Activity Of Soil Microflora Research Articles

Bacillus tequilensis influences metabolite production in tomato and restores soil microbial diversity during Fusarium oxysporum infection.

This study evaluates cellular damage, metabolite profiling, and defence-related gene expression in tomato plants and soil microflora during Fusarium wilt disease after treatment with B. tequilensis PBE-1. Histochemical analysis showed that PBE-1 was the primary line of defence through lignin deposition and reduced cell damage. GC-MS revealed that PBE-1 treatment ameliorated stress caused by F. oxysporum infection. PBE-1 also improved transpiration, photosynthesis, and stomatal conductance in tomato. qRT-PCR suggested that the defence-related genes FLS2, SERK, NOS, WRKYT, NHO, SAUR, and MYC2, which spread infection, were highly upregulated during F. oxysporum infection, but either downregulated or expressed normally in PBE-1 + P treated plants. This indicates that the plant not only perceives the bio-control agent as a non-pathogen entity but its presence in normal metabolism and gene expression within the host plant is maintained. The study further corroborated findings that application of PBE-1 does not cause ecological disturbances in the rhizosphere. Activity of soil microflora across four treatments, measured by Average Well Colour Development (AWCD), showed continuous increases from weeks 1 to 4 post-pathogen infection, with distinct substrate usage patterns like tannic and fumaric acids impacting microbial energy source utilization and diversity. Principal Component Analysis (PCA) and diversity indices like McIntosh, Shannon, and Simpson further illustrated significant microbial community shifts over the study period. In conclusion, our findings demonstrate that B. tequilensis PBE-1 is an ideal bio-agent for field application during Fusarium wilt disease management in tomato.

Influence of mineral fertilizer on soil microflora

The biomass of organic matter entering the soil after a particular crop affects the formation of humus, the phytosanitary state of the soil, and agricultural crops can use nutrients from plant residues much more efficiently than from mineral fertilizers. The article presents the results of many years of experiments on the study of the effect of stubble and root residues on the biological activity of soddy-podzolic soil using the application method in a field six-field crop rotation in the conditions of the Republic of Mari El. The experimental part of the work was carried out in the field on the experimental field of the Mari Research Institute of Agriculture - a branch of the Federal State Budgetary Scientific Institution FARC of the North-East according to the experience laid down in 1998. The repetition of options is three times, the location of the plots is systematic. It has been established that the activity of soil microflora mainly depends on the presence of organic matter in the soil. The highest activity of cellulose-destroying microorganisms on a natural background of fertility is observed in the second crop rotation when manure is applied for potatoes - 22.9% in the first period of exposure and 54.7% in the second period of exposure. The lowest biological activity of the soil for the first 45 days was noted in the grain-grass crop rotation (83% of cereals) - 17.7% and 43.4% - in the second period of exposure. This is due to the deficiency of organic substances due to their insufficient intake. The application of mineral fertilizers at a dose of N60P60K60 for pre-sowing cultivation significantly increases the biological activity of the soil in relation to the unfertilized background, and a rather high intensity of decomposition of flax cloth was observed in the second crop rotation - for the first 45 days - 24.9%, for 90 days - 56.8%. Correlation analysis (1998-2019) between the average value of canvas decomposition under crops for the entire growing season and the value of the hydrothermal coefficient (HTC) showed a close direct relationship, which in the first exposure period (45 days) was 0.87-0.90, in the second period of exposure - 0.86...0.89.

The effect of crop rotation on the soil biological activity

The current paper has presented the results of long-term experiments on the study of the biological activity of sod-podzolic soil by the application method in field crop rotations. The experimental part of the work was carried out on the experimental plots of the Mari Research Institute of Agriculture, a branch of the FSBSI FARC of the North-East in 1996–2020. The trials were laid down in 1996 and 1998. The trial was laid down in two factors. Factor A included such types of crop rotations as grain-grasses crop rotations (oats + clover, clover of 1 year of use, winter crops, vetch-oat mixture for grain, spring wheat, barley as a control grain crop); the first rotation of crops (annual leguminous grasses, winter crops, barley, potatoes, vetch-oat mixture for grain, spring wheat); the second rotation of crops (vetch-oat mix[1]ture for grain, spring wheat, potatoes fertilized with manure (80 t/ha), barley + clover, clover of 1 year of use, winter crops); the third rotation of crops (barley + clover, clover of 1 year of use, clover of 2 years of use, winter crops, pota[1]toes, oats). Factor B included application of mineral fertilizers: control grain crop (without fertilizers); N60P60K60. There has been established that the activity of soil microflora mainly depended on the presence of organic matter in the soil. The largest activity of cellulose-destroying microorganisms against a natural background of fertility was identified in the second rotation of crops, with the introduction 23.9% of manure for potatoes in the first period (45 days) and 54.7% in the second period (90 days) of exposure. The slightest biological activity of the soil was identified in the grain-grasses crop rotation (with 83% of grain crops); it was 17.7% in the first 45 days and 43.4% in the second period of exposure. That was caused by the deficit of organic matter. The introduction of mineral fertilizers in a dose of N60P60K60 under pre-sowing tillage significantly increased the soil biological activity in comparison to the unfertilized background, and a fairly high intensity of flax decomposition was observed in the second rotation of crops with 24.9% in 45 days and 56.8% in 90 days. Correlation analysis (1998-2019) between the mean flax decomposition under crops for the entire vegetation period and the value of the hydrothermal coefficient (HThC) showed a close direct correlation, which in the first and second periods of exposure was 0.87–0.90 and 0.86–0.89, respectively.

Investigation of biological activity of recultivated iron ore processing wastes of Abagur agglomeration and processing plant, Novokuznetsk

The problem of biotransformation of man-caused disturbed lands is of great importance for the restoration of soil fertility. The leading role in this process is played by soil microorganisms. Toxic industrial waste can make negative adjustments to the species composition of soil microflora (can cause mutation of many microorganisms, as well as the death of some of them). Under certain conditions, in the presence of harmful substances, new microorganisms can arise that decompose precisely those substances that cause soil pollution. Consequently, a new microflora appears, capable of carrying out its trophic functions on an inductive basis on industrially contaminated substrates. As a man-caused control, a mineral substrate of the tailing dump of Abagurskaya agglomeration and processing plant JSC, unfavorable for the vital activity of soil microflora, where, due to the absence of plant residues and other carbon-containing components, an extremely low level of intensity of enzymatic hydrolytic processes was used. The introduction of organic matter containing sewage sludge (WWS) into the substrate as a recultivator creates favorable conditions for the formation of a stable vegetation cover. The presence of an organic component in the mineral substrate of the iron-containing tailings waste creates favorable conditions for the vital activity of microflora. Carbon-containing compounds of technozems create a certain pool of microorganisms. The products of their vital activity create the basis for the formation of an organic-mineral substrate, favorable conditions for the growth of higher plants and the creation of a stable phytocenosis. For the induced manifestation of enzymatic activity under these extreme conditions, a considerable time is required for the bacterial forms introduced from the outside to be able to fix their presence. The maximum activity, comparable both after 1 month and after 3 months with the natural control, was noted on the experimental site with the placement of WWS as a soil conditioner. The presence of WWS and intensive accumulation of leaf litter and other plant residues contribute to the favorable development of cellulose-degrading bacteria, among which rod-shaped forms of the genus Clostridium predominate. The quantitative indicators of the enzymatic activity of technozems are close to the natural level and significantly exceed those of technogenic control.

Comparative Study of the Rhizospheric Microflora of Sunflower Cultivars Helianthus annuus (Asteráceae, Magnoliópsida) Grown on Soils with Anthropogenic Polyelemental Anomalies

In a laboratory pot experiment, two mutant cultivars of sunflower (Helianthus annuus cv. r2p2 and Helianthus annuus cv. r5n1) were grown on soils with anthropogenic polyelemental anomalies and on a background control soil, and a comparative analysis of their rhizospheric microflora was carried out. The numbers of soil bacteria, actinomycetes and micromycetes, as well as the numbers of rhizospheric microorganisms resistant to Zn2+, Pb2+, and Cu2+ ions were estimated in the rhizosphere of sunflower cultivars. Quantitative changes in the sunflower rhizospheric microboceno-ses, formed under the influence of both the plant genotype and technogenic soil pollution, were revealed. A pronounced stimulation of the rhizospheric microorganisms of all groups studied was found when plants were cultivated on the technogenically contaminated soil from PJSC Kosogorsk Metallurgical Plant. In this case, cultivar differences were observed, namely: the maximal number of bacteria and actinomycetes was revealed in the rhizosphere of H. annuus cv. r2p2, whilst the maximal number of micromycetes was revealed in the rhizosphere of H. annuus cv. r5n1. An increased number of microorganisms resistant to lead ions was revealed in the rhizosphere of H. annuus cv. r2p2. The observed changes in the structure of rhizospheric microbial communities of the sunflower cultivars manifested in the stimulation of the growth and activity of soil microflora can be in demand for phytoremediation of technogenically contaminated soil.

Pea cultivar Blauwschokker for the phytostimulation of biodiesel degradation in agricultural soil

Phytoremediation is a cost-effective and ecologically friendly process that involves the use of plants to uptake, accumulate, translocate, stabilize, or degrade pollutants. The present study was conducted to demonstrate the potential of pea (Pisum sativum L. spp. sativum) cultivar Blauwschokker to phytostimulate biodiesel degradation in an agricultural soil, considering the influence of biological remediation on selected physiological parameters of plants and the amount and activity of soil microflora. Biodiesel was spiked into soil in dose of 50 g kg−1 of dry mass soil. The results of the study showed that the rate of biodiesel degradation in the vegetated soil was higher than that occurring by natural attenuation. At the same time, biodiesel showed a positive effect on the growth, development, and activity of soil bacteria and fungi. Moreover, the obtained results showed an improvement in physiological parameters of plants, including an increase in chlorophyll a and total chlorophyll content and higher relative water content in leaves in the presence of biodiesel.

Occurrence and microbial degradation of fipronil residues in tropical highland rhizosphere soils of Kerala, India

ABSTRACTThe aim of the current study was to analyze the abundance and activity of soil microflora in response to fipronil residues, as well as conjointly to isolate and identify bacteria for the bioremediation of fipronil contaminated soils in the cardamom plantations of Idukki district, Kerala. Soil samples collected from rhizosphere areas of six completely different cardamom plantations were analyzed for fipronil residues, physicochemical properties, biochemical properties, and microbial abundance. Biodegradation studies using isolated bacteria were done both in liquid medium and in soil microcosm fortified with fipronil. Fipronil residues were detected in all sampling sites. Canonical correlation analysis revealed that the influence of fipronil on soil physicochemical properties was more pronounced than that on soil microbial properties. The presence of fipronil residues in the soil did not adversely affect bacterial abundance and activity. Two bacterial strains Staphylococcus arlettae and Bacillus thuringiensis could degrade fipronil in both liquid culture and soil. Paired sample T-test and degradation kinetic study recorded that the bacterial strain S. arlettae was more efficient (81.94%) in fipronil degradation than B. thuringiensis (65.98%). The results revealed the potential for in situ bioremediation of fipronil contaminated soil by bioaugmentation using efficient bacterial isolates.

Nitrogen Release from Slow-Release Fertilizers in Soils with Different Microbial Activities

Soil microbial activity is recognized as an important factor affecting nitrogen (N) release from slow-release fertilizers. However, studies on the effect of size and activity of soil microflora on fertilizer degradation have provided contrasting results. To date, no clear relationships exist between soil microbial activity and the release of N from slow-release fertilizers. Hence, the aim of this study was to better understand such relationships by determining the release of N from three slow-release fertilizers in soils with different microbial activities. Soils were amended with urea-formaldehyde (UF), isobutylidene diurea (IBDU), and crotonylidene diurea (CDU). Urea, a soluble fertilizer, was used as the control. Fertilized soil samples were placed in a leaching system, and the release of N was determined by measuring ammonium-N and nitrate-N concentrations in leachates during 90 d of incubation. Non-linear regression was used to fit N leaching rate to a first-order model. In all the treated soils, N was released in the order: urea (89%–100%) > IBDU (59%–94%) > UF (46%–73%) > CDU (44%–56%). At the end of incubation, N released from CDU did not differ (P > 0.05) among soils. On the contrary, UF and IBDU released significantly lower (P < 0.05) amounts of N in the soil with higher microbial activity and lower pH. The rate constant (K0) for UF was lower (P < 0.05) in the soil with lower pH. Taken together, our results indicated that soil microbial size and microbial activity had a marginal effect on fertilizer mineralization.

Biotechnology for Recultivation of Oil Polluted Soils

&lt;p&gt;All the biotechnologies intended for improvement of environmental conditions are based on the ability of microorganisms for hydrocarbon oxidizing. In the development of biotechnological approaches for soil re-cultivation the extent of soil pollution has to be taken into account. Among the advantages of a technology employing mineral nutrient substrates for enhancing the oxygenizing activity of soil microflora its cost-effectiveness is very important. When dealing with highly polluted soils, more complex methods for soil restoration are called for; however, these are much more labour-extensive and time-consuming. Experimental investigations have been performed to study the effect of oil pollutants on the ability of soil microflora to assist the destruction of hydrocarbons. Variation in the activity of indigenous soil microflora was investigated using three major groups of bacteria, &lt;em&gt;i.e. &lt;/em&gt;Heterotrophs, Actinomycetes and microfungus cultures. The presence of oil in amounts constituting up to 5% is found to stimulate the growth and oxygenizing activity of the soil biocenosis. Thus the residual oil samples were exposed into the soil microflora for a time period of 60 days and then analyzed by gas-liquid chromatography (GLC). The results obtained reveal significant changes in the molecular-mass distributions of saturated hydrocarbons C&lt;sub&gt;9&lt;/sub&gt;-C&lt;sub&gt;32&lt;/sub&gt;. An addition of stimulating nutrient substrates is found to enhance the biochemical activity of soil microorganisms. Thus a 60 days' contact with soil microflora resulted in destruction of 80–85% of the saturated oil hydrocarbons, mostly C&lt;sub&gt;9&lt;/sub&gt;-C&lt;sub&gt;15&lt;/sub&gt; and C&lt;sub&gt;20&lt;/sub&gt;-C&lt;sub&gt;31&lt;/sub&gt; compounds. However, the occurrence of 10% oil pollutants exerts an inhibiting effect on the indigenous soil microflora; therefore, only an insignificant amount of hydrocarbons undergoes degradation.&lt;/p&gt;

Regulatory ecotoxicity testing of nanomaterials – proposed modifications of OECD test guidelines based on laboratory experience with silver and titanium dioxide nanoparticles

Regulatory ecotoxicity testing of chemicals is of societal importance and a large effort is undertaken at the OECD to ensure that OECD test guidelines (TGs) for nanomaterials (NMs) are available. Significant progress to support the adaptation of selected TGs to NMs was achieved in the context of the project MARINA (http://www.marina-fp7.eu/) funded within the 7th European Framework Program. Eight OECD TGs were adapted based on the testing of at least one ion-releasing NM (Ag) and two inert NMs (TiO2). With the materials applied, two main variants of NMs (ion releasing vs. inert NMs) were addressed. As the modifications of the test guidelines refer to general test topics (e.g. test duration or measuring principle), we assume that the described approaches and modifications will be suitable for the testing of further NMs with other chemical compositions. Firm proposals for modification of protocols with scientific justification(s) are presented for the following tests: growth inhibition using the green algae Raphidocelis subcapitata (formerly: Pseudokirchneriella subcapitata; TG 201), acute toxicity with the crustacean Daphnia magna (TG 202), development toxicity with the fish Danio rerio (TG 210), reproduction of the sediment-living worm Lumbriculus variegatus (TG 225), activity of soil microflora (TGs 216, 217), and reproduction of the invertebrates (Enchytraeus crypticus, Eisenia fetida, TGs 220, 222). Additionally, test descriptions for two further test systems (root elongation of plants in hydroponic culture; test on fish cells) are presented. Ecotoxicological data obtained with the modified test guidelines for TiO2 NMs and Ag NM and detailed method descriptions are available.

Change of biological activity of soils under the influence of ameliorative loosening

Ameliorative loosening of soils improved its water-air and food regimes and intensified aerobic microorganisms with the increased levels of energetic activity. The number of aerobic cellulose decomposing bacteria in topsoil increased with respect to control group by 17.8%, while that in the subsurface layer increased by 8.8%. Intensity of linen fabric decomposition increased, on average, by 14.0–28.6% and catalase activity increased by 8.7–24.4%. Increased activity of soil microflora provides activation of soil respiration and high crop yields.

Evaluation of White yam (Dioscorea rotundata) genotypes for arbuscular mycorrhizal colonization, leaf nutrient concentrations and tuber yield under NPK fertilizer application

Yield decline in yam may not only be due to soil nutrient depletion but also to the activity of soil microflora. Arbuscular mycorrhizal (AM) symbiosis helps in plant nutrition but may be affected by the application of fertilizer. The effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on the AM colonization, leaf nutrient concentrations, and tuber yields of eleven genotypes of Dioscorea rotundata were investigated at Ibadan, Nigeria. The soil was ferric luvisol. Eleven genotypes were selected from the previously conducted screening of 75 genotypes of D. rotundata for fertilizer response. Four application rates: 0, 200, 400, and 600 kg ha−1 of NPK 15-15-15 were applied in a split plot design with four replications. Fertilizer rate was the main plot and variety was the sub plot. Percentage AM colonization was significantly reduced at 600 kg ha−1 but not at lower rates when compared to zero rate and it was negatively correlated with leaf N, P, and zinc (Zn) concentrations. Leaf N concentrations were significantly increased at 200 kg ha−1 in five genotypes and at 600 kg ha−1 in two genotypes compared to zero application. Leaf P and K concentrations were decreased with the application of fertilizer in most of the genotypes. The NPK fertilizer of 15-15-15 at the rate of 200–400 kg ha−1 gave yield response in eight genotypes of D. rotundata, with minimal or no effect on their AM colonization when compared to zero application. Long term study on the effect of fertilizer application on AM symbiosis in yam is recommended.

Reversing agriculture from intensive to sustainable improves soil quality in a semiarid South Italian soil

Intensive agriculture (IA) is widespread in South Italy, although it requires frequent tillage, large amounts of fertilizers and irrigation water. We have assessed the efficacy of reversing IA to sustainable agriculture (SA) in recovering quality of a typical South Italy soil (Lithic Haploxeralf). This reversion, lasting from 2000 to 2007, replaced 75% of nutrients formerly supplied inorganically by farmyard manuring and reduced the tillage frequency. Several chemical and biochemical properties, functionally related to C and N mineralisation–immobilisation processes and to P and S nutrient cycles, were monitored annually from 2005 to 2007 in the spring. Reversing IA to SA decreased soil bulk density, almost doubled the soil organic matter (SOM) as favoured the immobilisation of C and N, increased most soil microbial indicators but decreased contents of nitrate, mineral N and K2SO4-extractable C. The K2SO4-extractable C/K2SO4-extractable organic N ratio suggested that substrate quality rather than the mass of readily available C and N affected biomass and activity of soil microflora. Also, the largely higher 10-day-evolved CO2–C-to-inorganic N ratio under SA than IA indicated that higher C mineralisation, associated with higher microbial biomass N immobilisation, occurred under SA than IA. Decreases in most soil enzyme activities under IA, compared to SA, were much higher than concomitant decreases in SOM content. Soil salinity and sodicity were always higher in IA than SA soil, although not critically high, likely due to the intensive inorganic fertilisation as irrigation waters were qualitatively and quantitatively the same between the two soils. Thus, we suggest that the cumulative small but long-term saline (osmotic) and sodic (dispersing) effects in IA soil decreased the microbial variables more than total organic C and increased soil bulk density.

Fluorescein diacetate hydrolysis, respiration and microbial biomass in freshly amended soils

The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been utilised to estimate the potential microbial activity of soil freshly amended with a wide range of organic amendments and compared to the size and activity of soil microflora, measured by the microbial biomass C (B C) and CO2 evolution, respectively. Three different composting mixtures at different phases of the composting process were added to a semi-arid soil and incubated for 2 months under laboratory conditions. The addition of the organic amendment immediately increased B C and both measures of microbial activity (FDA and CO2 evolution). Highly significant correlations were found between FDA hydrolysis and B C for soil amended with the three composting mixtures (r = 0.81–0.96; P < 0.01), regardless of the origin, composition and degree of stability of the organic amendments. FDA hydrolysis, conversely to CO2 evolution, was unaffected by the disturbance caused by the soil amendment, indicating that the two parameters probably reflect different aspects of soil microbial activity. FDA hydrolysis could serve as an alternative estimation of the microbial biomass in freshly amended soils, despite the disturbance caused by the exogenous organic matter.

Habitat function of agricultural soils as affected by heavy metals and polycyclic aromatic hydrocarbons contamination

Ecotoxic activity of soils polluted with polycyclic aromatic hydrocarbon (PAH) and heavy metals (HM) was evaluated in pot and laboratory experiments. Plants and soil microorganisms were chosen as test organisms and six different soil materials were used in the study. The applied levels of HM and PAH were aimed to reflect environmental conditions in the “worst case” situation. Zn 2+, Pb 2+ and Cd 2+ were introduced to the soils as an aqueous solution of the mixture of salts at the concentrations corresponding to 1000, 500 and 3 mg kg −1, respectively. Mixture of four PAH compounds (flourene, anthracene, pyrene and chrysene) as a CH 2Cl 2 solution was applied at levels of 10–100 mg ∑4PAH kg −1. Population and activity of soil microflora was evaluated as measured of total bacteria counts, intensity of respiration and enzyme activity (dehydrogenases and phosphatases). Effect on plants was evaluated on the base of the growth (plant at an early stage of their development) and yield (mature plant) measurements. The results indicate that combined effect of PAH and heavy metals on soil microorganisms activity and on some plants at an early stage of their development can be stronger than in soils amended with HM or PAH separately. Reaction of tested organisms was related to soil properties, PAH concentration, time and plant species. Mature plants (maize) were insensitive to the applied levels of both group of contaminants.

The influence of various heavy metal compounds on the development and activity of soil micro-organisms

The influence of various concentrations of lead, zinc, copper, arsenic and mercury on development and activity of soil microflora are defined. Groups of micro-organisms important for soil fertility were considered. Different factors, e.g. soil type, type of metal compound and its concentrations, influencing the effect of heavy metals on soil microflora were also studied. The relative toxicity of the compounds used could be put in the following order: Hg ( metallic) > CuSO 4 > HgCl 2 > Hg 2 Cl 2 > HgO > As 2 O 3 > ZnSO 4 > NaHASO 4 > Pb( NO 3) 2. Of the micro-organisms investigated fungi and actinomycetes were the most resistant to all the metals used. Azotobacter sp. and nitrifiers appeared to be the most sensitive. The results of these investigations suggest that it would be possible to use microbiological methods in order to estimate the degree of soil pollution by various metals and compounds.

Soil environment and activity of soil microflora in the Negev desert

Biological activity in the soil was investigated in three Negev plant communities with a view to evaluating the controlling environmental factors. Specific features of group composition and dynamic behavior in microbial populations were investigated. Among environmental factors, the most important role is played by soil moisture, but it is effective only if organic matter is available.

Underground dry weight in the grassland communities ofArrhenatheretum elatioris alopecuretosum pratensis R. Tx. 1937 andMesobrometum erecti stipetosum Vicherek 1960

The meadow plant communities,Arrhenatheretum elatioris alopecuretosum pratensis R. Tx. 1937 andMesobrometum erecti stipetosumVicherek 1960, were chosen for investigations of the underground plant parts. Apparent differences in underground dry weight and its seasonal changes in both the communities were observed. Differences in the soil environment in different periods of the year are reflected in the character of time changes in underground dry weight. The soil environment affects not only the total underground biomass and their changes in time, but also the activity of soil microflora and, consequently, the decomposition rate of dead underground plant parts.