Microbial Respiration Research Articles

Challenges in viticulture practices in a changing environment: Can green waste amendment benefit soil properties of vineyards in the Mediterranean?

In Southeastern France, viticulture is of great social, cultural, and economic importance. This sector is threatened by climate change particularly in the Mediterranean (longer droughts and more frequent heat waves) where soils are poor in organic matter and weakly developed. Since organic amendment can strongly modify soil properties and consequently the final products (grapes and wine), the effects of sustainable practices on soil characteristics have to be carefully assessed. This seasonal field survey focuses on the effects green waste amendment (GWA), i.e. semi-composted green wastes, have on vineyard soil functionality. The effects of GWA were compared with those of grass cover (GC), known as a sustainable practice. Soils were collected in vineyards under organic practices (Bouches-du-Rhône and Var, France) over four seasons and physico-chemical (Total C and N, pHwater, pHKCL, EC, WHC, copper content and soil organic carbon SOC) and biological (microbial respiration and biomass, microbial catabolic structure, earthworm abundance and biomass) properties were characterized. Both practices were beneficial to soil physicochemical properties. For example, under both practices, higher (2 fold) Total N and SOC on late spring were observed. Both GWA and GC favored soil microbial communities, with microbial respiration having doubled and tripled on late spring. Similar results were observed for microbial biomass and both bacterial and fungal catabolic diversities (increased approximately by half) over summer. These benefits were particularly prominent during drought season (June and August), and probably linked to a shift in microbial communities as revealed by catabolic profiles. GWA also favored abundance and biomass of earthworm during winter. These findings reveal the potential GWA to counteract the effect of tillage, to mitigate the stress from drought and to improve overall soil functionality in vineyards.

Dung beetles drive direct and indirect changes in ecosystem multifunctionality

Abstract Measuring ecosystem multifunctionality (EMF) could be a valuable method for assessing whether nature‐based solutions, such as introducing non‐native species to benefit ecosystem functioning, yield net positive outcomes. While EMF metrics may provide a coarse overview of the functioning of a system, such metrics can obscure the interactions among multiple simultaneously occurring ecosystem functions. This could limit the predictive value and overall efficacy of EMF metrics for the management of environmental change impacts on ecosystem functioning. We carried out a mesocosm experiment with dung beetle temporal species richness (diversity) treatments in a pasture ecosystem in Aotearoa New Zealand and quantified cascading biotic and abiotic effects of introduced dung beetles (Onthophagus binodis and Onitis alexis) on multiple ecosystem functions. We measured nine individual ecosystem functions affected by dung beetles, including dung removal, total soil carbon, nitrogen, phosphorus, soil microbial respiration, nitrate N, ammonium N, anaerobically mineralisable N and pasture biomass production. We first tested the effects of temporal dung beetle diversity on the nine individual ecosystem functions. We then tested how introduced dung beetle temporal diversity affects ecosystem multifunctionality by calculating EMF metrics using the averaging, threshold and the Hill numbers approaches. Finally, to investigate the underlying interactions among individual functions, we tested the direct and indirect effects of introduced dung beetles on the nine ecosystem functions using structural equation modelling (SEM). Only one out of the nine individual ecosystem functions was significantly affected by dung beetle introductions, whereas five of the six calculated EMF metrics increased significantly with temporal diversity of introduced dung beetles. However, when modelled within an SEM framework, dung beetle temporal diversity was found to directly affect dung removal, but with cascading effects on total N and anaerobically mineralisable N. Our results suggest that introducing and increasing dung beetle temporal diversity enhances the provisioning of multiple ecosystem functions, but that our ability to detect and explain changes in ecosystem multifunctionality is critically dependent on how EMF is quantified. Read the free Plain Language Summary for this article on the Journal blog.

Productivity and health of soil cultivated with forage cactus (Opuntia cochenillifera (L.) Mill.) with combined use of topsoil and biochar

Agricultural production in semi-arid environments represents a significant challenge, as these are areas that have soils with limited nutrient availability and scarcity of precipitation, which require adaptive and innovative strategies. The application of biochar to improve soil quality and increase productivity has been well studied. However, there is still a gap regarding the use of biochar with the technique of incorporating different topsoils on plant development and soil health. This technique has emerged as an alternative for producers to increase soil fertility. This technique is emerging as an alternative for producers to enhance soil fertility. The hypothesis of the present study is that the use of biochar associated with the topsoil technique increases the productivity and yield of cactus, mainly by changing the properties of the soil and its microbiological interactions. To test this hypothesis, we used different sources of biochar (bean husk, coffee grounds and soursop residue) in association with two types of topsoil (Acrisol and Luvisol). Our analyzes revealed changes on plants development, chemical and microbiological soil attributes. The topsoil technique significantly interfered with mean cladode length (COM), stem diameter (DI), plant height (AL), pH, Na+, K+ and urease enzymatic activity, while biochar had a significant effect on microbial respiration rate. In general, our results expand the knowledge about the use of biochar associated with topsoil, suggesting it as a promising, low-cost way that guarantees the conservation and health of the agroecosystem, contributing with important information for the development of alternative technologies to conventional ones.

Prediction of Distributed River Sediment Respiration Rates Using Community‐Generated Data and Machine Learning

AbstractRiver sediment microbial respiration is a key indicator of ecosystem functioning and the biogeochemical fluxes across this critical zone link surface and subsurface waters. As such, there is tremendous interest in measuring and mapping these respiration rates. Respiration observations are expensive and labor intensive; there is limited data available to the community. An open science, collaborative initiative is collecting samples for respiration rate analysis and multi‐scale metadata; this evolving data set is being used for making machine learning (ML) predictions at unsampled sites to help inform continued community engagement. However, it is a challenge to find an optimum configuration for ML models to work with this feature‐rich (i.e., 100+ possible input variables) data set. Here, we present results from a two‐tiered approach to managing the analysis of this complex data set: (a) a stacked ensemble of models that automatically optimizes hyperparameters and manages the training of many models and (b) feature permutation importance to detect the most important features in the models. The major elements of this workflow are modular, portable, open, and cloud‐based thus making this implementation a potential template for other applications. The models developed here predict that sediment organic matter chemistry is one of the most important features for predicting sediment respiration rate. Other larger‐scale, important features fall into the categories of climatic, ecological, geological, and fluvial settings. Leveraging these larger‐scale features to generate data‐driven estimates of river sediment respiration rates reveals spatially consistent but heterogeneous patterns across the river network of the Columbia River Basin.

Effects of conservation agriculture technologies on soil macrofauna community attributes in rainfed agriculture system

AbstractInappropriate rainfed crop management, especially wrong tillage and crop residue management, led to reduce the diversity of soil biological quality, especially soil macrofauna community, in semiarid region. This study was conducted to investigate the effect of 5 year conservation agriculture operation techniques on the quality and the diversity indices of soil macrofauna community in the rainfed lands in the west of Iran. This experiment was carried out in the statistical format of split‐split plots based on a randomized completely block design with three replications. The main treatments include control or conventional tillage, compound tillage, chisel tillage, and direct cultivation (no tillage) with three sub‐treatments of plant residues (no residues, one‐third, and two‐thirds of plant residues) in rainfed wheat (Triticum aestivum) rotation with rainfed chickpea (Cicer arietinum). Changes in soil biological quality indicators, such as soil microbial respiration were measured. Also, the indicators related to the population of soil macrofauna, including biodiversity index, uniformity index, and species richness, were measured and the effect of treatments on the measured indicators were compared with the classical statistical method of analysis of variance and Duncan's mean comparison test. The results showed that conservation agricultural treatments, including no‐tillage treatment, have led to significant increase of 19% and 15% of macrofauna biodiversity index in wheat and chickpea, respectively. Also, keeping one‐third of the wheat residues has led to an 18% increase in the biodiversity index of the soil macrofauna during the evaluation period. Biodiversity index and taxonomic richness of soil macrofauna were generally higher in the years of wheat than chickpea, and on the contrary, the species uniformity index of soil macrofauna biological community was higher in chickpea than wheat.

Clay soil amendment suppressed microbial enzymatic activities while increasing nitrogen availability in sandy soils

AbstractConservation management practices often produced positive but limited desirable outcomes in US Southeast sandy soils, likely due to their intrinsically low clay contents that constrain the soil's capacity to preserve organic carbon (C) and nutrients. In the field, we tested the effectiveness of a novel approach, that is, clay soil amendment, to improve sandy soils. In October 2017, clay‐rich soils (25% clay) were spread at 25 metric tons ha−1 and tilled onto a sandy soil (1.9% clay) in the field, which was further mixed by light tillage at 0‐ to 15‐cm depth, followed by planting winter cover crop mixtures (cereal rye, crimson clover, and winter pea). The crop rotation was cotton and corn with cover crop mixtures planted in the winter fallow season. Soils (0–15 cm) were collected in August 2021 and subjected to physio‐biochemical analyses. Clay amendment increased soil clay content to 3.4%, which improved nitrogen (N) availability by 51% but inhibited the activities of C (β‐d‐cellubiosidase [CB]; β‐xylosidase [BX]; N‐acetyl‐β‐glucosaminidase [NAG]) and N (leucine aminopeptidase [LAP]) cycling enzymes, resulting in up to 78% reduction in microbial respiration. A follow‐up kinetic study on BG and LAP enzymes suggested that clay addition can have different impacts on enzymes with diverse biological origins through distinct mechanisms. Clay addition can potentially improve sandy soils by stabilizing the organic inputs in soils. However, more research is required to understand its long‐term impacts making this approach practical.

Does montane meadow restoration influence the mineral association and stability of soil carbon?

Soil carbon (C) stability is an important consideration for management that aims to increase long-term C storage. The fraction of soil C allocated to physico-chemically protected mineral-associated organic matter (MAOM) is a common soil C stability benchmark. However, the reality of soil C persistence is more complex than MAOM content alone—particularly in ecosystems such as meadows with high rates of belowground C inputs that can stimulate MAOM decomposition. Here, we combined three metrics of soil C persistence to characterize soil C stability across a meadow restoration chronosequence averaging belowground C gains of 330 g C m−2 y−1 for ~20 y. The metrics were: (1) the fraction of soil C in MAOM and particulate organic matter (POM), (2) the susceptibility of soil C to decomposition under varying temperatures, and (3) the utilization of MAOM-C by microbes. Two metrics suggested soil C stability may increase following montane meadow restoration. As soil C concentration increased with restoration, C storage in MAOM, but not POM, increased (metric 1). The susceptibility of MAOM-C to decomposition (microbial respiration relative to MAOM-C) decreased with increasing soil C concentration across temperatures (metric 2). Stable isotope results could not definitively determine the source of carbon dioxide efflux (metric 3) but generate hypotheses for future research to address. We posit that C sequestered following montane meadow restoration could be stable, with implications for regional C storage objectives. Further, our data point toward complex mineral-associated C dynamics including the potential importance of plant inputs for MAOM formation in meadow soils.

Climate Change and Soil Health: Explainable Artificial Intelligence Reveals Microbiome Response to Warming

Climate change presents an unprecedented global challenge, demanding collective action to both mitigate its effects and adapt to its consequences. Soil health and function are profoundly impacted by climate change, particularly evident in the sensitivity of soil microbial respiration to warming, known as Q10. Q10 measures the rate of microbial respiration’s increase with a temperature rise of 10 degrees Celsius, playing a pivotal role in understanding soil carbon dynamics in response to climate change. Leveraging machine learning techniques, particularly explainable artificial intelligence (XAI), offers a promising avenue to analyze complex data and identify biomarkers crucial for developing innovative climate change mitigation strategies. This research aims to evaluate the extent to which chemical, physical, and microbiological soil characteristics are associated with high or low Q10 values, utilizing XAI approaches. The Extra Trees Classifier algorithm was employed, yielding an average accuracy of 0.923±0.009, an average AUCROC of 0.964±0.004, and an average AUCPRC of 0.963±0.006. Additionally, through XAI techniques, we elucidate the significant features contributing to the prediction of Q10 classes. The XAI analysis shows that the temperature sensitivity of soil respiration increases with microbiome variables but decreases with non-microbiome variables beyond a threshold. Our findings underscore the critical role of the soil microbiome in predicting soil Q10 dynamics, providing valuable insights for developing targeted climate change mitigation strategies.

Dissolved organic matter released from beach wrack is source-specific and molecularly highly diverse

Beach wrack is an important supplier of nutrients and organic matter to sandy beach ecosystems and underlying subterranean estuaries (STEs), producing metabolic hotspots in these otherwise organic carbon- and nutrient-poor environments. To assess the impact of beach wrack type (e.g., marine, terrestrial, plant, animal) and environmental settings (e.g., tidal inundation, precipitation, and solar irradiation) on nutrient and dissolved organic matter (DOM) release, a series of leaching experiments was conducted. Quantities of leached nutrients and dissolved organic carbon (DOC) were determined, and DOM molecular composition was investigated using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Millimolar—to molar amounts of DOC and dissolved nitrogen were released from the beach cast per kg dry weight, with type of wrack and leaching medium (fresh- vs. saltwater) exerting the biggest influences. Exemplary for animal cast, jellyfish leached up to two 100-fold more, mostly organic, nitrogen compared to all other beach wrack types. FT-ICR-MS data of solid-phase extracted DOM indicated that beach wrack releases compounds with putative mono- and oligosaccharide-, amino acid- and vitamin-type molecular formulae, which likely serve as valuable substrate for heterotrophic microorganisms. DOM from the brown seaweed Fucus sp. was more aromatic than seawater DOM and even beach wrack of terrestrial origin, probably from structural components and secondary metabolites such as phlorotannins. We conclude that DOM and nutrient release from beach wrack strongly depends on wrack type and leaching medium, may obscure molecular provenance proxies (e.g., terrestrial indices), and adds a nutritional boost to infiltrating sea- and rainwater which likely impact microbial respiration rates in the STE.

Emissions of CO2 and CH4 from Agricultural Soil with Kitchen Compost at Different Temperatures

Emissions of CO2 from the soil are mainly derived from soil microbial respiration, whereas CH4 emissions originate from anaerobic degradation of organic matter via microbial processes. Kitchen waste compost is used in the agricultural sector to improve soil quality. However, abiotic CO2 and CH4 emissions from soils amended with kitchen waste compost under aerobic conditions remain uncertain. Temperature plays an important role in organic matter decomposition in both biotic and abiotic pathways. This study aimed to evaluate biotic and abiotic emissions of CO2 and CH4 from soils receiving kitchen compost at different temperatures. Ten grams of soil amended with or without 0.1 g kitchen compost (1%) were sterilized or non-sterilized. The mixture and soil-only samples were incubated in 100-mL glass bottles at 20, 30, and 35 °C for 28 d under an aerobic condition. The results showed that CO2 and CH4 emissions increased at higher temperatures and compost application rates (p < 0.05). Emissions of CO2 mainly occurred via biotic pathways. Abiotic processes were potential pathways for CH4 generation, particularly at high temperatures of 35 °C. There was 20–24% of C in kitchen compost changed to CO2 and less than 0.1% to CH4. Our results suggest that global warming enhances abiotic CO2 and CH4 emissions and may contribute to further global warming.

E-peroxone with a novel GDE decorated with hydrophobic membrane for the degradation of pyridine: Stability, byproducts and toxicity

E-peroxone process is an emerging electrochemical oxidation process, based on ozone and the in-situ cathodic generation of H2O2, but the stability of cathode is one of the key restraining factors. In this study, we designed a multilayer gas diffusion electrode (GDE) decorated with a commercial hydrophobic membrane for the degradation of pyridine. It was found that a proper control of membrane pore sizes and hot-pressing temperature can significantly promote the GDE stability. Subsequently, key operational parameters of the constructed E-peroxone system were investigated, including the ozone concentration, current density, pH value, electrolyte type and initial concentration of pyridine. The degradation pathways were proposed according to six identified transformation products. The toxicity variation along the degradation progress was evaluated with microbial respiration tests and Toxicity Estimation Software Tool (T.E.S.T.) calculation and an efficient detoxification capacity of E-peroxone was observed. This research provides a theoretical basis and technical support for the development of highly efficient and stable E-peroxone system for the elimination of toxic organic contaminants.

Lignite reduces carbon and nitrogen loss from litter in commercial broiler housing

The loss of carbon and nitrogen from broiler litter limits nutrient recycling and is damaging to the environment. This study investigated lignite, a low-rank brown coal, as an amendment to reduce the loss of carbon and nitrogen from broiler litter over 3 consecutive grow-out cycles, November 2021 to May 2022, at a commercially operated farm in Victoria, Australia. Lignite-treated litter contained significantly more carbon and nitrogen, with an increase of 70.1 g/bird and 12.6 g/bird for carbon and nitrogen, respectively. Lignite also reduced aerobic microbial respiration, with a 46.0% reduction in CO2 flux recorded in week 7 of the study, resulting in reduced mass loss. It is expected that this is a key mechanism responsible for nutrient retention in litter following treatment with lignite. Furthermore, lignite treatment lowered litter moisture content by 7, 6 and 3 percentage points for grow-out 1, 2 and 3, respectively. These findings present lignite as a beneficial litter amendment for increasing the nutrient value of waste and reducing carbon dioxide emissions. The study highlights the potential of lignite to reduce the environmental impact of poultry production and presents an alternative use for lignite as an existing resource.

Phosphate limitation enhances malic acid production on nitrogen-rich molasses with Ustilago trichophora

BackgroundAn important step in replacing petrochemical products with sustainable, cost-effective alternatives is the use of feedstocks other than, e.g., pure glucose in the fermentative production of platform chemicals. Ustilaginaceae offer the advantages of a wide substrate spectrum and naturally produce a versatile range of value-added compounds under nitrogen limitation. A promising candidate is the dicarboxylic acid malic acid, which may be applied as an acidulant in the food industry, a chelating agent in pharmaceuticals, or in biobased polymer production. However, fermentable residue streams from the food and agricultural industry with high nitrogen content, e.g., sugar beet molasses, are unsuited for processes with Ustilaginaceae, as they result in low product yields due to high biomass and low product formation.ResultsThis study uncovers challenges in evaluating complex feedstock applicability for microbial production processes, highlighting the role of secondary substrate limitations, internal storage molecules, and incomplete assimilation of these substrates. A microliter-scale screening method with online monitoring of microbial respiration was developed using malic acid production with Ustilago trichophora on molasses as an application example. Investigation into nitrogen, phosphate, sulphate, and magnesium limitations on a defined minimal medium demonstrated successful malic acid production under nitrogen and phosphate limitation. Furthermore, a reduction of nitrogen and phosphate in the elemental composition of U. trichophora was revealed under the respective secondary substrate limitation. These adaptive changes in combination with the intricate metabolic response hinder mathematical prediction of product formation and make the presented screening methodology for complex feedstocks imperative. In the next step, the screening was transferred to a molasses-based complex medium. It was determined that the organism assimilated only 25% and 50% of the elemental nitrogen and phosphorus present in molasses, respectively. Due to the overall low content of bioavailable phosphorus in molasses, the replacement of the state-of-the-art nitrogen limitation was shown to increase malic acid production by 65%.ConclusionThe identification of phosphate as a superior secondary substrate limitation for enhanced malic acid production opens up new opportunities for the effective utilization of molasses as a more sustainable and cost-effective substrate than, e.g., pure glucose for biobased platform chemical production.

Aquatic processing enhances the loss of aged carbon from drained and burned peatlands.

Water-logged peatlands store tremendous amounts of soil carbon (C) globally, accumulating C over millennia. As peatlands become disturbed by human activity, these long-term C stores are getting destabilized and ultimately released as greenhouse gases that may exacerbate climate change. Oxidation of the dissolved organic carbon (DOC) mobilized from disturbed soils to streams and canals may be one avenue for the transfer of previously stored, millennia-aged C to the atmosphere. However, it remains unknown whether aged peat-derived DOC undergoes oxidation to carbon dioxide (CO2) following disturbance. Here, we use a new approach to measure the radiocarbon content of CO2 produced from the oxidation of DOC in canals overlying peatland soils that have undergone widespread disturbance in Indonesia. This work shows for the first time that aged DOC mobilized from drained and burned peatland soils is susceptible to oxidation by both microbial respiration and photomineralization over aquatic travel times for DOC. The bulk radiocarbon age of CO2 produced during canal oxidation ranged from modern to ~1300 years before present. These ages for CO2 were most strongly influenced by canal water depth, which was proportional to the water table level where DOC is mobilized from disturbed soils to canals. Canal microbes preferentially respired older or younger organic C pools to CO2, and this may have been facilitated by the use of a small particulate organic C pool over the dissolved pool. Given that high densities of canals are generally associated with lower water tables and higher fire risk, our findings suggest that peatland areas with high canal density may be a hotspot for the loss of aged C on the landscape. Taken together, the results of this study show how and why aquatic processing of organic C on the landscape can enhance the transfer of long-term peat C stores to the atmosphere following disturbance.

Biological Assessment of Green Waste and Dredged Sediment Co-Composting for Nursery Plant Cultivation

Co-composting efficiently reclaims dredged sediments (S) and green waste (GW), creating stable products for agricultural applications. However, the use of S-GW co-composts can be limited by legislative thresholds, especially for co-composts with a high S percentage. The evaluation of S-GW co-compost stability by biological assessment can allow for a better understanding of S and GW recycling, as well as the S-GW co-compost application. For this purpose, the microbial biomass, composition, respiration, and eco-enzyme stoichiometry (EST) were assessed, coupled with chemical analysis, in the co-composting of S and GW in different ratios. The Photinia x fraseri and Viburnum tinus L. growth was monitored in a plant trial, comparing the studied co-composts with a control substrate. The EST approach was applied as an indicator of the co-composting stability during the process and after the plant cultivation. The chemical and biological parameters confirmed the suitability of co-composting in the GW and S recovery and the EST approach highlighted a better stability for the 3S:1GW co-compost at the end of the process and after plant cultivation. Viburnum tinus showed a similar growth to the control, while Photinia x fraseri resulted in being more sensitive to the co-compost. The biological assessments were good indicators of the S-GW compost stability for their application in crop cultivation.

A Geochemical Mechanism for &gt;10 m Apparent Downward Offsets of Magnetic Reversals Inferred From Comparison of Two Scotia Sea Drill Sites

AbstractWe document an apparent downward displacement of the Matuyama‐Brunhes magnetic reversal by ∼20 m at Scotia Sea International Ocean Discovery Program Site U1538 (Pirie Basin) by comparison with the well‐defined paleomagnetic record at nearby Site U1537 (Dove Basin). Detailed stratigraphic correlation between the two sites is possible due to similar lithologic variations. However, the two sites have distinctly different porewater geochemistry. Notably, Site U1538 indicates a greater demand for electron acceptors to oxidize organic carbon and Fe2+ enrichment below the depth of SO42− depletion. Magnetic parameters indicate enrichment of an authigenic magnetic mineral with strong remanence properties around the depth of SO42− depletion (∼46 m at Site U1538) relative to magnetic parameters at correlative depths at Site U1537. Fe2+ enrichment below the depth of SO42− depletion is not predicted based on the energetically favorable order of electron acceptors for microbial respiration but is documented here and in other depositional settings. This indicates Fe2+ production exceeds the production of H2S by SO42− reduction, providing a geochemical environment that favors the production and preservation of ferrimagnetic remanence‐bearing iron sulfides over paramagnetic pyrite and, thus, a mechanism for deep chemical remanent magnetization acquisition at depths of tens of meters. The influence of authigenic ferrimagnetic iron sulfides on paleomagnetic signals can be difficult to demonstrate with magnetic properties alone; therefore, this finding has implications for evaluating the fidelity of magnetostratigraphic records with complementary geochemical data. Such situations should be considered in other depositional environments with similar porewater Fe2+ accumulation below the SO42− reduction depth.

Tomato yield and soil chemical properties influenced by low–molecular–weight organic acids in calcareous soil

&lt;p&gt;Calcareous soils have restrictive characteristics that limit and pose a challenge for crop production; in this environment, plants can exude low-molecular-weight organic acids (LMWOAs). This study aimed to verify the influence of exogenously applied LMWOAs in calcareous soils on tomato yield and the chemical characteristics of soil and leachate. &lt;em&gt;Solanum lycopersicum&lt;/em&gt; L. seedlings were grown in pots containing calcareous soil in a greenhouse, fertilized by drip irrigation with Steiner nutrient solution in which the treatments 0.1 mM citric acid (CA), 0.1 mM oxalic acid (OA), 0.01 mM salicylic acid (SA) and a control without LMWOAs (T0) were prepared, applied during the whole growth cycle. The experiment was repeated four times, with twenty replicates per treatment, under a completely randomized design. The yield per plant was quantified, while pH and microbial respiration (RMS) were measured in the soil. The pH, electrical conductivity (EC), oxidation-reduction potential (ORP), carbonate (CO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;2–&lt;/sup&gt;), and bicarbonate (HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt;) contents were quantified in the leachates. SA application reduced the soil pH (8.75). SA and CA improved the fruit yield per plant by 11% and 33%, respectively (p &amp;lt; 0.05). CA induced a 1.7% reduction in leachate pH (p &amp;lt; 0.05) and a 15.9% increase in HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt; content (p &amp;lt; 0.05). SA decreased EC and CO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;2–&lt;/sup&gt; concentrations by 8.9 and 23.1% (p &amp;lt; 0.05), but increased HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt; content by 23.1 % (p &amp;lt; 0.05). The use of LMWOAs as a strategy in the management of calcareous soils can promote favorable conditions for tomato yield per plant.&lt;/p&gt;

Compost and Mineral Fertilizer Application Affects Soil Microbial Activity and Nutrient Mineralization in an Ultisol

ABSTRACT Organic additions help improve soil biophysical qualities, but they are insufficient to supply nutrient demand and could result in unintentional nutrient immobilization in soils, particularly soils with low fertility status. A 16-week laboratory incubation study was conducted to determine how the method of application of compost and inorganic fertilizers influence microbial respiration, nitrogen (N), and phosphorus (P) mineralization. Topsoil (500 g, 0–15 cm) was amended with compost (0, 5, and 10 g kg−1) and either inorganic N (50 kg N ha−1) or P (30 kg P ha−1). Two soil amendment strategies, applying compost and inorganic fertilizer separately to opposite sides of the soil using a divider and mixing them evenly throughout the soil, were compared for their effects on microbial activity and nutrient mineralization. The cumulative amounts of carbon dioxide (CO2) evolved were measured fortnightly using the static CO2 absorption method and inorganic N and P mineralization. N mineralization was unaffected by the method of compost and inorganic fertilizer application (p > .05), while at the end of day 42, available P in separate applications of compost and mineral N fertilizers was 33% greater than combined applications. Compost and inorganic P fertilizer had favorable N priming effects, but compost and inorganic N had negative effects. The different N priming effects of compost and inorganic N and P fertilizers may be attributable to microbial nutrient demand. The data suggest that composting with conventional fertilizers may change microbial nutrient demand and crop nutrient availability.

Biodegradation of poly-3-hydroxybutyrate after soil inoculation with microbial consortium: Soil microbiome and plant responses to the changed environment

Biodegradable plastics play a vital role in addressing global plastics disposal challenges. Poly-3-hydroxybutyrate (P3HB) is a biodegradable bacterial intracellular storage polymer with substantial usage potential in agriculture. Poly-3-hydroxybutyrate and its degradation products are non-toxic; however, previous studies suggest that P3HB biodegradation negatively affects plant growth because the microorganisms compete with plants for nutrients. One possible solution to this issue could be inoculating soil with a consortium of plant growth-promoting and N-fixing microorganisms. To test this hypothesis, we conducted a pot experiment using lettuce (Lactuca sativa L. var. capitata L.) grown in soil amended with two doses (1 % and 5 % w/w) of P3HB and microbial inoculant (MI). We tested five experimental variations: P3HB 1 %, P3HB 1 % + MI, P3HB 5 %, P3HB 5 % + MI, and MI, to assess the impact of added microorganisms on plant growth and P3HB biodegradation. The efficient P3HB degradation, which was directly dependent on the amount of bioplastics added, was coupled with the preferential utilization of P3HB as a carbon (C) source. Due to the increased demand for nutrients in P3HB-amended soil by microbial degraders, respiration and enzyme activities were enhanced. This indicated an increased mineralisation of C as well as nitrogen (N), sulphur (S), and phosphorus (P). Microbial inoculation introduced specific bacterial taxa that further improved degradation efficiency and nutrient turnover (N, S, and P) in P3HB-amended soil. Notably, soil acidification related to P3HB was not the primary factor affecting plant growth inhibition. However, despite plant growth-promoting rhizobacteria and N2-fixing microorganisms originating from MI, plant biomass yield remained limited, suggesting that these microorganisms were not entirely successful in mitigating the growth inhibition caused by P3HB.

Fungal composition associated with host tree identity mediates nutrient addition effects on wood microbial respiration.

Fungi are key decomposers of deadwood, but the impact of anthropogenic changes in nutrients and temperature on fungal community and its consequences for wood microbial respiration are not well understood. Here, we examined how nitrogen and phosphorus additions (field experiment) and warming (laboratory experiment) together influence fungal composition and microbial respiration from decomposing wood of angiosperms and gymnosperms in a subtropical forest. Nutrient additions significantly increased wood microbial respiration via fungal composition, but effects varied with nutrient types and taxonomic groups. Specifically, phosphorus addition significantly increased wood microbial respiration (65%) through decreased acid phosphatase activity and increased abundance of fast-decaying fungi (e.g., white rot), while nitrogen addition marginally increased it (30%). Phosphorus addition caused a greater increase in microbial respiration in gymnosperms than in angiosperms (83.3% vs. 46.9%), which was associated with an increase in Basidiomycota:Ascomycota operational taxonomic unit abundance in gymnosperms but a decrease in angiosperms. The temperature dependencies of microbial respiration were remarkably constant across nutrient levels, consistent with metabolic scaling theory hypotheses. This is because there was no significant interaction between temperature and wood phosphorus availability or fungal composition, or the interaction among the three factors. Our results highlight the key role of tree identity in regulating nutrient response of wood microbial respiration through controlling fungal composition. Given that the range of angiosperm species may expand under climate warming and forest management, our data suggest that expansion will decrease nutrient effects on forest carbon cycling in forests previously dominated by gymnosperm species.