Soil multifunctionality of paddy field is explained by soil pH rather than microbial diversity after 8-years of repeated applications of biochar and nitrogen fertilizer

Effects of biochar and compost on the abundant and rare microbial communities assembly and multifunctionality in pesticide-contaminated soil under freeze‒thaw cycles

Biochar and compost are effective ways to improve soil quality and reduce pesticide pollution. However, the effects of them on the abundant and rare microbial communities in freeze‒thaw soil need to be further clarified. Therefore, this study took biochar, compost, and their combination as examples to explore their effects on the abundant and rare microbial communities and multifunctionality in glyphosate, imidacloprid and pyraclostrobin contaminated soil under freeze‒thaw cycles. We found that freeze‒thaw cycles enhanced the functional groups and surface aromaticity of biochar and compost, thereby improving the adsorption capacity. Biochar and compost reduced the concentration and half-life of three pesticides and enhanced the degradation function of rare taxa in soil. Biochar and compost improved the structure composition and co-occurrence relationship of abundant and rare taxa. Meanwhile, the assembly processes of abundant and rare sub-communities were mainly driven by stochastic processes and the Combined treatment promoted the transition from dispersal limitation to homogenizing dispersal and homogeneous selection. Moreover, the Combined treatment significantly improved the multifunctionality before and after freezing and thawing by increasing the diversity of rare taxa and assembly processes. The results provide new insights for farmland soil remediation in seasonal frozen areas, especially the soil functional cycle of abundant and rare microorganisms.

Non-flooding conditions caused by water table drawdown alter microbial network complexity and decrease multifunctionality in alpine wetland soils

Several soil functions of alpine wetland depend on microbial communities, including carbon storage and nutrient cycling, and soil microbes are highly sensitive to hydrological conditions. Wetland degradation is often accompanied by a decline in water table. With the water table drawdown, the effects of microbial network complexity on various soil functions remain insufficiently understood. In this research, we quantified soil multifunctionality of flooded and non-flooded sites in the Lalu Wetland on the Tibetan Plateau. We employed high-throughput sequencing to investigate the microbial community responses to water table depth changes, as well as the relationships between microbial network properties and soil multifunctionality. Our findings revealed a substantial reduction in soil multifunctionality at both surface and subsurface soil layers (0-20 cm and 20-40 cm) in non-flooded sites compared to flooded sites. The α-diversity of bacteria in the surface soil of non-flooded sites was significantly lower than that in flooded sites. Microbial network properties (including the number of nodes, number of edges, average degree, density, and modularity of co-occurrence networks) exhibited significant correlations with soil multifunctionality. This study underscores the adverse impact of non-flooded conditions resulting from water table drawdown on soil multifunctionality in alpine wetland soils, driven by alterations in microbial community structure. Additionally, we identified soil pH and moisture content as pivotal abiotic factors influencing soil multifunctionality, with microbial network complexity emerging as a valuable predictor of multifunctionality.

Foliar application protected vegetable against poisonous element cadmium and mitigated human health risks

Foliar application has been reported as an effective method to facilitate plant growth and mitigate cadmium (Cd) accumulation. However, the application of foliar fertilizers on plant production, Cd uptake and health risks of Solanaceae family remains unknown. In this study, four foliar fertilizers were applied to investigate their effects on the production, Cd accumulation and human health risk assessment of two varieties of pepper (Capsicum annuum L.) and eggplant (Solanum melongena L.), respectively. Compared with CK, the foliar application increased vegetable production to 104.16 %-123.70 % in peppers, and 100.83 %-105.17 % in eggplants, accordingly. The application of foliar fertilizers largely decreased Cd TF (transportation factor) by up to 23.32 % in JY, 18.37 % in GJ of pepper varieties, and up to 14.47 % in ZL, 15.24 % in HGR of eggplant varieties. Moreover, Cd BAF (bioaccumulation factor) also declined to different extents after the application of foliar fertilizers. As for human health risk assessments, foliar application diminished the hazard index (HI) and carcinogenic risk (CR) of both pepper and eggplant varieties. The results concluded that the application of composed foliar fertilizers was most effective, and could be a promising alternative for the improvement of vegetable production and mitigation of vegetable Cd accumulation and human health risks as well. The results further highlighted the understanding of foliar fertilizer application on vegetable production and health risks, which benefited better vegetable safe production and further guaranteed human health.

Long-Term Straw Incorporation under Controlled Irrigation Improves Soil Quality of Paddy Field and Rice Yield in Northeast China

Soil quality is an indicator of the ability to ensure ecological security and sustainable soil usage. The effects of long-term straw incorporation and different irrigation regimes on the yield and soil quality of paddy fields in cold regions remain unclear. This study established four treatments: controlled irrigation + continuous straw incorporation for 3 years (C3), controlled irrigation + continuous straw incorporation for 7 years (C7), flooded irrigation + continuous straw incorporation for 3 years (F3), and flooded irrigation + continuous straw incorporation for 7 years (F7). Analysis was conducted on the impact of various irrigation regimes and straw incorporation years on the physicochemical characteristics and quality of the soil. The soil quality index (SQI) for rice fields was computed using separate datasets for each treatment. The soil nitrate nitrogen, available phosphorus, soil organic carbon, and soil organic matter contents of the C7 were 93.51%, 5.80%, 8.90%, and 8.26% higher compared to C3, respectively. In addition, the yield of the C7 treatment was 5.18%, 4.89%, and 10.32% higher than those of F3, C3, and F7, respectively. The validity of the minimum data set (MDS) was verified by correlation, Ef and ER, which indicated that the MDS of all treatments were able to provide a valid evaluation of soil quality. The MDS based SQI of C7 was 11.05%, 11.97%, and 27.71% higher than that of F3, C3, and F7, respectively. Overall, long-term straw incorporation combined with controlled irrigation increases yield and soil quality in paddy fields in cold regions. This study provides a thorough assessment of soil quality concerning irrigation regimes and straw incorporation years to preserve food security and the sustainability of agricultural output. Additionally, it offers a basis for soil quality diagnosis of paddy fields in the Northeast China.

Biodiversity of network modules drives ecosystem functioning in biochar-amended paddy soil

Introduction

Soil microbes are central in governing soil multifunctionality and driving ecological processes. Despite biochar application has been reported to enhance soil biodiversity, its impacts on soil multifunctionality and the relationships between soil taxonomic biodiversity and ecosystem functioning remain controversial in paddy soil.

Methods

Herein, we characterized the biodiversity information on soil communities, including bacteria, fungi, protists, and nematodes, and tested their effects on twelve ecosystem metrics (including functions related to enzyme activities, nutrient provisioning, and element cycling) in biochar-amended paddy soil.

Results

The biochar amendment augmented soil multifunctionality by 20.1 and 35.7% in the early stage, while the effects were diminished in the late stage. Moreover, the soil microbial diversity and core modules were significantly correlated with soil multifunctionality.

Discussion

Our analysis revealed that not just soil microbial diversity, but specifically the biodiversity within the identified microbial modules, had a more pronounced impact on ecosystem functions. These modules, comprising diverse microbial taxa, especially protists, played key roles in driving ecosystem functioning in biochar-amended paddy soils. This highlights the importance of understanding the structure and interactions within microbial communities to fully comprehend the impact of biochar on soil ecosystem functioning in the agricultural ecosystem.

Bacteria drive soil multifunctionality while fungi are effective only at low pathogen abundance

The positive correlation between soil biodiversity and multifunctionality has gained widespread recognition. However, the impact of plant pathogens on soil multifunctionality and its relationship with microbial diversity remains understudied. To address this knowledge gap, we collected soil samples from three Hami melon (Cucumis melo L.) planting sites with varying monoculture durations (1, 3, and 5 years). We sequenced the bacterial and fungal communities in these samples and quantified multifunctionality. The results revealed a significant increase in the relative abundance of fungal pathogens over the years of planting, which influenced the correlations between microbial diversity and multifunctionality at a threshold value of 0.01. Both bacterial and fungal richness positively influenced multifunctionality when fungal pathogen abundance was low (< 0.01), whereas only bacterial richness showed a positive correlation with multifunctionality under high fungal pathogen abundance (> 0.01) conditions. Both bacterial and fungal communities were primarily governed by deterministic processes. However, only bacterial community assembly drove soil multifunctionality, showing positive correlations with multifunctionality dissimilarity under low fungal pathogen abundance condition and negative correlations under high fungal pathogen abundance condition, reflecting distinct pathogen pressures. Structural equaling modeling further confirmed the distinct roles of bacterial and fungal richness and composition in promoting multifunctionality under different fungal pathogen condition. Our findings provide evidence that shifts in fungal pathogen abundance alter the balance and interactions between biodiversity and multifunctionality and highlight the importance of engineering biotic interactions in determining soil functioning in agroecosystems.

Toward an intensive understanding of sewer sediment prokaryotic community assembly and function

Prokaryotic communities play important roles in sewer sediment ecosystems, but the community composition, functional potential, and assembly mechanisms of sewer sediment prokaryotic communities are still poorly understood. Here, we studied the sediment prokaryotic communities in different urban functional areas (multifunctional, commercial, and residential areas) through 16S rRNA gene amplicon sequencing. Our results suggested that the compositions of prokaryotic communities varied significantly among functional areas. Desulfomicrobium, Desulfovibrio, and Desulfobacter involved in the sulfur cycle and some hydrolytic fermentation bacteria were enriched in multifunctional area, while Methanospirillum and Methanoregulaceae, which were related to methane metabolism were significantly discriminant taxa in the commercial area. Physicochemical properties were closely related to overall community changes (p < 0.001), especially the nutrient levels of sediments (i.e., total nitrogen and total phosphorus) and sediment pH. Network analysis revealed that the prokaryotic community network of the residential area sediment was more complex than the other functional areas, suggesting higher stability of the prokaryotic community in the residential area. Stochastic processes dominated the construction of the prokaryotic community. These results expand our understanding of the characteristics of prokaryotic communities in sewer sediment, providing a new perspective for studying sewer sediment prokaryotic community structure.

Responses of Soil Microbial Survival Strategies and Functional Changes to Wet-Dry Cycle Events

Soil microbial taxa have different functional ecological characteristics that influence the direction and intensity of plant-soil feedback responses to changes in the soil environment. However, the responses of soil microbial survival strategies to wet and dry events are poorly understood. In this study, soil physicochemical properties, enzyme activity, and high-throughput sequencing results were comprehensively anal0079zed in the irrigated cropland ecological zone of the northern plains of the Yellow River floodplain of China, where Oryza sativa was grown for a long period of time, converted to Zea mays after a year, and then Glycine max was planted. The results showed that different plant cultivations in a paddy-dryland rotation system affected soil physicochemical properties and enzyme activity, and G. max field cultivation resulted in higher total carbon, total nitrogen, soil total organic carbon, and available nitrogen content while significantly increasing α-glucosidase, β-glucosidase, and alkaline phosphatase activities in the soil. In addition, crop rotation altered the r/K-strategist bacteria, and the soil environment was the main factor affecting the community structure of r/K-strategist bacteria. The co-occurrence network revealed the inter-relationship between r/K-strategist bacteria and fungi, and with the succession of land rotation, the G. max sample plot exhibited more stable network relationships. Random forest analysis further indicated the importance of soil electrical conductivity, total carbon, total nitrogen, soil total organic carbon, available nitrogen, and α-glucosidase in the composition of soil microbial communities under wet-dry events and revealed significant correlations with r/K-strategist bacteria. Based on the functional predictions of microorganisms, wet-dry conversion altered the functions of bacteria and fungi and led to a more significant correlation between soil nutrient cycling taxa and environmental changes. This study contributes to a deeper understanding of microbial functional groups while helping to further our understanding of the potential functions of soil microbial functional groups in soil ecosystems.

Enhancing rice quality and productivity: Multifunctional biochar for arsenic, cadmium, and bacterial control in paddy soil

The perilousness of arsenic and cadmium (As-Cd) toxicity in water and soil presents a substantial hazard to the ecosystem and human well-being. Additionally, this metal (loids) (MLs) can have a deleterious effect on rice quality and yield, owing to the existence of toxic stress. In response to the pressing concern of reducing the MLs accumulation in rice grain, this study has prepared magnesium-manganese-modified corn-stover biochar (MMCB), magnesium-manganese-modified eggshell char (MMEB), and a combination of both (MMCEB). To test the effectiveness of these amendments, several pot trials were conducted, utilizing 1% and 2% application rates. The research discovered that the MMEB followed by MMCEB treatment at a 2% rate yielded the most significant paddy and rice quality, compared to the untreated control (CON) and MMCB. MMEB and MMCEB also extensively decreased the MLs content in the grain than CON, thereby demonstrating the potential to enrich food security and human healthiness. In addition, MMEB and MMCEB augmented the microbial community configuration in the paddy soil, including As-Cd detoxifying bacteria, and decreased bioavailable form of the MLs in the soil compared to the CON. The amendments also augmented Fe/Mn-plaque which captured a considerable quantity of As-Cd in comparison to the CON. In conclusion, the utilization of multifunctional biochar, such as MMEB and MMCEB, is an encouraging approach to diminish MLs aggregation in rice grain and increase rice yield for the reparation of paddy soils via transforming microbiota especially enhancing As-Cd detoxifying taxa, thereby improving agroecology, food security, and human and animal health.

Improved sea rice yield and accelerated di-2-ethylhexyl phthalate (DEHP) degradation by straw carbonization returning in coastal saline soils

Di-2-ethylhexyl phthalate, a persistent organic contaminant, is widely distributed in the environment and poses substantial threats to human health; however, there have been few investigations regarding the risks and remediation of DEHP in coastal saline soils. In this work, we studied the influences of straw carbonization returning on sea rice yield and DEHP degradation. Straw carbonization returning significantly increased soil nutrients and reduced salt stress to improve sea rice yield. DEHP degradation efficiency was enhanced to a maximum of 78.27% in straw carbonized return with 60% sea rice, mainly attributed to the high pH value, high soil organic matter and enriched potential DEHP degraders of Nocardioides, Mycobacterium and Bradyrhizobium. Some key genes related to metabolism (esterase and cytochrome P450) and DEHP-degradation (pht4, pht5, pcaG, dmpB, catA and fadA) were elevated and explained the accelerated DEHP degradation, shifting from the benzoic acid pathway to the protocatechuate pathway in straw carbonization returning. The results obtained in this study provide a deep and comprehensive understanding of sea rice yield improvement and DEHP degradation mechanisms in coastal paddy soil by a straw carbonization returning strategy.

Interactive effects of biochar and chemical fertilizer on water and nitrogen dynamics, soil properties and maize yield under different irrigation methods

Long-term application of nitrogen (N) fertilizer adversely degrades soil and decreases crop yield. Biochar amendment with N fertilizer not only can increase yield but also can improve the soil. A 3-year field experiment was conducted to determine the effect of biochar doses with N fertilizer on maize yield and soil N and water dynamics under border irrigation (BI) and drip irrigation (DI) methods. Treatments were 260 kg N ha-1 without biochar addition and combined with low, medium, and high doses of biochar, namely, 15.5 t ha-1, 30.7 t ha-1, and 45.3 t ha-1 (NB0, NB1, NB2, and NB3), respectively. The biochar doses and irrigation methods significantly (p < 0.05) increased maize growth and yield characteristics, irrigation water use efficiency (IWUE), and fertilizer N use efficiency (FNUE) and enhanced the soil properties. In the BI and DI method, the NB1, NB2, and NB3 treatments increased yield by 4.96%-6.10%, 8.36%-9.85%, and 9.65%-11.41%, respectively, compared to NB0. In terms of IWUE and FNUE, the non-biochar treatment had lower IWUE and FNUE compared to biochar combined with N fertilizer treatments under both BI and DI methods. In the BI method, the IWUE in NB2 and NB3 ranged from 3.36 to 3.43 kg kg-1, and in DI, it was maximum, ranging from 5.70 to 5.94 kg kg-1. Similarly, these medium and high doses of biochar increased the FNUE of maize. The FNUEs in NB2 and NB3 under BI ranged from 38.72 to 38.95 kg kg-1 and from 38.89 to 39.58 kg kg-1, while FNUEs of these same treatments under DI ranged from 48.26 to 49.58 kg kg-1 and from 48.92 to 50.28 kg kg-1. The effect of biochar was more obvious in DI as compared to the BI method because soil water content (SWC) and soil N concentrations (SNCs) were higher at rhizosphere soil layers under DI. Biochar improved SWC and SNC at 0-20 cm and 20-40 cm soil layers and decreased below 60-cm soil layers. In contrast, despite biochar-controlled SWC and SNCs, still, values of these parameters were higher in deeper soil layers. In the BI method, the SNCs were higher at 60-80 cm and 80-100 cm compared to the top and middle soil layers. Depth-wise results of SNC demonstrated that the biochar's ability to store SNC was further enhanced in the DI method. Moreover, biochar increased soil organic matter (OM) and soil aggregate stability and maintained pH. The NB0 treatment increased soil OM by 11.11%-14.60%, NB2 by 14.29%-19.42%, and NB3 by 21.98%-23.78% in both irrigation methods. This increased OM resulted in improved average soil aggregates stability by 2.45%-11.71% and 4.52%-14.66% in the BI and DI method, respectively. The results of our study revealed that combined application of N fertilizer with a medium dose of biochar under the DI method would be the best management practice, which will significantly increase crop yield, improve SWC, enrich SNC and OM, improve soil structure, and maintain pH.

Characteristics prediction of hydrothermal biochar using data enhanced interpretable machine learning

Hydrothermal biochar is a promising sustainable soil remediation agent for plant growth. Demands for biochar properties differ due to the diversity of soil environment. In order to achieve accurate biochar properties prediction and overcome the interpretability bottleneck of machine learning models, this study established a series of data-enhanced machine learning models and conducted relevant sensitivity analysis. Compared with traditional support vector machine, artificial neural network, and random forest models, the accuracy after data enhancement increased in average from 5.8% to 15.8%, where the optimal random forest model showed the average of accuracy was 94.89%. According to sensitivity analysis results, the essential factors influencing the predicting results of the models were reaction temperature, reaction pressure, and specific element of biomass feedstock. As a result, data-enhanced interpretable machine learning proved promising for the characteristics prediction of hydrothermal biochar.

Tofu by-product soy whey substitutes urea: Reduced ammonia volatilization, enhanced soil fertility and improved fruit quality in cherry tomato production

Soy whey is an abundant, nutrient-rich and safe wastewater produced in tofu processing, so it is necessary to valorize it instead of discarding it as sewage. Whether soy whey can be used as a fertilizer substitute for agricultural production is unclear. In this study, the effects of soy whey serving as a nitrogen source to substitute urea on soil NH₃ volatilization, dissolved organic matter (DOM) components and cherry tomato qualities were investigated by soil column experiment. Results showed that the soil NH₄⁺-N concentrations and pH values of the 50% soy whey fertilizer combined with 50% urea (50%-SW) and 100% soy whey fertilizer (100%-SW) treatments were lower than those of 100% urea treatment (CKU). Compared with CKU, 50%-SW and 100%-SW treatments increased the abundance of ammonia oxidizing bacteria (AOB) by 6.52-100.89%, protease activity by 66.22-83.78%, the contents of total organic carbon (TOC) by 16.97-35.64%, humification index (HIX) of soil DOM by 13.57-17.99%, and average weight per fruit of cherry tomato by 13.46-18.56%, respectively. Moreover, soy whey as liquid organic fertilizer reduced the soil NH₃ volatilization by 18.65-25.27% and the fertilization cost by 25.94-51.87% compared with CKU. This study provides a promising option with economic and environmental benefits for soy whey utilization and cherry tomato production, which contributes to the win-win effectiveness of sustainable production for both the soy products industry and agriculture.

Effects of biochar and freeze‒thaw cycles on the bacterial community and multifunctionality in a cold black soil area

Global climate change has altered soil freeze‒thaw cycle events, and little is known about soil microbe response to and multifunctionality regarding freeze‒thaw cycles. Therefore, in this study, biochar was used as a material to place under seasonal freeze-thaw cycling conditions. The purpose of this study was to explore the ability of biochar to regulate the function of freeze-thaw soil cycles to ensure spring sowing and food production. The results showed that biochar significantly increased the richness and diversity of soil bacteria before and after freezing-thawing. In the freezing period, the B50 treatment had the greatest improvement effect (2.6% and 5.5%, respectively), while in the thawing period, the B75 treatment had the best improvement effect. Biochar changed the composition and distribution characteristics of the bacterial structure and enhanced the multifunctionality of freeze-thaw soil and the stability of the bacterial symbiotic network. Compared with the CK treatment, the topological characteristics of the bacterial ecological network of the B50 treatment increased the most. They were 0.89 (Avg.degree), 9.79 (Modularity), 9 (Nodes), and 255 (Links). The freeze-thaw cycle decreased the richness and diversity of the bacterial community and changed the composition and distribution of the bacterial community, and the total bacterial population decreased by 658 (CK), 394 (B25), 644 (B50) and 86 (B75) during the thawing period compared with the freezing period. The soil multifunctionality in the freezing period was higher than that during the thawing period, indicating that the freeze-thaw cycle reduced soil ecological function. From the perspective of abiotic analysis, the decrease in soil multifunctionality was due to the decrease in soil nutrients, enzyme activities, soil basic respiration and other singular functions. From the perspective of bacteria, the decrease in soil multifunctionality was mainly due to the change in the Actinobacteriota group. This work expands the understanding of biochar ecology in cold black soil. These results are conducive to the sustainable development of soil ecological function in cold regions and ultimately ensure crop growth and food productivity.

Effects of nitrogen and phosphorus supply levels and ratios on soil microbial diversity-ecosystem multifunctionality relationships in a coastal nontidal wetland

Human activities have changed the levels and ratios of nitrogen (N) and phosphorus (P) in wetland ecosystems. However, the effects of N and P levels and ratios on wetland soil microbial community and ecosystem multifunctionality remain unclear, especially on the relationships between soil microbial diversity and ecosystem multifunctionality. In this study, the effects of a 7-year experimental nutrient addition on the soil microbial community and ecosystem multifunctionality (12 function variables related to carbon, N, and P cycling) were assessed by combining three N and P supply levels with three N:P supply ratios in a coastal nontidal wetland ecosystem. According to the obtained results, the N and P supply levels significantly affected soil bacterial community composition, as well as ecosystem multifunctionality, while no significant effects of N:P supply ratios were observed. Although N and P supply levels did not significantly affect bacterial and fungal diversity, they both changed the complexity of bacterial and fungal networks. Soil ecosystem multifunctionality was significantly and positively correlated with bacterial diversity rather than fungal diversity. Moreover, the correlation coefficient between bacterial diversity and ecosystem multifunctionality showed an increasing-decreasing trend with increasing N and P supply levels and an increasing trend with increasing N:P supply ratios. However, the correlation coefficient between bacterial diversity and ecosystem multifunctionality was not significantly correlated with bacterial network complexity. The current study provides new insights into the impacts of N and P levels and ratios on soil microbial community and ecosystem multifunctionality in a coastal nontidal wetland. In particular, the present study highlighted that changes in N and P supply levels and ratios lead to changes in the relationship between soil bacterial diversity and ecosystem multifunctionality, which should be considered in related studies to accurately predict the responses of ecosystem multifunctionality to N and P inputs in coastal nontidal wetlands.

Effects of biochar on plant growth and hydro-chemical properties of recycled concrete aggregate

Biochar has been used as a sustainable amendment to mitigate environmental risks, improve plant growth and soil properties. This study conducted laboratory column tests to investigate the effects of plant-biochar interactions on shrub growth, hydraulic properties and nutrient contents of recycled concrete aggregates (RCAs). In total, three test conditions, namely, vegetated RCA without biochar (R), with 5 % biochar (R5) and 10 % biochar (R10) were subject to drying. With biochar application, total N, P and K of RCA increased by >100 %, 200 % and 31 %, respectively, while pH reduced to 8.3. With shrub growth, the lowest RCA pH was reduced to 7.8. The leaf area index (LAI) of shrub increased by 51 % due to biochar amendment, while the differences in shoot height were insignificant. The water retention capacity of RCA was enhanced by improving the saturated water content and air-entry value by 27 % and 100 %. The slope of the soil suction-LAI correlation for biochar amend cases was 1.6 times lower than R. This indicates that biochar may limit the increase of matric suction and prevent excessive water loss during drying. However, the differences between R5 and R10 were not significant. Therefore, 5 % biochar amendment is highly suggested as it can substantially improve plant growth and soil hydraulic properties during drying.

Effects of biochar and arbuscular mycorrhizal fungi on winter wheat growth and soil N2O emissions in different phosphorus environments

INTRODUCTION

Promoting crop growth and regulating denitrification process are two main ways to reduce soil N₂O emissions in agricultural systems. However, how biochar and arbuscular mycorrhizal fungi (AMF) can regulate crop growth and denitrification in soils with different phosphorus (P) supplies to influence N₂O emission remains largely unknown.

METHOD

Here, an eight-week greenhouse and one-year field experiments biochar and/or AMF (only in greenhouse experiment) additions under low and high P environments were conducted to characterize the effects on wheat (Triticum aestivum L.) growth and N₂O emission.

RESULTS

With low P supply, AMF addition decreased leaf Mn concentration (indicates carboxylate-releasing P-acquisition strategies), whereas biochar addition increased leaf Mn concentration, suggesting biochar and AMF addition regulated root morphological and physiological traits to capture P. Compared with low P supply, the high P significantly promoted wheat growth (by 16-34%), nutrient content (by 33-218%) and yield (by 33-41%), but suppressed soil N₂O emissions (by 32-95%). Biochar and/or AMF addition exhibited either no or negative effects on wheat biomass and nutrient content in greenhouse, and biochar addition promoted wheat yield only under high P environment in field. However, biochar and/or AMF addition decreased soil N₂O emissions by 24-93% and 32% in greenhouse and field experiments, respectively. This decrease was associated mainly with the diminished abundance of N₂O-producing denitrifiers (nirK and nirS types, by 17-59%, respectively) and the increased abundance of N₂O-consuming denitrifiers (nosZ type, by 35-65%), and also with the increased wheat nutrient content, yield and leaf Mn concentration.

DISCUSSION

These findings suggest that strengthening the plant-soil-microbe interactions can mitigate soil N₂O emissions via manipulating plant nutrient acquisition and soil denitrification.