Microbial physiological traits are key determinants of soil organic carbon (SOC) accumulation under long-term fertilization, yet their adaptability to carbon (C) and nutrient gradients, and the corresponding C feedback effects, remain largely unexplored. Here, we conducted a 33-year field experiment with mineral and mineral-organic combined fertilization (NPKM) across two contrasting soil types (nutrient-rich vs. nutrient-poor). The 18O-H2O tracer method and amino sugar biomarker approaches were used to explore the trends of microbial C use efficiency (CUE) and microbial C pump efficacy (MCP), while metagenomic analysis and environmental variables were integrated to clarify the intrinsic and extrinsic effects of long-term fertilization on these microbial traits. Our results revealed divergent responses of SOC fractions to NPKM across soil types: relative to the control (CK), NPKM increased particulate organic carbon (POC) by 130% in nutrient-rich soils, the 33.46% rise in mineral-associated organic carbon (MAOC); in contrast, only MAOC exhibited a significant increase (80.86%) in nutrient-poor soils. Further analysis confirmed that microbial physiological traits drove the changes in POC and MAOC depending on soil nutrient status under long-term fertilization. Specifically, in nutrient-poor soils, NPKM enhanced MAOC by increasing CUE (100%) and MCP (45.34%), an effect mediated by C-degradation functional genes. In nutrient-rich soils, NPKM promoted POC by improving CUE (48.48%), a process regulated by abiotic factors. These findings highlight that initial nutrient levels regulate microbial physiological traits, thereby dictating the accumulation dynamics of different C fractions, which offers a theoretical basis for targeted agricultural C management strategies.

Soil microbially derived carbon is essential for soil carbon sequestration, yet its dynamics under organic matter addition in croplands remain poorly understood, largely owing to the interactions among microbial carbon, nitrogen, and phosphorus metabolic functions and their divergent responses to soil environmental changes. Here, based on a long-term field experiment, we investigated the effects of combined application of chemical fertilizer with straw or manure on microbially derived carbon accumulation in soils. The 18O-H2O tracer method and soil extracellular enzyme were used to quantify microbial carbon use efficiency and carbon acquisition capacity, and metagenomic sequencing was performed to determine microbial carbon, nitrogen and phosphorus functional genes, aiming to unravel the intrinsic relationship between microbial metabolism and microbially derived carbon. The results showed that, compared to the chemical fertilizer treatment, the chemical fertilizer treatments with straw or manure both significantly increased the accumulation of microbially derived carbon. Furthermore, the microbially derived carbon was significantly positively correlated with microbial carbon use efficiency but negatively correlated with carbon acquisition capacity. Specifically, chemical fertilizer treatments with straw or manure increased microbial carbon use efficiency but reduced carbon acquisition capacity, thereby shifting the microbial metabolic pattern from a "high decomposition" state to a "high utilization" state, which associated with the retention of microbially derived carbon. Correlation analysis showed that microbial carbon use efficiency was significantly positively correlated with nitrate nitrogen, SOC but negatively with microbial carbon and nitrogen functional genes (e.g., those involved in disaccharide metabolism, dissimilatory nitrate reduction, and nitrogen fixation), whereas carbon acquisition capacity exhibited the opposite pattern. Especially, the increased nitrate nitrogen and SOC under chemical fertilizer with straw or manure effectively alleviated microbial resource limitation and were negatively correlated with both nitrogen and carbon functional genes. These findings elucidate the role of nitrogen and carbon availability in regulating the relationships among microbial metabolic functions, carbon acquisition and utilization, improving our understanding of the mechanisms governing microbial-derived carbon accumulation under organic matter addition.

Soil inorganic carbon (SIC) is traditionally considered as geochemically inert, but its content can change at interannual scale, particularly in response to agricultural management practices. This study investigates how potassium chloride (KCl) fertilization influences SIC turnover in the topsoil, a process overlooked in previous studies. Using soils from a 33-year-long-term fertilization experiment, we assessed the impact of KCl fertilization on SIC content, isotopic signature (δ13C), and the community composition of carbonic anhydrase (CA)-harboring microorganisms, which catalyze the reversible hydration of CO2. KCl fertilization induced a shift towards lighter δ13C values, indicative of new biogenic CO2 incorporation into carbonates. This shift was dependent on increased abundance of CA-encoding genes and changes in microbial community composition, particularly among Pseudomonadota and Actinobacteriota. Despite KCl fertilization reduced soil acidification, pH was not identified as a key driver influencing the content and δ13C of SIC. Instead, the higher zinc (Zn) availability under KCl fertilization was closely correlated with the increasing SIC content and decreasing δ13C. Zinc is a catalytic metal cofactor for CA and therefore, its availability showed a tight positive relationship to CA gene abundance. The process was further stimulated by the P fertilization applied as superphosphate and introduced Ca2+ for carbonate precipitation to increase the SIC content. Concluding, intensive SIC turnover induced by KCl fertilization over decades, and increased the CA gene abundance suggest a biotic regulation mediated by Zn mobilization. This study provides decadal SIC accrual through microbial processes, highlighting the potential for management to increase inorganic carbon retention in soils. Our findings emphasize the need to consider both biotic and abiotic factors in soil carbon models of frequently disturbed agricultural systems.

Mineral nutrients are very crucial for plant survival and adaptation, playing a dynamic role in their growth, development, and production. Among these mineral nutrients, nitrogen (N), phosphorus (P), and potassium (K) stand out as essential macronutrients due to their pivotal and interconnecting roles in supporting plant growth, development, and stress adaptation. Plants developed a transport system to maintain balanced nutrients for sustainable crop productivity and environmental resilience. Although considerable research has focused on the NPK transport system, their integrated roles in coordinating mineral nutrition and stress tolerance remain insufficiently explored in wheat (Triticum aestivum L., 2n = 42, AABBDD). In the current study, we identified 21 N-related, 45 P-related, and 43 K-related transporter genes in T. aestivum, confirmed through the presence of conserved signature domains. These NPK-transporters in T. aestivum and A. thaliana were found as highly conserved within each subgroup, supported by phylogenetic, gene structure, and motif analysis. The protein-protein interaction (PPI) network analysis suggests coordinated regulatory networks among nutrient transporters. Gene Ontology (GO) enrichment analysis revealed that NPK transporters are involved not only in nutrient transport but also in various signaling pathways. The expression profiling in response to biotic and abiotic stresses revealed the differential regulation of NPKs in T. aestivum. Three identified candidates for NPK transporters (TaAMT2, TaPHT4.3, TaKT3) were further subjected to a combined abiotic stress and NPK application assay. The results revealed that the NPK availability modulates T. aestivum adaptation to combined abiotic stresses. Furthermore, the green fluorescent protein GFP revealed that the candidate genes were localized in the plasma membrane. Our study is a foundation to identify co-regulatory candidates for developing wheat varieties that maintain nutrition and yield under the complex stress scenarios of modern agriculture.

Soil acidification is a critical global issue threatening agricultural productivity and ecosystem health. In recent years， human activities have intensified soil acidification， posing significant challenges to food security and sustainable agriculture. Acidified soils are characterized by a decline in pH， increased activity of toxic metal ions， and nutrient depletion， leading to soil structure degradation and restricted plant growth. This article systematically summarizes the main driving factors of soil acidification in farmland， including non-human factors （weathering and leaching， nutrient absorption， organic matter decomposition， root exudates release， lightning volcanic eruption and deposition， microbial activity， etc.） and human factors （unreasonable agricultural management， climate change， etc.）， and further analyzes the main processes of microbial-mediated soil acidification affecting nutrient cycling. To address soil acidification， existing mitigation strategies are summarized， such as lime application， balanced fertilization， organic matter management， biochar application， and the promotion of acid-tolerant crops. However， due to the diversity of soil types， the complexity of acidification processes， and variations in crop types and cultivation practices， the effectiveness of these measures varies significantly. By providing a comprehensive synthesis and outlook and considering the context of climate change， this study explores future research directions， offering both theoretical foundations and practical guidance for the scientific management of soil acidification and the advancement of sustainable agriculture.

The balance of carbon (C), nitrogen (N), and phosphorus (P) stoichiometry fundamentally regulates nutrient cycling and microbial metabolism in terrestrial ecosystems. However, the mechanisms through which long-term fertilization and climate jointly shape multidimensional stoichiometric networks and microbial life history strategies remain unclear. In this study, six long-term (27-44 years) fertilization experiments across a 17 degrees latitudinal gradient in China were examined under three treatments: no fertilizer (CK), mineral fertilizer (CF), and mineral plus manure fertilizer (CFM). By integrating ecological stoichiometry with metagenomic approaches, this study assessed how fertilization and climate affect soil, resource, microbial, and enzyme stoichiometry, and how these stoichiometric shifts influence microbial life history strategies. Results showed that long-term fertilization altered stoichiometric patterns, strengthening network connectivity among soil, resource, microbial, and enzymatic stoichiometry. CFM reduced soil and microbial C:P and N:P ratios by 35-70 % and decreased DOC:Olsen-P and DON:Olsen-P by up to 95 %. These shifts restructured microbial life history strategies, promoting a transition from resource acquisition (A) to growth yield (Y) strategies, with Y strategists increasing to 45-56 % under fertilization. Moreover, available resource and microbial stoichiometry, particularly DOC:Olsen-P and DON:Olsen-P ratios, were the primary predictors of microbial strategies, linking stoichiometric balance to microbial energetic allocation. Fertilization and climate jointly regulated microbial life history strategies by alleviating C:P and N:P imbalances and promoting stoichiometric homeostasis. Overall, these findings establish a mechanistic framework connecting nutrient supply, stoichiometric regulation, and microbial adaptation, thereby providing theoretical guidance for optimizing fertilization practices and maintaining soil nutrient sustainability across climatic regions.

Dissolved organic carbon (DOC), the most labile fraction of soil organic carbon (SOC), plays a vital role in ecosystem functioning and soil productivity. However, the influence of long-term green manure application on DOC composition and its role in soil aggregate formation and carbon stabilization remains unclear. This study investigated changes in DOC composition and their effects on aggregate stability and carbon sequestration in two rice-green manure rotation trials long-5 years in Jingzhou (JZ) and 36 years in Qiyang (QY), China. Treatments included rice-winter fallow (WF), rice-Chinese milk vetch (MV), rice-oilseed rape (RP), and rice-ryegrass (RG). At the JZ test site, 5-year MV incorporation slightly improved aggregate stability, measured by mean weight diameter (MWD) and geometric mean diameter (GMD), but without significant changes. In contrast, at QY, 36-year MV and RG incorporation significantly enhanced both MWD and GMD. Green manure addition increased SOC and DOC contents and enhanced the molecular complexity of DOC, reflected by higher molecular weight, aromaticity, and humification degree. DOC was primarily derived from plant residues and microbial metabolites, with green manure application enhancing microbial contributions. Fluorescence spectroscopy identified three DOC components: bioavailable, humic-like, and protein-like. While DOC composition at JZ remained largely unchanged after 5 years of MV incorporation, 36 years of MV and RG incorporation at QY facilitated the transformation of protein-like into humic-like components. SOC, humic-like DOC, and the humification index (HIX), were the key drivers of aggregate stability, showing direct positive effects on aggregate MWD. Humic-like DOC indirectly promoted SOC accumulation through increased DOC aromaticity and enhanced humification. Our findings highlight the central role of humic-like DOC in enhancing SOC sequestration and soil aggregate stabilization, underscoring the long-term benefits of green manure in sustainable agriculture.

Long-term positioning tests can systematically reveal the evolution characteristics of soil fertility and crop productivity, and reflect the spatiotemporal changes in soil quality and their driving factors. While soil microorganisms mediating nutrient cycling are crucial for maintaining crop productivity and the long-term resilience of agricultural ecosystems, how prolonged use of different fertilization strategies affects their functional capacity remains insufficiently understood. In this study, we applied metagenomic sequencing to investigate how three fertilization treatments, namely (i) N0 receiving only phosphorus (P) and potassium (K) fertilizers, (ii) N250 receiving conventional urea + P and K, and (iii) F250 receiving humic acid urea + P and K, influence soil microbial communities, functional genes related to C and N cycling, and associated soil properties in a long-term field experiment. The F250 treatment significantly increased average annual yields of wheat and maize to 7166.21 kg hm−2 and 8309.96 kg hm−2, respectively. These values were 148.66% and 73.47% higher than those under N0, and 8.22% and 11.64% higher than those under N250. Compared with N0, both N250 and F250 signally augmented soil nitrate, ammonium, total nitrogen (TN), and soil organic carbon (SOC), altered microbial community composition, and enhanced the relative abundance of genes engaged in C fixation and methane oxidation. Both treatments also promoted denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Relative to N250, F250 specifically enriched the beneficial bacterial genus Pedobacter, further increased the abundance of the C fixation gene pccA, and markedly upregulated the DNRA gene nrfA. Soil TN and SOC were identified as the key environmental factors regulating microbial community structure and the functional potential of C and N cycling pathways. Collectively, our findings provide a mechanistic understanding of how long-term application of humic acid urea enhances crop productivity by modulating the genetic potential of soil microorganisms in biogeochemical cycles, offering a biological foundation for optimizing fertilization strategies in sustainable agriculture.

Conventional and mineral phosphorus (P) fertilizers face depletion risks, but organo-mineral fertilization strategies can reduce P demand in crops. This study examines the long-term effects of applying manure (e.g., sludge, compost) alongside mineral fertilizers (NPKM) on P availability and microbial P cycling in maize and rice agroecosystems across diverse regions of China. We assessed how different fertilization strategies affect soil P availability, phosphatase activity, and the abundance of genes linked to P mineralization, solubilization, transport, and regulation. NPKM treatments significantly increased plant-available P and phosphatase activity, especially in maize, compared to inorganic (NPK) and control (CK) treatments. Enhanced P availability stemmed mainly from microbial-driven P mineralization, indicated by higher phosphatase activity and more abundant P mineralization genes, with no notable impact on P solubilization genes across treatments. Soil pH correlated positively with P solubilization and regulatory processes, highlighting environmental factors' role in P availability and associated microbial processes. Our long-term study demonstrates that combining mineral fertilizers with manure enhances P bioavailability by stimulating microbial mineralization, thereby supporting sustainable P management in agroecosystems.

Rhizosphere microbiomes are pivotal for crop fitness, but the principles underlying microbial assembly during root-soil interactions across soils with different nutrient statuses remain elusive. We examined the microbiomes in the rhizosphere and bulk soils of maize plants grown under six long-term (≥ 29 yr) fertilization experiments in three soil types across middle temperate to subtropical zones. The assembly of rhizosphere microbial communities was primarily driven by deterministic processes. Plant selection interacted with soil types and fertilization regimes to shape the structure and function of rhizosphere microbiomes. Predictive functional profiling showed that, to adapt to nutrient-deficient conditions, maize recruited more rhizobacteria involved in nutrient availability from bulk soil, although these functions were performed by different species. Metagenomic analyses confirmed that the number of significantly enriched Kyoto Encyclopedia of Genes and Genomes Orthology functional categories in the rhizosphere microbial community was significantly higher without fertilization than with fertilization. Notably, some key genes involved in carbon, nitrogen, and phosphorus cycling and purine metabolism were dominantly enriched in the rhizosphere soil without fertilizer input. In conclusion, our results show that maize selects microbes at the root-soil interface based on microbial functional traits beneficial to its own performance, rather than selecting particular species.

Cropland expansion has caused the loss of soil organic carbon(SOC)and the degradation of microbial communities.Fallowing is an important strategy for soil restoration,and fungi are critical in soil fertilization.This study compared the soil properties and fungal assemblage in two adjacent environments(farmland vs.fallowing)using a 30-year field experiment composed of five treatments:fallowing and agricultural management under no fertilization,chemical fertilization,and chemical fertilization plus cow manure or crop straw.The fallowed soil had more diverse fungi and maintained higher SOC than the artificially managed treatments.Importantly,the relative abundance of Chaetomiaceae was positively correlated with all the carbon components(SOC,dissolved organic carbon,and microbial biomass carbon)simultaneously.An RNA-Seq of Trichocladium uniseriatum,the key fungus affiliated with Chaetomiaceae,showed that straw addition significantly upregulated the genes for T.uniseriatum melanogenesis,resulting in recalcitrant necromass formation.A remarkable carbon dioxide(CO2)assimilation capacity of T.uniseriatum was revealed using 13C-labelling assay.Therefore,T.uniseriatum improved SOC storage directly by CO2 fixation and indirectly by melanogenesis.Fertilization of agricultural systems can stimulate the growth of T.uniseriatum.Inoculation of T.uniseriatum promoted crop growth,facilitating carbon absorption from the roots.This study highlights that the valuable microbial species resources preserved in fallowed soils can improve farmland ecosystems.

Soil organic carbon (SOC) has various pools with different stabilization mechanisms. It is unclear how these SOC pools respond to various mineral and organic amendments depending on a large climate-soil gradient. Here, we studied in three zonal soils: Ferralic Cambisol (subtropic), Calcaric Cambisol (warm-temperate) and Luvic Phaeozem (mid-temperate) under 23-year mineral, straw and manure amendments. Six SOC sub-pools were isolated: unprotected, physically, chemically, biochemically, physico-chemically and physico-biochemically protected pools. Compared to initial level, SOC and most sub-pools increased in the three soils under manure application ( p < 0.05), but little under straw and mineral amendments. The Luvic Phaeozems had much higher sequestration efficiencies of bulk SOC (27%) and its five sub-pools (5–7%) more than the Calcaric Cambisol (9%, 1–2%) and Ferralic Cambisol (9%, 0.5–1%). In contrast, Ferralic Cambisol had highest sequestration efficiency of unprotected pool (7%). The Calcaric Cambisol had divergent patterns of the six SOC pools compared with Luvic Phaeozems and Ferralic Cambisol, due to the low clay content. With the build-up of bulk SOC, the building-up abilities of non-protected, physically-, chemically- and biochemically-protected pools depended on soil type, while the building-up abilities of physico-chemically- and physico-biochemically-protected pools were convergent (12–19%) among soils. In conclusion, the Luvic Phaeozems had much higher build-up ability of bulk SOC and most sub-pools than the other two soils. With the build-up of SOC, the physico-chemically- and physico-biochemically-protected pools (most stable) had convergent response rates among soils, while the other pools had divergent response rates. Graphical Abstract

The chemical composition of soil organic matter (SOM) is the basis for its stabilization and functions. However, it is not clear how SOM chemical composition varies among size fractions under long-term fertilizations across a climate gradient. We explored this question in three soils: Ferralic Cambisol (subtropics), Calcaric Cambisol (warm temperate zone) and Luvic Phaeozem (mid-temperate zone) under five amendments: Control, N, NPK, NPK + Straw and NPK + Manure. The molecular composition of coarse particulate (cPOM, 250–2000 μm), fine particulate (fPOM, 53–250 μm) and mineral-associated OM (MAOM, <53 μm) were measured by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Among the three soils, the molecular composition of whole SOM diverged greatly, with much more relative abundances of aliphatic compounds and N-containing compounds in the Calcaric Cambisol and the Luvic Phaeozem, respectively. Within the Luvic Phaeozem (clay loam) and Ferralic Cambisol (clay), the molecular composition of SOM mainly varied among physical sizes, with selective preservations of aromatics and lignin in POM and enrichments of N-containing compounds in MAOM, but not amending regimes (even straw and manure incorporations). By contrast, the molecular composition of SOM changed little among physical sizes under various amendments in the Calcaric Cambisol (sandy loam). In conclusion, soil type, not quantity and quality of amendments, primarily regulated the molecular composition of SOM across the climate gradient. Moreover, the divergence of SOM molecular composition among physical size fractions was related to soil texture, with higher divergence in clay and clay loam but reverse in sandy loam soil.

为探明不同氮效率小麦品种的微生物学特性差异,于2018-2020年开展大田试验,研究0(N0)和165kg/hm2(N1)2个施氮水平处理下,氮高效品种"许科168"和氮低效品种"郑品麦8号"的根系活力、根际土壤酶活性和微生物群落多样性的差异.结果表明,随生育进程推进小麦根系活力表现为先增加后降低,孕穗期根系活力最强.在孕穗期,与郑品麦8号相比,许科168的根系活力、β-葡萄糖苷酶、亮氨酸氮基肽酶和多酚氧化酶活性在N0和N1处理下均增加.N0处理下,许科168的细菌群落丰富度指数和多样性指数大部分显著高于郑品麦8号,N1处理下2个品种差异不显著.同一处理,2个品种的优势门丰度也有一定差别,N0处理下,许科168的酸酐菌门和奇古菌门均高于郑品麦8号;N1处理下,许科168的酸酐菌门比郑品麦8号降低了 37.23％,奇古菌门则增加了 13.30％;GP6属和亚硝基球藻属为优势属,其中许科168的亚硝基球藻属在2种氮水平下均明显高于郑品麦8号.总之,氮高效小麦品种许科168在N0和N1处理下均具有较高的根系活力和根际土壤酶活性;在N0处理下具有较高的丰富度指数和多样性指数,这都可能引起根际微环境的变化,也可能因为栽培措施(施氮)不同而有所改变.本研究可以为当地适宜小麦品种筛选和适当施肥提供参考.

The objective of this study was to verify the applicability of the critical nitrogen concentration dilution curve of wheat under different nitrogen application rates in the field and discuss the feasibility of using the nitrogen nutrition index (NNI) to optimize nitrogen fertilizer application. Experiments with different wheat varieties were carried out in Xinxiang (Henan Province, China) for two consecutive years, using four nitrogen application rates: 0, 165, 247.5, and 288.75 kg ha−1. Values of aboveground dry matter (t ha−1) and nitrogen concentration (%) were measured at each sampling date to develop the critical nitrogen concentration (Nc) equation. The relationship between Nc and aboveground dry matter (DM) was respectively described by a power function for 2018 and 2019 (Nc = 5.25DM −0.47, R2 = 0.931; and Nc = 5.30 DM −0.47, R2 = 0.924). Differences in dilution model parameters between years indicated that the nitrogen accumulation capacity in 2019 was slightly higher than that in 2018 and the slope of the Nc dilution curve was the same under the same aboveground biomass. Based on the Nc dilution model, the NNI model was established, which can be used to objectively and quantitatively diagnose nitrogen status. The results of nitrogen fertilizer regulation based on Nc and NNI were consistent with results of the nitrogen application rate based on yield indicators. The best nitrogen level was the 247.5 kg ha−1. Since Nc has reasonable biological significance, the model was accurate, simple, and with clear biological significance. It can be directly used in assessing nitrogen demand of crops and also in complex models of crop nitrogen dynamics. This will provide new ideas for timely and accurate fertilization.

Quantifying soil structural dynamics and aggregate turnover is important in understanding soil organic carbon (SOC) stocks, particularly over decadal and larger time scales. Until now it has remained unclear clear how soil aggregate size and its associated carbon respond to both long-term soil fertility and climate change. Here, we explore changes in soil structure and aggregate organic C (OC) stocks under different fertilization practices by combining field chronosequence SOC measurements with dynamic and process modeling in a long-term wheat -maize field experiment on the North China Plain. The fertilization practices comprise no fertilization (CK), chemical fertilization (NPK), and combined manure and NPK treatments (MNPK). The experimental measure-ments included the mass of OC stocks in different soil aggregate size classes. We used this information to calibrate parameters of the Carbon, Aggregation, and Structure Turnover (CAST) model and to predict future changes in aggregate structure and the resulting OC stocks using the RCP2.6 scenarios that were defined by the outputs of five future climate models from IPCC projection. With trends towards a wetter climate and increasing soil moisture under the RCP2.6 scenarios for the region, soil OC stocks will increase in all three treatments, with the strongest increase under MNPK due to exogenous C inputs. The CAST model output further suggests that changes in microaggregate (250-53 mu m) OC stocks in the NPK and MNPK treatments accounted for 78.6 % and 75.3 % of the calculated change in total SOC stocks between the early and late 21st century. In conclusion, our combined data and modeling approach describes changes in soil aggregate C, identifies the primary soil aggregate size class of microaggregates involved in C sequestration in an agricultural soil, and predicts the role of Fluvaquent soils on the North China Plain as a future C sink.

IntroductionInappropriate residue and nutrient management leads to soil degradation and the decline of soil quality and water storage capacity. MethodsAn ongoing field experiment has been conducted since 2011 to investigate the effects of straw mulching (SM), and straw mulching combined with organic fertilizer (SM+O), on winter wheat yield, including a control treatment (CK, no straw). We studied the effects of these treatments on soil microbial biomass nitrogen and carbon, soil enzyme activity in 2019, photosynthetic parameters, evapotranspiration (ET), water use efficiency (WUE), and yields over five consecutive years (2015-2019). We also analyzed the soil organic carbon, soil structure, field capacity, and saturated hydraulic conductivity in 2015 and 2019. ResultsResults indicate that compared with CK, SM and SM+O treatments increased the proportion of >0.25mm aggregates, soil organic carbon, field capacity, and saturated hydraulic conductivity, but decreased the soil bulk density. In addition, the SM and SM+O treatments also increased soil microbial biomass nitrogen and carbon, the activity of soil enzymes, and decreased the carbon-nitrogen ratio of microbial biomass. Therefore, SM and SM+O treatments both increased the leaf water use efficiency (LWUE) and photosynthetic rate (Pn), and improved the yields and water use efficiency (WUE) of winter wheat. The combination SM (4.5 t/ha)+O (0.75 t/ha) was more effective than SM alone, and both treatments were superior to the control. ConclusionBased on the results of this study, SM+O is recommended as the most effective cultivation practice.

为探明生物炭对河南潮土区土壤氨挥发和小麦氮素吸收的影响,本研究设置不施肥(CK)、氮磷钾化肥(NPK)、生物炭(BC)、化肥配施生物炭(BC+NPK)4个处理,测定小麦季土壤氨挥发速率、籽粒产量和氮素吸收量.结果表明,在小麦基肥期,CK和BC处理氨挥发速率相对稳定,平均速率在0.06kg·hm-2·d-1左右,且无显著差异.而NPK和BC+NPK处理氨挥发速率在基肥施入后2～3 d达到峰值,分别为0.86和1.25 kg·hm-2·d-1,BC+NPK处理较NPK处理显著提高45.35％.在小麦追肥期,NPK和BC+NPK处理土壤氨挥发速率最大值分别为0.96和1.07 kg·hm-2·d-1,且均在追肥后第7天达到最大值.与NPK处理相比,BC+NPK处理导致土壤氨挥发累积量增加9.45％,在基肥期和追肥期分别增加了5.47％和13.44％.整个小麦生育期,BC+NPK处理的土壤铵态氮含量平均值为21.61 mg·kg-1,较NPK处理显著增加17.29％,氨挥发速率与土壤铵态氮含量呈极显著正相关关系.与不施肥条件相比,施用生物炭使小麦籽粒产量及地上部吸氮量分别提升0.23 t·hm-2和6.12％,差异不显著;化肥配施生物炭使小麦地上部吸氮量提升6.44％,但差异不显著.综上,在河南潮土区,施用生物炭通过提升土壤铵态氮含量进而增加了土壤氨挥发速率及累积量,但对小麦产量及氮素吸收的提升效果不显著.本研究为生物炭在黄淮海平原潮土区的合理利用提供了科学依据.

To understand the long-term effects of combined organic and chemical nitrogen fertilization on soil organic C (SOC) and total N (TN), we conducted a 30-year field experiment with a wheat-maize rotation system on the Huang-Huai Hai Plain during 1990-2019. The experimental treatments consisted of five fertilizer regimes: no fertilizer (control), chemical fertilizer only (NPK), chemical fertilizer with straw (NPKS), chemical fertilizer with manure (NPKM), and 1.5 times the rate of NPKM (1.5NPKM). The NPK, NPKS, and NPKM treatments had equal N inputs. The crop yields were measured over the whole experimental duration. Soil samples were collected from the topsoil (0-10 and 10-20 cm) and subsoil (20-40 cm) layers for assessing soil aggregates and taking SOC and TN measurements. Compared with the NPK treatment, the SOC and TN contents increased significantly in both the topsoil (24.1-44.4% for SOC and 22.8-47.7% for TN) and subsoil layers (22.0-47.9% for SOC and 19.8-41.8% for TN) for the organically amended treatments (NPKS, NPKM and 1.5NPKM) after 30 years, while no significant differences were found for the average annual crop yields over the 30 years of the experiment. The 0-10 cm layer of the NPKS treatment and the 20-40 cm layer of the NPKM treatment had significantly higher macroaggregate fraction mass proportions (19.8 and 27.0%) than the NPK treatment. However, the 0-10 and 20-40 cm layers of the 1.5NPKM treatment had significantly lower macroaggregate fraction mass proportions (-19.2 and -29.1%) than the control. The analysis showed that the higher SOC and TN in the soil of organically amended treatments compared to the NPK treatment were related to the increases in SOC and TN protected in the stable fractions (i.e., free microaggregates and microaggregates within macroaggregates), in which the contributions of the stable fractions were 81.1-91.7% of the increase in SOC and 83.3-94.0% of the increase in TN, respectively. The relationships between average C inputs and both stable SOC and TN stocks were significantly positive with R-2 values of 0.74 and 0.72 (P<0.01) for the whole 40 cm soil profile, which indicates the importance of N for soil C storage. The results of our study provide key evidence that long-term combined organic and chemical nitrogen fertilization, while maintaining reasonable total N inputs, benefited soil C and N storage in both the topsoil and subsoil layers.

The decomposition processes of crop residues, which represent the largest organic carbon input in agricultural ecosystems, are determined by soil microbes. However, the impact of different long-term fertilization practices on residue decomposition has not been clearly established. In this study, a microcosm experiment using 13C-labeled maize residues and high-throughput sequencing was performed to investigate bacterial and fungal microbes utilizing straw-derived carbon in soils under separate regimes of long-term fertilization (CK: no fertilizer; NPK: mineral fertilizers; NPKS: mineral fertilizers plus straw). During the 60-day incubation period, a total of 524 bacterial OTUs and 72 fungal OTUs, which utilized straw-derived carbon, were identified and were found to be primarily distributed in the bacterial phyla of Proteobacteria, Actinobacteria and Bacteroidetes, and the fungal class of Sordariomycetes within Ascomycota. The three fertilized soils exhibited distinct straw-utilizing microbial communities along the decomposition process, in which key bacterial taxa (Flavobacterium, Nocardioides, Pseudomonas, Pseudoxanthomonas, Agromyces and Herpetosiphon) and key fungal taxa (Pleosporaceae, Lasiosphaeriaceae and Chaetomiaceae) exhibited significantly positive relationships with extracellular enzymes activities, thereby accelerating the straw decomposition process. Furthermore, due to higher nutrient availability, microbes can rapidly respond to straw addition, therefore, more bacteria and fungi, which are referred to as rapid responders, were identified in NPK and NPKS soils, relative to CK soils. Hierarchical and variation Partitioning (HP) analysis revealed a strong potential impact of multiple edaphic factors in shaping the microbial community to utilize the straw-derived carbon. N resources (NO3−-N and TN) and β-glucosidase were found to be significantly positively correlated with microbial utilizers’ community. In conclusion, our findings elucidate the processes of establishment of microbial community and straw decomposition, as well as the association between microbial communities and edaphic factors under different long-term fertilization regimes.