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The intensive use of chemical fertilizers in China to maintain high crop yields has led to significant environmental degradation and destabilized crop production. Returning straw to soil presents a potential alternative to reduce chemical fertilizer requirements and enhance soil fertility. This study investigates the effects of different nitrogen (N) input levels and straw additions on crop phosphorus (P) uptake and soil P availability based on a long-term N-fertilizer trial. The treatments included no fertilizer input (CK), conventional (NPK), reduced NPK (0.75NPK), and straw-amended (SNPK) treatments. Results indicate that SNPK significantly enhances shoot P uptake and crop yields by 43.7-61.9% and 29.3-39.6%, respectively. The SNPK treatment improved rhizosphere P availability and increased the phosphorus activation coefficient (PAC) by 1.72-fold compared to NPK alone. The enhanced soil P availability under SNPK was primarily attributed to an abundance of functional microbes, leading to higher P storage in the microbial biomass P pool and its turnover. Additionally, SNPK promoted root exudate and phosphate-mobilizing microbes, enhancing P mobilization and uptake. Nitrogen fertilization primarily influenced root functional traits related to P acquisition. These findings provide valuable insights for developing effective fertilizer management strategies in maize-oilseed rape rotation systems, emphasizing the benefits of integrating straw with chemical fertilizers.

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In the present study, persistence and degradation of tembotrione, a triketone herbicide, was studied in loamy soil collected from maize field. Effects of organic amendments, moistures and temperatures on tembotrione dissipation were evaluated. Soil samples were processed according to the modified QuEChERS involving dichloromethane solvent and MgSO4 without PSA. Analysis using LC-MS/MS showed >95% recoveries of tembotrione its two metabolites TCMBA and M5 from fortified soils. Tembotrione residues dissipated with time and 85.55 to 98.53% dissipation was found on 90th day under different treatments. Tembotrione dissipation increased with temperature and moisture content of the soil. Among organic amendments, highest dissipation was observed in vermicompost amended soil. Minimum and maximum half-lives of tembotrione were recorded under 35 °C (15.7 days) and air-dry (33 days) conditions, respectively. Residues of tembotrione declined with time while that of TCMBA increased steadily up to 10-45th day in different treatments and declined thereafter. Residues of M5 were not detected in our experiments. Tembotrione persistence was negatively correlated with the organic carbon (%), moisture regimes, and temperature. A good correlation between soil microbial biomass carbon and degradation was found. A two-way ANOVA indicated significant differences between the treatments at 95% confidence level (p < 0.05).

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While freeze-thaw cycle (FTC) can influence greenhouse gas emissions, the specific greenhouse gas that responds most strongly to FTC, as well as the underlying mechanisms, remain unclear. Here, we conducted a meta-analysis to explore the responses of global warming potential (GWP) and the fluxes of CO2 and N2O to FTC. Our results showed that FTC treatment significantly increased GWP, N2O flux, cumulative GWP, and cumulative N2O emissions by 23.1 %, 53.2 %, 14.5 %, and 164.6 %, respectively, but did not affect CO2 flux, indicating that the enhanced GWP during the FTC period may be primarily due to the contribution of N2O flux rather than CO2 flux. The responses of GWP (+68.6 %), CO2 (21.0 %), and N2O fluxes (136.3 %) in croplands was higher than those in other ecosystems, exhibiting a strong dependence on ecosystem types. The effect size of FTC treatment on greenhouse gas emissions escalated with decreasing freezing temperature and diminished with increasing FTC frequency. Moreover, mean annual temperature (MAT) and FTC patterns were key factors influencing GWP during the FTC period. These findings provide critical insights into the variations in greenhouse gas emissions due to FTC and its influencing factors, allowing for more accurate predictions of the future impact of global climate change on GWP.

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The salinity and alkalinity of soils are two fundamental factors that limit plant growth and productivity. For that reason, a field study conducted at Sakha Agric. Res. Station in Egypt during the 2022-2023 winter season aimed to assess the impact of gypsum (G), compost (C), and zinc foliar application in two images, traditional (Z1 as ZnSO4) and nanoform (Z2 as N-ZnO), on alleviating the saline-sodic conditions of the soil and its impact on wheat productivity. The results showed that the combination of gypsum, compost, and N-ZnO foliar spray (G + C + Z2) decreased the soil electrical conductivity (EC), sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) by 14.81%, 40.60%, and 35.10%, respectively. Additionally, compared to the control, the G + C + Z2 treatment showed improved nutrient content and uptake as well as superior wheat biomass parameters, such as the highest grain yield (7.07 Mg ha-1), plant height (98.0 cm), 1000-grain weight (57.03 g), and straw yield (9.93 Mg ha-1). Interestingly, foliar application of N-ZnO was more effective than ZnSO4 in promoting wheat productivity. Principal component analysis highlighted a negative correlation between increased grain yield and the soil EC and SAR, whereas the soil organic matter (OM), infiltration rate (IR), and plant nutrient content were found to be positively correlated. Furthermore, employing the k-nearest neighbors technique, it was predicted that the wheat grain yield would rise to 7.25 t ha-1 under certain soil parameters, such as EC (5.54 dS m-1), ESP (10.02%), OM (1.41%), bulk density (1.30 g cm-3), infiltration rate (1.15 cm h-1), and SAR (7.80%). These results demonstrate how adding compost and gypsum to foliar N-ZnO can improve the soil quality, increase the wheat yield, and improve the nutrient uptake, all of which can support sustainable agriculture.

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Freeze-thaw (FT) events profoundly perturb the biochemical processes of soil and water in mid- and high-latitude regions, especially the riparian zones that are often recognized as the hotspots of soil-water interactions and thus one of the most sensitive ecosystems to future climate change. However, it remains largely unknown how the heterogeneously composed and progressively discharged meltwater affect the biochemical cycling of the neighbor soil. In this study, stream water from a valley in the Chinese Loess Plateau was frozen at -10°C for 12 hours, and the meltwater (at +10°C) progressively discharged at three stages (T1 ∼ T3) was respectively added to rewet the soil collected from the same stream bed (Soil+T1 ∼ Soil+T3). Our results show that: (1) Approximately 65% of the total dissolved organic carbon and 53% of the total NO3--N were preferentially discharged at the first stage T1, with enrichment ratios of 1.60 ∼ 1.94. (2) The dissolved organic matter discharged at T1 was noticeably more biodegradable with significantly lower SUVA254 but higher HIX, and also predominated with humic-like, dissolved microbial metabolite-like, and fulvic acid-like components. (3) After added to the soil, the meltwater discharged at T1 (e.g., Soil+T1) significantly accelerated the mineralization of soil organic carbon with 2.4 ∼ 8.07-folded k factor after fitted into the first-order kinetics equation, triggering 125 ∼ 152% more total CO2 emissions. Adding T1 also promoted significantly more accumulation of soil microbial biomass carbon after 15 days of incubation, especially on the FT soil. Overall, the preferential discharge of the nutrient-enriched meltwater with more biodegradable DOM components at the initial melting stage significantly promoted the microbial growth and respiratory activities in the recipient soil, and triggered sizable CO2 emission pulses. This reveals a common but long-ignored phenomenon in cold riparian zones, where progressive freeze-thaw can partition and thus shift the DOM compositions in stream water over melting time, and in turn profoundly perturb the biochemical cycles of the neighbor soil body.

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Seasonal variations directly impact the biochemical and microbial properties of the soil, influence carbon and nutrient cycling within the soil system. Soils under tree plantation (TP) are rich in organic matter and microbial population, making them more susceptible to seasonal variation. We studied the effect of seasonal variations in soil chemical properties (pH, electrical conductivity (EC), total organic carbon (TOC), total nitrogen (TN), C/N ratio etc) and microclimate (moisture and temperature) on microbial respiration (SR), biomass, and carbon (C) utilization efficiency under 13 years old Kadamb (Anthocephalus cadamba Miq.), Simaraubha (Simarouba glauca DC), and Litchi (Litchi chinensis Sonn.) based TPs in middle Gangetic region. In contrast to higher SR and metabolic quotient (qCO2) in winter, the microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) in fall > summer > spring > winter, irrespective of TPs. The positive relationship between qCO2 and C/N ratios strongly supports the dependence of microbes on soil carbon for respiration. qCO2 had a significantly positive relationship with soil moisture (MC) and Electrical conductivity (EC), but a significantly negative relationship with temperature and pH. Higher MBN/TN and MBC/TOC ratios fall under simaraubha, and litchi-based TPs indicated more nitrogen (N) and carbon accumulation into microbial biomass. The seasonal variation of MBC/MBN ratios signifies the changes in microbial communities and fungi dominate over bacteria during winter, as bacteria have a lower C/N ratio than fungi. Stepwise regression analysis suggested that soil properties and micro-climate regulated microbial biomass and SR differ with TPs. Thus, the study indicates that microbial activities and biomass production can significantly influence by soil properties and seasonal variations under TPs.

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Background: Sequestering carbon dioxide (CO2) in agricultural soils promises climate change mitigation as well as sustainable ecosystem services. In order to stabilize crop residues as soil carbon (C), addition of mineral nutrients in excess to crop needs is suggested as an inevitable practice. However, the effect of two macronutrients i.e., nitrogen (N) & phosphorus (P), on C cycling has been found contradictory. Mineral N usually decreases whereas mineral P increases the soil organic C (SOC) mineralization and microbial biomass. How the addition of these macronutrients in inorganic form to an organic-matter poor soil affect C cycling remains to be investigated. Methods: To reconcile this contradiction, we tested the effect of mineral N (120 kg N ha-1) and/or P (60 kg N ha-1) in presence or absence of maize litter (1 g C kg-1 soil) on C cycling in an organic-matter poor soil (0.87% SOC) in a laboratory incubation. Soil respiration was measured periodically during the incubation whereas various soil variables were measured at the end of the incubation. Results: Contrary to literature, P addition stimulated soil C mineralization very briefly at start of incubation period and released similar total cumulative CO2-C as in control soil. We attributed this to low organic C content of the soil as P addition could desorb very low amounts of labile C for microbial use. Adding N with litter built up the largest microbial biomass (144% higher) without inducing any further increase in CO2-C release compared to litter only addition. However, adding P with litter did not induce any increase in microbial biomass. Co-application of inorganic N and P significantly increased C mineralization in presence (19% with respect to only litter amended) as well as absence (41% with respect to control soil) of litter. Overall, our study indicates that the combined application of inorganic N and P stabilizes added organic matter while depletes the already unamended soil.

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Plants affect soil microorganisms through the release of root exudates under pollution stress. This process may affect rhizosphere priming effect (RPE) and alter the rate of soil organic matter decomposition. However, the influence of plants on the decomposition of organic matter in soil subjected to pollution stress remains unclear. We studied the effects of exposure to perfluorooctanesulfonic (PFOS) and its alternative, chlorinated polyfluoroalkyl ether sulfonic (F-53B), at concentrations of 0.1 mg/kg and 50 mg/kg on the RPE of reed. We conducted our experiments in an artificial climate chamber and used the natural 13C tracer method to determine RPE. In the PFOS-exposed groups, the RPE was negative, with values of -11.45 mg C kg-1 soil d-1 in the low PFOS group and -8.04 mg C kg-1 soil d-1 in the high PFOS group. In contrast, in the F-53B-exposed groups, the RPE was positive, with values of 8.26 mg C kg-1 soil d-1 in the low F-53B group and 12.18 mg C kg-1 soil d-1 in the high F-53B group. Exposure of reeds to PFOS/F-53B stress resulted in differential effects on extracellular enzyme activities. The observed positive and negative RPE phenomena could be attributed to variations in extracellular enzyme activities. In conclusion, RPE responded differently under PFOS/F-53B exposure.

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Pyrolyzing biomass (e.g., crop straw) to produce biochar is a sustainable strategy in agricultural farmlands. Straw-derived biochar could increase soil organic carbon (SOC) and microbial-derived carbon (C) compared to no addition, while it is imperative to understand the effects of straw-derived biochar compared to its feedstock (e.g., straw). We retrieved 321 and 387 observations to investigate the effects of straw-derived biochar on microbial-derived C (e.g., microbial biomass C (MBC) and microbial necromass C (MNC)) taking no addition and straw as control, respectively. Notably, straw-derived biochar significantly increased dissolved organic C (DOC) by 24.9% and provided available substrates for microbial utilization, thus improving MBC by 16.7% and MNC by 19.7% compared to no addition. Nevertheless, compared to its feedstock (crop straw), straw-derived biochar significantly decreased MBC by 26.1% and MNC by 18.0% attributed to lower DOC, supported by a positive correlation between MBC and DOC (R2 = 0.53). A negative correlation between changes in MBC and SOC indicated the adverse of microbial activity for C accrual under conversion from straw to biochar. Moreover, soil layer, experiment duration, and initial C/N ratio are the crucial factors affecting MBC under the conversion from straw to biochar. Specifically, with significant variations among subgroups, when compared to straw addition, straw-derived biochar had lower reduction in MBC observed on 0-5 cm layers, mean annual precipitation ≥550 mm, mean annual temperature ≥10 °C, clay loam soil, experiment duration≥1 yr, initial SOC≥14 g kg-1, pH≥8, and bulk density ≥1.28 g cm-3. Straw-derived biochar even increased MBC by 32.8% in an anaerobic environment, associated with biochar produced under limited oxygen and anaerobic microorganisms dominating the microbial community. This study concludes that the conversion from crop straw to biochar increases SOC but constrains microbial-derived C, which may disturb the microbial-mediated C-cycling process.

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Sugarcane/soybean intercropping and reduced nitrogen (N) application as an important sustainable agricultural pattern can increase crop primary productivity and improve soil ecological functions, thereby affecting soil organic carbon (SOC) input and turnover. To explore the potential mechanism of sugarcane/soybean intercropping affecting SOC sequestration, a two-factor long-term field experiment was carried out, which included planting pattern (sugarcane monocropping (MS), sugarcane/soybean 1:1 intercropping (SB1), and sugarcane/soybean 1:2 intercropping (SB2)) and nitrogen addition levels (reduced N application (N1: 300 kg·hm-2) and conventional N application (N2: 525 kg·hm-2)). The results showed that the shoot and root C fixation in the sugarcane/soybean intercropping system were significantly higher than those in the sugarcane monocropping system during the whole growth period of sugarcane, and the N application level had no significant effect on the C fixation of plants in the intercropping system. Sugarcane/soybean intercropping also increased the contents of total organic C (TOC), labile organic C fraction [microbial biomass C (MBC) and dissolved organic C (DOC)] in the soil during the growth period of sugarcane, and this effect was more obvious at the N1 level. We further analyzed the relationship between plant C sequestration and SOC fraction content using regression equations and found that both plant shoot and root C sequestration were significantly correlated with TOC, MBC, and DOC content. This suggests that sugarcane/soybean intercropping increases the amount of C input to the soil by improving crop shoot and root C sequestration, which then promotes the content of each SOC fraction. The results of this study indicate that sugarcane/soybean intercropping and reduced N application patterns can synergistically improve plant and soil C fixation, which is of great significance for improving crop yields, increasing soil fertility, and reducing greenhouse gas emissions from agricultural fields.

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An 11-year nitrogen addition experiment reveals that for both plants and soil microorganisms, the ruderal strategists had higher productivity but lower stability, while the tolerant strategists had higher stability and lower productivity, leading to the tradeoff between productivity and stability within and across above- and below-ground communities.

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Soil organic carbon (SOC) is known to vary among different ecosystems and soilscapes, yet the degree of variation remains uncertain. Comparing SOC levels in undisturbed ecosystems like forests with those in gradually altered ecosystems can provide valuable insights into the impact of land use on carbon dynamics. This study aimed to evaluate the effects of different land uses on soil fertility parameters in the tropical region of Kerala, focusing on forests as well as cultivated agricultural landscape such as coconut, pepper, tapioca, acacia plantations, and mixed home garden cropping systems. Significant variations were observed among different crops and land use systems in terms of soil fertility. Forests exhibited the highest SOC content at 3.78 g kg-1, while acacia plantations showed the lowest at 0.76 g kg-1. Additionally, various soil properties such as different carbon fractions (e.g., humic acid, fulvic acid), total nitrogen, carbon, available nutrients, physical properties, aggregate size fractions, microbial biomass carbon, and spectral signatures differed significantly across the different land uses. These findings suggest a decline in soil fertility in altered ecosystems compared to adjacent forest soils, highlighting the vital role of forests in conserving natural resources and maintaining soil health. In addition, among the different landscapes studied, mixed cropping systems of home gardens sustained soil fertility better than monocropping systems. The observed variations in soil physicochemical properties among different land use types indicate a threat to sustainable crop production. Effective management practices aimed at improving soil fertility and sustaining crop production in these altered ecosystems are essential. This study highlights the importance of adopting appropriate management strategies to conserve soil health and ensure sustainable crop production in tropical landscapes like Kerala. The holistic approach adopted in this study, encompassing a wide range of soil fertility parameters across various land uses, along with its implications for sustainable land management, adds significant novelty and relevance to the existing literature on soil dynamics in tropical regions like Kerala.

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Fungal necromass carbon (FNC) contributes significantly to the build-up of soil organic carbon (SOC) by supplying abundant recalcitrant polymeric melanin present in the fungal cell wall. However, the influence of a wide range of conservation practices and associated factors on FNC accumulation and contribution to SOC in global croplands remains unexplored. Here, a meta-analysis was performed using 873 observations across three continents, together with structural equation modeling, to evaluate conservation practices and factors responsible for the enhancement of FNC and SOC. FNC content (8.39 g kg-1) of North American soils was highest compared to FNC content of Asian and European soils. The structural equation models showed a significant (p < 0.05) positive influence of microbial biomass carbon (MBC), soil pH, and clay contents on the accumulation of FNC. Soil C/N ratio and climate factors, however, had only minor influences on FNC accumulation. Notably, the main driver of FNC was MBC, which is mainly influenced by the soil total N and geographic factors in the study areas. Typical 5 cropland practices had significant effect size (p < 0.05) on FNC, leading to an increase of 12 % to 26 %, and the FNC content was greatest under straw amendment (26 %). Fungal necromass accumulation efficiency ranged from 23 % to 45 % depending on cropland practices: non- and reduced tillage was the most efficient (45 %), followed by crop coverage (32 %), straw amendment (30 %), and manure application (27 %), while N fertilization had the lowest efficiency (23 %). We conclude that FNC contributes to over a quarter of SOC, highlighting its major role in enhancing C sequestration worldwide. Conservation practices, particularly non-tillage or reduced tillage, are important to enhance C sequestration from FNC in croplands.

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Forest defoliators are one of the major biological disturbances to forest ecosystems. As one of the abnormal nutrient input paths into forest ecosystems, frass deposition from the pest outbreak plays a critical role in regulating soil organic carbon (SOC) in forest ecosystems. However, how frass deposition affects SOC and its fractions in forests remains unclear. Based on a severe outbreak of defoliator in an oak-sweetgum mixed forest in Jigong Mountain in 2014, we compared the difference in SOC between plots with and without frass deposition for 4 consecutive years. The results showed that frass deposition led to a significant increase of 25.1 % in soil microbial biomass C (MBC) and 32.0 % in dissolved organic C (DOC) in 2014, which further escalated to 50.4 % and 50.6 % in the subsequent year (2015), respectively. The response of SOC to frass deposition lagged behind MBC and DOC. Specifically, there was no change in SOC in 2014, but a significant increase (50.9 %) was observed in the subsequent 2-3 years. The positive dependences of MBC and DOC upon fine root biomass were negated under frass deposition, while the relationship between SOC and fine root biomass remained unaffected. Soil organic carbon and DOC showed non-linear responses to frass amount and the changed soil nitrogen content. Our finding that the response of SOC to frass deposition lagged behind soil labile C indicates that SOC exhibits a certain resilience towards forest disturbance. The findings also imply that investigating the long-term impacts of frass deposition on SOC in forests would contribute to the scientific assessment of forest C cycling under disturbance.

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Water is an important constraint on alfalfa (Medicago sativa) production in arid and semiarid areas, and alternate irrigation in root areas has water-saving potential for alfalfa production. To investigate the impact of alternate partial root-zone irrigation (APRI) on the rhizosphere soil microorganisms of alfalfa, this study subjected alfalfa plants to different irrigation methods and irrigation levels. The growth status and rhizosphere soil microbial community diversity of alfalfa plants under alternate root-zone watering treatment were analyzed through laboratory experiments and high-throughput sequencing. The results showed that at soil moisture levels of 80% field moisture capacity (FMC) and 60% FMC, APRI had no significant impact on the biomass or nodule number of alfalfa. However, 40% FMC significantly reduced the individual plant dry weight, chlorophyll content, and nodule number of the alfalfa plants. APRI increased the relative abundance of Actinomycetes in the alfalfa rhizosphere soil. Moreover, at 60% FMC, the MBC and MBN of rhizosphere, relative abundance of Actinobacteria and unclassified K fungi and Chao 1 index of bacteria significantly increased under APRI treatment. While relative abundance of Ascomycetes and Proteobacteria in the alfalfa rhizosphere significantly reduced under 60% FMC + APRI treatment. In summary, under the same irrigation conditions, APRI did not significantly affect the growth of alfalfa in the short term. And 60%FMC + APRI treatment did significantly affect the groups, structure and diversity of the rhizosphere soil microbial communities.

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Atmospheric nitrogen (N) deposition in forests can affect soil microbial growth and turnover directly through increasing N availability and indirectly through altering plant-derived carbon (C) availability for microbes. This impacts microbial residues (i.e., amino sugars), a major component of soil organic carbon (SOC). Previous studies in forests have so far focused on the impact of understory N addition on microbes and microbial residues, but the effect of N deposition through plant canopy, the major pathway of N deposition in nature, has not been explicitly explored. In this study, we investigated whether and how the quantities (25 and 50 kg N ha-1 year-1) and modes (canopy and understory) of N addition affect soil microbial residues in a temperate broadleaf forest under 10-year N additions. Our results showed that N addition enhanced the concentrations of soil amino sugars and microbial residual C (MRC) but not their relative contributions to SOC, and this effect on amino sugars and MRC was closely related to the quantities and modes of N addition. In the topsoil, high-N addition significantly increased the concentrations of amino sugars and MRC, regardless of the N addition mode. In the subsoil, only canopy N addition positively affected amino sugars and MRC, implying that the indirect pathway via plants plays a more important role. Neither canopy nor understory N addition significantly affected soil microbial biomass (as represented by phospholipid fatty acids), community composition and activity, suggesting that enhanced microbial residues under N deposition likely stem from increased microbial turnover. These findings indicate that understory N addition may underestimate the impact of N deposition on microbial residues and SOC, highlighting that the processes of canopy N uptake and plant-derived C availability to microbes should be taken into consideration when predicting the impact of N deposition on the C sequestration in temperate forests.

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Microbial necromass carbon (MNC) accounts for a large fraction of soil organic carbon (SOC) in terrestrial ecosystems. Yet our understanding of the fate of this large carbon pool under long-term warming is uncertain. Here, we show that 14 years of soil warming (+4°C) in a temperate forest resulted in a reduction in MNC by 11% (0-10 cm) and 33% (10-20 cm). Warming caused a decrease in the content of MNC due to a decline in microbial biomass carbon and reduced microbial carbon use efficiency. This reduction was primarily caused by warming-induced limitations in available soil phosphorus, which, in turn, constrained the production of microbial biomass. Conversely, warming increased the activity of soil extracellular enzymes, specifically N-acetylglucosaminidase and leucine aminopeptidase, which accelerated the decomposition of MNC. These findings collectively demonstrate that decoupling of MNC formation and decomposition underlie the observed MNC loss under climate warming, which could affect SOC content in temperate forest ecosystems more widespread.

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Anthropogenic activities have raised nitrogen (N) input worldwide with profound implications for soil carbon (C) cycling in ecosystems. The specific impacts of N input on soil organic matter (SOM) pools differing in microbial availability remain debatable. For the first time, we used a much-improved approach by effectively combining the 13C natural abundance in SOM with 21 years of C3-C4 vegetation conversion and long-term incubation. This allows to distinguish the impact of N input on SOM pools with various turnover times. We found that N input reduced the mineralization of all SOM pools, with labile pools having greater sensitivity to N than stable ones. The suppression in SOM mineralization was notably higher in the very labile pool (18%-52%) than the labile and stable (11%-47%) and the very stable pool (3%-21%) compared to that in the unfertilized control soil. The very labile C pool made a strong contribution (up to 60%) to total CO2 release and also contributed to 74%-96% of suppressed CO2 with N input. This suppression of SOM mineralization by N was initially attributed to the decreased microbial biomass and soil functions. Over the long-term, the shift in bacterial community toward Proteobacteria and reduction in functional genes for labile C degradation were the primary drivers. In conclusion, the higher the availability of the SOM pools, the stronger the suppression of their mineralization by N input. Labile SOM pools are highly sensitive to N availability and may hold a greater potential for C sequestration under N input at global scale.

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Processes of water retention and movement and the hydraulic conductivity are altered in the rhizosphere. The aim of this study was to investigate the physical-hydric properties of soil aggregates in the rhizosphere of annual ryegrass (Lolium multiflorum) cropped in a Kandiudalfic Eutrudox, taking into account aspects related to soil aggregate stability. Soil aggregates from rhizosphere soil (RZS) and soil between plant rows (SBP) were used to determine soil water retention curves (SWRCs) and saturated hydraulic conductivity (Ksat). In addition, properties related to soil aggregate stability, such as water-dispersible clay, soil organic carbon (SOC), and microbial activity, were also assessed. The higher microbial activity observed in the RZS was facilitated by increased SOC and microbial activity, resulting in improved soil aggregation (less water-dispersible clay). For nearly all measured matric potentials, RZS had a higher water content than SBP. This was attributed to the stability of aggregates, increase in SOC content, and the root exudates, which improved soil water retention. The increase in total porosity in RZS was associated with improved soil aggregation, which prevents deterioration of the soil pore space and results in higher Ksat and hydraulic conductivity as a function of the effective relative saturation in RZS compared to SBP.

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With mounting demand for high-quality agricultural products and the relentless exploitation of arable land resources, finding sustainable ways to safely cultivate food crops is becoming ever more important. Here, we investigated the effects of the integrated cropping technique "straw return + intercropping" on the soil aggregates as well as the microbial biomass carbon (MBC) content, enzyme activities and microbial diversity in soils of maize and soybean crops. Our results show that in comparison to straw removal and monoculture, straw return and intercropping increase the rhizosphere's MBC content (59.10%) of soil, along with urease (47.82%), sucrase (57.14%), catalase (16.14%) and acid phosphatase (40.66%) activities as well as the microbial diversity under maize and soybean. Under the same straw treatment, the yield of maize when intercropped surpassed that when grown in monoculture, with the land equivalent ratio of the intercropping treatment under straw return being highest. Overall, the intercropping of maize and soybean is beneficial for the healthy development of sustainable agriculture in the black soil region of northeast China, especially when combined with straw return to fields.