted by wheat roots promote positive feedback interactions in the fava bean rhizosphere, improving soil enzyme activities and overall plant performance in a wheat-fava bean intercropping system.

Background: Intercropping is vital for enhancing soil quality improvement and improving ecological services. Objective: This study integrated the analysis of rhizosphere metabolites and microbial communities to elucidate the mechanism by which the long-term intercropping could regulate the soil rhizosphere microecology and promote the faba bean growth. Method: Two planting modes, faba bean single cropping and faba bean-wheat intercropping, along with the planting durations of 1 and 9 years, were established to investigate the wilt disease occurrence. The growth indicators, the soil physical and chemical properties, the rhizosphere microbial communities, and the changes in rhizosphere metabolites of faba bean were measured. Results: Continuous cropping can lead to poor soil conditions and high incidence of faba bean disease, while intercropping can alleviate the occurrence of diseases. Compared with monoculture for 1 year, monoculture for 9 year can promote the growth of faba bean by 12.89-29.19 %, reduce the incidence rate of fusarium wilt by 41.38%, increase the proportion of large aggregates with R> 0.25 mm by 18.87% by reducing the soil bulk density by 6.67%, average weight diameter 23.16%, geometric mean diameter 26.51 %, maintaining soil pH stability and increasing soil organic matter by 30.74% can improve soil structure, and the disease control effect is more significant. It is also possible to reduce the relative abundance of Fusarium by 8.93% by improving the soil microbial community structure. In addition, metabolomics analysis also showed that long-term intercropping promotes the secretion of flavonoids and terpenoids in the rhizosphere soil of faba bean, enhancing their resistance. Through correlation analysis, it was found that soil microbial activity is closely related to key metabolites in crop rhizosphere. The secretion and synthesis of flavonoids and terpenes can reduce the abundance of faba bean pathogens and alleviate their disease occurrence. Conclusion: The faba bean-wheat long-term intercropping improved the soil physical and chemical properties, reconstructed the microbial community structure, and reduced the pathogenic bacteria abundance through rhizosphere metabolites, thereby maintaining soil quality improvement and promoting healthy faba bean growth.

Interspecies interactions play a crucial role in the yield and disease control benefits of intercropping. Plants release allelochemicals that influence the establishment and growth of other species. Diverse intercropping environmental factors combined with various agronomic practices can be critical for regulating interspecies interactions. Field experiments were conducted in a wheat–faba bean intercropping system, incorporating three planting densities, three row spacing configurations, and four nitrogen application levels to identify the optimal planting practices. These findings were validated through pot experiments. In the wheat faba bean intercropping system, the combination of D3.5 planting density, R30 row spacing, and an N2 nitrogen application rate (90 kg·ha−1) resulted in the highest production of DIMBOA and its degradation product MBOA in wheat tissues, leading to optimal crop growth, and significantly enhanced wheat yield and effectively controlled faba bean wilt disease. Correlation analysis revealed that DIMBOA and MBOA contents were positively associated with wheat yield, biomass, and plant height, while exhibiting a negative correlation with the incidence rate and disease index of faba bean. Effective crop management practices are essential for promoting wheat and faba bean growth. Benzoxazinoids (BXs) play a pivotal role as the key factors in disease control and yield improvement.

Pesticide stress significantly reduces crop productivity. This study investigated wheat-fava bean intercropping combined with nano zinc oxide (nZnO) application as a strategy to alleviate pyroxasulfone (PYR) stress on fava beans. We examined the effect on plant growth, the rhizosphere microenvironment, and PYR degradation. The combined treatment effectively reduced the PYR toxicity and promoted fava bean growth. It enhanced plant antioxidant enzyme activities and soil nutrient cycling enzymes, leading to increased PYR degradation and decreased number of soil PYR residues. Furthermore, these treatments stimulated the secretion of rhizosphere flavonoids and organic acids, enriching beneficial bacterial communities, specifically Sphingomonas, Gemmatimonas, and Streptomyces. Functional predictions using FAPROTAX indicated significant changes in carbon, nitrogen, and sulfur cycling, suggesting a crucial microbial role in accelerating PYR degradation and improving plant resilience. These findings present a promising and sustainable agricultural strategy to mitigate pesticide pressure.

The allelopathic compounds in the soil can be accumulated through the continuous cultivation of faba bean, intensifying the soilborne disease advancement. In this study, we aimed to elucidate the photosynthesis-related mechanisms by which benzoic acid, an allelopathic compound, promotes faba bean Fusarium wilt (Fusarium commune) development. The sample plants were treated with and without F. commune and exposed to varying concentrations of benzoic acid. The effects on seedling growth, Fusarium wilt occurrence, nutrient absorption, photosynthetic pigments, chlorophyll fluorescence, photosynthetic enzyme activities, photosynthetic assimilates, and the levels of pathogenesis-related (PR) gene expression were explored. Compared with the control, F. commune inoculation substantially decreased the leaf growth and increased the Fusarium wilt instances. Different from the F. commune-alone treatment, the treatment of benzoic acid and F. commune decreased the zinc, magnesium, manganese, iron, total phosphorus, total nitrogen, and total potassium in roots and leaves; reduced carotenoid, chlorophyll a, and chlorophyll b levels; decreased the quantum yield and photochemical quenching coefficient of PSII; increased the non-photochemical quenching coefficient; reduced the activities of H+-ATPase, ribulose bisphosphate carboxylase, fructose-1,6-bisphosphatase, sucrose synthase, and activator; increased starch content; decreased soluble sugar and sucrose levels; and upregulated PR1, PR2, and PR10 in leaves. Additionally, benzoic acid and F. commune treatment further reduced leaf growth and increased Fusarium wilt occurrence in faba bean. The investigation indicated that benzoic acid exacerbated the Fusarium wilt development and inhibited faba bean growth by reducing mineral nutrient absorption and impairing photosynthesis. This research might provide more information and enhance our understanding of plant soilborne disease in agriculture.

Context: Rice blast, caused by the fungus Magnaporthe oryzae, is the most important disease of rice globally. Variety mixture can greatly reduce the incidence of rice blast and increase yield. However, the effectiveness of variety mixture as a disease control method varies across studies, and no overarching synthesis of the available data has been made to date. Objective: Here, we synthesized the available experimental data on the effect of variety mixture on rice blast and yield by quantifying the disease reduction and yield gain in mixtures of glutinous and hybrid rice cultivars in relation to nitrogen (N) fertilization and the use of fungicides. Methods: We searched the global literature for field studies on disease control and yield benefits from variety mixture in rice and synthesized 1255 observations from 38 publications using meta-analysis and meta-regression. Results: The disease odds were reduced by 68 % on average in variety mixtures as compared to pure stands, and the reduction was substantially greater in blast-susceptible glutinous rice varieties (80 %) than in the more blastresistant hybrid rice varieties (34 %). Variety mixture provided a similar level of disease control in glutinous rice as the use of fungicides. Blast-resistant hybrid rice varieties became susceptible to blast at high fertilizer N input but the disease controlling effect of mixture was unaffected by fertilizer N input. The relative yield total in mixture relative to pure stands increased with disease pressure; from 1.08 to 1.36 if the disease incidence in the pure stands increased from 0 % to 100 %. At the same time, the relative yield increased from 0.92 to 1.06 for hybrid rice (land share 0.84), and from 0.16 to 0.30 for glutinous rice (land share 0.16). Conclusions: Variety mixture significantly decreases blast incidence while increasing grain yield of rice as compared with pure stands. The level of blast control by mixture is not significantly impacted by the quantity of N fertilizer, the use of fungicides, or the phase of the epidemic. The control effectiveness of variety mixture on susceptible cultivars is similar to that of fungicides. The relative increase in yield due to variety mixture is greater at high than low disease incidence in the pure stands. Implications: Variety mixture offers a sustainable and environmental friendly solution for promoting the cultivation of indigenous rice varieties with high market and cultural value but low resistance to blast.

Context Long-term continuous monoculture has led to frequent cropping obstacles that significantly restrict wheat production. Intercropping of wheat and faba bean is considered an effective strategy to mitigate these challenges, whereas the long-term effects of intercropping on wheat yield remain unexplored. Objective This study aimed to assess the impact of long-term intercropping on wheat rhizosphere soil physicochemical properties, arbuscular mycorrhizal fungi (AMF) community composition, and root nitrogen transporter gene expression, with elucidating the synergistic mechanisms underlying yield enhancement. Methods A field experiment was conducted to compare two planting modes, wheat monocropping (M) and wheat-faba bean intercropping (I), over two durations (2 and 10 years) to examine their effects on wheat yield, soil physicochemical properties, AMF communities, and root nitrogen transporter gene expression. Results Intercropping increased wheat yield compared to monocropping, with the highest yield observed after 10 years of intercropping. Long-term intercropping improved wheat rhizosphere soil structure, significantly increased nutrient content, and enhanced soil fertility. It also increased AMF colonization ability, richness, and diversity, while regulating the AMF community structure, which promoted the expression of nitrogen transporter genes in wheat roots, improving nitrogen absorption, and ultimately boosting yield. These beneficial effects were more pronounced after long-term intercropping. Conclusion Long-term wheat-faba bean intercropping enhanced the AMF community composition, improved the soil physicochemical properties, enhanced the nitrogen transport efficiency, promoted wheat growth, and ultimately increased production. Implications Long-term intercropping contributes to promoting sustainable agricultural production.

Benzoxazinoids (BXs) synthesised by cereal plants are vital for stress resistance. However, information regarding the induction of specific BXs (DIBOA, DIMBOA, and MBOA) in wheat by typical cereal-legume intercropping systems, such as wheat/faba bean, and their effects on neighbouring intercropping crops, remains limited. To address this knowledge gap, pot and field planting experiments were conducted to examine the influence of intercropped faba bean (IF) on the synthesis and secretion of BXs in wheat, their subsequent absorption by faba bean, and their impact on plant growth. Results showed that under both planting conditions, IF could induce an increase in the concentration of BXs in the shoots (leaves and stems) and underground (roots) parts of intercropped wheat (IW), as well as in the rhizosphere soil (p < 0.05), with the highest concentration in the leaves, reaching up to 78.0 μg/g. The concentration of BXs in various organs of IW was higher under field conditions than under potted conditions, and showed a pattern of leaves > roots > stems > rhizosphere. DIMBOA, induced to synthesise and secrete in the wheat rhizosphere, underwent accelerated degradation and reduced half-life due to the soil environment, which is rich in diverse microorganisms and organic residues. In addition, compared to monoculture faba bean (MF) with trace levels of BXs, all three BXs types were detected in the rhizosphere, roots, and shoots of IF, and all significantly increased (p < 0.05). The BXs absorbed by IF exhibited varying degrees of negative correlation with the growth parameters of wheat and faba bean, but the negative impact on growth was limited. In summary, our research findings enhance the understanding of the secretion of BXs induced by legume crops in cereal-legume intercropping systems and their absorption in interspecific interactions among legume crops.

Excessive soil cadmium (Cd) and the accumulation of pathogens pose serious threats to legume growth. However, it remains unclear whether intercropping (IFcd) and its combined treatment with silicon nanoparticles (Si-NPs) (IFcd + Si) can alleviate these challenges under Cd stress, as well as the underlying mechanisms involved. This study systematically elucidated the mechanism of faba bean-wheat intercropping and Si-NPs regulating faba bean growth under Cd stress using rhizosphere metabolomics and 16 S rRNA microbiome analysis. The results showed that IFcd and IFcd + Si treatments significantly reduced Cd accumulation by 17.3

Long-term continuous monocropping of faba bean destroys the soil ecological balance and increases the occurrence of Fusarium wilt. This study investigated the effects of nitrogen management on soil quality and Fusarium wilt under 1 and 9 years of monocropping at four nitrogen levels (N0-N3; 0, 45, 90 and 135 kg·hm-2 nitrogen fertilizer, respectively). Compared with 1 year of monocropping, 9 years of monocropping significantly reduced plant growth and promoted the occurrence of Fusarium wilt. Under 9 years of monocropping, N1-N3 significantly increased plant height by 13.53%-34.84% and reduced the disease incidence by 7.21%-12.26% compared with N0, with N2 (90 kg·hm-2) exhibiting the best effect. Compared with N0, N2 reduced soil bulk density by 9.40% and simultaneously enhanced the percentage of soil aggregates with R > 0.25 mm by 17.54%. N2 altered the community structure and composition of soil bacteria and fungi; specifically, it increased the abundance of Arthrobacter while decreasing that of Fusarium and Gibberella. Moreover, N2 contributed to increasing soil urease activity by 40.41%, soil neutral phosphatase activity by 22.59% and soil organic matter by 20.08%. Thus, applying 90 kg·hm-2 nitrogen fertilizer effectively enhances soil quality and mitigates Fusarium wilt under continuous monocropping of faba bean.

The regulatory action of BXs secreted by wheat on the pathogenicity of FOF causing Fusarium wilt in faba bean were analyzed. DIMBOA and MBOA weakened the pathogenicity of FOF. A large number of pathogenic bacteria in continuous cropping soil infect faba bean plants, leading to the occurrence of wilt disease, which restricts their production. Faba bean–wheat intercropping is often used to alleviate this disease. This study investigates the effect of benzoxazinoids (BXs) secreted by wheat root on the pathogenicity of Fusarium oxysporum f. sp. Fabae (FOF) and underlying molecular mechanisms. The effects of DIMBOA(2,4-dihydroxy-7-methoxy-1,4-benzoxazine-4-one) and MBOA(6-methoxybenzoxazolin-2-one) on the activity of cell-wall-degrading enzymes in FOF(cellulase, pectinase, amylase, and protease), FOF Toxin (fusaric acid, FA) content were investigated through indoor culture experiments. The effect of BXs on the metabolic level of FOF was analyzed by metabonomics to explore the ecological function of benzoxazines intercropping control of Fusarium wilt in faba bean. The results show that the Exogenous addition of DIMBOA and MBOA decreased the activity of plant-cell-wall-degrading enzymes and fusaric acid content and significantly weakened the pathogenicity of FOF. DIMBOA and MBOA significantly inhibited the pathogenicity of FOF, and metabolome analysis showed that DIMBOA and MBOA reduced the pathogenicity of FOF by down-regulating related pathways such as nucleotide metabolism and linoleic acid metabolism, thus effectively controlling the occurrence of Fusarium wilt in faba bean.

Modern high input-based intensive cropping systems often lead to accumulation of phenolic acids in the soil which promote the development of soil diseases. While this can be suppressed by intercropping. This research assessed the impact of intercropping on Fusarium wilt from the perspective of soil acidification under cinnamic acid and Fusarium commune stress. The treatments were not inoculated with F. commune, while the faba beans were inoculated with this pathogen. Infected plants were also treated with cinnamic acid. The development of wilt, together with seedling dry weight, soil chemical properties, soil enzymes, soil amino acids, microbial diversity, and the community structure and composition from monocropping and intercropping systems, were investigated. Under the combined stress of cinnamic acid and F. commune, relative to monocropping, intercropping with wheat increased the soil pH value, reduced most of the soil amino acid contents, increased bacterial community diversity, and modified the community structures and compositions of bacteria and fungi, increased the abundance of both Sphingomonas and radyrhizobium and reduced Fusarium and increased soil enzyme activities and nutrient; moreover, it promoted plant growth, and reduced the disease index. Intercropping alleviated soil acidification and suppressed faba bean’s Fusarium wilt following F. commune infection and cinnamic acid stress.

Intercropping of wheat/faba bean is a common practice within the legume-cereal family. However, the benefits of nitrogen (N) fertilizer-optimized synergistic intercropping in improving faba bean productivity while controlling the prevalence of chocolate spot disease have not been established. This study conducted continuous field experiments spanning two planting seasons to investigate two key findings: (i) Optimizing N fertilizer application can enhance the productivity of intercropped faba bean. (ii) The percentage severity index (PSI) during the period of maximum prevalence rate (Rmax) of faba bean chocolate spot disease poses a substantial challenge to faba bean yield. The results indicated that the land equivalent ratio and transgressive overyielding index for each intercropping treatment increased with higher N fertilizer application, exceeding a value of 1, and the land saving proportion also exceeded 0. Intercropping primarily enhances productivity, as measured by the harvest index (HI), by amplifying the complementary effect rather than the selection effect, thus improving the net benefit of intercropping. The HI of single and intercropped faba bean increased with the N1 and N2 treatments in both planting seasons. However, the HI of single and intercropped faba bean at the N3 level decreased significantly, ranging from 17.85 to 29.62%. Furthermore, a notable negative correlation was established between the PSI during critical epidemic (initial epidemic, maximum epidemic rate, and late epidemic) periods and observed and expected faba bean yields. As the PSI increased, faba bean yields decreased, and the PSI of intercropping at different periods was lower than that observed in the single cropping. Additionally, intercropping with the optimized N fertilizer treatment (N2 treatment) exhibited an enhanced relative control effect on chocolate spot disease in faba bean, ranging from 35.21 to 52.36%. This finding confirmed the productivity advantage of intercropping faba bean. In conclusion, this study suggested that optimizing N fertilizer application can enhance the productivity of intercropped faba bean. Wheat/faba bean intercropping effectively controlled the PSI during the period of Rmax, which would otherwise threaten faba bean yield. Consequently, this practice ensured sustained advantages of wheat/faba bean intercropping.