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Landfill cover soil is the environmental interface between landfills and the atmosphere and plays an important role in mitigating CH 4 emission from landfills. Here, stable isotope probing microcosms with CH 4 or CH 4 and dimethyl sulfide (DMS) were carried out to characterize activity and community structure of methanotrophs in landfill cover soils under DMS stress. The CH 4 oxidation activity in the landfill cover soils was not obviously influenced at the DMS concentration of 0.05%, while it was inhibited at the DMS concentrations of 0.1% and 0.2%. DMS-S was mainly oxidized to sulfate (SO 4 2- ) in the landfill cover soils. In the landfill cover soils, DMS could inhibit the expression of bacteria and decrease the abundances of pmoA and mmoX genes, while it could prompt the expression of pmoA and mmoX genes. γ-Proteobacteria methanotrophs including Methylocaldum, Methylobacter, Crenothrix and unclassified Methylococcaceae and α-Proteobacteria methanotrophs Methylocystis dominated in assimilating CH 4 in the landfill cover soils. Of them, Methylobacter and Crenothrix had strong tolerance to DMS or DMS could promote the growth and activity of Methylobacter and Crenothrix, while Methylocaldum had weak tolerance to DMS and showed an inhibitory effect. Metagenomic analyses showed that methanotrophs had the genes of methanethiol oxidation and could metabolize CH 4 and methanethiol simultaneously in the landfill cover soils. These findings suggested that methanotrophs might metabolize sulfur compounds in the landfill cover soils, which may provide the potential application in engineering for co-removal of CH 4 and sulfur compounds., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Carbofuran (CAS) is one of extensively used carbamate pesticides, which is considered as a derivative or a candidate of carbofuran (CAN) for its lower toxicity and persistence. Nevertheless, CAS could be degraded into its toxic metabolites, imposing potential risks on ecological safety. In this paper, biochars, derived from rice straw (RS), chicken manure (CM), corn straw (CS) and tire rubber (TR), were applied in CAS-contaminated soil to explore their effects on the dissipation of CAS and its metabolites. The dissipation rate of CAS was depressed by the amendment of biochar, mainly because biochar inhibited the hydrolysis of CAS by elevating soil pH value. Nevertheless, CS has efficiently enhanced the dissipation of CAN by almost 2-times for its promotion in hydrolysis and biodegradation. CS and CM improved biodegradation by altering the composition and structure of the microbial communities, exhibiting potential for facilitating bioremediation of CAS and CAN. Moreover, steam activated biochar accelerated the dissipation rate by 1.7-2.9 times and 1.3-2.4 times for CAS and CAN, respectively. This study investigated the effects of biochar on CAS and its toxic metabolites as well as possible governing mechanisms, providing rational instruction for biochar application in ambient atmosphere., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Excessive application of phosphorus (P) fertilizer to the agriculture soil can lead to the P loss to the aquatic ecosystem. Three soils from different land use (tea, paddy, and vegetable soils) were treated with biogas slurry (BS) at rate of 79.8 kg ha -1 , anionic polyacrylamide (PAM) at rate of 12.5, 25 and 50 kg ha -1 , Gypsum (Gy) at rate of 5t ha -1 , and the control (Ck) without treatment, to control P losses in a laboratory batch experiment. The soil solution was analyzed for total P (TP), dissolved reactive P (DRP) and total dissolved P (TDP). Particulate P (PP) and dissolved unreactive P (DURP) were calculated by subtracting DRP from TP and TDP, respectively. The DRP was within a range of 68-98% of TP whereas PP varied in a range of 2-32% of TP and DURP was within a range of 0.1-19% of TP, depending on soil types and different treatments. The addition of PAM at a high rate and Gy together on the soil after BS application reduced the release of TP by 54, 46, and 51% and that of DRP by 61, 49, and 53% for tea, paddy and vegetable soils, respectively. However, the application of BS with PAM alone promoted the release of DRP by 77, 86, 70% for tea, paddy, and vegetable soils, respectively. This study suggests that the synergic application of PAM and Gy on soils after BS addition can be a good strategy to reduce P losses., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Biochars derived from rice straw (RS), corn straw (CS), chicken manure (CM) and tire rubber (TR) were applied to soil to investigate their effects on the dissipation of cyazofamid and its metabolite CCIM (4-chloro-5-p-tolylimidazole-2-carbonitrile), with high acute toxicity compared to cyazofamid. The enhancement of cyazofamid dissipation followed the order of CS > RS > CM, whereas TR depressed the cyazofamid dissipation. Adsorption, hydrolysis and microbial degradation were all involved in cyazofamid dissipation. CM and CS enhanced the contribution of biodegradation to cyazofamid dissipation, which might be related with the shifted microbial community. More importantly, CCIM residual was drastically increased by 8-15 times after biochar application, regardless of biochar type. In total, this study shed light on the issue of build-up of metabolites in biochar-amended soil, especially for metabolites having higher toxicities than parent compounds, providing new insights into potential risk of biochar application for soil remediation., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Using manure-derived-biochar as an alternative phosphorus (P) source has bright future prospects to improve soil P status. A 98-day microcosm incubation experiment was set up for two soils which were amended with manure biochar at proportions of 0, 0.5% and 1.5%. Swine manure samples were air-dried and manure biochar was prepared by pyrolysis at 400 °C for 4 h. As determined by P-31 nuclear magnetic resonance ((31)P NMR) spectroscopy, manure biochar mainly increased the contents and fractions of orthophosphate and pyrophosphate in two soils, while decreased those of monoesters (P<0.05). At the end of incubation, 1.5% of manure biochar raised soil pH by 0.5 and 0.6 units, cation exchange capacity by 16.9% and 32.2%, and soil total P by 82.1% and 81.1% for silt loam and clay loam soils, respectively, as compared with those soils without biochar. Simultaneously, 1.5% of manure biochar decreased acid phosphomonoesterase activities by 18.6% and 34.0% for clay loam and silt loam, respectively; while it increased alkaline phosphomonoesterase activities by 28.5% and 95.1% for clay loam and silt loam, respectively. The enhancement of soil P availability after manure biochar addition was firstly due to the orthophosphate and pyrophosphate as the major P species in manure biochar which directly increased contents of soil inorganic P, and also attributed to the decomposition of some organic P like monoesters by enhanced alkaline phosphomonoesterase activities from manure biochar addition., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Ecological stoichiometry provides a powerful tool for integrating microbial biomass stoichiometry with ecosystem processes, opening far-reaching possibilities for linking microbial dynamics to soil carbon (C) metabolism in response to agricultural nutrient management. Despite its importance to crop yield, the role of phosphorus (P) with respect to ecological stoichiometry and soil C sequestration in paddy fields remains poorly understood, which limits our ability to predict nutrient-related soil C cycling. Here, we collected soil samples from a paddy field experiment after seven years of superphosphate application along a gradient of 0, 30, 60, and 90 (P-0 through P-90, respectively) kg.ha-1.yr-1 in order to evaluate the role of exogenous P on soil C sequestration through regulating microbial stoichiometry. P fertilization increased soil total organic C and labile organic C by 1-14% and 4-96%, respectively, while rice yield is a function of the activities of soil β-1,4-glucosidase (BG), acid phosphatase (AP), and the level of available soil P through a stepwise linear regression model. P input induced C limitation, as reflected by decreases in the ratios of C:P in soil and microbial biomass. An eco-enzymatic ratio indicating microbial investment in C vs. P acquisition, i.e., ln(BG): ln(AP), changed the ecological function of microbial C acquisition, and was stoichiometrically related to P input. This mechanism drove a shift in soil resource availability by increasing bacterial community richness and diversity, and stimulated soil C sequestration in the paddy field by enhancing C-degradation-related bacteria for the breakdown of plant-derived carbon sources. Therefore, the decline in the C:P stoichiometric ratio of soil microorganism biomass under P input was beneficial for soil C sequestration, which offered a "win-win" relationship for the maximum balance point between C sequestration and P availability for rice production in the face of climate change.

Agricultural fertilization may change processes of elemental biogeochemical cycles and alter the ecological function. Ecoenzymatic stoichiometric feature plays a critical role in global soil carbon (C) metabolism, driving element cycles, and mediating atmospheric composition in response to agricultural nutrient management. Despite the importance on crop growth, the role of phosphorous (P) in compliance with eco-stoichiometry on soil C and nitrogen (N) sequestration in the paddy field remains poorly understood in the context of climate change. Here, we collected soil samples from a field experiment after 6 years of chemical P application at a gradient of 0 (P-0), 30 (P-30), 60 (P-60), and 90 (P-90) kg ha(-1) in order to evaluate the role of P on stoichiometric properties in terms of soil chemical, microbial biomass, and eco-enzyme activities as well as greenhouse gas (GHG: CO2, N2O and CH4) emissions. Continuous P input increased soil total organic C and N by 1.3-9.2% and 3%-13%, respectively. P input induced C and N limitations as indicated by the decreased ratio of C:P and N:P in the soil and microbial biomass. A synergistic mechanism among the ecoenzymatic stoichiometry, which regulated the ecological function of microbial C and N acquisition and were stoichiometrically related to P input, stimulated soil C and N sequestration in the paddy field. The lower emissions of N2O and CH4 under the higher P application (P-60 and P-90) in July and the insignificant difference in N2O emission in August compared to P-30; however, continuous P input enhanced CO2 fluxes for both samplings. There is a technical conflict for simultaneously regulating three types of GHGs in terms of the eco-stoichiometry mechanism under P fertilization. Thus, it is recommended that the P input in paddy fields not exceed 60 kg ha(-1) may maximize soil C sequestration, minimize P export, and guarantee grain yields.

Bacterial populations (CFU) have been shown to oscillate in wavelike patterns after nutrient impulses in previous studies. The amplitudes and periods of oscillations could possibly be used as indicators of soil health analogous to the stability and resilience of biological populations widely accepted as indicators for ecosystem health. Limited plant and animal disease outbreaks can also be viewed as a manifestation of a healthy soil ecosystem. Two pot experiments were carried out to verify whether damping-off of beet seedlings by Pythium ultimum, measured as area under the disease progress curve (AUDPC), fluctuated over time after incorporation of organic materials into organic versus conventional soils, and to investigate whether daily dynamics of AUDPCs were linked to the dynamics of microbial populations and chemical parameters. AUDPCs oscillated significantly over time when Pythium bioassays were initiated daily after addition of ground grass and clover shoots (GC) into unplanted soils. Similar oscillations with significant harmonics of AUDPC were also observed in composted manure (CM)-amended soils but with smaller amplitudes than in GC-amended soils. The AUDPC harmonics in amended soils had periods similar to those of CFU of copiotrophic bacteria. Cross-correlation analysis demonstrated that periodic fluctuations of P. ultimum infections (AUDPCs) did not coincide with those of copiotrophic CFU but were shifted in phase. It appears that competition or antagonism from some fast-growing bacteria influenced pathogen infections, because these bacterial populations were growing and dying. Soil chemical variables, including pH, dissolved organic carbon, and NO(3)(-)-N, and NH(4)(+)-N contents, changed significantly in the initial 7 days after a nutrient impulse into soils. These changes were cross-correlated with copiotrophic CFU with time lags of approximately 1 to 2 days but were seldom associated with daily changes in AUDPCs. Organically managed soils always had lower AUDPC ratios of amended to nonamended treatments, indicating that organic materials showed stronger suppressive abilities to P. ultimum in organic than in conventional soils. The oscillations in AUDPCs and copiotrophic CFU in amended organic soil also had smaller amplitudes than in amended conventional soil. These results suggested that organically managed soils had a greater resistance and resilience to the disturbance of the amendments and, therefore, could be considered healthier than conventionally managed soils.

An undisturbed heavy clay soil column experiment was conducted to examine the influence of the new nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP), on nitrogen and soil salt-ion leaching. Regular urea was selected as the nitrogen source in the soil. The results showed that the cumulative leaching losses of soil nitrate-N under the treatment of urea with DMPP were from 57.5% to 63.3% lower than those of the treatment of urea without DMPP. The use of nitrification inhibitors as nitrate leaching retardants may be a proposal in regulations to prevent groundwater contaminant. However, there were no great difference between urea and urea with DMPP treatments on ammonium-N leaching. Moreover, the soil salt-ion leaching losses of Ca2+, Mg2+, K+, and Na+ were reduced from 26.6% to 28.8%, 21.3% to 27.8%, 33.3% to 35.5%, and 21.7% to 32.1%, respectively. So, the leaching losses of soil salt-ion were declined for nitrification inhibitor DMPP addition, being beneficial to shallow groundwater protection and growth of crop. These results indicated the possibility of ammonium or ammonium producing compounds using nitrification inhibitor DMPP to control the nitrate and nutrient cation leaching losses, minimizing the risk of nitrate pollution in shallow groundwater.