Accurate assessment of nitrogen status in oilseed flax is crucial for optimizing nitrogen use efficiency (NUE) and promoting sustainable agricultural practices. The nitrogen nutrition index (NNI) serves as a key diagnostic tool; however, its response to the interaction between nitrogen fertilization and planting density remains poorly understood. To address this knowledge gap, a field experiment was conducted using three nitrogen application rates (0 (N-0), 75 (N-75), and 150 (N-1050) kg ha(-)(1)) and three planting densities (4.5 (N-450), 7.5 (N-750), and 10.5 (N-1050) x 10(6) plants ha(-)(1)) to reveal the effects of nitrogen and planting density on dry matter and nitrogen accumulation, leaf area index (LAI), critical nitrogen dilution curve parameters, and ecaluating subsequent impacts on nitrogen nutition status and yield. Results showed that the high-density treatment (D-1050) and high-nitrogen treatment (N-150) significantly enhanced dry matter (DM) accumulation during the later growth stages of flax. The effect of high nitrogen on DM shifted from inhibitory during vegetative growth to promotive during reproductive growth. Planting density had a significant positive effect on DM of oilseed flax. The combination of high nitrogen and high density (N150D1050) substantially promoted DM accumulation at Kernel and Maturity stages. Both nitrogen application and planting density exerted significant effects on leaf area index (LAI), with the highest LAI values consistently observed under the combined high nitrogen and high density treatment. High nitrogen application suppressed nitrogen accumulation under low planting density but significantly enhanced it under high density. A significant nitrogen x density interaction was evident for the critical nitrogen dilution curve parameter A1 and A2. A1 was estimated with high precision and exhibited a nonlinear response to nitrogen, peaking at moderate application rates (N-75) under medium planting density (D-750). In contrast, parameter A2 showed greater estimation uncertainty but pronounced sensitivity to treatments, with its value sharply declining under high nitrogen, particularly at medium density (N150D750). Higher planting densities generally reduced A2 across all nitrogen levels. A major contribution of vegetative-stage DM and LAI to parameter A1; in contrast, parameter A2 was overwhelmingly contributed by seedling DM. All nitrogen treatments resulted in nitrogen deficiency (NNI < 1) at maturity. The effectiveness of nitrogen application on NNI was highly dependent on planting density. Under low density, high nitrogen maintained superior nitrogen nutrition status through maturity. At medium density, only moderate nitrogen ensured adequate nitrogen supply at the grain-filling stage, while high nitrogen led to late-stage deficiency. Under high density, high nitrogen improved early vegetative nitrogen status, and the high density itself helped maintain nitrogen concentrations during reproductive growth. In conclusion, nitrogen and planting density interactively regulate oilseed flax growth through coordinated effects on dry matter accumulation, LAI development, and nitrogen dynamics, thereby modifying the critical nitrogen dilution curve parameters (A1 and A2) and shaping the temporal pattern of nitrogen nutrition status (NNI) throughout the growth cycle. The N75D750 treatment increased oilseed flax yield by 4.1 %-16.2 %, effectively balancing yield improvement with resource efficiency.

Content: Lodging has been a limiting factor for the achievement of high grain yield in oilseed flax (Linum usitatissimum L.) production. However, the potential mechanism by which silicon fertilizer and sowing width affect the lodging of oilseed flax and enhance its lodging resistance remains unclear. Objective: This study aims to investigate the effects and underlying mechanisms of sowing width combined with silicon fertilizer application on lodging resistance and yield formation in oilseed flax. Methods: a two-year field experiment was conducted at the Dingxi Oilseed Crops Research Institute to investigate the effects of different silicon application rates (Si0, 0 kg ha(-1); Si1, 75 kg ha(-1); Si2, 150 kg ha(-1)) under two sowing patterns (R0, conventional strip sowing; R1, wide uniform sowing) on lodging resistance and yield performance in oilseed flax. Results: The combination of wide uniform sowing and silicon fertilizer application significantly increased the silicon content in oilseed flax stems, agronomic silicon use efficiency, and partial factor productivity of silicon, resulting in a yield increase of 14.18-23.97%. Under the condition of wide uniform sowing, the Si1 level significantly increased plant height, stem diameter, wall thickness, stem density, stem strength, and bending resistance in oilseed flax compared to both Si0 and Si2 levels. The mechanism is that silicon application enhances the activities of 4CL, PAL and CAD enzymes, upregulates the expression of F5H1 genes, and promotes the accumulation of soluble sugar, starch, cellulose and lignin. Random forest model analysis revealed that stem silicon content and lignin accumulation are key drivers for enhancing lodging resistance. Conclusion: The application of 75 kg ha(-1) silicon fertilizer under the wide uniform sowing method was beneficial to improve the lodging resistance and grain yield of oilseed flax. Implications: The results of this study provide a theoretical basis for understanding the yield enhancement and efficiency in lodging resistance improvement mechanisms of oilseed flax, as a low-silicon crop, under wide uniform sowing technology, while offering technical support for "high-quality, high-yield, and high-efficiency" cultivation practices in the rainfed agricultural areas of Longzhong.

Soil salinity restricts the yield of winter Brassica rapa, yet it remains unclear whether gamma-aminobutyric acid (GABA) alleviates salt stress through universal physiological responses or genotype-specific regulatory patterns. To resolve this question, salt-tolerant KY and salt-sensitive Qin were subjected to four treatments: blank control (CK), sole GABA supplementation(G), single salt stress(S), and combined salt stress plus GABA(S+G). Multiple indicators covering seedling growth status, membrane impairment, reactive oxygen species buildup, antioxidant performance, Na+/K+ balance and ion transportation were measured. Transcriptome profiling, DIA proteomic detection and qRT-PCR confirmation were also conducted for multi-omics exploration. Exogenous GABA relieved salt-triggered growth suppression, oxidative injury and ion disorder across both genotypes, with KY displaying stronger physiological and molecular responses associated with salt stress adaptation. Under NaCl stress conditions, KY possessed stronger antioxidant buffering potential, steadier Na+/K+ homeostasis, as well as enhanced native capacities to take in K+ and expel Na+. Omics data identified a KY-enriched regulatory module associated with phenylpropanoid and flavonoid metabolism, where BrPAL2, BrCSE, BrGSTU25, BrGASA7 and BrCYP74A were identified as candidate genes potentially associated with GABA-responsive salt tolerance. Collectively, GABA exerts non-universal salt-mitigating effects; its protective performance depends on genotype-matched coordination of physiological defense, ionic equilibrium and stress-responsive molecular pathways. These findings provide insights into genotype-dependent GABA responses and may contribute to future evaluation of GABA application and saline-adapted germplasm improvement in B. rapa.

This study focuses on the symbiotic system between plateau-specific rhizobia and leguminous plants in Qinghai Province, northeastern Qinghai Plateau. Aiming at addressing the current issues in this region, such as farmland nitrogen imbalance, low nitrogen fertilizer use efficiency, and prominent ecological and environmental problems, a multi-disciplinary approach was adopted to systematically explore the nitrogen-fixing mechanism of this symbiotic system, its quantitative contribution to farmland nitrogen balance, and to develop rhizobial inoculants and planting patterns suitable for the plateau. The research provides theoretical and technical support for the sustainable development of plateau agriculture. The results show that the symbiotic system formed by plateau-specific rhizobia and leguminous plants can effectively increase farmland nitrogen input, improve soil nitrogen pool status, and reduce the risk of nitrogen loss. It is of great significance for promoting the development of green agriculture in Qinghai and facilitating the achievement of the "dual carbon" goals.

Temperature-induced lipocalins (TILs) are a class of thermoregulated lipid-transporting proteins crucial for plant stress responses. However, systematic research on the TIL gene family remains relatively limited. In the present study, we conducted a comparative analysis of the TIL gene family in five Brassicaceae species (Arabidopsis thaliana, Brassica rapa L., Brassica rapa subsp. pekinensis, Brassica juncea L., and Brassica napus L.), identifying a total of 23 TIL genes. Analyses of their gene structures, evolutionary relationships, conserved motifs, and cis-acting elements showed extensive collinearity, close homology, and functional conservation, implying they may possess similar biological functions across different Brassicaceae species. The Brassica rapa TIL1 (BrTIL1) gene was significantly upregulated under low-temperature stress. Functional validation showed that Arabidopsis thaliana plants overexpressing BrTIL1 exhibited higher survival rates, soluble protein levels, and peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) activities under low-temperature conditions, confirming that BrTIL1 positively regulates cold tolerance. The BrTIL1 protein was localized to the cell membrane. A yeast two-hybrid screen identified six proteins interacting with BrTIL1. The genes encoding these interacting proteins exhibited differential expression under low-temperature stress, suggesting they may affect the functional activity of BrTIL1. In summary, this study provides a systematic analysis of the TIL gene family in five Brassicaceae species, elucidates the role of BrTIL1 in cold tolerance, and establishes a foundation for deciphering the molecular mechanisms of the cold stress response in Brassicaceae species.

Wide-width precision sowing has been reported to improve wheat yield and enhance water-nitrogen use efficiency. However, systematic studies on the combined effects of reduced nitrogen application and wide-width precision sowing on wheat yield formation, nitrogen uptake and utilization, and soil water-nitrogen dynamics remain insufficient. Field experiments were conducted during the 2024 similar to 2025 growing seasons in a typical dryland agricultural region of northwest China. A two-factor randomized block design was employed with four nitrogen application rates (N-0: 0 kg center dot hm(-2); N-1: 75 kg center dot hm(-2); N-2: 150 kg center dot hm(-2); N-3: 225 kg center dot hm(-2)) and two sowing methods: conventional drill sowing (R-0, sowing width of 5 cm with 20 cm row spacing) and wide-width precision sowing (R-1, sowing width of 10 cm with 20 cm row spacing). The effects of reduced nitrogen application combined with wide-width precision sowing on aboveground dry matter accumulation, nitrogen accumulation, soil nitrogen dynamics, stage-wise water consumption, water-nitrogen use efficiency, and wheat yield were investigated. The results showed that, under the same nitrogen application rate, wide-width precision sowing enhanced wheat nitrogen uptake and aboveground dry matter accumulation and modified water consumption patterns across growth stages compared with conventional drill sowing, resulting in increases in grain yield (10.72%), water use efficiency (5.19%), and nitrogen partial factor productivity (10.29%). In addition, reduced nitrogen application effectively decreased soil nitrogen accumulation. Under wide-width precision sowing, a nitrogen application rate of 150 kg center dot hm(-2) improved resource use efficiency without significantly reducing wheat yield, whereas a nitrogen application rate of 75 kg center dot hm(-2) achieved the highest nitrogen use efficiency. Overall, the combination of wide-width precision sowing and moderate nitrogen reduction may provide an effective agronomic option for improving water and nitrogen use efficiency while maintaining stable wheat production in the arid and semi-arid regions of northwest China.

Context: Diversified crop rotation is crucial for improving agricultural nitrogen utilization efficiency (NUE) and mitigating environmental pollution. However, the mechanisms by which preceding crops regulate N supply and utilization through residual N effects remain inadequately understood. Research questions: Within long-term rotations, how do different preceding crops influence the fate of fertilizer N (including its residual effect), regulate soil N supply, and consequently determine the N uptake and utilization efficiency of subsequent crops? We hypothesized that a shift in preceding crop species would improve soil residual N retention and availability, which in turn would promote residual N utilization by the following crop, leading to enhanced NUE and reduced N loss at the system level. Method: Using continuous 15N isotopic labeling and micro-plot techniques in typical Loess Plateau cropping systems (oilseed flax, potato, and wheat), we systematically quantified the fate of current and residual fertilizer N. Results: Our results showed substantial increases in oilseed flax grain yield (47.7-68.0 %) and N accumulation (45.1-61.7 %) under crop rotations compared to continuous cropping. Although soil-derived N constituted the majority of crops uptake (61.1-78.3 %), fertilizer N contributed substantially: 17.6-23.0 % from current-season and 7.2-16.7 % from residual fertilizer N. Crop rotations enhanced plant N accumulation from current and residual fertilizer N by 51.2-89.2 % and 48.3-255.0 %, respectively, with potato as the preceding crop showing the strongest residual N utilization. Potato served as the preceding crop (FWPF, WFPF) improved seasonal N recovery and residual N retention, thereby supplying more N to subsequent flax and reducing N loss. The FWPF system achieved the highest residual N utilization efficiency. In contrast, the WFPF and WPWF systems significantly enhanced the current-season fertilizer N utilization efficiency of oilseed flax than other treatments, while also exhibiting lower N loss rates compared to continuous cropping. Conclusion: Crop rotations enhance NUE and mitigate N loss by enhancing N uptake, reprogramming N utilization patterns, and improving synchronization of N supply between preceding and subsequent crops. Implication: These findings establish a theoretical and practical basis for designing sustainable, high-NUE rotations in Loess Plateau dryland agriculture.

A field experiment was conducted in three ecological zones to evaluate the effects of broadcast sowing (BS), drill sowing (DS), and ridge-furrow precision sowing (RFS) on winter rapeseed (Brassica rapa L.) grown in lightly saline-alkaline soils, using two cultivars (L6 and L7). RFS improved soil temperature and soil moisture conditions across the zones. Its warming effect was most pronounced in the JT zone, where soil temperatures at seedling and flowering stages were 9.7% and 10.3% higher than under BS, respectively. RFS also showed a moisture-conservation advantage at regreening, with soil moisture 13.8% and 6.6% higher than under BS and DS, respectively. In addition, RFS reduced soil salinity and increased soil total carbon, available potassium, and ammonium nitrogen contents. Plants under RFS showed higher SPAD values, net photosynthetic rates, and transpiration rates at seedling and regreening stages, along with higher antioxidant enzyme activities and lower MDA accumulation. RFS advanced key phenological stages, improved overwintering survival, and produced the highest yield. Compared with BS and DS, respectively, RFS increased the mean yield of L6 by 11.46% and 6.97%, and that of L7 by 16.02% and 10.52%. Overall, RFS promoted yield formation by improving soil conditions, photosynthetic activity, and stress resistance.

Oilseed flax production in northwest China's drylands is constrained by simplistic planting systems and low water productivity. We conducted a three-year field experiment on the semi-arid Loess Plateau to evaluate intercropping as a sustainable intensification strategy. The objective was to assess the effects of different strip configurations in maize/oilseed flax intercropping on system productivity, soil water use, and crop physiological adaptation. A two-factorial randomized block design was used. The treatments comprised three cropping systems (maize monoculture, oilseed flax monoculture, and maize/oilseed flax intercropping) and three strip configurations with specific row ratios: I42 (2 rows of maize: 4 rows of oilseed flax), I63 (3:6), and I84 (4:8). Intercropping significantly increased biomass and grain yield relative to monoculture, with the I84 configuration achieving the highest land equivalent ratio (LER). Soil water storage (0 -80 cm) increased by 8.6% and 6.3% relative to maize and oilseed flax monocultures, respectively. I84 further improved storage by 6.5%-18.9% over narrower configurations. The I84 system alleviated shading stress, leading to significant increases in key photosynthetic parameters of 14.6%-45.2% (P < 0.05) and leaf water use efficiency of 0.8%-44.0% (P < 0.05). These physiological improvements coincided with a rebalancing of endogenous hormones (ABA, CTK, JA, SA). Optimized strip intercropping enhances system productivity by synchronously improving soil water retention and inducing coordinated aboveground-belowground physiological adaptations. This study demonstrates that optimized strip configuration (I84) enhances intercropping productivity by integrating photosynthetic performance, soil water utilization, and hormonal responses in a maize/oilseed flax system.

Soil conditioner has good performance in improving soil environment and solving soil barrier problems. The purpose of this study was to analyze the effects of different types of soil conditioners on the distribution of soil aggregates and the yield of corn, and to find out the suitable soil conditioners for improving the barren soil in the Yellow River irrigation area. The treatments include no soil conditioner (CK), cow dung organic fertilizer soil conditioner with different organic matter contents (Om-20%, Om-30%, Om-40%, Om-45%), humic acid soil conditioner (Hu-20%) and amino acid soil conditioner (Am-25%). The result indicated that different types of soil conditioners promoted the formation of aggregates with particle size > 0.25 mm, improved the stability of aggregates, and increased the content of organic carbon and total nitrogen in macroaggregates. Compared with CK, the contents of organic carbon and total nitrogen of various soil conditioners in macroaggregates increased by 20.08-48.89% and 8.36-42.86%, respectively. The organic carbon content of macroaggregates under Am-25% treatment was significantly increased by 7.15% compared with Hu-20% treatment. The contents of available phosphorus, available potassium, organic carbon and total nitrogen under Am-25% treatment was increased by 6.37-45.86%, 6.29-22.39%, 3.49-12.05% and 2.64-19.74% than that of cow dung organic fertilizer soil conditioner treatments, respectively. Correlation analysis and structural equation model analysis showed that macroaggregates with particle size greater than 0.25 mm were positively correlated with corn hay yield. Aggregate stability and chemical properties accounted for 71% of corn hay yield changes, and organic carbon mainly affected corn hay yield through soil C/N ratio. Therefore, the application of soil conditioner, especially amino acid soil conditioner, to the barren soil in the Yellow River irrigation area can improve the physical and chemical properties of soil, promote the formation of macroaggregates, improve the stability of aggregates, and promote the high and stable yield of corn.

Green manure (GM) is promising for use in sustainable agriculture, but its impacts on nitrogen emissions from farmland and crop productivity are unclear. Thus, we conducted a meta-analysis based on 2,616 data pairs from 218 studies to clarify the effects of GM. GM enhanced soil nitrogen retention to increase the crop yield and nitrogen use efficiency (NUE) by 3.71 % and 24.41 %, respectively, and reduce ammonia (NH3) emissions by 9.09 %, but with no significant impact on nitrous oxide (N2O) emissions. GM was most effective in low-quality soil and warm, humid climates, especially legume GM. Combining GM with high nitrogen fertilizer use may further reduce NH3 emissions. Machine learning models showed that GM could increase global maize and rice yields by 9.78 % and 11.10 %, respectively, and reduce NH3 emissions from major crops by 9.92 %, but increase N2O emissions from paddy fields by 9.45 %. In general, GM can enhance crop productivity and reduce agricultural environmental costs to promote green development.

Context Accurate monitoring of crop nitrogen status is the premise of precise nitrogen application. However, there is a lack of general diagnostic approach for the nitrogen status of oilseed flax, and the mechanism of nitrogen fertilizer managements influencing oilseed flax grain yield and agronomic nitrogen use efficiency (aNUE) is still unclear. Objectives or methods Six nitrogen application rates (0 (N0), 60 (N60), 90 (N90), 120 (N120), 150 (N150), and 180 (N180) kg hm(-2)) and three split application methods (T1, 100 % of nitrogen at pre-sowing; T2, 2/3 of nitrogen at pre-sowing + 1/3 at budding stage; T3, 1/3 of nitrogen at pre-sowing + 1/3 at branching stage + 1/3 at budding stage) were designed. A critical nitrogen concentration model for oilseed flax was constructed. Then, the effects of different nitrogen fertilizer managements on dry matter and nitrogen accumulation, distribution, translocation, grain yield, and aNUE, as well as relationships between these indices and plant accumulated N deficit (Nand)/nitrogen nutrition index (NNI) of oilseed flax were analyzed. Results The dry matter-based critical nitrogen concentration model for oilseed flax was Y= 2.4507X-0.33473, with an R2 of 0.91294. Compared with the traditional nitrogen application rate (N180), nitrogen reduction by 33 % (N120) reduced the full-season NNI, nitrogen accumulation, and TransN (pre-anthesis nitrogen translocation from vegetative organs to reproductive organs) by 8.91 %-19.77 %, 10.80 %, and 10.53 %, respectively (p < 0.05), and increased Nand, dry matter accumulation, proportions of dry matter allocated to leaves (PDL) and reproductive organs (PDR) at maturity stage, TransD (pre-anthesis dry matter translocation from vegetative organs to reproductive organs), TransD rate, grain yield, and aNUE by 73.42 %-118.31 %, 4.24 %, 4.81 %, 3.02 %, 9.73 %, 15.89 %, 7.43 %, and 121.92 %, respectively (p < 0.05). Compared with T1, T2 increased the dry matter accumulation, PDL, PDR, TransD, nitrogen accumulation, proportion of nitrogen allocated to reproductive organs at maturity stage, grain yield, and aNUE by 4.99 %, 45.42 %, 4.00 %, 21.80 %, 11.24 %, 8.87 %, 4.09 %, and 50.95 %, respectively (p < 0.05). Conclusions or implications Among the nitrogen fertilizer managements, the optimal mode N120T2 could improve oilseed flax nitrogen status, coordinate the source-sink relationship in plants to efficiently use photosynthetic assimilates, and promote the translocation of photosynthetic assimilates to sink organs in the late growth stage, thereby increasing the grain yield and aNUE. This study will provide a technical means for precise nitrogen fertilization and yield increase in oilseed flax in the semi-arid region in China.

The stem nonstructural carbohydrate translocation efficiency could affect crop yield and lodging. However, the relationship between yield, lodging, and nonstructural carbohydrate transportation under high-density planting in rapeseed remains unclear. Therefore, field experiments with six varieties and two densities were conducted in 2020-2022 to investigate the effects of planting density on rapeseed yield, the limiting factors for yield increase under high-density planting, and the photosynthetic carbon metabolism characteristics of typical dense-tolerant materials. Results showed that: (1) As density increased, the yield of C31 (tall plant) significantly increased while that of N91 (short plant) significantly decreased with the largest decrease rate during the two growing seasons. The lodging index significantly increased as well under high density. Among the six varieties, the lowest lodging angle and stem lodging index of the upper parts were C31. (2) High-density planting reduced chloroplast density and chloroplast size, net photosynthetic rate, and enzyme activities of photosynthetic carbon metabolism. It also decreased starch content in leaves, stems, and siliques as well as the nonstructural carbohydrates (NSC) transport amount and rate in stems. The NSC transport volume and transport rate in stems were significantly positively correlated with yield per plant and negatively correlated with the lodging index. (3) Under high-density planting, the NSC translocation rate and translocation amount in stems for C31 were significantly greater than those for N91. The density-tolerant material C31 had greater individual yield and lodging resistance as greater above-ground dry matter accumulation, stronger photosynthetic carbon metabolism, and NSC transport abilities under high-density planting.

Soil aggregate is a basic structural unit of soil, consisting of primary particles (sand, silt, clay), cementing materials and pores. Specific and independent microhabitats composed of soil aggregates of different particle sizes are biochemical reactors for soil nitrogen transformation. Differences in the physical and chemical properties of microhabitats lead to different microbial differentiation characteristics, which further influence key processes of the nitrogen cycle. The fixation and transformation of nitrogen is carried out by large, small and microaggregates together. However, the relative contribution of aggregates of different particle sizes to the key process of the nitrogen cycle is not clear, nor is the interception and retention of different forms of nitrogen. This paper reviews studies on nitrogen transformation during nitrification and denitrification at the soil aggregate scale. We summarize recent advances in aggregate-microbe interactions and key nitrogen cycling processes within aggregates, with emphasis on microbial differentiation patterns. Future research should prioritize two directions: (1) Enhancing the monitoring and quantification of in-situ soil, particularly through 15N isotope tracing technology to clarify the fate of exogenous nitrogen and plant-microbe competition for nitrogen forms; (2) Development of predictive models for aggregate spatial distribution based on microbial environmental thresholds. These efforts will promote long-term supply and efficient utilization of soil nitrogen, and provide a solid scientific foundation for advancing the theory of micro-scale nitrogen cycling.

Oilseed flax (Linum usitatissimum L.), an annual plant in the Linaceae family, is a significant oil crop cultivated in the high-altitude arid regions of China. Until now, the Decision Support System for Agrotechnology Transfer (DSSAT) model has not been used to simulate the growth of flax. This study aims to develop a new flax model for DSSAT, based on field data collected from 2020 to 2023 in the arid regions of Dingxi and Yuzhong, China. We utilized the CSM-CROPGRO-Canola as a template for genetic coefficient adjustment, along with modifications to the water and nitrogen balance modules. This model was used to analyze the response of flax yield to weather factors (maximum temperature, minimum temperature, and precipitation) and nitrogen fertilizer application during dry years, normal years, and wet years over the past 30 years. The results indicate that the flax model demonstrates good predictive accuracy with a low root mean square error (RMSE) and high index of agreement (D-index) in simulating key stages such as the anthesis and maturity phases, as well as in predicting biomass, leaf area index, yield, and soil moisture content. In addition, flax yield exhibited varying degrees of sensitivity to maximum temperature, minimum temperature, precipitation, and nitrogen fertilizer under different precipitation years. Therefore, in dry years, it is recommended to prioritize temperature and moisture management while applying nitrogen fertilizer cautiously, while in normal years, a balance between water and nitrogen use should be maintained to optimize fertilization effects. In wet years, nitrogen utilization should be maximized to enhance yields. The yield of flax under different precipitation conditions follows this trend: wet years > normal years > dry years. This study demonstrated the significant practical value of developing a flax model in the arid regions of China.

Soil aggregates highly regulate nitrogen (N) turnover, yet their functions in regulating N retention under long-term crop rotation remain unclear. This study used 15N-labeled fertilizer N to investigate how different-sized soil aggregates regulate fertilizer N retention and redistribution under long-term crop rotation systems. The results revealed that large macroaggregates exhibited a more pronounced depletion of fertilizer N (enrichment factor, Ef: 0.73−0.95) than of total N (Ef: 0.93−1.00). In contrast, macroaggregates and microaggregates enriched fertilizer N (Ef: 1.00−1.16). Crucially, we found a temporal divergence: after harvest (with new 15N-labeled fertilizer application), macroaggregates preferentially sequestered new N (current-season fertilizer N), whereas microaggregates dominated the stabilization of old N (previous-year fertilizer N) in the absence of 15N-labeled fertilizer in 2024. This functional specialization is driven by aggregate turnover, whereby disintegrating macroaggregates release old N for stabilization in microaggregates, while reforming macroaggregates encapsulate new N. The accelerated release of fertilizer N from these macroaggregates during crop cultivation supplies N to crops, while their reformation concurrently enriches new N. This process underscores the dual functions of macroaggregates in both supplying N to crops and enriching new N. Ultimately, crop rotations reinforce this beneficial dynamic by restructuring soil aggregation, leading to a marked expansion of the soil N pool, with fertilizer N storage increasing by 27.11−111.68% and total N storage by 2.94−14.22% compared to continuous cropping. Our findings establish the functional heterogeneity of soil aggregates as a key mechanism for long-term fertilizer N retention and stabilization. This provides a mechanistic basis for optimizing N management under crop rotations.

Diversified crop rotations are proposed to enhance agricultural system productivity, stability, and climate resilience. Oilseed flax, a crucial oilseed crop in rain-fed agricultural systems of China, faces increasing challenges under climate change due to conventional monoculture practices. Therefore, our eight-year field experiment in northwest China's rain-fed region assessed how integrating potato and wheat into flax monoculture affects oilseed flax productivity and soil health. The research results revealed that: In initial years, diversified rotation increased oilseed flax productivity and soil carbon sequestration, with minor positive effects on soil bacterial communities. As rotations progressed, these benefits amplified due to accumulated system functionality and increased precipitation. The wheat -* potato -* wheat -* oilseed flax (WPWF) treatment achieved the maximum average grain yield of oilseed flax (70.2 % increase) and sustainable yield index (SYI, 63.9 % increase) over two crop rotation cycles, alongside a lower coefficient of variation (CV), compared with continuous oilseed flax monoculture (Cont F). Notably, soil carbon sequestration and bacterial diversity correlated positively with the oilseed flax productivity. Overall, soil organic carbon (SOC) storage under the crop rotation systems increased by 8.4 %-19.9 % and 10.7 %-30.7 %, respectively, compared with the Cont F in 2016 and 2020. Through integrated comprehensive evaluation and economic benefits analysis, the WFPF and WPWF systems are validated as regionally optimal rotations. It provides farmers with flexible implementation options to select context-adapted sequences based on local conditions. This study highlights diversified crop rotations as essential for long-term food security, soil health and farmers' income growth.

Above- and below-ground interactions play a crucial role in achieving higher yields in intercropping systems. Nonetheless, it remains unclear how these interactions impact intercropping crop growth and regulate interspecific relationships. This study aimed to quantify the impact of above- and below-ground interactions on crop yield by determining the dynamics of dry matter accumulation, photosynthetically active radiation (PAR) transmittance, and leaf area index (LAI) in intercropped wheat and maize. Three below-ground intensities were set for an intercropping system: no root separation (CI: complete interaction below ground), 48 μm nylon mesh separation (PI: partial interaction below ground), and 0.12 mm plastic sheet separation (NI: no interaction below ground). Two densities were set for maize: low (45,000 plants hm−2) and high (52,500 plants hm−2). At the same time, corresponding monoculture treatments were established. The grain yields in the CI and PI treatments were, on average, 23.7% and 13.7% higher than those in the NI treatment at high and low maize densities, respectively. Additionally, the grain yield for high density was 12.3% higher than that of low density in the CI treatment. The dry matter accumulation of intercropped wheat under the CI and PI treatments was, on average, 9.1%, 14.5%, and 9.0% higher than that in the NI treatment at the flowering, filling, and maturity stages, respectively. The dry matter accumulation of intercropped maize at the blister, milk, and physiological maturity stages increased by 41.4%, 32.1%, and 27.8%, respectively, under the CI treatment compared to the NI treatment. The PAR transmittance and LAI of maize at the V6 stage were significantly increased by increasing the intensity of below-ground interactions. This study showed that complete below-ground interaction contributed to a significant increase in the competitiveness of intercropped wheat with respect to maize (Awm) under the high-density maize treatment, especially at the filling stage of wheat. Moreover, the CI treatment enhanced the recovery effects of maize (Rm) after wheat harvesting. Increasing the intensity of below-ground interactions can significantly enhance the Awm and Rm in intercropping systems, favoring the accumulation of crop dry matter mass and light energy utilization to increase system yields.