Enhancing soil carbon sequestration in croplands is crucial for improving crop productivity and achieving agricultural sustainability. Intercropping has been shown to increase grain yield by improving phosphorus (P)utilization efficiency. However, the underlying mechanisms of soil carbon sequestration, including soil organic carbon (SOC) and soil inorganic carbon (SIC), under intercropping and P-fertilizer application remain ambiguous. To address this knowledge gap, we conducted a 13-year long-term field experiment to investigate how intercropping and P fertilization affect soil carbon sequestration by analyzing SOC fractions (particulate organic carbon (POC), mineral-associated organic carbon (MAOC)), crop root biomass, and soil mineral properties (iron-/calcium-bound organic carbon, exchangeable cations, and iron/aluminum oxides). The results show that intercropping significantly increased soil total carbon and SOC concentrations compared with monoculture by 2.2 % and 5.8 %, respectively. A P-application rate of 80 kg P ha- 1 decreased SIC concentrations by 3.6 % and 4.2 %, and decreased soil total carbon concentrations by 2.4 % and 2.7 % compared to no fertilization and 40 kg P ha- 1 P-fertilization, respectively. Furthermore, intercropping significantly increased POC and MAOC concentrations by 15.3 % and 2.3 %. The POC concentration was positively correlated to crop root biomass. The MAOC concentration was positively correlated to the iron-bound organic carbon concentration. The decline in SIC concentration induced by P application (e.g., 80 kg P ha- 1) was strongly associated with reduced exchangeable soil calcium and magnesium concentrations. The results from this study imply that intercropping can enhance soil total carbon sequestration by mitigating the negative impacts of excessive P-application (e.g., 80 kg P ha-1) on soil biogeochemical processes. Collectively, our work highlights the importance of implementing intercropping practices as an alternative to excessive P-application for promoting sustainable agricultural production.

Post-wheat green manuring is a key practice for reducing synthetic fertilizer use and enhancing soil fertility. However, its impact on nitrous oxide (N2O) emissions is variable, necessitating integrated strategies for effective mitigation. Based on a 15-year field experiment and an incubation experiment, this study evaluated how incorporating attapulgite clay into a high-efficiency green manuring system with 30% chemical fertilizer reduction (G+F70) affects N2O emissions. Compared with conventional fertilization (F100), the G+F70 system increased wheat yield by 9.4% on average and improved soil quality index by 184.5%. This improvement was attributed to enhancements in soil organic matter, total nitrogen, mineral nitrogen, dissolved organic nitrogen, microbial biomass carbon, available potassium and enzyme activities. Relative to G+F70 alone, the incorporation of attapulgite reduced accumulated N2O emissions by 23.4% (field) and 13.3% (incubation), lowered the N2O emission factor and yield-scaled N2O emission intensity by 41.5% and 26.2%. Attapulgite reduced soil ammonium content, nitrification potential (NP), and the (narG+nirK)/nosZ ratio, while increasing nosZ gene abundance. Random forest analysis identified nosZ as a primary predictor of N2O emissions, with NP and denitrification potential (DNP) also contributing. Partial least squares path showed NP positively correlated with N2O emissions and nosZ negatively correlated, whereas DNP had no direct effect, inconsistent with its contribution in random forest. Therefore, both DNP and denitrification completeness should be considered for N2O mitigation. In conclusion, integrating attapulgite into the post-wheat green manuring system with reduced fertilizer sustains yield and soil fertility while effectively mitigating N2O emissions by modulating key microbial nitrogen transformation processes.

Context and Objectives Intercropping provides a vital way to enhance productivity, resource use efficiency, and other ecosystem functions in agroecosystems. Traditional strip intercropping is based on narrow strips and is hard to mechanize. Wide strip intercropping offers improved compatibility with mechanization, but the yield advantage and the underlying mechanisms require examination. We compared the yield advantages of narrow and wide strip intercropping, explored the potential of including a fodder crop after harvest of the early-sown species and we quantified the border row effects in wide strip intercropping. Methods We conducted a two-year field experiment in northwest China with wheat/maize, pea/maize, oilseed rape/maize, and wheat/soybean intercropping in both narrow and wide strip intercrops, and corresponding monocultures. In wide strip intercropping, Sudangrass was planted after wheat, while common vetch was planted after harvesting peas and oilseed rape. Productivity, border row effects, and plant functional traits were measured to illuminate mechanisms underlying the advantages of intercropping. Results and Conclusions Both narrow and wide strip intercropping showed a productivity advantage. The land equivalent Ratio (LER) of wide strip intercropping ranged from 1.04 to 1.20 based on grain yield, which was lower than the range of the LER of narrow strip intercropping (1.11–1.36). This difference was primarily due to a lower maize partial LER in wide strip intercropping. Planting a fodder or green manure crop after the harvest of early-maturing crops increased the biomass-based LER of wide strip intercropping. Maize exhibited higher productivity in border rows compared to inner rows, especially in pea/maize and oilseed rape/maize intercropping, which was related to functional traits. Significance The results demonstrate that the wide strip intercropping sustains yields through border row recovery (resource reallocation post-harvest) and optimized planting strategy with temporal niche exploitation. Mechanization-adaptable wide strip intercropping offers a scalable solution for sustainable agricultural intensification.

Green manure, also known as cover crops, is a clean source of organic manure. Partial substitution of N fertilizer with green manure provides a sustainable field management approach for alleviating soil degradation and global warming. However, whether biochar can enhance the environmental benefits of green manure remains unclear. To address this, a 2-year field trial was conducted with four treatments: monoculture maize with conventional N (N100) or 70% conventional N (N70), maize intercropping with green manure (i.e., common vetch) with 70% conventional N (GN70), and GN70 combined maize straw biochar (GN70M). Compared with N100, GN70 maintained maize yield, shoot dry weight, and N uptake. Notably, GN70M increased maize shoot dry weight and N uptake by 11.3% and 15.2% compared to N100, and by 11.0% and 9.1% compared to GN70, respectively. GN70M enhanced soil SOM, NO3–-N, and MBC, resulting in a 29.2% and 40.3% increase in soil quality index relative to N100 and GN70, respectively. Cumulative CO2 emission and global warming potential (GWP) in GN70 were 26.3% and 24.4% lower than N100. GN70M further decreased cumulative CO2, N2O emissions, and GWP by 36.3%, 41.7%, and 36.9% compared to N100, and reduced soil cumulative N2O emissions by 35.1% compared to GN70. GN70 enhanced ecosystem C budget (NECB) by 4386 kg C ha–1yr–1 and reduced C footprint (CF) by 17994 kg CO2-eq ha–1 yr–1 compared with N100. Relative to N100 and GN70, GN70M enhanced NECB by 6910 kg C ha–1yr–1 and 2523 kg C ha–1yr–1, while decreasing CF by 30379 kg CO2-eq ha–1 yr–1 and 12369 kg CO2-eq ha–1 yr–1, respectively. Moreover, GN70M increased net ecosystem economic benefit by 2518 CNY ha-1 yr–1 compared to N100. In conclusion, co-utilization of green manure and biochar with 30% N reduction enhanced soil quality and offered environmental benefits while maintaining maize high-yield, providing a novel insight for eco-efficient maize production.

Zeolite application and green manure have the potential to reduce N fertilizer input and N2O emissions. However, mechanistic insights into the roles of nitrifier and denitrifier communities remain scarce. A two-year field trial was conducted with treatments under monoculture maize (MM) and maize intercropping common vetch (IMC) cropping system with conventional N (N100), 70% conventional N (N70), and N70 combined with zeolite (N70Z), respectively. Compared with N100-MM, N70-IMC reduced N2O emissions by 10.1%, while N70Z-IMC achieved a substantially greater reduction of 36.9%. At two key N2O emission peaks, green manure substitute 30% chemical N reduced soil labile C and N concentrations, regardless of zeolite application, which was conducive to decreasing the abundance and activity of N2O-producer. Specifically, relative to N100-MM, both N70-IMC and N70Z-IMC decreased the gene abundances of AOA-amoA, AOB-amoA, and narG, as well as the diversity and habitat niche width (Bcom) of narG and nirS type denitrifier. Zeolite application (N70Z-IMC) further stimulated the N2O-reducer, enhancing nosZI and nosZII gene abundances and nosZI type denitrifier diversity and Bcom compared to N100-MM. Furthermore, N70Z-IMC reduced the relative abundances of key genera within AOA-amoA (Nitrososphaera), AOB-amoA (Nitrosospira), narG (Serratia), and nirS (Alcaligenes, Azospira, etc.) type communities, which were positively correlated with N2O emissions. PLS-PM confirmed that functional microbial abundance, diversity, and key genera were primary direct drivers of N2O emissions, while assembly processes and niche breadth exert indirect effects. This study elucidates the underlying mechanism of N2O emission mitigation induced by the combined utilization of green manure and zeolite.

Green manuring enhances multiple agroecosystem services functions, yet its impact on net greenhouse gas mitigation remains controversial, primarily due to a limited number of long-term experiments. To address these challenges, this study investigated the long-term effects of green manure (GM) rotations on 100-cm-depth soil organic carbon (SOC) sequestration, N2O emissions, and crop yields based on eight long-term experimental sites (7-16 years) in China's upland cropping systems combined with process-based modeling. The results demonstrated that green manuring significantly increased SOC concentration by 8.8 %-14.4 % (p < 0.001) across 0-100 cm soil profiles compared to fallow system, with annual SOC sequestration rates reaching 0.95-1.16 Mg C ha(-1) yr(-1) (p < 0.001). Notably, topsoil layer (0-40 cm) contributed 67.5 % of total profile SOC accumulation. Green manuring can replace approximately 40 % of synthetic fertilizers of N while maintaining long-term yield stability, though with potential trade-offs in elevated N2O emissions. The optimal net global warming potential (NGWP) reached -16.47 Mg CO2-eq ha(-1) yr(-1) under GM-based system with 30 % reduction in fertilizer N. Meanwhile, under the condition that GM substitution for fertilizer N achieved no yield reduction, the greenhouse gas intensity (GHGI) was optimized within the substitution rate range of 20 %-40 %. The results from process-based modeling demonstrate that substituting 30 % of N fertilizer with GM achieves optimal soil C sequestration while maintaining stable crop yields. These findings provide direct evidence that GM rotation increases C sequestration, addressing previous knowledge gaps in understanding the C sequestration and emission reduction effects of GM-based rotation.

Soil dissolved organic matter (DOM) serves as an important carbon (C) source for microorganisms and significantly regulated by green manure and cattle manure. However, the molecular mechanisms by which these two organic fertilization practices influence soil C accrual remain unclear. In this study, we used Fourier transform ion cyclotron resonance mass spectrometry and high-throughput sequencing to analyze soil DOM composition and microbial diversity across three soil depths (0-20, 20-40, and 40-60 cm) in a 33-year field fertilization experiment annually treated with chemical fertilizer (CF), cattle manure (CM), and green manure (GM). Compared to CF, both CM and GM promoted soil C sequestration, increasing total soil organic C (SOC) by 53.0-64.8%, dissolved organic C by 61.0-159.4%, and heavy fraction organic C by 47.4-64.7% at the 0-20 cm depth. GM was more efficient than CM in enhancing SOC stock, despite a threefold lower total C input (102.3 vs. 320.1 Mg C ha-1). Although both CM and GM significantly altered fungal, rather than bacterial, community structures, CM drove a shift toward r-strategists, while GM favored C-efficient K-strategists at the 0-60 cm depth, and such differences were primarily correlated with exogenous substrate quality. Molecular composition analysis of soil DOM showed that GM increased the relative abundance of plant-derived lignin-like compounds, while CM enhanced tannin and condensed aromatic compounds. Our findings underscore the long-term effects of CM and GM on soil C sequestration in calcareous desert soils, with GM being a more C-efficient fertilization practice for sustainable agricultural development.

Green manuring is essential for improving soil quality and nutrient uptake. With the gradual depletion of phosphorus (P) resources, more attention is being paid to the role of green manures in cultivation systems, such as maize-green manure intercropping, to find possible pathways for enhancing soil P utilization. A maize-green manure intercropping experiment was started in 2009 to investigate the effects and mechanisms for enhancing P uptake and yield in maize. Three species of green manures (hairy vetch (HV), needle leaf pea (NP), sweet pea (SP)) and a sole maize treatment (CK) were used, resulting in four treatments (CK, HVT, NPT, and SPT) in the experiment. During 2020-2023, the intercropping treatments enhanced maize yields in 2020 and 2021, particularly in HVT with increases of 13.7% (1.96 t ha-1) and 13.0% (2.13 t ha-1) compared with CK, respectively. Grain P accumulation of maize was significantly higher in the intercropping treatments than CK in 2020, 2021, and 2023, and with an average increase of 10.6% over the four years (5.2% for NPT, 10.8% for SPT and 15.9% for HVT) compared with CK. Intercropping promoted maize growth with a greater root length density and a higher organic acid release rate. HVT changed the soil properties more dramatically than the other treatments, with increases in the acid phosphatase and alkaline phosphatase activities of 29.8 and 38.5%, respectively, in the topsoil (0-15 cm), while the soil pH was reduced by 0.37 units compared to CK (pH=8.44). Intercropping treatments facilitated the conversion of non-labile P to mod-labile P and stimulated the growth of soil bacteria in the topsoil. Compared with CK, the relative abundance of Gemmatimonadota, known for accumulating polyphosphate, and Actinobacteriota, a prominent source of bioactive compounds, increased significantly in the intercropping treatments, especially in HVT and SPT. A PLS-PM analysis showed that intercropping promoted soil P mobilization and the enrichment of beneficial bacteria by regulating maize root morphology and physiology. Our results highlight that maize-green manure intercropping optimizes root traits, soil properties and bacterial composition, which contribute to greater maize P uptake and yield, providing an effective strategy for sustainable crop production.

[Objective]Intercropping maize with leguminous green manure can achieve fertilizer conservation and efficiency improvement.Biochar application is an effective measure to mitigate gaseous nitrogen loss form farmland.However,the impacts of nitrogen reduction under intercropping green manure combined with the biochar application on gaseous nitrogen loss and the system's nitrogen footprint remain unclear.This study aimed to evaluate this comprehensive practice to provide a technical approach for the green maize production in oasis irrigation areas of Northwest China.[Method]A two-factor field experiment was set up in 2021 at Wuwei Oasis Agricultural Experimental Station in Gansu Province.The experiment employed a two-factorial design.The main factor was nitrogen application system,including conventional nitrogen application(N100),30%nitrogen reduction(N70),and 30%nitrogen reduction combined with sesbania biochar(N70S).The second factors were cropping patterns,including maize monoculture(MM)and maize intercropping with common vetch(IMC).Six treatments were formed:N100-MM,N100-IMC,N70-MM,N70-IMC,N70S-MM,and N70S-IMC.From 2024 to 2025,maize yield,nitrogen absorption and soil physicochemical properties were measured,nitrous oxide emission and ammonia volatilization were monitored,and the nitrogen footprint of the system was quantified by life cycle assessment method.[Result]Compared with N100,N70 decreased maize grain yield,aboveground biomass and nitrogen absorption by 7.9%,6.1%and 4.7%,respectively.In contrast,N70S increased grain yield and biomass by 8.6%and 2.7%,respectively.IMC increased the yield by 3.8%compared with MM.Notably,N70S-IMC increased grain yield,aboveground biomass and nitrogen absorption by 12.6%,4.3%and 4.0%,respectively,compared with N100-MM.The N70 reduced cumulative N2O emissions and NH3 volatilization by 16.0%to 25.2%and 9.9%to 24.7%,respectively,relative to N100.The N70S further reduced these emissions by 24.8%to 27.7%and 17.6%to 43.9%,respectively.Compared with N100-MM,N70-IMC and N70S-IMC reduced cumulative N2O emissions by 12.1%to 20.1%and 20.1%to 35.8%and NH3 volatilization by 15.3%to 24.3%and 11.2%to 20.1%,respectively.Soil analysis showed that,compared with N100-MM,N70-IMC decreased soil ammonium nitrogen(NH4+-N),nitrate nitrogen(NO3--N),and microbial nitrogen(MBN)by 17.6%,15.6%,and 9.6%,respectively.While N70S-IMC decreased NH4+-N and soluble organic nitrogen(DON)by 15.6%and 7.3%,respectively,but increased total nitrogen(TN)and MBN by 3.9%and 25.0%,respectively.Random forest analysis indicated that soil NO3--N,NH4+-N,MBN and DON were the key factors driving N2O emissions,while NH3 volatilization was mainly driven by NO3--N,NH4+-N and TN.Life cycle assessment indicated that the nitrogen footprint under N70-IMC and N70S-IMC was decreased by 28.9%and 39.7%,respectively,compared with the N100-MM.Furthermore,the nitrogen footprint of the N70S-IMC treatment was 10.4%lower than that under N70-MM.[Conclusion]The combination of maize-green manure intercropping,30%nitrogen reduction,and sesbania biochar application increased grain yield and nitrogen absorption,improved key soil properties,and lowered N2O emissions,NH3 volatilization,and the system's nitrogen footprint,which was an effective path for green and sustainable maize production in the Northwest Oasis Irrigation District.

Organic amendments increase soil organic carbon (SOC) but may reduce belowground R-diversity or increase compositional similarity among soil communities in agroecosystems, a phenomenon known as biotic homogenization. However, it remains unclear whether and how biotic homogenization in turn mediates SOC accumulation in response to organic amendments, particularly in wheat/maize intercropping systems prevalent in Northwest China. To address this, we used amplicon sequencing to investigate the role of soil biota in SOC accumulation under wheat and maize strips in a long-term intercropping experiment (since 1988) with three organic amendments (wheat straw, mixed straw & cow manure, and cow manure) and one chemical fertilizer (Chemical). Results showed that the cow manure (Manure) led to significantly higher SOC than the straw and Chemical treatments for both crops. Notably, the R-diversity of soil biota was the primary driver of SOC variation. Compared with Chemical treatment, Manure significantly reduced R-diversity, reflecting biotic homogenization, but the mechanisms differed by crop: in maize soils, fungi significantly reduced the turnover component, whereas in wheat soils, protists significantly reduced the nestedness component. Core species driving biotic homogenization were positively correlated with SOC and significantly enriched under Manure treatment. Network analysis showed that core species in maize soils were linked to bacteria exhibiting functionally distinct R-diversity across treatments, whereas core species in wheat soils were associated with bacteria lacking such functional differentiation. Overall, our study demonstrates positive yet crop-specific effects of biotic homogenization on SOC accumulation in wheat/maize intercropping under organic amendments. These findings highlight the potential for targeted use of organic amendments to shape soil community composition and optimize SOC in intercropping systems.

Intercropping has been demonstrated to enhance crop productivity and phosphorus (P) uptake, in which root-microbe interactions played crucial roles. Our previous results showed that this beneficial effect of intercropping depends largely on a match between root traits and rhizosphere processes. However, little is known about the role of soil microbial communities in underground processes. Using a long-term field experiment with three P-fertilizer application rates and five cropping systems of maize, we integrated crop productivity, root physiological traits, root morphological traits and microbial amplicon sequencing data. Our findings revealed that intercropping significantly enhanced maize crop productivity and P uptake, accompanied by increased plasticity of morphological and physiological root traits compared with monoculture. Additionally, intercropping with different companion crops significantly altered the soil microbial community structure of maize, while P-fertilizer application rates had minimal effect. Network analysis showed that intercropping promoted more complex and stable microbial networks characterized with increased cooperative relationships, relative to monoculture. The relative abundance of keystones enriched in intercropping systems were positively correlated with crop productivity and P uptake, explaining 41.11

Green manure is widely employed to substitute chemical N fertilizer. However, the potential of further alleviating N2O emission when combined with efficient management technologies has not been fully explored. To reduce this research gap, a 2-year field experiment was conducted in northwestern China. The aim was to investigate the impact of zeolite application on N2O emission in the maize-common vetch intercropping system under 30

Metal elements in soil are important factors that affect crop yield and quality. As organic manures, the application of green manures can improve soil quality and crop yield. However, there are still insufficient studies on the effects of soil quality improvement, elemental content changes and microbial community changes under multi-year green manure intercropping. This study aims to explore the effects of multi-year green manure intercropping, and further explore the relationship between microbial community and metal element content. In this study, data pertaining to soil properties, enzymatic activities, and maize yield were collected. The metal content was measured using ICP-OES in this study, and the microbial groups were classified based on metagenomic to explore their correlation. The results revealed that intercropping of green manure for many years was beneficial to increase maize yield. Multi-year intercropping increases maize yield by improving soil quality, regulating element content, and influencing microbial communities. Multi-year green manure intercropping had a significant effect on soil elemental content, increasing the content of Ca, Ca, Mg, Al, and Fe, and decreasing the content of Pb and Mn. Multi-year intercropping with green manure contribute positively to soil quality improvements, including enhancing soil carbon sequestration and accumulation, reducing soil bulk density, and elevating soil alkaline enzyme activity. The microbial community has a significant positive impact on Ca, Mg and Al contents, and a significant negative impact on Pb and Mn contents. And there are 30 genera could be used as potential biomarkers to predict changes in soil metal element content.

Intercropping crops with green manure offers a sustainable strategy to reduce nitrogen fertilizer dependency, enhance yields, and improve land use efficiency. While beneficial soil microorganisms are known to be key drivers of improved soil fertility and crop productivity, the differential responses of specific functional microbial communities to agronomic practices and their precise contributions to overall community structure and ecosystem function remain unclear. Here, we investigate how four key functional groups (NPK nutrient absorption [NPK], pathogen antagonism [PA], drought resisting [DR], and plastic degradation [PD]) driver ecosystem functions in a long-term maize-green manure intercropping field experiment. We found that green manure intercropping significantly decreased the Shannon and Simpson diversity and alterd four soil health-associated functional community composition. Moreover, green manure intercropping improved species connections and increased the network’s overall complexity. Crucially, we identified 11 novel core microbial genera with previously unrecognized roles in underpinning soil multifunctionality. Importantly, green manure-driven restructuring of the bacterial community optimizes functional redundancy, offering a novel pathway for the targeted manipulation of microbial communities and the optimization of agroecosystem functions.

Healthy soil is essential for maintaining food security and enhancing ecosystem functions. Green manure application improves soil fertility and is an alternative to chemical fertilizers; however, research on optimizing soil health assessment systems and providing comprehensive and accurate information for local farmland green manure management models remains limited. In this study, we used maize and potato intercropped with green manure farmland in the main crop production area of a semi-arid irrigation area in Northwest China as the research object, integrated the regional soil environment characteristics, and used principal component analysis and other methods to establish a minimum index data set including physicochemical, biological, and yield indices. A soil health assessment system applicable to the study region was constructed and optimized by drawing the scoring curve. The results showed that green manure treatment exerted a positive effect on the soil bulk density, nutrient content, extracellular enzyme activity, and the yield of maize and potato fields. This evaluation method showed that both green manure treatments could improve the soil health index of two major crop fields, with scores of 6.9 (3.7-8.6) and 6.2 (4.5-7.0) for maize and potato farmland, respectively, with a greater positive effect caused on maize. This evaluation system can not only reflect the soil conditions of farmland accurately given the application of green manure in the semi-arid irrigation areas of northwest China but also provide reference for the promotion of organic fertilizers such as green manure and the resolution of regional soil health differences.

Species-diverse plant communities can promote the accumulation of soil organic carbon (SOC) and nitrogen (SON) in both natural and semi-natural ecosystems. It is not clear however, how the accumulation and depth distribution of soil C and N might be affected in species-diverse croplands. Using a 15-year crop diversity field experiment, we ask how SOC and SON accumulation and vertical distribution (0-to-100 cm soil depth) changes in response to agricultural diversity, expressed as crop rotation (temporal effect) and intercropping (spatial effect) of staple crop species including wheat and faba bean (C3) and maize (C4). We found that rotation and inter-cropping across crop combinations altered the depths at which C and N were stored, over the 0-100 cm soil profile, but not the total C and N stored. There was greater SOC storage over the 0-100 cm soil profile in faba bean/maize intercropping than maize-faba bean rotation. Total SOC between 0 and 40 cm soil depth in inter-cropping increased by 125-164 kg C ha-1 yr-1 compared to rotation systems across crop combinations. However, rotations increased SOC at 60-80 cm in depth by 104 kg ha-1 yr-1 compared to intercropping. Also, SON stocks in rotation systems, at 60-80 cm, increased by 18 kg ha-1 yr-1 compared to intercropping systems. The accumulation and vertical distribution of SOC3 derived from roots of wheat and faba bean contributed to increase total SOC stocks and SOC vertical distribution. SOC4 derived from roots of maize did not have the same effect. Crop ro-tations promoted deeper root-associated SOC3 accumulation whereas intercropping promoted shallower root-associated SOC3 accumulation. Our study demonstrates how the type of crop diversification influences soil C and N sequestration via regulating root distribution, root composition and root decomposition. These findings have practical implications for soil C and N management in croplands.

Context or Problem: Global food security is threatened by plant disease, and crop diversification often promotes productivity through reduced disease and facilitation for increased nutrient acquisition. However, whether such facilitation is a factor in disease resistance is unknown. Objective or Research Question: Investigate how crop diversity affects crop productivity and rust disease on maize, and whether competition or facilitation between crop species correspond with resistance. Methods: Five irrigated intercropping experiments with different fertilization and crop combinations were conducted at two sites for four years. Productivity (542 data points) and disease severity (27150 data points) of maize monoculture, maize - legume and maize - non-legume intercropping were compared. A meta-analysis of literature was performed to confirm the broader applicability of results from these field experiments. Results: Legume-based intercropping increased the aboveground biomass of intercropped maize by 8% and grain yields by 10% in comparison to non-legume-based intercropping. Disease severity on maize intercropped with legumes was reduced by 45% and 48%, compared to monocultures of maize and maize intercropped with nonlegumes, respectively. Moreover, as interactions among intercrops became more facilitative, the concentrations of zinc (Zn), copper (Cu) and iron (Fe) in maize increased, and these increases were highly correlated with decreasing disease severity. The global meta-analysis was consistent with our field experiments, as lower disease severity was associated with greater intensity of interspecific facilitation or with lower intensity of interspecific competition. Conclusions or Significance: Lower disease severity was closely related to enhanced acquisition of nutrients that can enhance the resistance to crop diseases, driven by stronger interspecific facilitative effects in intercropping systems. Facilitative effects on maize was increased by the identity of leguminous companion crop species, and was increased by sufficient irrigation, but reduced by applications of nitrogen and phosphorus fertilizers. Implications: Our findings identify a novel facilitative mechanism in general and advance the understanding of the facilitative mechanisms that underly disease control through crop diversification.

Green manure is a crucial strategy for increasing cereal yield and mitigating environmental burden while reducing chemical N fertilizer. To effectively tackle climate change, finding ways to reduce nitrous oxide (N2O) emissions from green manuring systems is vital. Herein, field and 15N labeled microcosm experiments were arranged to investigate the effect and mechanisms of green manuring and zeolite application on N2O emission. Both experiments comprised four treatments: conventional chemical N (N100), 70 % chemical N (N70), N70 with green manure (N70 + CV), and N70 + CV combined with zeolite (N70 + CV + Z). Compared with N100, both N70 + CV and N70 + CV + Z maintained maize yield, cumulative N2O emissions decreased by 37.7 % and 34.9 % in N70 + CV + Z in 2022-yr and 2023-yr, and by 12.8 % in N70 + CV in 2022-yr. Moreover, the reduction of N2O emission primarily occurred after incorporating green manure. The N100 and N70 + CV demonstrated a similar transformed proportion of chemical N to N2O (i.e., 4.9 % and 4.7 %) while reducing it to 2.7 % in N70 + CV + Z. Additionally, a mere 0.7 % of green manure N was transformed to N2O in both N70 + CV and N70 + CV + Z treatments. Compared with N100, both N70 + CV and N70 + CV + Z decreased the relative abundances of ammonia oxidation microbes, increased denitrifier and the ratios of (nirK + nirS)/nosZ and norBC/nosZ. Furthermore, compared with N70 + CV, N70 + CV + Z decreased the relative abundances of N2O-producer and the ratios of (nirK + nirS)/nosZ and norBC/nosZ in denitrification. These findings revealed that the reduction of N2O emissions resulting from green manure replaced chemical N was mainly due to weakened nitrification, while zeolite reduced N2O emissions attributed to enhanced conversion of N2O to N2. Moreover, certain key N-cycling functional bacteria, such as Phycisphaerae, Rubrobacteria, and Thermoflexia, were positively correlated with N2O emission. In contrast, Dehalococcoidia, Gammaproteobacteria, and Betaproteobacteria were negatively correlated with N2O emission. This investigation uncovered the underlying mechanisms for effectively reducing N2O emissions through green manuring combined with zeolite.

Organic fertilization in agroecosystems is an efficient fertilization management for sequestering carbon (C). Microbial metabolism affects C sequestration by influencing the rate of soil C mineralization, however, the responses of microbial metabolism limitation and soil respiration to different organic fertilizations remain unclear. Here, an experiment started from 1988 in a dry land of Northwest China was used to explore the mechanisms of C sequestration under five typical fertilization managements, namely no fertilization (CK), mineral nitrogen fertilizer (NF), wheat straw (WS), cattle manure (CM), and green manure (GM). The results indicated that the WS, CM, and GM treatments increased C sequestration rates by 28.3 %, 119.4 %, and 72.1 % in the 0-60 cm layer, compared with NF, whereas C sequestration efficiency was the greatest in the GM treatment. In addition, organic fertilization treatments increased the contents of soil nutrients across all the soil layers to varying degrees, and the activities of C, nitrogen (N), and phosphorus (P) -related enzyme in 0-60 cm soil layer also increased by 219.1 similar to 236.9 %, 236.7 similar to 774.5 %, and 2.5 similar to 36.5 % compared with NF. Enzymatic stoichiometry indicated that the soil microbial metabolism across all soil layer was mainly limited by P. Organic fertilization alleviated the microbial P limitation and decreased the microbial metabolic quotient (qCO(2)) in 0-20 cm soil layer. And GM treatment showed the lowest P limitation and qCO(2) in all soil layers. The partial least square path model demonstrated that microbial P limitation was the main driver affecting qCO(2). Alleviating the microbial P limitation decreased unnecessary C loss during microbial catabolism, converting more C to MBC, thereby increasing CUE and lowering qCO(2). In summary, green manuring is the most efficient practice to benefit C sequestration across all fertilization managements in this study.

Maize intercropped with leguminous green manure (LGM) has been proven as a sustainable plantation practice for enhancing crop yield and soil fertility. However, a comprehensive understanding of how intercropped legumes coordinate the above- and below-ground performance during maize growth under low to high N application remains elusive. This study aimed to investigate the effects of biological C and N input on soil fertility and maize growth by regulating soil enzyme activities in maize/LGM intercropping systems. A three-year field trial was conducted in northwestern China, where maize was intercropped with two LGMs, namely common vetch and pea, under no N (N0, 0 kg ha- 1) and conventional N (N330, 330 kg ha- 1) applications. The grain yield of intercropped maize ranged from 10.54 to 11.08 t ha- 1, representing a significant increase of 6.6-12.1 % compared to monoculture maize in the N0 treatment. Nitrogen application substantially increased maize grain yield by 39.2-52.0 % across cropping systems relative to the N0 treatments, while minor differences were observed in maize yield between cropping systems in the N330 treatments. Compared with monoculture maize, intercropped with LGMs increased C input by 16.7-79.2 % at maize V9 stage and 81.1-140.3 % at the R6 stage. The biological N fixation of intercropped LGMs was 62.7-89.5 kg ha- 1 and 8.0-12.8 kg ha- 1 in the N0 and N330 treatments, respectively. Biological C and N input greatly facilitated soil enzyme activities and the associated nutrient cycling, consequently improving soil fertility. Soil organic matter and total N in the intercropping systems significantly increased by 4.4-14.3 % relative to monoculture across maize growth stages, irrespective of N levels. Furthermore, increased soil fertility was closely associated with nutrient stoichiometry, which in turn facilitated maize nutrient uptake and shoot recovery growth in the intercropping systems. Overall, these findings highlight that increased biological C and N input to belowground enhances soil C and nutrient cycling by regulating the involved enzyme activities, which in turn improves maize nutrient uptake and growth, forming a coordinated loop of C and nutrient flow in the maize and legume intercropping systems. Maize intercropped with LGMs is a sustainable practice that improves soil fertility and promotes maize growth by augmenting biological C and N input.