Potassium (K) homeostasis critically orchestrates photosynthetic performance through mesophyll conductance (g m) regulation-a key bottleneck limiting CO2 assimilation under K deficiency. While K deprivation reduces g m via anatomical alterations, the mechanistic interplay between subcellular K+ distribution and chloroplast-level structural determinants remains elusive. Field experiments using two Brassica napus L. cultivars with contrasting K utilization efficiencies (KUtE) were employed to resolve how subcellular K+ dynamics regulate g m through hierarchical structural modifications. Under mild K deficiency (50% of sufficient K supply), reduced vacuolar K+ restricted mesophyll cell expansion, increasing cell density and reducing the intercellular airspace (f ias). Despite elevated gas-phase CO2 diffusion resistance, liquid-phase conductance was maintained. Under severe K deficiency (K deprivation), reduced chloroplastic K+ decreased chloroplast density and size, lowering the chloroplast surface area facing intercellular airspaces (S c/S). Cytosolic K+ depletion further increased cytosolic CO2 transport resistance. The g m reduction was stronger in the low-KUtE cultivar, consistent with its sharper subcellular K+ decline. Hydroponic experiments further confirmed that subcellular K+ depletion reduced vacuolar metal ions but induced accumulations of organic acids and sugars, while Na+ and sugars increased in chloroplasts, disrupting osmotic balance and aggravating structural impairment. These findings reveal that subcellular K+ regulates g m by remodeling mesophyll and chloroplast structures.

Electron shuttles (ESs) critically enhance microbial extracellular electron transfer (EET), a key biogeochemical process that drives iron cycling and the activation of nutrients like phosphorus. However, existing studies are largely qualitative, focusing on EET pathway identification or current density measurements without quantitatively resolving the underlying energetics. Here, we establish an atomic force microscopy-based single-cell and single-molecule force spectroscopy platform, enabling the first direct quantification of microbial-ES-mineral interfacial energies. We find that riboflavin amplifies the adhesion energy between Shewanella oneidensis MR-1 and ferrihydrite-phosphate complex from 0.81 ± 0.064 fJ to 1.92 ± 0.049 fJ, accelerating microbe-mineral bonding up to 5-fold and boosting electron utilization efficiency from 0.015-0.028 h-1 to 0.048-0.12 h-1 across diverse Fe(III) minerals. We further reveal riboflavin binding hotspots on outer membrane c-Cyts, with a binding free energy of -25.6 kJ mol-1. These thermodynamic findings facilitate EET, which in turn significantly enhances the bioavailability of iron and phosphorus. For the first time, we quantified microbial cell-mineral and ES-cell binding energetics, thereby bridging interfacial thermodynamics across molecular and cellular scales to establish a mechanistic basis for EET and its role in nutrient mobilization. Such insights open avenues for control of ES-mediated functions in nutrient cycling, pollutant transformation, and sustainable bioenergy.

Diversified cropping systems are recognized as a pathway to sustainable intensification, yet systematic evidence quantifying the contribution of non-legume crops, such as rapeseed, remains fragmented. A global meta-analysis was conducted on 155 studies worldwide that compared diversified cropping systems incorporating rapeseed. This analysis was aimed at quantitatively assessing the effects of rapeseed integration on crop yield and soil fertility, and identifying the key modulating factors. The findings indicated that integrating rapeseed significantly increased crop yields, but the magnitude varied considerably among practices: crop rotation (3.9%), intercropping (14.8%), cover cropping (18.5%), and green manure (6.2%). Rapeseed integration substantially enhanced soil fertility indicators, increasing soil organic matter (SOM) by 4.1%, total nitrogen (TN) by 1.9%, macroaggregate stability by 24.8%, promoting soil enzyme activities and bacterial diversity, and reducing pest incidence. These soil fertility benefits also showed heterogeneity across cropping systems, with the greatest SOM and TN enhancement occurring in rotation system. Yield and soil fertility benefits were most pronounced on low-fertility soils (SOM<25 g kg(-1), TN<0.7 g kg(-1)). Nitrogen fertilization was identified as an important modulator of rapeseed-induced yield benefits, with temperature, precipitation, initial SOM, and TN as key contextual factors governing these benefits. Specifically, higher N inputs reduced yield gains in low-fertility soils and cool or dry climates. These observed effects may be partially attributable to hypothesized mechanisms, including improved nutrient cycling, activation of soil microbial communities, and biofumigation, though these pathways require further experimental validation. The magnitude of these benefits depends substantially on site-specific soil fertility and N management, highlighting the necessity of tailored integration strategies to maximize benefits. This study offers valuable insights for the benefits of integrating rapeseed into diversified cropping systems, particularly in fertility-limited cereal rotations, as a strategy to achieve synergistic gains in productivity and soil fertility.

Maintaining soil fertility through balanced fertilization is essential for ensuring high crop productivity in intensive paddy-upland rotation systems. In this study, a meta-analysis of 141 published studies was conducted to evaluate the effects of different fertilization regimes on soil chemical properties and crop yields in predominant paddy-upland rotation systems. Relative to balanced fertilization (BF), both no fertilization (CK) and unbalanced fertilization (UF) significantly reduced soil organic matter (SOM) (16.6% and 7.2%), total N (11.3% and 4.9%), total P (14.6% and 7.1%), available P (41.0% and 22.9%), and available K (13.0% and 11.0%). In contrast, the combined application of chemical fertilizer with organic manure (F+M) or straw return (F+S) significantly increased SOM (16.5% and 9.6%), total N (14.9% and 8.7%), total P (29.2% and 16.6%), available P (37.6% and14.7%), and available K (9.1% and 12.9%). Notably, the response of soil fertility to fertilization regimes differed between oilseed rape–rice (OR) and wheat–rice (WR) rotations. The WR rotation showed greater declines in SOM and total N under CK treatment than the OR rotation. While F+S treatment was more effective in improving soil available P in OR rotation, F+M treatment produced better outcomes in WR rotation. These soil responses were reflected in crop yields, with a more severe rice yield reduction under CK in the WR (45.0%) than in the OR rotation (29.2%). The greatest yield increases were associated with the F+S treatment in OR and the F+M treatment in WR. Random Forest analysis and linear regression identified SOM, available P, and total N as the primary factors governing rice yield. These results suggest that integrated nutrient management combining chemical fertilizers with organic amendments is crucial for sustaining soil fertility and productivity in paddy-upland rotations, and that tailored fertilization strategies should be developed based on specific rice-based cropping systems.

Purpose Crop rotations (upland-upland and paddy-upland) are widely practiced in the Yangtze River Basin, where water and fertilization management strongly influence soil phosphorus (P) dynamics. However, the mechanisms by which nitrogen (N) fertilization strategies affect soil P speciation and microbial communities across these systems remain unclear. Methods Based on an 11-year field experiment, this study investigated soil P speciation, microbial communities, and soil physicochemical properties under different N regimes (single-season vs. dual-season) in the paddy-upland (rice-oilseed rape, RO) and upland-upland (corn-oilseed rape, CO) rotations. Using sequential P fractionation and high-throughput sequencing, we examined the responses of soil P speciation and microbial communities to varying N fertilization strategies. Results N fertilization significantly enhanced soil P availability. The balanced dual-season fertilization (N150-150) achieved the highest available P (AP) in RO (30.26 mg/kg), nearly double that in CO (14.79 mg/kg). N fertilization decreased soil pH in CO but maintained near-neutral pH in RO. Rotation mode was the primary driver of microbial community structure, with distinct taxa enriched in each system ( Actinobacteria in CO, Chloroflexi in RO). Soil pH droved microbial variation in CO, whereas soil organic matter and AP were key drivers in RO. Conclusion Water management serves as the overarching determinant of soil environment, within which N fertilization acts as a key regulatory factor. The balanced dual-season N application (N150-150) was associated with the highest P availability and microbial diversity in the rice-oilseed rape rotation system. N fertilization improves P availability by modulating soil properties and microbial communities, and the balanced dual-season strategy synergistically boosts P supply, promotes soil biodiversity, and supports sustainable cropping intensification in the Yangtze River Basin.

Straw return is a key agronomic practice for enhancing soil organic carbon (SOC) storage in agricultural ecosystems. However, the mechanisms governing its allocation between labile and stable carbon fractions, as well as the environmental thresholds regulating this process, remain inadequately understood. This knowledge gap constrains the accurate assessment and optimization of its regional carbon sequestration potential. To address this, the present study synthesizes data from a global meta-analysis of 102 published studies and three located long-term field experiments, including 303 paired observations for SOC, 145 for DOC, 134 for MBC, 102 for POC and 96 for MAOC, to systematically quantify the effects of straw return on SOC fractions and identify their key controlling factors. Results show that straw return increased SOC by an average of 9.8%, with distinct responses observed among different carbon fractions. Among the labile fractions, POC exhibited the highest increase (27.0%), while MAOC showed a more modest gain of 9.5%. This pattern reflects a dynamic characterized by rapid turnover of labile components versus slow accrual of stable carbon. Path analysis confirmed that MAOC was the primary contributor to the net increase in SOC following straw return, with POC being secondary. Random forest analysis further indicated that experimental duration and straw return amount were the major drivers of SOC, mean annual temperature and mean annual precipitation were the key predictors of POC and experimental duration was the dominant factor controlling MAOC. Straw application rate significantly influenced DOC, whereas MBC was primarily regulated by inherent soil properties. The study also identified a threshold effect of initial SOC content, with a critical value of approximately 8.93 g/kg. When the initial soil SOC is below this threshold, straw return is more conducive to the accumulation of POC and is accompanied by an increase in MAOC, demonstrating high carbon sequestration potential. In contrast, in carbon-rich soils approaching saturation, the carbon sequestration effect of straw return was significantly attenuated. In summary, the carbon sequestration efficacy of straw return is manifested not only in the increase of total SOC but, more critically, in the coordinated accumulation of labile and stable fractions. This process is constrained by the interactive effects of climate, initial soil carbon status and management practices. Future cropland carbon management should integrate the compositional dynamics of SOC fractions and the threshold behaviours of key drivers to develop regionally tailored straw return strategies, thereby maximizing soil carbon sequestration potential.

Diversified cropping rotations combining species with contrasting phosphorus (P) use strategies can improve yields and sustainability, yet the physiological basis for interspecific differences in internal P-use efficiency (PUE) remain elusive. We investigated species-specific temporal dynamics of leaf P allocation plasticity, resorption capacity, and their coordination with lipid metabolism and photosynthesis in a rice (Oryza sativa L.)-rapeseed (Brassica napus L.) rotation. Rice exhibited higher PUE and P resorption efficiency than rapeseed, associated with its greater and progressively increasing allocation to inorganic-P (Pi) during expansion, and prolonged P remobilisation spanning over half of the leaf lifespan. This extended remobilisation was enabled by efficient Pi export and coordinated degradation of lipid-P and nucleic acid-P. In contrast, rapeseed minimised lipid-P investment to sustain Pi and metabolic-P above photosynthetic thresholds and confined P resorption to a short senescence phase (c. 12.5% of lifespan). Under P deficiency, rapeseed enhanced phospholipids replacement and accelerated P resorbed from nucleic acid and metabolic-P pools, while rice maintained high P resorption via simultaneous degradation of phospholipids and nucleic acids. These findings demonstrate that a higher inorganic/organic P ratio and prolonged internal P recycling underlie enhanced PUE, offering insights into optimising crop selection and precision P management in sustainable cropping systems.

Microorganisms can be divided into abundant and rare microbial taxa, which play a vital role in soil nutrient cycling. However, it remains unclear how paddy-upland rotation patterns and stages affect soil abundant and rare microbial taxa and their roles in soil multi-nutrient cycling. In this study, we investigated the differences in abundant and rare microbial taxa between oilseed rape-rice (OR) and wheat-rice (WR) rotations in upland and paddy stages through an 8-year field experiment, and their roles in soil nutrient cycling were also explored. The results showed that crop rotation patterns significantly altered the composition of both abundant and rare microbial communities in paddy-upland rotation systems. Bacterial taxa were more affected by crop rotation patterns than fungal taxa. Compared with the WR rotation, the OR rotation increased the relative abundance of rare bacterial taxa but decreased that of rare fungal taxa, particularly in the paddy stage. Additionally, the OR rotation significantly increased the Chao1 index of rare bacterial taxa, but decreased the Shannon index of rare fungal taxa. PLFA analysis showed higher soil viable microbial biomass in the upland than in the paddy stage. Compared with the WR rotation, the viable microbial biomass in the soil of the OR rotation decreased by 17.7 % during the upland stage, but increased by 22.3 % during the paddy stage. In the upland stage, rare bacterial taxa were primarily influenced by viable microbial biomass (including bacterial PLFAs, gram-positive bacteria and gram-negative bacteria). The composition of rare fungal taxa was affected by viable microbial biomass, as well as nitrate nitrogen, potentially mineralizable nitrogen, and dissolved organic nitrogen (DON). In the paddy stage, both abundant and rare bacterial and fungal taxa were mainly influenced by DON and free amino acids. Compared with the WR rotation, the OR rotation improved the soil multi-nutrient cycling index, increased by 44.6 % and 143.3 % in the upland and paddy stages, respectively. Crop rotation regulated soil multi-nutrient cycling mainly by influencing rare bacterial taxa and viable microbial biomass in both upland and paddy stages. Therefore, this study highlights the critical role of rare bacterial taxa in soil multi-nutrient cycling within paddy-upland rotation systems.

Nitrogen (N) is the primary driver of yield in rapeseed (Brassica napus L.) yield, however the crop is commonly cultivated under intensive N fertilization with low nitrogen use efficiency (NUE), resulting in substantial N surplus and potential environmental risks. Improving crop NUE is therefore critical for sustainable agricultural development; however, the effectiveness of conventional N management appears to have reached its limits in some rapeseed-growing regions, suggesting that hidden or co-limiting factors may constrain further gains in NUE. Among these, severe deficiencies in soil available magnesium (Mg), widely observed in the major rapeseed production area, have emerged as a critical but often overlooked factor limiting both yield and NUE. To quantify the effects of Mg fertilization on rapeseed yield and N fertilizer use efficiency under varying N inputs, field experiments were conducted using a two-factor factorial (N × Mg) design with three N rates and three Mg rates. At harvest, seed yield and its components, N and Mg uptake, and NUE were determined. In parallel, seeding biomass, root morphology, inorganic N concentration, and activities of N assimilation enzymes were measured in individual organs, and the expression of BnNRT1.1a/b and BnNRT2.1a/b was analyzed in roots. Under no N supply (0 kg N ha-1), Mg application had no significant effect on rapeseed yield. In contrast, under sufficient N supply (180 and 270 kg N ha-1), Mg fertilization significantly increased seed yield, largely driven by increasing pod number per plant, with average gains of 15.4% and 18.7%, respectively. Mg application also increased NUE by an average of 1.35 kg/kg under sufficient N supply, primarily by improving N uptake efficiency (NUpE), which increased by 8.9%. Under sufficient N conditions, Mg application also improved root morphology, upregulated the expression of BnNRT1.1a and BnNRT1.1b, and enhanced the activities of key N assimilation enzymes. Together, these effects promoted N uptake, assimilation, and storage in rapeseed seedlings.,These results demonstrate that integrated N and Mg management can substantially improve rapeseed yield and NUE. Therefore, beyond optimizing N management, adequate Mg nutrition should be recognized as a critical strategy for enhancing NUE, particularly in regions with low phytoavailable Mg in soils.

Low nitrogen (N) use efficiency (NUE) constrains sustainable rice production. Although flavonoids have been implicated in improving crop NUE, the direct physiological mechanisms underlying catechin-induced NUE enhancement remain elusive. Here, hydroponic experiments were conducted with high-NUE and low-NUE varieties to analyze the effects of catechin on rice growth, NUE, N content, key enzyme activities involved in N pathways, and the expression of genes related to N transport and assimilation. A concentration screening experiment (0, 5, 10, 20, and 50 mg l-1 catechin) identified 20 mg l-1 as the optimal concentration for maximizing growth performance and NUE improvement across the two rice varieties and three N levels tested. Catechin exhibited a dual regulatory mechanism by simultaneously enhancing ammonium transport capacity and N assimilation efficiency. Specifically, it up-regulated the expression of an ammonium transporter gene (OsAMT1;2) and boosted the activities of key N assimilation enzymes including nitrate reductase, glutamine synthetase, and glutamate synthase. These coordinated responses resulted in a 15.9% elevation in free amino acid content and 28.5% improvement in NUE. Notably, a low-NUE variety demonstrated greater responsiveness to catechin under low-N levels, while a high-NUE variety exhibited a stronger response under medium-N levels. The structural equation modeling revealed that enhanced ammonium transport served as the primary driver of NUE improvement. These findings establish that catechin systemically optimizes N metabolism by synchronizing transport capacity with assimilation efficiency, providing a novel phyto-stimulant strategy particularly effective for improving N-scavenging capacity in low-NUE varieties under N-limited conditions.

Timely and accurate diagnosis of crop nutrient deficiencies using imagery is essential for advancing precision agriculture. Conventional approaches relying on RGB imagery are limited by their narrow spectral range, whereas multispectral (MS) imagery offers richer spectral information for crop monitoring. However, transferring deep learning models trained on RGB data to the MS domain is problematic due to spectral-domain shifts. To address this issue, we developed a deep transfer learning framework for classifying nitrogen, phosphorus, and potassium deficiencies in oilseed rape using unmanned aerial vehicle (UAV) imagery. UAV imagery was collected from four experimental fields in Wuhan and Wuxue, China, between 2021 and 2025. Representative deep learning architectures (VGG16, ResNet50, GoogLeNet, and MobileNetV2) were evaluated on both RGB and MS data, followed by multi-strategy transfer learning and the integration of a channel attention mechanism to enhance cross-modal feature representation. The results indicate that GoogLeNet consistently achieved the highest classification accuracy across both modalities. MS-based classification (F1-score = 0.849) outperformed RGB-based classification (0.831). The fine-tuning (FT) strategy further improved F1-scores to 0.844 (RGB) and 0.865 (MS), while reducing trainable parameter count by 76.3% and accelerating model convergence. Incorporating a Squeeze-and-Excitation (SE) module increased the MS F1-score to 0.914 and shortened training time by 35.7%. On an independent cross-year validation, the optimal MS-based model achieved a competitive F1-score of 0.787, demonstrating reliable generalization. Overall, this study highlights the promising potential of deep transfer learning for efficient, robust nutrient-stress monitoring in precision agriculture.

Abstract The stabilization of soil organic carbon in agricultural lands is crucial for mitigating climate change and enhancing soil fertility. While organic amendments like manure and biochar enhance carbon sequestration, their micro-scale mechanisms at the soil aggregate level remain unclear. Here we integrated analyses of enzyme activities, iron-bound organic carbon, iron oxides, and microbial communities across soil aggregates to clarify these mechanisms. Compared with conventional fertilization, manure increased the activities of cellobiohydrolase, β-1,4-glucosidase, β-1,4-N-acetylglucosaminidase, and phosphatase by 92%, 147%, 202%, and 89%, respectively, while increasing iron-bound organic carbon content (288%) and ferrihydrite-like iron oxide content (4%). Manure also boosted the abundance of iron-oxidizing bacteria and the expression of iron-oxidation related genes ( coxA, coxB ). In contrast, biochar inhibited polyphenol activities (33–54%) and reduced carbon mineralization (2.6–17.3%). These findings indicate that pig manure stabilizes carbon via a microbial-mediated iron gate, whereas biochar stabilizes carbon mainly through a physical enzyme latch driven by enzyme suppression.

Soil nitrogen supply capacity is primarily regulated by the transformations of organic nitrogen, which are microbial mediated processes in soils. This study aimed to investigate soil nitrogen cycling functional genes and their roles in soil nitrogen supply capacity in rice-rapeseed (RR) and rice–wheat (RW) rotation. Soil samples were collected from a 7-year field experiment, and the abundance of soil nitrogen cycling functional genes was analyzed through metagenomic analysis. Soil inorganic nitrogen (SIN) and potentially mineralizable nitrogen (PMN) determined by anaerobic incubation were used as indicators of soil nitrogen supply capacity. Soil nitrogen supply capacity and the particulate organic matter content were higher in RR rotation than in RW rotation. The abundances of nitrogen cycling functional genes, including amiABC, gdh, nxrA, nxrB, narG and norB, were also greater in RR rotation than in RW rotation. These functional genes of nitrogen cycling involved in organic nitrogen metabolism, nitrification and denitrification processes, the abundances of these genes were significantly positively correlated with soil nitrogen supply capacity (P < 0.05). Both the abundances of soil nitrogen cycling functional genes and the contents of soil organic carbon and total nitrogen jointly contributed to soil nitrogen supply capacity. However, the contribution of nitrogen cycling functional genes (0.34) was less than that of soil organic carbon and total nitrogen (0.67). Both the advantage in the substrate quantity and availability and the subsequent advantage in the abundances of nitrogen cycling functional genes of RR rotation over RW rotation contributed jointly to greater soil nitrogen supply capacity in upland crop season in the former than the latter rotation.

The combination of extracellular depolymerization and intracellular amino acid metabolism jointly shapes soil organic nitrogen (SON) mineralization, but whether agricultural management alters the relative importance of these stages remains unclear. We combined measurements of N mineralization rates, SON pools, and extracellular enzyme activities with metagenomic and metabolomic analyses in a nine-year field experiment comprising three rice-based rotations: fallow-rice (FR), oilseed rape-rice (OR), and wheat-rice (WR), each managed with or without NPK fertilization. Relative to the WR rotation, the FR and OR rotations significantly increased soil N mineralization rates by 36%–60% and 16%–23%, respectively. The FR and OR rotations were characterized by larger pools of total N, protein, and dissolved organic N, higher potential activities of β-N-acetylglucosaminidase and protease, and greater relative abundances of genes encoding these enzymes. Amino acids and peptides were relatively depleted during incubation. Compared with WR rotation, the FR and OR rotations showed greater relative enrichment of amino acid and peptide related metabolites and higher relative abundances of genes involved in amino acid metabolic pathways, particularly alanine, aspartate, and glutamate metabolism and arginine biosynthesis. The relative abundances of genes encoding key enzymes, including glutamate dehydrogenase and acetylornithine aminotransferase, were positively associated with N mineralization rates. NPK fertilization increased N mineralization rates and was associated with higher relative abundances of genes encoding leucine aminopeptidase and genes involved in arginine biosynthesis, but it decreased the relative abundance of genes encoding protease. Collectively, our results show that crop rotation and fertilization regulate different stages of the SON mineralization pathway. Crop rotation effects are linked to coordinated variation in substrate supply, activities of organic N-depolymerizing enzymes, and potential for amino acid metabolism, while fertilization shifts microbial N acquisition toward low-molecular-weight organic N.

Organic amendment has been proven to be an effective strategy for increasing soil carbon (C) sequestration. However, the pathways which different organic amendments regulate C accumulation and stabilization processes may vary due to their differing inherent properties. Field experiments with four treatments, viz. CK, no fertilizer; CF, conventional chemical fertilizer; CFM, chemical fertilizer with manure; CFB, chemical fertilizer with biochar were conducted to elucidate the differential mechanisms governing soil aggregate C flow pathways mediated by organic amendments. The results demonstrated that CFM and CFB treatments increased SOC content by 12 % and 21 % respectively compared to CF treatment. Specifically, biochar increased C stabilization through structural optimization of aggregates (>2 mm macroaggregates increased by 4 %) and improved C sequestration across all aggregate sizes (5-24 % increase in SOC content). Nuclear magnetic resonance (NMR) analysis revealed distinct stabilization pathways: CFB preferentially elevated aromatic C proportions (15 %-29 % increase), while CFM promoted alkyl C accumulation (38 %-64 % increase). Biochar directly introduced recalcitrant aromatic compounds, whereas manure facilitated microbial conversion of labile C to alkyl C. delta C-13 fractionation analysis further delineated distinct stabilization pathways: CF accelerated native SOC depletion through preferential utilization of labile components, biochar facilitated C stabilization in via physicochemical protection, while manure balanced metabolic partitioning and kinetic fractionation during microbial processing. These findings underscore biochar's superiority in long-term C sequestration via physicochemical stabilization and manure's efficacy in optimizing C turnover efficiency, providing mechanistic foundations for precision organic amendment strategies in sustainable soil management.

The synergistic effects of nitrogen (N) and potassium (K) fertilizers on soil biological characteristics remain poorly understood. To address this, a six-year continuous field experiment with rapeseed was conducted, incorporating four N and K application treatments: no N and K (CK), N alone (N), K alone (K), and combined N and K (NK). Soil samples collected at three key growth stages of rapeseed were analyzed using 16S rRNA gene high-throughput sequencing. Results showed that compared to N treatment, the NK combination significantly increased soil inorganic N content during the overwintering stage (at 65 days after planting) by 103.1%. This increase was closely associated with shifts in soil bacterial community structure, changes in the predicted abundance of nitrogen-cycling functional genes, and the restoration of bacterial co-occurrence networks. While N application alone strongly altered the soil microbial community and elevated the predicted abundance of nitrification and denitrification genes, K application alone had no significant effect. In contrast, the combined application of N and K not only reduced the predicted abundance of these N-loss-related genes but also enhanced bacterial network modularity, effectively mitigating the negative effects of N-only fertilization. These findings highlight the importance of balanced nutrient management in maintaining the functional stability of soil microbial ecosystems.

Efficient nitrogen (N) management is critical for maximising yield while minimising environmental impacts in oilseed rape production. While Unmanned Aerial Vehicle (UAV)-based monitoring of N status has advanced rapidly, translating estimated N status into actionable fertilization strategies remains limited. This study proposes a multistage N topdressing recommendation framework for winter oilseed rape that integrates UAV multispectral data with prior agronomic knowledge using machine learning algorithms. The framework accurately estimated the nitrogen nutrition index (NNI), with the random forest model performing best (r2 =0.73 and RMSE = 0.11) for the validation dataset. By integrating estimated NNI, critical NNI thresholds, and optimal N uptake levels, dynamic, stage-specific N fertilizer topdressing rates were computed. A field experiment with varying basal N fertilizer rates was conducted to validate the framework, with UAV-guided topdressing performed after each monitoring event. Compared with the local conventional fertilization practice, the UAV-guided treatment with 90 kg N/ha basal fertilizer rates significantly improved yield by 20.2 % and N use efficiency by 80.1 %. This study bridges the gap between remote sensing-based diagnostics and in-field N fertilization, offering a feasible data-driven approach for real-time N management to enhance productivity and sustainability in oilseed rape cultivation.

Increasing soil organic matter (SOM) content is pivotal for soil health and climate change mitigation, yet the mechanisms governing long-term carbon (C) stabilization via organic amendments remains controversial. We performed a meta-analysis of 540 observations from 45 studies, analyzed by solid-state 13C NMR spectroscopy, to evaluate the responses of SOM chemical composition and its driving factors to organic amendments. The dataset predominantly comprises cropland soils from Asia, under temperate and subtropical climates, with a focus on major soil types. Functional groups of SOM were associated with climate, soil, and amendment properties, identifying the key factors influencing C stabilization. Organic amendments increased aromatic C by 11%, driving a substantial 52% increase in SOC content compared with mineral-only fertilization. Organic amendment properties and climate factors explained 77% of SOC increase, with nitrogen (N) content identified as key predictors of aromatic groups. The most favorable conditions for aromatic C accumulation included high precipitation (>1000 mm), low temperature (<8°C), and were observed in soils characterized by high initial organic C (>20 g kg−1), total N (>1 g kg−1) contents, and acidic conditions (pH < 6), which are conditions that reflect slow decomposition rates and partial oxygen limitation. Our finding suggests that amendment strategies should account for both the intrinsic quality (e.g., C/N ratio) of the amendment and the extrinsic climatic conditions to optimize persistent C pool formation.

Purpose: Real-time monitoring of essential nutrient status is crucial for improving fertilizer efficiency and enhancing crop productivity. Hyperspectral and multispectral remote sensing provide effective, non-invasive tools for estimating crop leaf nitrogen, phosphorus, and potassium content (LNC, LPC, and LKC). Therefore, a comprehensive evaluation of these technologies is needed. Methods: We conducted a meta-analysis of studies from 2000 to 2023 to identify spectral bands for estimating LNC, LPC, and LKC. Subsequently, nutrient estimation models using Partial Least Squares Regression (PLSR), Random Forest (RF), and Support Vector Regression (SVR) were developed based on 4 years of oilseed rape field data, to verify identified the sensitive bands. Results: The meta-analysis revealed an increasing research focus on nutrient estimation from 2017 to 2023, with wheat and rice as the primary crops investigated. Among the three nutrients, LNC was the most frequently analyzed. Commonly adopted modeling approaches included PLSR, Artificial Neural Networks (ANN), SVR, and RF. At the canopy level, LNC exhibited its most sensitive bands within 550-2030 nm, while at the leaf level, the sensitive range was 400-780 nm. LPC was responsive in 517-995 nm and 2030-2269 nm at the canopy level, while responsive in 545-995 nm and around 2166 nm at the leaf level. The bands sensitive to LKC were observed in 519-976 nm and 1513-2058 nm at the canopy level, and 545-995 nm at the leaf level. The RF model consistently achieved the highest prediction accuracy among models based on the identified sensitive bands. At the canopy level, LNC was estimated with the highest accuracy (R2=0.81, RMSE=0.39 %), followed by LPC (R2=0.75, RMSE=0.09 %) and LKC (R2=0.70, RMSE=0.34 %). At the leaf level, LNC again showed the best performance (R2=0.82, RMSE=0.37 %), followed by LKC (R2=0.74, RMSE=0.30 %) outperforming LPC (R2=0.66, RMSE=0.09 %). Conclusions: This study provides a comprehensive evaluation of hyperspectral and multispectral technologies for crop nutrient estimation. The sensitive spectral bands and modeling approaches identified through meta-analysis enable accurate estimation of LNC, LPC, and LKC.

Potassium (K) is a prevalent limiting factor in terrestrial ecosystems, with approximately one-eighth of the world's soils undergoing K+ deficiency stress. Upon encountering K+ deficiency stress, leaf area (LA) declines before the net photosynthetic rate (An). The sequential alterations fundamentally represent the adaptive trade-off between survival and growth in plants subjected to K+ deficiency stress. This trade-off is hypothesized to be linked to the differences in the subcellular distribution of limited K+ resources. Thus, the K+ distribution and apparent concentration in subcellular compartments, along with the LA and An characteristics of rapeseed leaves at various developmental stages and K+ supply conditions were quantified to elucidate the mechanisms by which subcellular K+ regulates leaf growth and survival. The results revealed that during the early stages of K+ deficiency, leaves actively downregulate growth to sustain normal physiological functions. This is primarily accomplished by lowering the K+ distribution and apparent concentration in vacuoles, restricting LA expansion, and enhancing K+ distribution to chloroplasts to ensure An. Prolonged K+ deficiency decreased the apparent K+ concentration in chloroplasts below the critical threshold (37.8 mm), disrupting chloroplast structure and function, impairing An, and ultimately threatening the survival of rapeseed. Hence, sustaining an adequate concentration of K+ within chloroplasts is crucial for preserving leaf photosynthetic efficiency and ensuring survival under K+ deficiency stress. In conclusion, under K+ deficiency stress, leaves regulate LA and An by trade-offs in the K+ distribution between vacuoles and chloroplasts to coordinate growth and survival.