Soil Biochemical Activity Research Articles

Enhancing the phytoextraction capacity of chromium-contaminated soil by co-addition of garbage enzymes and microelectrolytic iron-carbon fillers

Most improved strategies for phytoextraction do not achieve a synergistic enhancement of chromium (Cr) accumulation capacity and biomass. This study investigated the impacts of co-addition of garbage enzyme (GE) and microelectrolytic iron-carbon filler (MF) on soil physicochemical properties, as well as form and uptake of Cr during aging and phytoextraction process. The response of rhizosphere microbial community to co-addition and its role in enhancing the remediation performance of ryegrass was further analyzed. Co-addition of GE and MF during the 12-day aging process resulted in an increase of nutrients, a shift from an oxidising to a reducing soil environment, a decrease of Cr(VI) content, and an enhancement of soil microbial community diversity and richness, creating a suitable environment for subsequent phytoextraction. During the 40-day phytoextraction process, co-addition played a crucial role in facilitating the establishment of a complex, efficient and interdependent ecological network among soil microorganisms and contributed to the evolution of microbial community composition and functional pathways. An increase in the relative abundance of Trichococcus, Azospirillum and g_norank_f_JG30-KF-CM45 elevated soil nutrient levels, while a decrease in the relative abundance of TM7a and Brucella reduced pathogen harbouring. Meanwhile, co-addition increased the relative abundance of Bacillus, Arthrobacter and Exiguobacterium, attenuated Cr phytotoxicity and improved soil biochemical activity. These markedly diminished oxidative damage and improved ryegrass growth by reducing malondialdehyde accumulation. In addition, regular additions of GE and the increase in relative abundance of norank_fnorank_o_Microtrichales led to rhizosphere acidification, which inhibited short-term Cr immobilization and contributed to a notable increase in phytoextraction efficiency. This study presents a strategy to enhance phytoremediation efficiency and soil quality during phytoextraction of Cr-contaminated soils.

Influence of Microalgae Biomasses Retrieved from Phycoremediation of Wastewaters on Yield of Lettuce, Soil Health, and Nitrogen Environmental Fate

The main purpose of this study was to investigate the effects of three microalgae strains, Chlorella vulgaris, Scenedesmus quadricauda, and Klebsormidium sp. K39, on the enhancement of lettuce yield and soil fertility and in mitigation of nitrogen losses in groundwater, focusing on some aspects of the complex soil-plant system. The experimental trials were carried in pots, and involved the application of microalgae cells at two different concentrations (50 and 500 mg kg− 1 of soil), alone or in combination with standard mineral fertilization. The yield, main morpho-biometric parameters, and protein content of lettuce seedlings, as well as the activities of key enzymes involved in the nitrogen pathway (nitrate reductase, glutamine synthase, and glutamate synthetase) at both root and shoot levels, were monitored and the results were compared to not-inoculated control plants. The nitrate leached due to over irrigation was also evaluated. Furthermore, even the effects of microalgae biostimulants on soil biochemical activity were analysed by monitoring fluorescein diacetate hydrolysis, dehydrogenase, acid and alkaline phosphomonoesterase, and urease activities. All treatments significantly improved lettuce growth, especially when combined with mineral fertilization, providing comparable levels to the control plants treated only with microalgae cells. Furthermore, microalgae treatments positively influenced soil biological activities, as evidenced by increased of the potential biochemical index of soil fertility (Mw). In conclusion, microalgae soil treatments may be considered as a viable strategy to assist growers in reducing the use of mineral fertilizers, with a view to improve plant growth as well as soil biological activity.

Mixing Compost and Biochar Can Enhance the Chemical and Biological Recovery of Soils Contaminated by Potentially Toxic Elements.

Biochar and compost are able to influence the mobility of potentially toxic elements (PTEs) in soil. As such, they can be useful in restoring the functionality of contaminated soils, albeit their effectiveness can vary substantially depending on the chemical and/or the (micro)biological endpoint that is targeted. To better explore the potential of the two amendments in the restoration of PTE-contaminated soils, biochar, compost (separately added at 3% w/w), and their mixtures (1:1, 3:1, and 1:3 biochar-to-compost ratios) were added to contaminated soil (i.e., 2362 mg kg-1 of Sb and 2801 mg kg-1 of Zn). Compost and its mixtures promoted an increase in soil fertility (e.g., total N; extractable P; and exchangeable K, Ca, and Mg), which was not found in the soil treated with biochar alone. All the tested amendments substantially reduced labile Zn in soil, while biochar alone was the most effective in reducing labile Sb in the treated soils (-11% vs. control), followed by compost (-4%) and biochar-compost mixtures (-8%). Compost (especially alone) increased soil biochemical activities (e.g., dehydrogenase, urease, and β-glucosidase), as well as soil respiration and the potential catabolic activity of soil microbial communities, while biochar alone (probably due to its high adsorptive capacity towards nutrients) mostly exhibited an inhibitory effect, which was partially mitigated in soils treated with both amendments. Overall, the biochar-compost combinations had a synergistic effect on both amendments, i.e., reducing PTE mobility and restoring soil biological functionality at the same time. This finding was supported by plant growth trials which showed increased Sb and Zn mineralomass values for rigid ryegrass (Lolium rigidum Gaud.) grown on biochar-compost mixtures, suggesting a potential use of rigid ryegrass in the compost-biochar-assisted phytoremediation of PTE-contaminated soils.

Elucidating the impact of biochar with different carbon/nitrogen ratios on soil biochemical properties and rhizosphere bacterial communities of flue-cured tobacco plants.

In agriculture, biochar (BC) and nitrogen (N) fertilizers are commonly used for improving soil fertility and crop productivity. However, it remains unclear how different levels of BC and N fertilizer affect soil fertility and crop productivity. This study elucidates the impact of different application rates of BC (0, 600, and 1200 kg/ha) and N fertilizer (105 and 126 kg/ha) on biomass accumulation, soil microbial biomass of carbon (SMC) and nitrogen (SMN), and soil biochemical properties, including soil organic carbon (SOC), total nitrogen (TN), soil nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N), urease (UE), acid phosphatase (ACP), catalase (CAT), and sucrase (SC) of tobacco plants. In addition, a high throughput amplicon sequencing technique was adopted to investigate the effect of different application rates of BC/N on rhizosphere bacterial communities of tobacco plants. The results confirm that high dosages of BC and N fertilizer (B1200N126) significantly enhance dry matter accumulation by 31.56% and 23.97% compared with control B0N105 and B0N126 under field conditions and 23.94% and 24.52% under pot experiment, respectively. The soil biochemical properties, SMC, and SMN significantly improved under the high application rate of BC and N fertilizer (B1200N126), while it negatively influenced the soil carbon/nitrogen ratio. Analysis of rhizosphere bacteriome through amplicon sequencing of 16S rRNA revealed that the structure, diversity, and composition of rhizosphere bacterial communities dramatically changed under different BC/N ratios. Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, and Acidobacteria were highly abundant bacterial phyla in the rhizosphere of tobacco plants under different treatments. Co-occurrence network analysis displayed fewer negative correlations among rhizosphere bacterial communities under high dosages of biochar and nitrogen (B1200N126) than other treatments, which showed less competition for resources among microbes. In addition, a redundancy analysis further proved a significant positive correlation among SMC, SMN, soil biochemical properties, and high dosage of biochar and nitrogen (B1200N126). Thus, we conclude that a high dosage of BC (1200 kg/ha) under a high application rate of N fertilizer (126 kg/ha) enhances the biomass accumulation of tobacco plants by improving the soil biochemical properties and activities of rhizosphere bacterial communities.

Animal manure digestate fertilization effect on the soil microbial activity and crop productivity in the northern part of temperate climate conditions-Lithuania

Microbial communities make up a significant portion of the soil, and their activity is crucial to the soil's ability to function. In this study, we aim to evaluate the influence of animal waste-based digestate as N source on soil microbial activity and crop productivity over a three-year period in a crop rotation system. Two experimental field trials using the same design were performed in the year 2018–2020 and 2019–2021, respectively. Four different fertilization treatments, namely Synthetic Nitrogen, Chicken manure digestate, Cow manure digestate, and Pig manure digestate split fertilized (90 kg ha−1 N and 80 kg ha−1 N), and unfertilized treatment (control) were studied while growing different annual crops (spring wheat, triticale, and barley). There was a more significant positive effect on the soil microbial biomass carbon noticeably observed after the first year of digestate application, with an increase of 20.2–75% when compared to the unamended soil. Soil dehydrogenase activity was a less sensitive indicator for the effect of fertilization on soil biochemical activity, but the average data from both experiments showed an increase in fertilized soils from 6.6 to 8.5% in fertilized soils. The soil moisture did not significantly influence the microbial biomass and the enzymatic activity. However, crop productivity consistently rose each successive year, a positive effect of digestate use. We deduced that the long-term application of animal manure digestate under natural conditions coupled with other variable factors such as seasonal conditions and agricultural management techniques significantly influenced the microbial biomass contents – a critical component of the biological state of the soil. Our findings will help identify how and what could make soil microbial communities and crop productivity vulnerable to seasonal changes in relation to the consistent application of animal manure digestate to agricultural soils and the agricultural techniques employed.

Effect of Reduced Tillage on Soil Enzyme Activity, Pests Pressure and Productivity of Organically Grown Spring Wheat Species

The possibility of using reduced tillage in organic farming is poorly recognized. The study aimed to assess the impact of the tillage method (shallow tillage and plowing) on soil biochemical activity, pest pressure, and grain yield of Triticum sphaerococcum, T. persicum, and T. aestivum ssp. vulgare, grown in organic farming systems. For this purpose, field experiments were conducted at three certified organic farms located in different regions of Poland. Enzyme activity was influenced to a greater extent by local soil and weather conditions compared to wheat species and the tillage method. Insect pests (Oulema spp.) slightly damaged the leaves of wheat, and the reduced tillage did not increase the damage. Under site conditions favorable for the development of diseases significantly fewer disease symptoms were observed in shallow tillage compared to plowing (powdery mildew by 9.6–46.1%; stripe rust by 15.5–89%; Septoria head blotch by 0–84.4%; Fusarium head blotch by 0–47.4%, Fusarium foot rot by 0–100%). T. aestivum was characterized by the highest yield and the yield stability in various locations and tillage methods. Ancient wheat species (T. sphaerococcum and T. persicum) had a higher yield in shallow tillage compared to plowing tillage (by 64% and 30%, respectively) only under effective weed control.

Influence of planting methods and organic amendments on rice yield and bacterial communities in the rhizosphere soil.

A comprehensive understanding of rice cultivation techniques and organic amendments affecting soil quality, enzyme activities and bacterial community structure is crucial. We investigated two planting methods (direct seeding and transplanting) of paddy rice (Oryza sativa) and organic amendments with rice straw and biochar on crop yield and soil biological and physicochemical properties. Rhizosphere bacterial communities at the maturity stage of rice growth were characterized through high-throughput 16S rRNA sequencing. Soil biochemical properties and enzyme activity levels were analyzed. Grain yield of paddy rice with transplanting increased 10.6% more than that with direct seeding. The application of rice straw increased grain yield by 7.1 and 8.2%, more than with biochar and the control, respectively. Compared to biochar and the control, the application of rice straw significantly increased sucrase, cellulase, protease, organic carbon, available phosphorus, nitrate, and ammonium. The application of biochar increased microbial biomass nitrogen and carbon, urease, pH, available nitrogen, and available potassium compared to the application of rice straw and the control. Principal coordinate analysis and dissimilarity distances confirmed significant differences among the microbial communities associated with planting methods and organic amendments. Bacteroidetes, Nitrospirae, Firmicutes, and Gemmatimonadetes abundance increased with rice straw relative to biochar and the control. The biochar addition was associated with significant increases in Chloroflexi, Patescibacteria, Proteobacteria, and Actinobacteria abundance. Pearson’s correlation analyzes showed that Chloroflexi, Bacteroidetes and Nitrospirae abundance was positively correlated with grain yield. The relative abundance of these bacteria in soil may be beneficial for improving grain yield. These results suggest that planting methods and organic amendments impact soil biochemical characteristics, enzyme activity levels, and microbial community composition.

Changes in litter input exert divergent effects on the soil microbial community and function in stands of different densities

Soil microbial communities influence soil biogeochemical cycling by affecting the production of extracellular enzymes and the release of carbon dioxide. Changes in litter input or stand density due to thinning can affect soil microbial communities and their function by altering soil biochemical properties. However, it is unclear how or to what extent different amounts of litter input affect soil microbial communities and their function in forest stands with different densities. Therefore, we simulated litter removal, 50 % litter reduction, normal litter input, and double litter increase under field conditions by applying different amounts of litter to soils with different stand densities in the laboratory. We then measured soil biochemical properties, microbial communities, enzyme activity, and respiration rate.Our results revealed that the responses of soil dissolved organic carbon and total nitrogen to litter input were more pronounced in the high-density forest stand with poor soil than in the low-density forest stand with nutrient-rich soil, which was mainly reflected in that the addition of litter significantly decreased the concentration of dissolved organic carbon while increasing the content of total nitrogen in the soil of the high-density forest stand. In comparison to the soil carbon component, the nitrogen component of the soil was more affected by stand density. The responses of soil fungal and bacterial communities to leaf litter treatment varied with stand density, as reflected primarily in changes in the relative abundances of Ascomycota, unclassified_K_fungi, and Proteobacteria, and changes in the relative abundances of their functional groups (ectomycorrhizal fungi, saprophytic fungi, pathogens, parasites, and bacteria involved in the nitrogen cycle). Soil fungal community responses to changes in litter input are more sensitive in the high-density forest with nutrient-poor soil than in the low-density forest stand. Furthermore, litter input inhibited the activities of soil β-glucuronidase, N-acetyl-β-d-glucosaminidase, and acid phosphatase more strongly in the low-density forest stand. Litter manipulation primarily affected enzymatic activity in the high-density forest stand by changing the diversity and composition of the soil fungal community. However, in the low-density forest stand, litter treatment affected soil enzyme activity, primarily through changes in soil bacterial and fungal community composition, as well as soil respiration through changes in bacterial richness (Chao 1) and community composition.We conclude that how the change in litter input impacts the soil microbial community and its function, or the magnitude of the effects, is largely dependent on soil quality. Relationships among soil variables, microbial communities, and function differ between stand densities. Our study contributes to an enhanced understanding of the impact of changes in litter input due to climate change or anthropogenic activities on soil biogeochemical cycles and can also guide rationally formulating forest management approaches to improve microbial function under climate change.

Integrative analyses of geochemical parameters-microbe interactions reveal the variation of bacterial community assembly in multiple metal(loid)s contaminated arable regions

Soil microbes play crucial roles in biochemical and geochemical processes in contaminated arable ecosystems. However, what factors determine the assembling process of soil bacterial community under multiple heavy metal (loid)s (HMs) stress and how communities respond to geochemical changes have rarely been understood. Therefore, a number of contaminated soils were sampled to explore the interactions among geochemical parameters, HMs and innate bacterial community. The results showed that soil biochemical activities were inhibited obviously with the increase of HMs. Significant differences were observed in bacterial composition and abundance in studied areas, with Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Firmicutes governing the bacterial community structure. Redundancy analysis and variation partition analysis revealed that about 67.33% of the variation in bacterial assemblages could be explained by physiochemical parameters (21.59%), biochemical parameters (11.64%), toxic metal (loid)s (9.11%) and the interaction effect of these variables (24.99%), among which total-arsenic and moisture were the main factors. Spearman correlation analysis also demonstrated that dehydrogenase, moisture and TOC have a positive correlation with bacterial community structure with As–Cd–Pb gradient. Altogether, this study would provide a comprehensive relationship between major environmental factors and bacterial assemblages, which could offer some baseline data to investigate the mechanisms of how communities respond to physiochemical changes.

Dynamics of soil properties under cotton - alfalfa crop rotation

The aim of the study: Monocrop cultivation is known to affect negatively soil physical properties and decrease soil fertility. To eliminate these undesirable consequences, application of mineral and/or organic fertilizers, as well as other agricultural practices, are employed. Other aspects of agronomy (soil cultivation, fertilizer and plant protection systems, the acquisition of new seeds) require significant material costs. Increasing the yield of agricultural crops, and cotton in particular, can be achieved by crop rotation. The aim of the study was to analyze some physico-chemical soil properties and dynamics of soil processes under cotton-alfalfa crop rotation. Location and time of the study. The research was carried out in 2014-2018 in the Northern Mugan in the Republic of Azerbaijan, as the region is one of the largest agricultural regions of the country, supplying cotton and grain. The studies were carried out on irrigated meadow serozem, or Endogleyic Calcisol, according to the WRB, soils of the Kura-Araks lowland of Azerbaijan. Methodology. Field and laboratory work was carried out according to generally accepted methods of soil science. The particle size distribution was determined by the pyrophosphate method; density, humus content, humidity, temperature, and morphological characteristics were determined using conventional methods. Statistical processing of the obtained data was carried out using the Microsoft Office Excel program. Main results. The long-term cotton crop was found to decrease agrophysical and agrochemical properties of soil. After three years of cotton production the humus content decreased by 20%, whereas the content of water-resistant aggregates increased by 40%, and soil permeability decreased three-fold, soil bulk density increased by 7%, all these resulting in the reduced cotton productivity. Crop rotation showed that soil fertility, decreased after three consecutive years of cotton growth, could be almost fully restored by following with two years of alfalfa crop. Conclusion. Compared with a monoculture of crops, crop rotation leads to a rearrangement in soil microflora and a change in soil biological and biochemical activity, helps to reduce the possibility of a unilateral influence of plants on soil, which in turn helps to restore soil fertility and obtain high sustainable crop yields in the cotton system. Therefore, the use of cotton-alfalfa crop rotations is very important for attaining the goal of increasing two-fold the production of all types of feed in Azerbaijan. To maintain potential fertility, obtain high sustainable yields of soil-protective, resource-saving crops, five-field cotton-alfalfa crop rotation is recommended for the farmers of the Mugan steppe.

Perna canaliculus as an Ecological Material in the Removal of o-Cresol Pollutants from Soil.

Soil contamination with cresol is a problem of the 21st century and poses a threat to soil microorganisms, humans, animals, and plants. The lack of precise data on the potential toxicity of o-cresol in soil microbiome and biochemical activity, as well as the search for effective remediation methods, inspired the aim of this study. Soil is subjected to four levels of contamination with o-cresol: 0, 0.1, 1, 10, and 50 mg o-cresol kg−1 dry matter (DM) of soil and the following are determined: the count of eight groups of microorganisms, colony development index (CD) and ecophysiological diversity index (EP) for organotrophic bacteria, actinobacteria and fungi, and the bacterial genetic diversity. Moreover, the responses of seven soil enzymes are investigated. Perna canaliculus is a recognized biosorbent of organic pollutants. Therefore, microbial biostimulation with Perna canaliculus shells is used to eliminate the negative effect of the phenolic compound on the soil microbiome. Fungi appears to be the microorganisms most sensitive to o-cresol, while Pseudomonas sp. is the least sensitive. In o-cresol-contaminated soils, the microbiome is represented mainly by the bacteria of the Proteobacteria and Firmicutes phyla. Acid phosphatase, alkaline phosphatase and urease can be regarded as sensitive indicators of soil disturbance. Perna canaliculus shells prove to be an effective biostimulator of soil under pressure with o-cresol.

Effect of planting method on C:N:P stoichiometry in soils, young silver fir (Abies alba Mill.) and stone pine (Pinus cembra L.) in the upper mountain zone of Karpaty Mountains

C/N/P stoichiometry offers important indicators of ecosystem function and productivity. The aim of this research was to determine how planting methods in biogroups influence C/N/P stoichiometry in soil and plants. We hypothesised that planting methods, consisting in different initial spacing and shape would affect the growth characteristics of trees, and consequently, change soil properties – microbiological activity, in particular. This research examined two species that have different ecological requirements, silver fir (Abies alba Mill.) and Swiss stone pine (Pinus cembra L.), grown in the upper mountain zone, 1200 m above sea level. We established 48 experimental plots with two planting methods and two species in 2011. The soil and plant samples for laboratory analysis were taken in September 2020. In the first planting method 49 seedlings at regular 1 × 1 m spacing in a square plot (PM1) were planted, while in the second method 50 seedlings in two rhombus plots with 50 × 50 cm spacing (PM2) were planted. We determined the basic physicochemical properties and enzymatic activity in soil samples, and we recorded the content of C, N and P in testing needle samples from the trees. We also calculated the C/N, C/P and N/P ratios for both the soil samples and the plants. We found that the formation of biogroups with smaller spacing during stand renewal influenced the selected soil properties; within the biogroups with smaller spacing, an increase in soil biochemical activity was found. Our research confirms that planting methods and species are essential contributors to the C/N/P stoichiometry of soils and plants. The C/N/P stoichiometry of the soil samples from the different species and the different planting methods ranged between 928/37/1 and 1087/42/1. In the case of the Swiss stone pine needles, we noted a narrower C/N/P stoichiometry compared to the fir needles, regardless of the planting method. C/N/P stoichiometry is a useful tool for reflecting the nutrient cycle in mountain ecosystems, and our research shows that in the case of species with higher ecological requirements, stoichiometry can indicate nutrient limitation. In higher mountainous locations, nitrogen and phosphorus deficiencies are the main limiting factor. In the case of fir trees, the method of planting helps to reduce nutrient limitation and improve growth characteristics.

Understanding rice growth-promoting potential of Enterobacter spp. isolated from long-term organic farming soil in India through a supervised learning approach.

This study addresses the plant beneficial enterobacteria present in rice rhizosphere and their efficiency for enhancing nitrogen uptake in rice plant. Using culturable approaches, the population of total diazotrophs present in rhizosphere samples collected from different organic rice fields of Sikkim were studied and recorded in the range between 4.62 to 4.97 log 10 CFU/g soil. All the isolated commonly occurred diazotrophic bacterial isolates were screened based on their ability to fix nitrogen in milligram per gram of sugar consumed under in-vitro condition with the reference check. In addition to nitrogen fixation, plant growth promoting traits such as production of indole-3-acetic acid and gibberellic acid were estimated using spectrophotometric approaches and compared against Bacillus subtilis as reference multi-potent plant growth promoting strain. In-vivo evaluation of these diazotrophic species in rice found improvement in both above and below ground responses in rice plant evaluated by estimating changes in chlorophyll concentration, plant biomass, root architecture, nitrogen uptake, microbial biomass and associated biochemical activity of soil. Further, the selected isolates were identified through DNA targeted analysis of 16S rRNA gene present in diazotrophs and which identified that the isolates belonged to the Enterobacter genus. Statistical models were prepared for deciphering the dynamics of plant growth improvement due to selective enrichment of rhizosphere bacteria and found significant (p<0.05) correlation between soil and plant parameters. This study concludes that Enterobacter spp. present in organic paddy soils of Sikkim having good nitrogen fixing abilities and whose selective enrichment in rhizosphere improved nitrogen uptake and plant growth promotion in rice plant.

Картографирование экологических свойств почв индустриального города Усолье-Сибирское

Results from studying urbanized territories highly depend on approaches and methods of interpreting data obtained in the course of investigations. A case study was made in the industrial city of Usolye-Sibirskoe (Irkutsk oblast, RF) to investigate and map the current ecological-and-biochemical status of soil cover affected by urbanization and technogenesis. T. V. Aristovskaya’s and M. V. Chugunova’s rapid method was used to reveal high indicators of the level of alkaline-acid conditions and biochemical activity of urban soils. The mapping enabled identification of the local features of the urban territory. A considerable part of it is occupied by soils with weak alkaline pH index (7.3–8.0). In absolute values, it is 6083.3 ha, or 77.2 %. The study determined a high and very high level of the soil biochemical activity. They occupy a large area of 6079.2 ha, i.e. 76 % of the city. A substantial increase in soil biochemical activity can lead to loss of a biogenous element, nitrogen, and this cannot be regarded as a positive phenomenon. Experimental data on the SBA – рН system for the residential zone of the city made it possible to determine a close correlation between them to be statistically significant.

Use of biostimulants obtained from okara in the bioremediation of soils polluted by imazamox

The objective of this study was to study under laboratory conditions the bioremediation effect of two biostimulants obtained from okara in a soil polluted by imazamox at a rate of 2.5 l ha-1 (manufacturer’s recommended rate). These biostimulants were obtained by enzymatic hydrolysis processes using one (subtilisine) and two (subtilisine and flavourzyme) enzymes. Their effects on soil enzymatic activities, the microbial community structure and the evolution of the herbicide in soil over a 90-day period. Both biostimulants stimulated the soil biochemical activity and microbial population. However, this stimulation was greater in the soil amended with the biostimulant with a higher percentage of low-molecular-weight proteins (<300 Da). Applying the biostimulants to the polluted soil decreased the inhibition of the biological properties. This decrease was also greater when the biostimulant had a higher content of low-molecular-weight proteins content. Consequently, the biostimulant obtained by hydrolytic processes using the subtilisin and flavourzyme enzymes would be of greater interest in the bioremediation process.

Bacterial diversity and enzymatic activity in a soil recently treated with tebuconazole

Tebuconazole is one of the most commonly used active substances from the group of triazoles, that exhibits high efficacy in plant protection against fungal diseases. It’s too frequent use may, however, pose risk to soil ecosystems, leading to changes in their biological diversity. This study was aimed at evaluating the effect of tebuconazole on population numbers, diversity, and structure of bacterial communities, and on the enzymatic activity of soil. Tebuconazole was introduced into the soil (sandy loam with pH 7.0) in the following doses in mg kg−1 DM (dry matter) of soil: 0.00 (C), 0.02 (O), and 10.0 (T). It caused changes in the population numbers of diversity of bacteria as well as in the biochemical activity of soil. It stimulated the proliferation of organotrophic bacteria and inhibited that of actinobacteria. The r-strategists were found to predominate among both the organotrophs and actinobacteria in the soil with tebuconazole addition. The amplicon sequencing of the 16S encoding gene (SSU rRNA) demonstrated tebuconazole to elicit changes in the structure of bacterial communities. In all soil samples, the prevailing taxon at the Phylum level turned out to be Proteobacteria, followed by Firmicutes and Actinobacteria, whereas the lowest counts were noted for Verrucomicrobia. The relative abundance of the bacteria at the Phylum level decreased in the soil under the influence of tebuconazole. The most sensitive to the effect of tebuconazole applied in a dose of 10.0 mg kg−1 turned out to be Acidobacteria, whereas the most resistant were Verrucomicrobia. The predominating taxon at the class level was Alphaproteobacteria, followed by Bacilli. Tebuconazole ensured favorable conditions for the development of bacteria from Kaistobacter and Bacillus genera as their OTUs were the highest in the soil treated with tebuconazole at 10.0 mg kg−1. In turn, Phenylobacterium and Rhodoplanes were sensitive to soil treatment with tebuconazole at doses of 0.02 mg kg−1 and 10.0 mg kg−1. Tebuconazole proved to be a strong inhibitor of urease and catalase activities, while in turn it enhanced activities of dehydrogenases, acid phosphatase, alkaline phosphatase, and arylsulfatase.

Biochemical attributes and establishment of tree seedlings in soil after urochloa decumbens cultivation in soil with deposition of iron mining residues

background: the recovery of areas impacted by mining activities is a major challenge and requires knowledge of how the biological and biochemical processes of the soil as well as the establishment of plant species are affected by mining residue. in this work, the influence of deposition of iron mining mud and tailings on soil biochemical attributes and the initial development of tree seedlings was studied in a simulated event in the greenhouse. pots (n = 27) with natural soil (2.0 kg) received deposition (280 ml) of iron mining mud or tailings and by three-month was cultivated with urochloa decumbens. at the end of this period, part of the pots was sampled and the soil biochemical activities were evaluated. then tree seedlings (schinus terebinthifolius and eremanthus incanus) were planted and cultivated for a year, when then shoot (sdw) and roots (rdw) dry weight were evaluated. results: deposition of iron mining mud and tailings did not affect microbial biomass carbon or basal soil respiration, however both conditions reduced (p < 0.05) β-glucosidase activities by up to 30%, and the easy extractable glomalin by about 19%. in addition, the mud deposition reduced (p < 0.05) the sdw and rdw of s. terebinthifolius by about 21% and 24%, respectively. nevertheless, uruchloa decumbens and eremanthus incanus had no variation in dry weight production between treatments, so they have good ability to grow settle in soil affected by mining residue. conclusion: this study shows that the sequential planting of u. decumbens and e. incanus can be an alternative for use in environments with deposition of iron mining tailings.

Changes in Pisum sativum L. Plants and in Soil as a Result of Application of Selected Foliar Fertilizers and Biostimulators

The aim of this study was to assess the effect of selected biostimulators and foliar fertilizers on plant development, plant yield, soil fertility and soil biochemical activity (dehydrogenases, phosphatases, catalases) during the cultivation of pea (Pisum sativum L.). A field experiment was conducted between 2016 and 2018 at the Gorzyń Experimental and Educational Station, Poznań University of Life Sciences in Poland. The following treatments were tested: (1) control; (2) Titanit; (3) Optysil; (4) Metalosate potassium; (5) Rooter; (6) Bolero Mo; (7) Adob Zn IDHA; (8) Adob B and (9) Adob 2.0 Mo. Adob Zn IDHA stimulated yields, especially under average moisture conditions and less so in drought conditions, and the differences compared to control amounted 8.36 and 4.3%, respectively. The results showed a close relationship between the effects of the biostimulators and foliar fertilizers and weather conditions during the study. It was not possible to determine whether any of the biostimulators or foliar fertilizers had a positive effect on pea seed yield in any year. Similarly, it was difficult to clearly determine the effect of the biostimulators and fertilizers on biochemical activity in the soil, although soil enzyme activity was influenced most by application of the Bolero Mo fertilizer. In all study years, biological nitrogen fixation was always greater after the application of a biostimulator/fertilizer treatment.

What Physical Aspects Influence Biochemical Activity in Soil in a Natural Landscape?

The objective of this paper was to evaluate the effect of depth, seasonality and phytophysiognomies on the biochemical activity of soils in native Cerrado biome. Additionally, we listed which chemical parameters influence the activity of the microbiota and enzymatic activity in these environments. We selected eight sampling areas of Cerradão (Forest) and four areas of Cerrado (shrub land) and evaluated the chemical characteristics and biochemical activity. The depth, sampling site and seasonality directly affected soil metabolic activity. Microbial biomass carbon was influenced by interaction between soil depth and sampling site and the enzyme activity tends to be higher in the superficial layer of the soil. The analysis of redundancy showed strong influence of environmental variables (phosphorus and CTC) on the biological activity of the soil. Thus, the metabolic activity of microorganisms is highly influenced by intrinsic soil characteristics of each sampling site.

Role of Chlorella sp. and rhamnolipid 90 in maintaining homeostasis in soil contaminated with bisphenol A

PurposeThe knowledge about the impact of BPA on soil health does not correspond to the great interest in its analogues. Therefore, a study was conducted to determine the potentially negative impact of BPA on the biochemical properties of soil. The study also evaluated the effectiveness of two biostimulants in eliminating potential homeostasis disorders caused by BPA.Materials and methodsA pot experiment was conducted under supervised conditions. BPA at five contamination levels was added to the soil of the granulometric composition of sandy loam at 0, 0.1, 2, 40 and 800 mg BPA kg−1 of a dry matter (DM) of soil. The biochemical activity of the soil was interpreted through the activity of dehydrogenases (Deh), urease (Ure), catalase (Cat), acid phosphatase (Pac), alkaline phosphatase (Pal), arylsulphatase (Aryl) and β-glucosidase (Glu) whose activity was determined on days 5, 15 and 45 of the study. The biostimulative potential of Chlorella sp. and rhamnolipid 90 (which eliminates the undesirable effects of BPA on the parameters) was expressed with IFB—the factor of the impact of increasing of bisphenol (BP) soil contamination levels. The response of spring barley to increasing BPA pressure was analysed with the plant resistance index (RS). The study was made more comprehensive by determination of the macronutrient content in the plants.Results and discussionThe sensitivity of individual enzymes to increasing bisphenol pressure on the 45th day of the experiment can be arranged in the following sequence: Deh > Ure > Glu > Pac > Cat > Aryl > Pal. Biostimulation of soil with Chlorella sp. gave better results than with rhamnolipid 90. A compilation of BPA 800 mg BPA kg−1 DM of soil and Chlorella sp. brought about an increase in the activity of Glu on the 45th day of the experiment and Pac, Pal and Aryl on the 5th day. Only at this contamination level did BPA stimulate the crop growth in all the parallel plots except in those biostimulated by Chlorella sp. Only algae significantly reduced the negative BPA impact on the N, Ca and K content in spring barley.ConclusionsThe experiment emphasised the significant inhibitory impact of BPA on the biochemical activity of soil which, in consequence, upset the microbial balance of soil processes. Chlorella sp. played a more important role in maintaining the soil homeostasis than rhamnolipid 90, which did not correspond to its negative impact on the yield of spring barley.