Addition Of Organic Matter Research Articles

Soil microbial activity improved while intensifying vegetable production by use of plant-based fertilisers, cover crops and reduced tillage

Frequent soil cultivation in intensive vegetable production is detrimental to soil quality. Combining several sustainable management techniques, such as increasing organic matter input and plant diversity, and reducing soil cultivation, could benefit biological soil quality. We designed a crop rotation with a system approach, combining plant-based fertilisers, cover crops and reduced tillage, while growing more crops (sustainable intensification, SI). We compared this approach to common practice (CP), where animal manure fertilisers, no cover crops and ploughing were employed in a standard organic crop rotation on sandy loam in Denmark. Treatments were initiated in 2017, and two sets of contrasts, each comparing across cropping systems and specific crop rotations, were investigated in the second and third year of implementation: lettuce-leek double-cropping (SI) vs. leek sole-cropping (CP), and onion-lettuce intercropping (SI) vs. lettuce-lettuce double-cropping (CP). Soil microbial activity was assessed by β-glucosidase and dehydrogenase activity and potential N mineralisation over 28-days incubation. Root growth was investigated using minirhizotrons. The risk of N leaching was estimated from soil mineral N content at 0–2.5 m depth in autumn. β-glucosidase and dehydrogenase activity increased by 27–107% under SI compared to CP in the third year after implementation. SI improved potential N mineralisation by 12–52 kg N ha−1 before and after spring fertilisation both years. Increased soil fertility under SI contributed to 1.3 to 2.3 times higher plant N uptake (except for lettuce/onion first year), and 1 to 2.7 times higher marketable yields, but only minimally affected root depth. Despite higher N fertilisation, risk of N leaching did not rise under SI. The beneficial effects of SI were attributed to the combination of higher N fertilisation (53–144 kg N ha−1 more) as organic matter addition (2–3 Mg carbon ha−1 more), growing cover crops, and reducing soil tillage. Combining these techniques is promising for improving soil microbial activity in a sustainable way for highly intensive organic vegetable production.

Elemental Sulfur and Organic Matter Amendment Drive Alkaline pH Neutralization and Mineral Weathering in Iron Ore Tailings Through Inducing Sulfur Oxidizing Bacteria.

Mineral weathering and alkaline pH neutralization are prerequisites to the ecoengineering of alkaline Fe-ore tailings into soil-like growth media (i.e., Technosols). These processes can be accelerated by the growth and physiological functions of tolerant sulfur oxidizing bacteria (SOB) in tailings. The present study characterized an indigenous SOB community enriched in the tailings, in response to the addition of elemental sulfur (S0) and organic matter (OM), as well as resultant S0oxidation, pH neutralization, and mineral weathering in a glasshouse experiment. The addition of S0 was found to have stimulated the growth of indigenous SOB, such as acidophilic Alicyclobacillaceae, Bacillaceae, and Hydrogenophilaceae in tailings. The OM amendment favored the growth of heterotrophic/mixotrophic SOB (e.g., class Alphaproteobacteria and Gammaproteobacteria). The resultant S0 oxidation neutralized the alkaline pH and enhanced the weathering of biotite-like minerals and formation of secondary minerals, such as ferrihydrite- and jarosite-like minerals. The improved physicochemical properties and secondary mineral formation facilitated organo-mineral associations that are critical to soil aggregate formation. From these findings, co-amendments of S0 and plant biomass (OM) can be applied to enhance the abundance of the indigenous SOB community in tailings and accelerate mineral weathering and geochemical changes for eco-engineered soil formation, as a sustainable option for rehabilitation of Fe ore tailings.

Soil organic carbon induces a decrease in erodibility of black soil with loess parent materials in northeast China

Abstract Although black soil in northeast China undergoes severe erosion, the contribution of parent materials, mainly Quaternary loess and non-loess sediments, to soil erodibility remains unclear. Considering the inheritance of ferromagnetic materials by parent materials, changes in magnetic parameters can successfully determine soil erodibility on a regional scale with a close climatic background. Here, we analysed the magnetic indicators of 142 samples from the black soil horizon formed on loess and non-loess sediments, covering areas of severe and slight erosion in the region to determine the effects of parent materials on the erodibility of black soil in northeast China. Both low-frequency magnetic susceptibility and frequency magnetic susceptibility (χfd) were proportional to the decrease in erosion rate due to erosion-induced leaching of ferromagnetic materials, and the change in χfd was narrow for black soil with loess parent materials, corresponding to relatively low soil erodibility. Compared with loess, the addition of soil organic matter could stabilise soils against erosion, thereby inducing a decrease in the erodibility of black soil formed on loess. Additionally, sustainable soil management policies to protect black soil from further erosion are necessary and urgent under the pressure of maintaining high grain yields and preventing erosion in northeast China.

Growth and Yield of Meranti Tomatoes (Lycopercium pipinelifoliu) Effect of Chrysanthemum Flower Waste Organic Fertilizer (Chrysanthemum morifolium) and Mutiara NPK Anorganic

The purpose of this study was to obtain the right dose of organic fertilizer combination of chrysanthemum flower waste and NPK Mutiara inorganic fertilizer to support the growth and efficiency of nutrient absorption levels of tomato meranti plants. The method used in this study was a complete randomized design (RAK) with 4 treatments and each treatment was repeated 6 time. The treatment made is P0: 500 kg ha-1 NPK Mutiara (100% NPK); P1: Dose of Organic Fertilizer Chrysanthemum Waste 15 Tons ha-1 + 25 % NPK; P2: Dose of Organic Fertilizer Chrysanthemum Waste 10 Tons ha-1 + 50 % NPK; P3: Dose of Organic Fertilizer Chrysanthemum Waste 5 Tons ha-1 + 75 % NPK. With observation parameters, namely plant height, number of leaves, leaf area, dry weight of upper plants, dry weight of lower plants, total dry weight of plants, leaf area index, net assimilation rate, and plant growth rate. The results showed that with the addition of organic matter of chrysanthemum waste fertilizer combined with NPK inorganic fertilizer was able to support the growth of meranti tomato plants in the vegetative phase of plants with a combined dose of chrysanthemum fertilizer 5 tons Ha-1 + 75% NPK showed the best results on plant height parameters, number of leaves and dry weight of plants.

Pottery vessels and technology of “colouring materials” in the central-western Mediterranean (Sardinia, Italy) during the Middle Neolithic: An interdisciplinary approach combining use-wear and chemical-physical analysis

Despite the wide occurrence of colour deposits adhering to the surfaces of several artefacts (specifically, pottery and lithic tools) in Early and Middle Neolithic sites of the Western Mediterranean regions, the chaîne opératoire of colouring materials has not been frequently addressed by systematic techno-functional studies. Particularly, the relationship between pottery function and coloured contents is generally overlooked.In this paper, the use of colouring materials by Middle Neolithic (4500–4000 cal BC) societies in Sardinia (Italy) is investigated, focusing on the archaeological findings from the open-air settlement of Su Mulinu Mannu-Terralba (OR). The aims are to identify the kind of materials, to provide a first assessment of the production methods and to evaluate the role assigned to pottery vessels in processing, handling, and using colouring materials. For these purposes, we apply an interdisciplinary approach, combining analysis of lithic artefacts, use-wear analysis of pottery, archaeometric identification of the chemical and mineralogical composition of geomaterials and colour deposits on artefacts by PXRD, ATR-FTIR and SEM-EDS analyses, and biomolecular analysis of organic residues from pottery by GC-FID and GC–MS.This study reveals the use of haematite-rich ochre as the exclusive red colour-producing geomaterial, processed in situ with basalt macro-tools. Use-wear associated with ochre deposits on pottery vessels points to the selection of some bowls and jars, respectively for processing and storing ochre as the single content or, possibly, as an ingredient of composite products. However, based on our data, the addition of organic materials to ochre is not definitely demonstrated. Beside the preparation of pigments, the occurrence of ochre as content in pottery vessels could be related to a broader range of purposes, encompassing both the technical and the symbolic realm. Overall, these results provide insights both on the technology of “colouring materials” and the use of pottery in the practices of Middle Neolithic groups.

How Can Plants Help Restore Degraded Tropical Soils?

In the tropics, anthropogenic activities can lead to water and wind erosion, a loss of biodiversity, and a reduction in sequestered carbon, fertility, and organic matter content in the soils concerned, potentially resulting in their degradation. This study therefore aims to identify the mechanisms used by plant species to restore degraded tropical soils and plant species characteristics that are best suited to achieve this through a critical scoping review of the peer-reviewed literature. Soil restoration leads to the re-establishment of ecosystem services and an increase in soil production potential, the regeneration of biodiversity, the stopping of organic matter losses, and the creation of favorable conditions for carbon sequestration and nitrogen fixation. The choice of appropriate plant species depends on the restoration objectives to be achieved. Five key mechanisms by which plant species contribute to restore degraded tropical soils include: (1) nitrogen fixation, (2) carbon sequestration, (3) organic matter addition, (4) structure stabilization, and (5) erosion control. The main characteristics of plant species and vegetation involved in these mechanisms are (a) the capacity to form symbiotic associations with N-fixing bacteria and mycorrhizae, (b) the production of abundant root biomass releasing litter and exudates, (c) roots having a high length density, branching intensity, and depth distribution, (d) the production of an abundant and easily decomposed above ground litter, (e) the production of a vast canopy, and (f) the presence of different vegetation strata. Targeting these characteristics will contribute to acting on several mechanisms simultaneously, which will increase the chance of success in tropical soil restoration.

Effects of Different Exogenous Organic Substrates on Soil Carbon and Nitrogen Mineralization and Their Priming Effects

The input of exogenous organic matter could affect the transformation of soil carbon (C) and nitrogen (N), and their C- and N-priming effects (CPE and NPE) play a key role in the balance of soil C and N. However, little is known about how the interaction effect between straw and straw biochar regulates CPE and NPE. Therefore, we conducted a 90-day incubation experiment, which included five treatments: no straw and straw biochar (CK), 1.5% straw (S), 0.53% straw biochar (B), 1.5% straw + 0.53% straw biochar (SB), and 1.5% straw + 1.06% straw biochar (SB1). Our findings revealed that cumulative soil CO2 emissions were increased by 95.52–216.53% through the short-term input of exogenous organic matter input; however, this trend gradually weakened with decreasing dissolved organic C (DOC) content. The cumulative NPE generated by the addition of exogenous organic matter was much smaller than the cumulative CPE. Under the B and S treatments, the cumulative CPE and NPE were negative throughout the entire incubation period. The SB treatment remarkably boosted the microbial biomass nitrogen (MBN) content; however, the SB1 treatment was more effective in inhibiting soil C and N mineralization processes than SB treatment. Moreover, the cumulative CPE and NPE were mainly regulated by N. We conclude that the combination of straw and straw biochar preferentially stimulated soil C mineralization, but that this effect decreased with time, which may be due to the consumption of labile DOC caused by the initial positive CPE, while soil N mineralization had a lag effect.

Soil Fertility Status as Influenced by Slope Gradient and Land Use Types in Southern Ethiopia

Understanding the effects of land use types and slope gradients on the physicochemical properties of soil is essential for sustainable soil management. Therefore, this study was conducted at the Azit subwatershed of Gedebano Gutazer Welene Woreda, Southern Ethiopia, with the objectives to evaluate the effect of land use types, examine the interaction of land use and slope gradient, and evaluate the effect of slope gradient on selected soil physicochemical properties. A total of 27 soil samples using a simple random sampling technique with randomized complete block design from 3 land use types (cultivated, eucalyptus, and grazing lands) ×3 slope gradients (upper 10–15%, middle 5–10%, and lower 2–5% slopes) ×3 replications and depth (0–20 cm) were collected. Results indicated that most of the physicochemical properties of soils were significantly ( P < 0.01 ) affected by land use and slope gradient. Silt and sand particles did not vary significantly ( P > 0.05 ) among the land use types. The interaction effect of land use and slope was not significant ( P > 0.05 ) for most of the soil properties except for organic carbon (OC). Results of data analysis also showed that soil fertility was low under cultivated and eucalyptus lands coupled with the upper slope gradient. Therefore, based on the study’s findings, it can be recommended that integrated soil fertility management practices, such as the addition of soil organic matter and appropriate use of inorganic fertilizers, need to be implemented to restore the lost soil fertility status on the cultivated land and ultimately increase agricultural productivity on a sustainable basis. Eucalyptus plantings should also gradually be replaced by those that assist the soil in restoring its fertility.

Descriptive analyses of bacterial communities in marine sediment microcosms spiked with fish wastes, emamectin benzoate, and oxytetracycline

In marine sediments surrounding salmon aquaculture sites, organic matter (OM) enrichment has been shown to influence resident bacterial community composition; however, additional effects on these communities due to combined use of the sea-lice therapeutant emamectin benzoate (EMB) and the widely used antibiotic oxytetracycline (OTC) are unknown. Here, we use sediment microcosms to assess the influence of OM, EMB, and OTC on benthic bacterial communities. Microcosms consisted of mud or sand sediments enriched with OM (fish and feed wastes) and spiked with EMB and OTC at environmentally-relevant concentrations. Samples were collected from initial matrices at the initiation of the trial and after 110 days for 16 S rRNA gene sequencing of the V3-V4 region and microbiome profiling. The addition of OM in both mud and sand sediments reduced alpha diversities; for example, an average of 1106 amplicon sequence variants (ASVs) were detected in mud with no OM addition, while only 729 and 596 ASVs were detected in mud with low OM and high OM, respectively. Sediments enriched with OM had higher relative abundances of Spirochaetota, Firmicutes, and Bacteroidota. For instance, Spirochaetota were detected in sediments with no OM with a relative abundance range of 0.01–1.2%, while in sediments enriched with OM relative abundance varied from 0.16% to 26.1%. In contrast, the addition of EMB (60 ng/g) or OTC (150 ng/g) did not result in distinct taxonomic shifts in the bacterial communities compared to un-spiked sediments during the timeline of this experiment. EMB and OTC concentrations may have been below effective inhibitor concentrations for taxa in these communities; further work should explore gene content and the presence of antibiotic resistance genes (ARGs) in sediment-dwelling bacteria.

The Influence of Atmospheric Pressure and Organic Loading on the Sustainability of Simultaneous Nitrification and Denitrification

In high-altitude regions, a diminished atmospheric oxygen content significantly impairs the aeration efficiency of municipal wastewater, posing a challenge to sustainable wastewater management. Consequently, conventional biological wastewater treatment methods necessitate elevated energy consumption in high-altitude areas, rendering them economically and environmentally unsustainable. The simultaneous nitrification and denitrification (SND) process, owing to its minimal oxygen requirements, emerges as a promising and sustainable solution in low-pressure environments. Additionally, owing to the unique lifestyle and natural conditions in plateau regions, the organic loading in municipal wastewater is often low. To comprehensively assess the impact of low pressure and organic loading on the SND process, three laboratory-scale reactors were implemented. This study revealed that low pressure and the introduction of organic matter enhanced both nitrogen removal performance and SND efficiency. The sludge volume index decreased by 93.5%, indicating a substantial improvement in the microbial aggregation ability and the formation of a more favorable SND sludge structure. 16S rRNA sequencing results demonstrated alterations in the microbial community structure due to low pressure and the addition of organic matter, leading to a substantial increase in the abundance of nitrifying and denitrifying bacteria. Furthermore, the prediction results of functional genes indicated the upregulation of genes related to the nitrification and denitrification processes with decreasing pressure and the addition of organic matter. This enhancement underlines the improved microbial nitrogen removal function. This study underscores the positive influence of low pressure and organic loading on the SND system, thereby substantially enhancing the economic and environmental sustainability of the SND process in plateau regions.

Biochar and Organic Fertilizer Co-Application Enhances Soil Carbon Priming, Increasing CO2 Fluxes in Two Contrasting Arable Soils.

Biochar soil amendments, along with non-tillage agriculture, are often proposed as a strategy for carbon sequestration. It is still questionable how the quality of biochar might influence the priming effect on soil organic matter and whether the addition of unprocessed organic amendments will affect biochar stability. In the study, six different biochars and three exogenous organic matter sources were added to two distinct arable soils. CO2 emission was monitored for 100 days of incubation and CO2 flux was estimated. Results showed that biochar increased soil CO2 fluxes. The highest peaks, up to 162 µg C-CO2 h-1 100 g-1, were recorded in treatments with food waste biochars, suggesting that they serve as a source of easily available carbon to soil microbes. Co-application of raw organic materials (manure and fresh clover biomass) enhanced CO2 emission and carbon losses, especially in sandy soil, where 0.85-1.1% of total carbon was lost in the short-term experiment. Biochar properties and content of labile C can stimulate CO2 emission; however, in a long-term period, this contribution is negligible. The findings of our study showed that more attention should be paid to priming effects caused by the addition of exogenous organic matter when applied to biochar-amended soils.

Crop rotation and inoculation increase soil bradyrhizobia population, soybean grain yields, and profitability.

Crop rotation and rhizobial inoculation are strategies to increase yield by means of organic matter addition and modulation of microbial diversity. However, the extent to which these agricultural practices change soil Bradyrhizobium populations, soybean grain yield, and economic benefits to farmers is unclear. Thus, this study aimed to evaluate the interaction between crop rotation and inoculation of soybean (Glycine max) cultivated in two contrasting soils (clayey and sandy soil) on biological nitrogen fixation components, grain yields, and profits. Field experiments with a three-year crop rotation system were carried out to compare effects of inoculation and crop rotations on soil chemical attributes, bradyrhizobia most probable number (MPN) and diversity, soybean nodulation, grain yield, and economic indicators of inoculation in different crop rotations. The crop rotation did not affect the soil MPN cells of bradyrhizobia, but the inoculation and the soil sampling time did, ranging from 3.61-4.42 to 4.40-4.82 in the sandy soil, while in the clayey soil they were from 5.19-6.34 to 6.61-7.14 in Log10 per g of soil with higher population after harvest of summer crops. In the clayey soil, crop rotation influenced soybean nodulation. The grain yield of inoculated soybean in the clayey soil was higher than that in the sandy soil. Soybean inoculation with Bradyrhizobium spp. increased the profitability of agricultural production systems by up to 45% in clayey soil and up to 7% in sandy soil.

Organic matter addition promotes Cd immobilization in alkaline paddy soils

Straw incorporation into the soil is a common agricultural practice, but its effect on soil cadmium (Cd) mobility is not well understood. We added 0–20 g kg−1 organic matters (OMs) with different C/N ratios to three spiked alkaline paddy soils that contained a realistically low concentration of total Cd (0.94 mg kg−1), and then investigated soil Cd solubility in alternate watering conditions. As current physical and chemical methods have difficulties in accurately determining the distribution and speciation of Cd in soil at a low concentration, we measured multiple soil properties to identify key factors regulating dissolved Cd concentration. For all three soils, pH and dissolved Cd concentration both decreased after flooding and increased after subsequent drying. OM addition significantly reduced soil Cd solubility at both flooding and drying stages. Random forest and linear regressions further confirmed that soil total organic carbon, rather than pH, dissolved organic carbon, or total inorganic carbon as previously suggested, was the primary predictor of Cd solubility. OMs with different C/N ratios had similar effects on soil Cd solubility, whereas the effect of OM addition rate depended on soil type. The results demonstrated the potential of straw incorporation for the remediation of Cd-contaminated alkaline paddy soils, through mechanisms that differ from those reported for acid soils.Graphical

Submersed Macrophyte Density Regulates Aquatic Greenhouse Gas Emissions

AbstractShallow freshwater ecosystems emit large amounts of greenhouse gases (GHGs), such as carbon dioxide (CO2) and methane (CH4), yet emissions are highly variable. The role that aquatic macrophytes play in regulating aquatic GHG emissions is uncertain despite their ability to dominate shallow waterbodies. Here, we studied the effects of submersed macrophyte (Ceratophyllum demersum) density on CO2 and CH4 concentrations and fluxes. We conducted a 61‐days experiment using mesocosms containing one of the following C. demersum density treatments: 0, 10, 20, or 30 individual shoots (n = 3). We found that high density C. demersum had the highest CO2 and CH4 surface water concentrations and emissions while there was no significant difference in CH4 in the low and medium densities and no plant control. The high density treatment lost biomass over the course of the experiment, indicating die‐off and additions of organic matter to the sediment. High organic matter loading and low dissolved oxygen likely stimulated GHG production in the high density treatment. Our results emphasize that submersed macrophyte density and periods of growth and dieback are important in regulating GHG emissions, which may help explain why shallow waterbodies are high yet variable sources of GHGs to the atmosphere.

Pertumbuhan Kacang Hijau (Vigna radiata L.) Melalui Aplikasi Biochar Pada Berbagai C-Organik Tanah

Green beans are one of the most popular food crops in Indonesia, many problems have resulted in a decrease in mung bean production so that efforts are needed to improve the growth and production of mung bean plants, one of which is by improving soil fertility through the addition of organic matter, namely the use of biochar and organic fertilizer goat manure. The purpose of this study was to analyze the optimal dose in the interaction of biochar and organic matter levels for the growth of mung bean plants. This research was conducted at JL. Kaliurang, Karangrejo village, Sumbersari District, Jember Regency from January to March 2023. The experiment used a Split Plot based on Group Random Design (RAK) consisting of two factors, the first factor was Organic matter (BO) with a level of 0%, 3%, 4% and the second factor was biochar with doses of 5 tons / ha, 10 tons / ha, 15 tons / ha and 20 tons / ha and each treatment was repeated 3 times. The results showed that the application of biochar 20 tons / ha most affected the parameters of plant height 42 HST of 49.38 cm and leaf length with a maximum average of 14.01 cm. In general, the addition of 3% organic matter and the application of biochar of 15 tons/ha and 20 tons/ha became the highest values for all parameter.

Comparative Study of Individual and Combined Application of Humic Acid, Wood Vinegar, and Biochar on Soil Zn Chemical Fractions and Its Uptake by Sour Orange (Citrus aurantium L.) Seedlings

ABSTRACT The addition of organic materials in arid and semi-arid regions not only improves the physicochemical and biological characteristics of the soil but also increases plant growth. In this study, the effect of individual and combined application of humic acid (HA) (150 mg kg−1 soil), wood vinegar (WV) (75-fold dilution), and biochars (corn straw biochar (CSB) and cotton residue biochar (CRB) each at 2% wt.) on the soil Zn chemical fractions and its uptake by Sour Orange (Citrus aurantium L.) seedlings were investigated in a calcareous soil. The results showed the CRB was more effective in increasing the Zn concentration in fractions with high bioavailability (soluble+exchangeable (WsEx) and organic (OM) forms) than the CSB. This may be due to its higher organic carbon content (74%) and electrical conductivity (3.52 dS m−1) than those for the CSB. There was no significant difference between HA and WV in terms of the effect on soil Zn chemical fractions. The CRB+WV and CRB+HA were the best treatments for enhancing the soil Zn bioavailability. The greatest increase in the shoot dry matter yield (2.5-fold) and Zn uptake (29%) was associated with the combined treatment of CRB+HA compared to the control. Furthermore, the shoot dry matter yield of Sour Orange seedlings had a significant and positive correlation with the Zn-WsEx fraction and Zn uptake. It could be concluded that among the treatments, the combined application of CRB+HA was the best in enhancing soil Zn bioavailability, Zn uptake and shoot dry matter yield of Sour Orange seedlings in the calcareous soil.

Effect of Enhanced Organic Material Addition during Reductive Soil Disinfestation on Disease Resistance, Yield Increase, and Microbial Community in Flue-Cured Tobacco

The addition of organic materials is pivotal for the efficacy of reductive soil disinfestation (RSD). However, data on the influence of varying amounts of organic matter during RSD on soil-borne disease mitigation, yield increase, and rhizosphere microecological health in the current flue-cured tobacco season remain limited. This study analyzed various organic material addition rates (CK, G0.8, G1.0, and G1.2) at two experimental sites (K and Y). The results indicated that increasing the application of organic material improved the soil physicochemical properties (pH, AN, AP, AK, OM, and C/N), mitigated the severity of black shank and Fusarium root rot, and amplified the tobacco yield. The K/YG1.2 treatment significantly reduced the Shannon and Sobs fungal indices across both sites, and enhanced the relative abundance of the bacteria Actinobacteria, Chloroflexi, Firmicutes, and Acidobacteriota, while decreasing the relative abundance of Ascomycota. The bacterial genera were predominantly represented by Sphingomonas and Bacillus, whereas the fungal genera were represented by Saitozyma, Mortierella, and Fusarium. The addition of organic materials during RSD substantially decreased the relative abundance of Mortierella and Fusarium. Using FUNGGuild and Tax4Fun to evaluate the application of adding organic matter during the RSD process, we identified that rhizosphere fungi in high application rates of flue-cured tobacco were primarily saprophytic or pathogenic saprophytes, which were mainly involved in the metabolism, environmental information processing, genetic information processing, and cellular processes. The results of the two experimental sites indicate that applying 15 t·ha−1 (K/YG1.2) of solid residues such as vegetables during RSD emerges as the optimal choice. This strategy is highly effective in guaranteeing the sterilization and pest control effect of the RSD process, facilitating the reconstruction of microbial community diversity, lowering pathogen abundance, managing soil-borne diseases that are prevalent in the current flue-cured tobacco season, and leading to an increase in tobacco yield.

Peracetic acid mode-of-action on aquaculture microbes evaluated by dual-staining flow cytometry

Flow cytometry with dual staining allows an exact quantification of live and dead cells. It is a potential tool for gaining new information on the mode-of-action of disinfection chemicals and supporting efficient microbial control in recirculating aquaculture systems (RAS). Here, we used a dual-staining flow cytometry to examine the disinfection efficiency of peracetic acid (PAA) against i) the fish pathogenic bacterium Aeromonas salmonicida and ii) on microbes present in RAS. The method allowed us to accurately quantify the A. salmonicida cell response to different PAA concentrations (1, 2, and 10 mg/L) in time and to calculate the PAA concentration needed to achieve 95% cell mortality (LC95 estimates). With the high PAA dose of 10 mg/L, LC95 was reached in <15 min, while with the intermediate dose of 2 mg/L, LC95 was reached only in the end of the 60 min trial and with the low 1 mg/L dose, the disinfection efficiency remained low. The addition of soluble organic matter increased the PAA decay and decreased the disinfection efficiency. In RAS water, disinfection efficiency increased with increasing PAA concentration (from 1 to 10 mg/L) but was significantly reduced with increasing organic matter concentration (TCOD from 7.6 to 30.3 mg O2/L). The increase in the proportion of dead cells was found to be a reliable proxy for disinfection efficiency in RAS water. In the pure cell culture, both the increase in the proportion of dead cells and the fraction of reduced live cells reflected the disinfection efficiency of PAA. Altogether, the study demonstrated the PAA mode-of-action on aquaculture microbes and showed that flow cytometry with dual staining allows fast and precise examination of microbial viability under different conditions.

The effect of biogeochemical redox oscillations on arsenic release from legacy mine tailings

Exposed and un-remediated metal(loid)-bearing mine tailings are susceptible to wind and water erosion that disperses toxic elements into the surrounding environment. Compost-assisted phytostabilization has been successfully applied to legacy tailings as an inexpensive, eco-friendly, and sustainable landscape rehabilitation that provides vegetative cover and subsurface scaffolding to inhibit offsite transport of contaminant laden particles. The possibility of augmented metal(loid) mobility from subsurface redox reactions driven by irrigation and organic amendments is known and arsenic (As) is of particular concern because of its high affinity for adsorption to reducible ferric (oxyhydr)oxide surface sites. However, the biogeochemical transformation of As in mine tailings during multiple redox oscillations has not yet been addressed. In the present study, a redox-stat reactor was used to control oscillations between 7 d oxic and 7 d anoxic half-cycles over a three-month period in mine tailings with and without amendment of compost-derived organic matter (OM) solution. Aqueous and solid phase analyses during and after redox oscillations by mass spectrometry and synchrotron X-ray absorption spectroscopy revealed that soluble OM addition stimulated pyrite oxidation, which resulted in accelerated acidification and increased aqueous sulfate activity. Soluble OM in the reactor solution significantly increased mobilization of As under anoxic half-cycles primarily through reductive dissolution of ferrihydrite. Microbially-mediated As reduction was also observed in compost treatments, which increased partitioning to the aqueous phase due to the lower affinity of As(III) for complexation on ferric surface sites, e.g. ferrihydrite. Oxic half-cycles showed As repartitioned to the solid phase concurrent with precipitation of ferrihydrite and jarosite. Multiple redox oscillations increased the crystallinity of Fe minerals in the Treatment reactors with compost solution due to the reductive dissolution of ferrihydrite and precipitation of jarosite. The release of As from tailings gradually decreased after repeated redox oscillations. The high sulfate, ferrous iron, and hydronium activity promoted the precipitation of jarosite, which sequestered arsenic. Our results indicated that redox oscillations under compost-assisted phytostabilization can promote As release that diminishes over time, which should inform remediation assessment and environmental risk assessment of mine site compost-assisted phytostabilization.

Studies on natural regeneration, floristic composition, biomass, carbon density and soil properties along an altitudinal gradient in the north-western Himalayas, India

In last few decades, the carbon dioxide concentration in the atmospheric has increased due to various anthropogenic activities. Therefore to understand carbon inventories for carbon dynamics are urgently needed to reduce the increasing emissions in global temperature.Cedrus deodara (Deodar) is aesthetically, socially, culturally and economically an important tree species of the temperate region in the Himalaya. Deodar-dominated forests have a great potential for storing carbon in the form of biomass and enhancing soil fertility through the addition of organic matter. Natural regeneration is one of the major problems in pure deodar stands owing to sensitive to exposure to sun and hindrance caused by needles in seed germination and anthropogenic causes. Therefore, the present investigation was carried to assess the floristic composition, natural regeneration status, carbon stock potential and soil physicochemical properties in C. deodara forest along the altitudinal gradient (1500 to 2400 m amsl). Three forest divisions viz., Seraj, Parvati and Kullu were selected and divided into three altitudinal ranges i.e., 1500–1800 m amsl (A1), 1800–2100 m amsl (A2) and 2100–2400 m amsl (A3). The results revealed that there was a significant variation in species composition, soil characteristics, natural regeneration and carbon stock along the altitudinal gradient. C. deodara forests in lower elevation ranges were found denser and natural regeneration was recorded the maximum in A2 and the minimum in A3. Whereas, the biomass and soil physico-chemical properties varied inversely along the altitudinal gradient; however, an increasing trend was observed for carbon stock potential along the altitude.